The full-hybrid system with a spark ignition engine is essential for the future powertrain systems in passenger cars. However, many aspects of three-way catalysts remain unclear, necessitating urgent clarification. Simultaneously, modeling the phenomenon and establishing numerical prediction technology are required. The effect of surface oxidation after exposure in abundant O ₂ surroundings encountered during not only fuel cut-off at deceleration, but also engine stop of HEV on the purification performance of Rh, which is one of the highest performing precious metals supported on three-way catalysts, was investigated by CO-O ₂ light-off test and XPS analysis in the previous research. The light-off curve started to rise at higher temperature in the case of pretreatment in the lean atmosphere than in the rich atmosphere, and the results of XPS analysis showed that the reversible oxide film was formed in the lean atmosphere. In this study, the CO-NO light-off test was repeated twice after lean atmosphere pretreatment. The rise of the second light-off curve was significantly faster and almost coincided with the light-off curve after hydrogen reduction treatment, suggesting that the oxide film formed in the lean atmosphere may be decomposed during the CO-NO light-off test. By adding the reactions that describe the decomposition of oxide film by carbon and nitrogen adsorbed on the surface to the detailed surface reaction model developed in the previous research, CO-NO light-off on Rh surface were simulated and could reasonably reproduce the result of experimental results. Through this research, the phenomenological model of oxide film formation and decomposition on Rh surface and the effect of Rh oxidation to the purification performance have been proposed.

In the context of increasingly stringent vehicle emission regulations, computer-aided engineering has been indispensable for optimizing the design and the operational strategies of emission control systems. This paper proposes a new filtration model for particulate filters that enables the accurate estimation of solid particle number emissions above 10 and 23 nm in diameter (SPN10 and SPN23, respectively). The model incorporates a persistent slip factor and a linear filtration efficiency of cake layers into the unit collector model proposed by Konstandopoulos and Johnson. This enhancement captures PM escape phenomena, such as a passage through interconnected large pores in filter walls. Simulations using a 1D + 1D two-channel framework with the proposed model successfully reproduced experimental results of SPN10 and SPN23 emissions downstream of a miniature gasoline particulate filter (GPF) tested with a synthetic particle generator. The model was also able to represent the observed continuous emissions during a cake filtration mode. Additional simulations using the same model parameters showed good agreement with experimental data of SPN10 and SPN23 emissions downstream of a full-size GPF tested with a gasoline direct injection (G-DI) engine under 5 steady-state operating conditions. The simulations revealed that particles in the 10–100 nm size range dominated the downstream SPN emissions despite their high filtration efficiency, whereas particles in the 100–200 nm size range were less significant. The proposed model is expected to contribute to the GPF developments to comply with the stringent emission regulations of the upcoming Euro 7.

Three-Way Catalysts (TWC) undergo thermal degradation under high exhaust gas temperatures, reducing the specific surface areas of precious metals on the catalyst surface due to sintering. This also reduces the Oxygen Storage Capacity (OSC) and the TWC conversion rate. Lowering the exhaust gas temperature is a solution to minimize performance deterioration. However, low temperatures reduce the effectiveness of catalyst reactions. Perturbation (dithering or rich-lean cycle) can enhance the TWC conversion rate. In this work, synthetic gas reactor experiments are carried out to measure the purification performance data of fresh and degraded catalysts under rich-lean perturbations at 400°C. A TWC model with elementary reactions covering surface reactions and OSCs is developed. The degradation performances in the axial direction are reported. The results show that the conversion rates reach 90% within the first 30% of the catalyst length. For the catalysts with and without degradation, when the conversion rate declines, the reaction rates are slower than the mass fluxes, indicating that the reaction rates are the rate-limiting factor for each purification reaction. It is observed that the degraded catalysts have fewer active sites, and the amount of oxygen storage and consumption is small. Conversion rates of gas species, OSC, and mass flux of major species of the fresh and degraded catalysts are also compared.

<div class="section abstract"><div class="htmlview paragraph">One way to decarbonize spark-ignition (SI) engines is to use alternative fuels to improve thermal efficiency. Compressed biomethane gas (CBG), mainly composed of methane and carbon dioxide produced from food waste, has attracted attention as an alternative fuel, but its carbon dioxide content is indeterminate. This study investigates the effects of carbon dioxide content on engine performance (thermal efficiency, etc.), emission characteristics, and turbulent burning velocity using a CBG surrogate fuel mixed with methane and carbon dioxide. A single-cylinder SI engine is used as the test engine, and experiments are conducted under different load conditions with a constant crank angle of 50% mass fraction burned (CA50). Engine performance is analyzed based on heat balance from in-cylinder pressure analysis. Emission characteristics are measured using an emission gas analyzer. Using the boundary conditions obtained from the experiments, parameters such as unstretched laminar burning velocity, flame stretch, and turbulent intensity are calculated numerically to predict the turbulent burning velocity, which is compared with the combustion duration obtained from the experiments. Experimental results show that thermal efficiency increased with an increasing carbon dioxide blending ratio of 0-10%. As for nitrogen oxides in the exhaust gas, the amount of nitrogen oxides emitted is suppressed by a decrease in the cylinder temperature with an increase in the carbon dioxide blending ratio. In addition, the turbulent burning velocity decreased with increasing carbon dioxide blending ratio due to a decrease in the unstretched laminar burning velocity.</div></div>

<div>A significant amount of chemical fuel energy in internal combustion engines is wasted through exhaust heat. Waste heat recovery (WHR) systems can transform the heat into electrical energy using thermoelectric generators (TEG). This work utilizes a 1D CFD model to demonstrate the potential of TEG-WHR in improving the thermal efficiency of mass-production, compressed natural gas (CNG) engines used in commercial 22-ton heavy-duty trucks. First, the TEG with heat exchanger experiments are performed to measure thermal and electrical performance data under different fin pitches and inlet gas conditions (Re number, temperature, gas flow rate). These data are used to develop and validate a TEG model, which considers user-defined functions of heat transfer and flow friction coefficients to reproduce measured thermal/electrical characteristics of the integrated TEG with its heat exchanger. The engine experiments are conducted based on the speed–torque map (51 test conditions) of the JE05 heavy-duty cycle using the turbocharged engine equipped with a multi-port injection system. The engine model is calibrated and validated against test data under base conditions (using production valve timings), optimal variable valve actuation (VVA), and variable compression ratio (VCR). Finally, the high-fidelity engine and TEG models are integrated to predict the electrical power generated by a compact TEG-WHR (three-layer, size: 1.3 × A4-paper). The integrated model considers a tradeoff between TEG-generated power and engine pumping loss. Simulation results show that the compact TEG can generate effective 20–701 W electrical powers, translating to about 0.03–1.07% brake thermal efficiency improvement.</div>

<div class="section abstract"><div class="htmlview paragraph">A major issue of battery electric vehicles (BEV) is optimizing driving range and energy consumption. Under actual driving, transient thermal and electrical performance changes could deteriorate the battery cells and pack. These performances can be investigated and controlled efficiently with a thermal management system (TMS) via model-based development. A complete battery pack contains multiple cells, bricks, and modules with numerous coolant pipes and flow channels. However, such an early modeling stage requires detailed cell geometry and specifications to estimate the thermal and electrochemical energies of the cell, module, and pack. To capture the dynamic performance changes of the LIB pack under real driving cycles, the thermal energy flow between the pack and its TMS must be well predicted. This study presents a BTMS model development and validation method for a 75-kWh battery pack used in mass-production, mid-size battery SUV under WLTC. Eighty thermocouples, pressure, and coolant flow sensors are installed on the different battery cells, bricks, and modules to capture the time-series thermal and electrical performance changes. The dual e-motor vehicle is tested on a chassis dynamometer to measure transient pressure drop, inlet-outlet coolant temperature, battery pack and brick temperature, and voltage. These data are used to validate the integrated battery pack and its TMS cooling circuit. The pack model consists of 4416 cells based on 2RC branches equivalent-circuit model (ECM) calibrated using an electrochemical Pseudo 2D approach. The integrated BTMS model includes all inlet and outlet cooling flow channels to validate its thermal and electrical performance under steady-state and WLTC tests. The total model can capture dynamic performance changes, such as pack and brick temperature, pressure drop, and voltage, with over 90% accuracy. The model can be used in complete vehicle model simulation with low computation time and high accuracy for future VTMS studies.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Electricity, e-fuel and H<sub>2</sub> are considered important recent and future sources of energy for heavy-duty vehicles. Heavy-duty battery electric vehicles (BEV) have many technical challenges. Therefore, internal combustion engines (ICE) powered by e-fuel and hydrogen can be used as an alternative to batteries in heavy-duty trucks. Selective catalytic reduction (SCR) systems are necessary for achieving the goals of zero-emission internal combustion engines that use e-fuel or H<sub>2</sub> as a fuel. The Japanese automotive industry mainly utilizes Cu-Zeolite-based SCR catalysts since vanadium-based catalysts have been difficult to be used to prevent the release of vanadium into the atmosphere due to the relatively low evaporation temperature.</div><div class="htmlview paragraph">This study investigated whether improving the conversion rate by pulsing the NH<sub>3</sub> supply was possible. Experiments were conducted in a mini-reactor with an inflow of simulated exhaust gas to examine the effect of the pulse amplitude, frequency, and duty ratio on the conversion rate when an NH<sub>3</sub> pulse supply was applied to a test piece Cu-chabazite catalyst. The results of the reactor experiment were compared with numerical simulations that considered the detailed surface reaction processes on the catalyst.</div><div class="htmlview paragraph">The experimental results showed that purification of NOx at low temperatures (200°C) improved from 45% to 62% by providing a pulsed supply of reducing agent (NH<sub>3</sub>) rather than a continuous supply. During the time when the pulse supply was off, the decomposition of ammonium nitrate (NH<sub>4</sub>NO<sub>3</sub>) was promoted, enhancing the conversion rate of NOx. The results of the simulations demonstrated that the gas concentrations and conversion rate in the catalyst and unique phenomena at low temperatures, such as the formation and decomposition of NH<sub>4</sub>NO<sub>3</sub> and the ammonia-blocking effect, could be accurately reproduced and simulated.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Performances of battery electric vehicles (BEV) are affected by the thermal imbalance in the battery packs under driving cycles. BEV thermal management system (VTMS) should be managed efficiently for optimal energy consumption and cabin comfort. Temperature changes in the brick, module, and pack under the repeated transient cycles must be understood for model-based development. The authors conducted chassis dynamometer experiments on a fully electric small crossover sports utility vehicle (SUV) to address this challenge. A BEV is tested using a hub-type, 4-wheel motor chassis dynamometer with an air blower under the Worldwide Harmonized Light Vehicles Test Cycle (WLTC) and Federal Test Procedures (FTP) with various ambient temperatures. The mid-size BEV with dual-motor featured 80 thermocouples mounted on the 74-kWh battery pack, including the cells, upper tray, side cover, and pack cover. The authors analyzed battery pack temperature distribution behavior by changing the battery’s initial state of charge (SOC) and cell temperatures.</div><div class="htmlview paragraph">Performance metric data such as battery voltage, current, SOC, pack temperature, coolant properties, pressure drop, and flow rate are recorded and analyzed. The results show the temperature variations under diverse driving conditions, with an average difference of 1°C between modules and 2.3°C between bricks in module 1, and a maximum temperature difference of 3.9°C is recorded in the battery pack. The results provide valuable insights into the optimal operational range for maintaining battery pack temperature stability. The measured results can provide a fundamental understanding of the peak temperature location on the brick-to-brick and pack-to-pack variation under transient cycles. These results provide a fundamental understanding of the thermal performance of battery brick, module, and pack, which can be used to develop a VTMS model.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Battery thermal management system (BTMS) significantly improves battery electric vehicle (BEV) performance, especially under cold weather. A tradeoff between battery power consumption and cabin heating performance must be considered in cold driving conditions. This preliminary study aims to develop an integrated battery pack and coolant channel model to predict the thermal behavior of a BEV thermal management system. In this study, we develop and calibrate the physical baseline model with testbench data using finite element and CFD software. First, an electrochemical battery cell 1D model (Pseudo-2D or P2D) is built and calibrated against the cell reference data. An integrated pack model consisting of four modules (each has 23 and 25 bricks and a total of 4416 cells) with coolant flow channels is developed using reference and benchmarked data. Then, the model is calibrated against experimental results from a mass-production, mid-size battery-electric SUV operated under cold driving conditions at a constant vehicle speed of 60 km/h for 5800 sec. The integrated model considers the heat transfer characteristics from cell-to-brick and brick-to-coolant channels. As a result, a thermodynamic model that can predict the average battery temperature rise, temperature changes, and pressure drops of the coolant of the battery pack is constructed. The result shows that the battery pack model can predict the coolant pressure drop of the pack with a mean absolute percentage error (MAPE) of 0.49 % and the coolant temperature rise with a 5.23% MAPE. The calibrated battery pack model can reasonably reproduce the terminal voltage with a MAPE of 0.30%. A 3D-CFD simulation result of the battery brick model is also reported on the cell-to-cell temperature distribution of 46 cells.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Synthetic fuels can significantly improve the combustion and emission characteristics of heavy-duty diesel engines toward decarbonizing heavy-duty propulsion systems. This work analyzes the effects of engine operating conditions and synthetic fuel properties on spray, combustion, and emissions (soot, NOx) using a supercharging single-cylinder engine experiment and KIVA-4 code combined with CHEMKIN-II and in-house phenomenological soot model. The blended fuel ratio is fixed at 80% diesel and 20% n-paraffin by volume (hereafter DP). Diesel, DP1 (diesel with n-pentane C5H12), DP2 (diesel with n-hexane C6H14), and DP3 (diesel with n-heptane C7H16) are used in engine-like-condition constant volume chamber (CVC) and engine experiments.</div><div class="htmlview paragraph">Boosted engine experiments (1080 rpm, common-rail injection pressure 160 MPa, multi-pulse injection) are performed using the same DP fuel groups under various main injection timings, pulse-injection intervals, and EGR = 0-40%. Once the 3D-CFD model is validated with the CVC and experimental engine data, in-cylinder combustion and emissions are analyzed. The CVC experiments show that DP2 and DP3 liquid penetrations are shorter than diesel oil. In engine tests, NOx did not change much for all DP fuels for the same engine operating condition. However, shorter-penetrated DP2 and DP3 reduce soot emissions by more than 60% and CO without worsening brake-specific fuel consumption compared to diesel oil. The 3D-CFD results show that n-hexane shifts the penetration of the high-carbon number to the low-carbon fuel. Vapor penetrations are found to be shortened by blending low-volatility fuels with diesel oil. Visualizations of the in-cylinder confirmed a decrease in the amount of soot formation near the wall for DP2 and DP3 fuels. In addition, equivalence ratio – temperature (phi-T) maps of these fuels indicate that at 40% EGR, soot emissions are reduced at lower equivalence ratios than diesel oil.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Pre-chamber (PC) natural gas and hydrogen (CH<sub>4</sub>-H<sub>2</sub>) combustion can improve thermal efficiency and greenhouse gas emissions from decarbonized stationary engines. However, the engine efficiency is worsened by prolonged combustion duration due to PC jet velocity extinction. This work investigates the impact of cylindrical PC internal shapes to increase its jet velocity and shorten combustion duration. A rapid compression and expansion machine (RCEM) is used to investigate the combustion characteristics of premixed CH<sub>4</sub> gas. The combustion images are recorded using a high-speed camera of 10,000 fps. The experiments are conducted using two types of long PC shapes with diameters <i>φ=</i>4 mm (hereafter, long<i>φ</i>4) and 5 mm (hereafter, long <i>φ</i>5), and their combustions are compared against a short PC shape (<i>φ</i>=12 mm). For all designs of the PC shapes, the PC holes are 6 with 2 mm in diameter. Initial recorded results using only CH<sub>4</sub> show that jet extinction does not occur using the short and long 5mm types. The combustion duration of <i>φ</i>=4 mm PC is the shortest compared to the short-type and 5 mm PC. With CH<sub>4</sub>-H<sub>2</sub> blending (0%H<sub>2</sub>, 10%H<sub>2</sub>, 20%H<sub>2</sub>) and 4 mm shape, the combustion durations of 10%H<sub>2</sub> and 20%H<sub>2</sub> can be shortened compared to the CH<sub>4</sub>-only case (0%H<sub>2</sub>). However, the jet extinction probability is not zero.</div><div class="htmlview paragraph">3D-CFD combustion simulations are performed using CONVERGE software, and a 1/6 sector-mesh, GRI-Mech 3.0, G-equation combustion, and law-of-wall models are utilized in conjunction with RNG k-epsilon turbulence model. Simulated in-cylinder pressure and burning rate are validated against the recorded data. PC jet velocity, turbulent kinetic energy (TKE) of the main chamber, PC jet temperature, total heat loss in PC, and PC heat loss rate of 12 mm, 4 mm, and 5 mm are compared. Experimental combustion images and 3D-CFD temperature distribution with and without H<sub>2</sub> blending are also reported. The results show that long PC types can accelerate the jet velocity and shorten combustion duration. The jet extinction can be prevented by designing a small PC diameter area larger than the nozzle’s cross-sectional area. With H<sub>2</sub> blending, laminar burning velocity increases, and the jet ejection timing can be advanced. The result shows that the combustion duration can be shortened by 15 degrees using CH<sub>4</sub>-20%H<sub>2</sub> against CH<sub>4</sub> only.</div></div>

<div>Regulations limiting greenhouse gas (GHG) emissions in the transport sector have become more restrictive in recent years, drawing interest to synthetic fuels such as e-fuels and biofuels that could “decarbonize” existing vehicles. This study focuses on the potential to increase the thermal efficiency of spark-ignition (SI) engines using ethanol as a renewable fuel, which requires a deep understanding of the effects of ethanol on combustion behavior with high compression ratios (CRs). An important phenomenon in this condition is pre-spark heat release (PSHR), which occurs in engines with high CRs in boosted conditions and changes the fuel reactivity, leading to changes in the burning velocity. Fuel blends containing ethanol display high octane sensitivity (OS) and limited low-temperature heat release (LTHR). Consequently, their burning velocities with PSHR may differ from that of gasoline. This study therefore aimed to clarify the effects of ethanol on SI combustion behavior under PSHR conditions. Combustion behavior was studied by performing single-cylinder engine experiments and chemical kinetics simulations. The experimental measurements were performed to characterize the relationship between the occurrence of PSHR and the main combustion duration. Analysis of this relationship showed that the ethanol-blended fuel has a lesser PSHR and a longer combustion duration than the non-ethanol fuel by approximately 5% in high engine load conditions. Simulations using input data from the experiments revealed that the ethanol-blended fuel has a lower laminar burning velocity due to the lower temperature in the unburned mixture caused by its PSHR. Additional simulations examining the chemical effect of partially oxidized reactants caused by PSHR on the laminar burning velocity showed that partially oxidized reactants increase the laminar burning velocity of the ethanol-blended fuel but decrease that of a reference fuel without ethanol. A large number of fuel radicals and oxides of the ethanol-blended fuel enhances chain-branching reactions in the pre-flame zone and possibly increases its laminar burning velocity. However, the thermodynamic effect of PSHR on laminar burning velocity exceeds the chemical effect, and thus the ethanol-blended fuel has a lower turbulent burning velocity in the PSHR conditions.</div>

Abstract

Using thermoelectric generators (TEG) to reduce exhaust heat loss from internal combustion engines can improve emissions and the fuel economy of conventional and electrified vehicles. However, TEG potentials have not been investigated in hybridized, compressed natural gas (CNG), twin-turbocharged, spark-ignited (SI) engines. This work demonstrates TEG's effectiveness in boosting a hybridized 3.0 L CNG engine using model-based development. TEG experiments are performed to measure thermal performances under different inlet gas conditions for model validations. Simplified user-defined functions of flow friction and heat transfer coefficients are used to calibrate the model. A fast-calibration model can reproduce measured heat transfer, pressure drop, and thermal performances. The engine performances are validated against measured 35 steady-state conditions from the production engine used in light-duty CNG trucks under the JE05 drive cycle. Next, the model is connected to the turbocharging system downstream of the well-calibrated 4-cylinder SI engine model. Under the peak performance condition (peak brake thermal efficiency BTE at 2400 RPM and 102 kW load), the results show that the engine BTE is improved by 0.56% using a 7×9 TEG module arrangement (3-sheet TEG with 1.5× A4 size). A 9×10 arrangement can enhance the BTE to 0.8%. Effective electrical power is generated up to 1.168 kW from the TEG, depending on the JE05 operating regions, without significant brake power loss.

This work investigates oxygen-storage capacity (OSC) changes during thermal degradation in modern three-way catalysts. Two experiments are performed using catalysts with different degradation degrees to evaluate OSC and reaction rates. The CO2 production test, where CO and O2 are supplied at a constant temperature, shows decreased CO2 production with more degraded catalysts and reduced purification. The CO2 production test is conducted using transient temperature increases, showing that the maximum CO2 production temperature increases with catalyst degradation. The results reveal an increase in activation energy in the oxygen desorption reaction caused by thermal degradation progresses and a decrease in OSC, resulting in temperature increases in the oxygen storage reaction. In the surface reaction and mass transport model considering the 30 elementary reactions, the predicted results are well-validated for CO2 production, enabling good oxygen storage predictions based on actual data. These results can be used to predict OSC by formulating the changes in active site density and activation energy due to degradation.

Abstract

This work demonstrates the enhancement of brake thermal efficiency (BTE) of an advanced, turbocharged, production-intent 2.2 L diesel engine with a thermoelectric waste heat recovery system (TEG-WHR). The integrated engine model with the TEG is developed using 0D/1D software. Experimental data from the corrugated fin TEG under fin pitch = 1.0–2.0 mm, inlet gas temperatures (200–300 °C), and mass flow rates (5.0–15.0 g/s) are used for validating the model. The TEG model can reproduce measured pressure drop, heat transfer, and thermal performance characteristics. A 1-cylinder engine model parented from the advanced turbocharged diesel engine is developed. Under motoring and firing conditions, measured exhaust pressure, temperature, velocity, mass flow rate, and enthalpy are validated under various valve timings. Finally, the 3-layer TEG model is connected to the 4-cylinder engine to maximize its performance under a highly efficient (peak BTE) operating condition at 2250 RPM. Optimal size and thermoelectric module arrangement of the TEG system in the engine system considering a tradeoff between the TEG generated electrical power and engine pumping losses are suggested. The effective power of 1.1 kW and 1.1 % BTE improvement are obtained from the 3-sheet TEG system. As a result, a 49.9 % engine BTE is demonstrated without brake power loss.

<title>Abstract</title>
The oxygen-depleted environment in the recompression stroke can convert gasoline fuel into light hydrocarbons due to thermal cracking, partial oxidation, and water-gas shift reactions. These reformate species can influence the combustion characteristics of gasoline direct injection homogeneous charge compression ignition (GDI-HCCI) engines. In this work, the combustion phenomena are investigated using a single-cylinder research engine under a medium load. The main combustion phases are experimentally advanced by direct fuel injection into the negative valve overlap (NVO) compared with that of intake stroke under single/double-pulse injections. NVO peak in-cylinder pressures are lower than that of motoring due to the limited O2 concentration, emphasizing that endothermic reactions occur during the overlap. This phenomenon limits the oxidation reactions, and the thermal effect is not pronounced. The zero-dimensional chemical kinetics results present the same increasing tendencies of classical reformed species of rich mixture such as C3H6, C2H4, CH4, CO, and H2 as functions of injection timings. Predicted ignition delays are shortened due to the additions of these reformed species. The influences of the reformates on the main combustion are confirmed by three-dimensional computational fluid dynamics (CFD) calculations, and the results show that OH radicals are advanced under NVO injections relative to intake stroke injections. Consequently, earlier heat release and cylinder pressure are noticeable. Parametric studies on the effects of injection pressure, double-pulse injection, and equivalence ratio on the combustion and emissions are also discussed experimentally.

Abstract

A combustion oscillation experiment showed combustion oscillation frequencies of around 350 Hz when only natural gas was used as fuel and approximately 200 and 400 Hz when a hydrogen–natural gas mixture was used. To analyze the resonant frequency, two- and four-region models considering unburned and burned regions of the combustor were developed. The experimental frequencies of the 100% natural gas condition were successfully predicted. Conversely, the experimentally observed frequencies under the hydrogen–natural gas condition were not accurately predicted. A swirler-combustor model was then constructed to get closer to the actual configuration and shape of the experimental setup. However, the model could not reproduce the experimental value under the hydrogen–natural gas condition. A whole piping model was then developed by adding a casing and an air supply pipe to the combustor. The resonant frequencies under both the 100% natural gas and hydrogen–natural gas conditions were successfully calculated. The model reproduced the range and change tendency of the experimentally measured oscillation frequency.

<title>Abstract</title>
Gasoline direct injection (GDI) and negative valve overlap (NVO) are standard strategies to control combustion characteristics and exhaust gas emissions in homogenous charge compression ignition (HCCI) engines. In this work, experimental data from a single-cylinder engine operated under the GDI-HCCI mode were analyzed. The experiments were performed at an equivalence ratio of 0.95 under a mid-load condition. A side-mounted injector delivered primary reference fuel with octane number 90 directly into the combustion chamber during the NVO. The measured results showed advanced combustion phase CA50 under the early start of injection (SOI) timings. Peak recompression pressures were lower than the motoring, emphasizing that the NVO reactions were net endothermic. Zero-dimensional kinetics calculations showed that classical reformate species increase almost linearly as a function of SOI timings.


This work also presents the effects of intake boosting pressure and single versus double pulses injections on CA50, burn duration CA10-90, peak cylinder pressure, combustion noise metrics, thermal efficiency, and emissions. The combustion noise metrics were over the engine constraint limit under advanced SOI timings, but a double-pulse injection could reduce the combustion noise metrics and NOx emission. Late fuel injection in the intake stroke could reduce NOx to a single digit.

Soot mass production was investigated in high-boosted diesel engine tests by changing various operating parameters. A mixed timescale subgrid model of large eddy simulation (LES) was applied to simulate the detailed mixture formation, combustion and soot formation influenced by turbulence in diesel engine combustion. The combustion model used a direct integration approach with an explicit ordinary differential equation (ODE) solver and additional parallelization by OpenMP. Soot mass production within a computation cell was determined from a phenomenological soot formation model developed by WASEDA University. The model was combined with the LES code and included the following important steps: particle inception, in which naphthalene was assumed to grow irreversibly to form soot
surface growth with the addition of C2H2
surface oxidation due to OH radicals and O2 attack
particle coagulation
and particle agglomeration. The computational results were compared with experimental data acquired under various EGR conditions. The results showed that the in-cylinder pressure and heat release rate obtained from the engine tests were in good agreement with the calculated values. In the soot emission calculation, the simulated results showed an exponential increase with increasing EGR rate. Furthermore, the steep increase in soot mass with increasing EGR rate from 30% EGR was reproduced. Changes in the soot mass and particle size characteristics with EGR rate were analyzed, and the process and spatial distribution of soot formation were studied.

<title>Abstract</title>
This work analyzed measured data from a single-cylinder engine operated under gasoline direction injection homogenous charge compression ignition (GDI-HCCI) mode. The experiments were conducted at a 0.95 equivalence ratio (φ) under 0.5 MPa indicated mean effective pressure and 1500RPM. A side-mounted injector delivered primary reference fuel (octane number 90) into the combustion chamber during negative valve overlap (NVO). Advanced combustion phase CA50 were observed as a function of the start of injection (SOI) timings. Under φ=0.95, peak NVO in-cylinder pressures were lower than motoring for single and split injections, emphasizing that NVO reactions were endothermic. Zero-dimensional kinetics calculations showed classical reformate species (C3H6, C2H4, CH4) from the NVO rich mixture increased almost linearly due to SOI timings, while H2 and CO were typically low. These kinetically reformed species shortened predicted ignition delays. This work also analyzed the effects of intake pressure and single versus double pulses injections on CA50, burn duration, peak cylinder pressure, combustion noise, thermal efficiency, and emissions. Advanced SOI (single-injection) generated excessive combustion noise metrics over constraint limits, but the double-pulse injection could significantly reduce the metrics (Ringing Intensity ≤ 5 MW/m2, Maximum Pressure Rise Rate = 0.6 MPa/CA) and NOx emission. The engine's net indicated thermal efficiency reached 41% under GDI-HCCI mode against 36% under SI mode for the same operating conditions. Under GDI-HCCI mode and without spark-ignition, late fuel injection in the intake stroke could reduce NOx to a single digit.

Performance predictions of advanced turbocharged engines are becoming difficult because conventional engine models are built using performance map data of turbochargers with a proportional integral derivative (PID) controller. Improving prediction capabilities under transient test cycles or real driving conditions is a challenging task. This study applies a machine learning technique to predict turbocharger performances with high accuracy under steady-state and transient conditions. The manipulated signals of engine speed and torque created based on Compressed High-Intensity Radiated Pulse (Chirp signal) and Amplitude-modulated Pseudo-Random Binary Signal (APRBS) are used as inputs to the engine testbed. Data from the engine experiments are used as training data for the AI-based turbocharger model. High prediction accuracy of the AI turbocharger model is achieved with the co-efficient of determination in the model, and cross-validation results are higher than 0.8. Further, an integrated engine model coupled with the AI turbocharger model is developed and simulated to compare its performance result against the conventional turbocharged engine model (performance map + PID controller). The results show that the diesel engine system's performance predictions can be achieved with reasonable accuracy using the integrated engine-AI turbocharger model. The results also confirm the suitability of the proposed method to develop the advanced turbocharger model.

<title>Abstract</title>
Gasoline direct injection (GDI) is a promising solution to increase engine thermal efficiency and reduce exhaust gas emissions. The GDI operation requires an understanding of fuel penetration and droplet size, which can be investigated numerically. In the numerical simulation, primary and secondary breakup phenomena are studied by the Kelvin-Helmholtz/Rayleigh-Taylor (KH-RT) wave breakup models. The models were initially developed for diesel fuel injection, and in the present work, the models are extended to the GDI application combined using large-eddy simulation (LES). The simulation is conducted using the KIVA4 code.


Measured data of experimental spray penetration and Mie-scattering image comparisons are carried out under non-reactive conditions at an ambient temperature of 613K and a density of 4.84 kg/m3. The spray penetration and structures using LES are compared with traditional Reynolds-Averaged Navier-Stokes (RANS). Grid size effects in the simulation using LES and RANS models are also investigated to find a reasonable cell size for future reactive gasoline spray/combustion studies. The fuel spray penetration and droplet size are dependent on specific parameters. Parametric studies on the effects of adjustable constants of the KH-RT models, such as time constants, size constants, and breakup length constant, are discussed. Liquid penetrations from the RANS turbulence model are similar to that of the LES turbulence model’s prediction. However, the RANS model is not able to capture the spray structure well.

<title>Abstract</title>
The turbulent combustion in gasoline engines is highly dependent on laminar flame speed SL. A major issue of the quasi-dimensional (QD) combustion model is an accurate prediction of the SL, which is unstable under low engine speeds and ultra-lean mixture. This work investigates the applicability of the combustion model with a refined SL correlation for evaluating the combustion characteristics of a high-tumble port gasoline engine operated under ultra-lean mixtures. The SL correlation is modified and validated for a five-component gasoline surrogate. Predicted SL values from the conventional and refined functions are compared with measurements taken from a constant-volume chamber under micro-gravity conditions. The SL data are measured at reference and elevated conditions. The results show that the conventional SL overpredicts the flame speeds under all conditions. Moreover, the conventional model predicts negative SL at equivalence ratio ϕ ≤ 0.3 and ϕ ≥ 1.9, while the revised SL is well validated against the measurements. The improved SL correlation is incorporated into the QD combustion model by a user-defined function. The engine data are measured at 1000–2000 rpm under engine load net indicated mean effective pressure (IMEPn) = 0.4–0.8 MPa and ϕ = 0.5. The predicted engine performances and combustions are well validated with the measured data, and the model sensitivity analysis also shows a good agreement with the engine experiments under cycle-by-cycle variations.

<title>Abstract</title>
Injected gasoline into the O2-depleted environment in the recompression stroke can be converted into light hydrocarbons due to thermal cracking, partial oxidation, and water-gas shift reaction. These reformate species influence the combustion phenomena of gasoline direct injection homogeneous charge compression ignition (GDI-HCCI) engines. In this work, a production-based single-cylinder research engine was boosted to reach IMEPn = 0.55 MPa in which its indicated efficiency peaks at 40–41%. Experimentally, the main combustion phases are advanced under single-pulse direct fuel injection into the negative valve overlap (NVO) compared with that of the intake stroke. NVO peak in-cylinder pressures are lower than that of motoring, which emphasizes that endothermic reaction occurs during the interval. Low O2 concentration could play a role in this evaporative charge cooling effect. This phenomenon limits the oxidation reaction, and the thermal effect is not pronounced. For understanding the recompression reaction phenomena, 0D simulation with three different chemical reaction mechanisms is studied to clarify that influences of direct injection timing in NVO on combustion advancements are kinetically limited by reforming. The 0D results show the same increasing tendencies of classical reformed species of rich-mixture such as C3H6, C2H4, CH4, CO, and H2 as functions of injection timings. By combining these reformed species into the main fuel-air mixture, predicted ignition delays are shortened.


The effects of the reformed species on the main combustion are confirmed by 3D-CFD calculation, and the results show that OH radical generation is advanced under NVO fuel injection compared with that of intake stroke conditions thus earlier heat release and cylinder pressure are noticeable. Also, parametric studies on injection pressure and double-pulse injections on engine combustion are performed experimentally.

In this study, reaction path analysis and modeling of NOx reduction phenomena by selective catalytic reduction (SCR) with NH3 over a Cu-chabazite catalyst were conducted considering changes in the valence state of Cu sites and local structure due to differences in ligands to the Cu sites. The analysis showed that in the Cu-chabazite catalyst, NOx was mainly reduced by adsorbed NH3 on divalent Cu sites accompanied by a change in valence state of Cu from divalent to monovalent. It is known that the activation energy of NOx reduction on a Cu-chabazite catalyst changes between low temperatures = 200 °C and mid to high temperatures = 300 °C. To express this phenomenon, a reversible hydrolysis reaction based on the difference in coordination state of hydroxyl groups (OH-) to Cu sites at low and high temperatures was introduced into the model. The results showed that NOx reduction phenomena can be expressed over a wide temperature range by using the activation energy specific to the Cu-chabazite catalyst. There are two types of ion-exchanged Cu in Cu-chabazite: single Al sites that balance with one Al and paired Al sites that balance with two Al in the zeolite structure. We showed by XAFS analysis that Cu at the single Al sites forms a Cu dimer at mid to high temperatures = 300 °C and serves as a reaction site for NH3 oxidation. Thus, NOx reduction can be expressed by a detailed kinetic model using rate parameters specific to the catalyst material. The difference between the single Al and paired Al sites was also important for developing a detailed kinetic model including side reactions.

© 2020 SAE International. All rights reserved. Natural gas has been used in spark-ignition (SI) engines of natural gas vehicles (NGVs) due to its resource availability and stable price compared to gasoline. It has the potential to reduce carbon monoxide emissions from the SI engines due to its high hydrogen-To-carbon ratio. However, short running distance is an issue of the NGVs. In this work, methodologies to improve the fuel economy of a heavy-duty commercial truck under the Japanese Heavy-Duty Driving Cycle (JE05) is proposed by numerical 1D-CFD modeling. The main objective is a comparative analysis to find an optimal fuel economy under three variable mechanisms, variable valve timing (VVT), variable valve actuation (VVA), and variable compression ratio (VCR). Experimental data are taken from a six-cylinder turbocharged SI engine fueled by city gas 13A. The 9.83 L production engine is a CR11 type with a multi-point injection system operated under a stoichiometric mixture. For minimizing optimal valve strategy selections and engine testing procedures, a one-dimensional engine model is developed in GT-Power software using experimental data and engine specifications provided by a project partner. The model is built using the same theory as of spark-ignition engines. Knock prediction is based on the Shell model, and a spark timing optimization logic is coupled to the model. In-cylinder pressure, rate of heat release, brake mean effective pressure, and maximum brake torque spark ignition timings are well reproduced, as compared with that of 12 experimental operating points under engine speed and load variations. In order to build a baseline brake specific fuel consumption (BSFC) map in the driving cycle, the simulation model is used to generate 51 BSFC points, as proposed in the JE05 cycle under speed-Torque changes. From the baseline engine model, the average fuel economy of the heavy-duty natural gas truck is 4.14 km/L. 0.5 % and 2.43% of simulated fuel economy improvements are found when the engine is operated under VVT and VVA mechanisms (fixed lifts), respectively. Significant fuel economy improvement is achieved at about 6.31% under VCR engine operation compared with the baseline engine model.

Battery models are being developed as a component of the powertrain systems of hybrid electric vehicles (HEVs) to predict the state of charge (SOC) accurately. Electrically heated catalysts (EHCs) can be employed in the powertrains of HEVs to reach the catalyst light off temperature in advance. However, EHCs draw power from the battery pack and hence sufficient energy needs to be stored to power auxiliary components. In series HEVs, the engine is primarily used to charge the battery pack. Therefore, it is important to develop a control strategy that triggers engine start/stop conditions and reduces the frequency of engine operation to minimize the equivalent fuel consumption. In this study, a battery pack model was constructed in MATLAB-Simulink to investigate the SOC variation of a high-power lithium ion battery during extreme engine cold start conditions (-7°C) with/without application of an EHC. The EHC was simulated in MATLAB to determine the energy required to heat the catalyst during cold start conditions. The effect of the EHC in emissions purification at-7°C was studied using a three-way catalyst (TWC) model. The EHC was operated only during the initial few seconds before the engine start to increase the bed temperature of the catalyst. This was found to have a significant impact on exhaust gas emissions even under cold start conditions. However, powering the EHC lowered the SOC of the battery pack, triggering the engine to run and consume more fuel. Hence, an engine ON/OFF control strategy was proposed to control the engine operation conditions and effectively charge the battery pack. The SOC variation of the battery pack and the effects on emissions and fuel consumption were simulated and compared with/without the EHC. The battery model was validated with a control strategy proposed in simulations at 23°C and a parameter study was conducted at-7°C.

Copyright © 2020 ASME. A quasi-dimensional (QD) simulation model is a preferred method to predict combustion in the gasoline engines with reliable results and shorter calculation time compared with multi-dimensional simulation. The combustion phenomena in spark ignition (SI) engines are highly turbulent, and at initial stage of the combustion process, turbulent flame speed highly depends on laminar burning velocity SL. A major parameter of the QD combustion model is an accurate prediction of the SL, which is unstable under low engine speed and ultra-lean mixture. This work investigates the applicability of the combustion model for evaluating the combustion characteristics of a hightumble port gasoline engine operated under ultra-lean mixture (equivalence ratio up to φ=0.5) which is out of the range of currently available SL functions initially developed for a single component fuel. In this study, the SL correlation is improved for a gasoline surrogate fuel (5 components). Predicted SL data from the conventional and improved functions are compared with experimental SL data taken from a constant-volume chamber under micro-gravity condition. The SL measurements are done at reference conditions at temperature of 300K, pressure of 0.1MPaa, and at elevated conditions whose temperature = 360K, pressure = 0.1, 0.3, and 0.5 MPaa. Results show that the conventional SL model over-predicts flame speeds under all conditions. Moreover, the model predicts negative SL at very lean (φ ≤0.3) and rich (φ ≥1.9) mixture while the revised SL is well validated with the measured data. The improved SL formula is then incorporated into the QD combustion model by a userdefined function in GT-Power simulation. The engine experimental data are taken at 1000 RPM and 2000 RPM under engine load IMEPn=0.4-0.8 MPa (with 0.1 increment) and φ ranges are up to 0.5. The results shows that the simulated engine performances and combustion characteristics are well validated with the experiments within 6% accuracy by using the QD combustion model coupled with the improved SL. A sensitivity analysis of the model is also in good agreement with the experiments under cyclic variation (averaged cycle, high IMEP or stable cycle, and low IMEP or unstable cycle).

The NOx-reducing activity of a Cu-chabazite selective catalytic reduction (SCR) catalyst was analyzed over a wide temperature range. The analysis was based on the ammonia SCR (NH3-SCR) mechanism and accounted for Cu redox chemistry and reactions at Brønsted acid sites. The reduction of NOx to N2 (De-NOx) at Cu sites was found to proceed via different paths at low and high temperatures. Consequently, the rate-limiting step of the SCR reaction at Cu sites varied with the temperature. The rate of NOx reduction at Cu sites below 200°C was determined by the rate of Cu oxidation. Conversely, the rate of NOx reduction above 300°C was determined by the rate of NH3 adsorption on Cu sites. Moreover, the redox state of the active Cu sites differed at low and high temperatures. To clarify the role of the chabazite Brønsted acid sites, experiments were also performed using a H-chabazite catalyst that lacks Cu sites. NOx reduction via the NO2-NH3 reaction was found to occur at Brønsted acid sites at high temperatures (up to 600°C). We also analyzed the chabazite catalyst's activity towards NH3 oxidation, which significantly affects NOx reduction at high temperatures. Cu sites were required for NH3 oxidation
NH3 was not oxidized in their absence. However, the formation of the by-product NO increased as the content of Brønsted acid sites in the Cu-chabazite catalyst decreased. It was therefore suggested that Brønsted acid sites contribute to the reduction of NO formed during NH3 oxidation. Numerical studies were conducted to develop an SCR reaction model that incorporates these processes. The resulting model accurately predicted the outcomes of NOx reduction experiments under diverse conditions including some involving transient temperature changes.

Three-way catalyst (TWC) converters are used to remove harmful substances (e.g., carbon monoxide (CO), nitrogen oxides (NOx), and hydrocarbons (HC)) emitted from gasoline engines. However, a large amount of emissions could be emitted before the TWC reaches its light-off temperature during a cold start. For hybrid electric vehicles (HEVs) powered by gasoline engines, the emission purification performance by TWC converters unfortunately deteriorates because of mode switching from engine to battery and vice versa, which can repeatedly generate cold start conditions for the TWCs. In this study, aiming to reduce emissions from series HEVs by early activation of TWCs, numerical simulations and experiments are carried out. An HEV is tested on a chassis dynamometer in the Worldwide Light-duty Test Cycle (WLTC) mode. The upstream and downstream gas conditions of the close-coupled catalyst converter are measured. A test piece is taken from the same catalyst and used in model gas experiments to decide the chemical reaction scheme and each corresponding reaction rate parameter. A 1-D numerical simulation TWC model, which includes 13 chemical species with 22 global reactions, is built using GT-Power, a commercial software by Gamma Technology. The TWC model is able to reproduce the close-coupled TWC's purification performance of CO, NOx, and HC. Furthermore, an electrically heated catalyst (EHC) model is added to the TWC model, aiming at faster heating up for early catalyst activation during the first warming up period from a cold start. The effects on emission reduction by EHC using a range of input power are investigated. It is found that the oxidation reactions can be activated earlier with the EHC installed
and the emission of CO and HC can be effectively reduced using a certain amount of power that can be sufficiently supplied by the existing lithium-ion battery on the series HEVs.

© 2019 SAE International and © 2019 SAE Naples Section. All rights reserved. In order to improve thermal efficiency of spark ignition (SI) engines, an improved technology to avoid irregular combustion under high load conditions of high compression ratio SI engines is required. In this study, the authors focused on high pressure gasoline direct injection in a high compression ratio SI engine, which its rapid air-fuel mixture formation, turbulence, and flame speed, are enhanced by high-speed fuel spray jet. Effects of fuel injection pressure, injection and spark ignition timing on combustion characteristics were experimentally and numerically investigated. It was found that the heat release rate was drastically increased by raising the fuel injection pressure. The numerical simulation results show that the high pressure gasoline direct injection enhanced small-scale turbulent intensity and fuel evaporation, simultaneously. These two effects were considered as the main factors to increase the flame propagation speed, suggesting a new combustion concept different from conventional SI combustion controlled by in-cylinder bulk flow. This combustion method enables the delay of fuel injection and spark ignition timing up to near top dead center (TDC) which leads to avoid pre-ignition and knocking by shortening the end-gas reaction time. Therefore, it was shown that the irregular combustion in a high compression ratio SI engine could be avoided by utilizing high pressure gasoline injection, which leads to improve partial load thermal efficiency without affecting the high load performance.

© 2019 SAE International. All Rights Reserved. This paper focuses on an assessment of predictive combustion model using a 0D/1D simulation tool under high load, different excess air ratio ?, and different combustion stabilities (based on coefficient of variation of indicated mean effective pressure COVimep). To consider that, crank angle resolved data of experimental pressure of 500 cycles are recorded under engine speed 1000 RPM and 2000 RPM, wide-open throttle, and ?=1.0, 1.42, 1.7, and 2.0. Firstly, model calibration is conducted using 18 cases at 2000 RPM using 500 cycle-averaged in-cylinder pressure to find optimized model constants. Then, the model constants are unchanged for other cases. Next, different cycle-averaged pressure data are used as inputs in the simulation based on the COVimep for studying sensitivity of the turbulent model constants. The simulation is conducted using 1D simulation software GT-Power. Firstly, a three-pressure analysis (TPA) model (intake, in-cylinder, exhaust) for experimental prediction and optimization of burn rate shape are studied. Boundary conditions such as the three pressure histories, intake/exhaust valves timings, boundary temperatures, and exhaust gas emissions are used as model inputs. Errors of indicated thermal efficiency, indicated mean effective pressure, and CA50 are within 3%. Predicted parameters from the TPA model such as air volumetric efficiency, trapped air/fuel vapor mass, trapped residual gas fraction, tumble, and surface temperature of the piston, head, and valves are used as initializations in the predictive combustion model. A built-in flame propagation model, termed as SITurb, is investigated whether it can replicate the in-cylinder pressure and burn rate shapes. A revised laminar flame speed correlation of five-component gasoline surrogate is incorporated in the combustion model via an encrypted dynamic link library file. The results show that thermodynamic histories of the combustion are reproducible under high load and stoichiometric-to-ultra-lean conditions. Under all cases, only turbulent flame speed multiplier needs to be calibrated.

ガソリンエンジンの熱効率改善に向けては，燃焼のサイクル間変動の抑制が必要である．本研究では，等間隔直交格子と境界埋込法の組み合わせを特徴とするエンジン用流体解析コードHINOCAを用い，ガソリンエンジンの燃焼のLES解析を実施してサイクル間変動の予測精度の検証と影響因子の分析を実施した．

Gasoline Direct Injection Homogeneous Charge Compression (GDI-HCCI) combustion is achieved by closing early the exhaust valves for trapping hot residual gases combined with direct fuel injection. The combustion is chemically controlled by multi-point auto-ignition which its main combustion phase can be controlled by direct injection timing of fuel. This work investigates the effect of single pulse injection timing on a supercharged GDI-HCCI combustion engine by using a four-stroke single cylinder engine with a side-mounted direct fuel injector.Injection of primary reference fuel PRF90 under the near-stoichiometric-boosted condition is studied. The fuel is injected during negative valve overlap (NVO) or recompression period for fuel reformation under low oxygen concentration and the injection is retarded to intake stroke for the homogeneous mixture. It is found that the early fuel injection in NVO period advances the combustion phasing compared with the retarded injection in the intake stroke. Noticeable slower combustion rate from intake stroke fuel injection is obtained compared with the NVO injection due to charge cooling effect. Zero dimensional combustion simulations with multiple chemical reaction mechanisms are simulated to provide chemical understanding from the effect of fuel injection timing on intermediate species generations. The species such as C2H4, C3H6, CH4, and H-2 are found to be formed during the NVO injection period from the calculations. The effects of single pulse injection timings on combustion characteristics such pressure rise rate, combustion stability, and emissions are also discussed in this study.

Primary work is to investigate premixed laminar flame propagation in a constant volume chamber of iso-octane/air combustion. Experimental and numerical results are investigated by comparing flame front displacements under lean to rich conditions. As the laminar flame depends on equivalence ratio, temperature, and pressure conditions, it is a main property for chemical reaction mechanism validation. Firstly, one-dimensional laminar flame burning velocities are predicted in order to validate a reduced chemical reaction mechanism. A set of laminar burning velocities with pressure, temperature, and mixture equivalence ratio dependences are combined into a 3D-CFD calculation to compare the predicted flame front displacements with that of experiments. It is found that the reaction mechanism is well validated under the coupled 1D-3D combustion calculations. Next, lean experiments are operated in a SI engine by boosting intake pressure to maintain high efficiency without output power penalty. The peak indicated thermal efficiency are finally achieved under lambda = 1.3 with intake manifold absolute pressure 150 kPa in experiment. Data of in-cylinder pressure and rate of heat release from the 3D-CFD simulations combined with the validated chemical reaction mechanism are reproduced. NOx emissions from experiment and simulation are also in good agreements under the lean-boost combustion. Further thermal efficiency improvements of the lean-boost SI engine are investigated numerically by using dilution rate, high induced in-cylinder flow, and high knock resistant fuel. The peak indicated thermal efficiency and load of the SI engine is achieved. In addition, methods to prevent knock for high efficiency spark ignition engine are also discussed.

Copyright © 2015 SAE International. The objective of this paper is to investigate the potential of lean burn combustion to improve the thermal efficiency of spark ignition engine. Experiments used a single cylinder gasoline spark ignition engine fueled with primary reference fuel of octane number 90, running at 4000 revolution per minute and at wide open throttle. Experiments were conducted at constant fueling rate and in order to lean the mixture, more air is introduced by boosted pressure from stoichiometric mixture to lean limit while maintaining the high output engine torque as possible. Experimental results show that the highest thermal efficiency is obtained at excess air ratio of 1.3 combined with absolute boosted pressure of 117 kPa. Three dimensional computational fluid dynamic simulation with detailed chemical reactions was conducted and compared with results obtained from experiments as based points. The potential to improve further the efficiency, exhaust gas recirculation (EGR), high engine swirl ratio and high research octane number are good candidates for this improvement. In further calculations, we use simulated EGR ratio, high engine swirl ratio, RON95 fuels. To prevent the combustion from knock in the simulations when ignition timing is at maximum brake torque, simulated pressure probes are mounted on each side of intake and exhaust valves to detect knock pressure. By using these methods, spark timing of the engine can be advanced thus improve the thermal efficiency. It is found that, by combining lean-boosted/EGR and high octane-number fuel, higher thermal efficiency of spark ignition engine can be achieved.

Copyright © 2015 SAE International. This paper aims to validate chemical kinetic mechanisms of surrogate gasoline three components fuel by calculating one-dimensional laminar burning velocity of iso-octane/air mixture. Next, the application of level-set method on premixed combustion without consideration the effect of turbulence eddies on flame front is also studied in three-dimensional computational fluid dynamic (3D-CFD) simulation. In the 3D CFD simulation, there is an option to calculate laminar burning velocity by using empirical correlations, however it is applicable only for particular initial pressure and temperature in spark ignition engine cases. One-dimensional burning velocities from lean to rich of iso-octane/air mixture are calculated by using CHEMKIN-PRO with detailed chemistry and transport phenomena as a function of different equivalence ratios, different unburnt temperature and pressure ranges. A set of laminar flame table is then combined with 3D-CFD calculations with chemical kinetic mechanisms to track flame front displacements. A high-speed video camera at a frame speed of 2000 frames/sec is used to record the experimental flame positions of iso-octane/air combustion in a cylindrical shape constant volume combustion chamber (CVC). Different fuel-air equivalence ratios φ from lean to rich mixtures, ranging from 0.8 to1.4, are investigated at initial temperature of 420 K and 0.3 MPa of ambient pressure. The coupled simulations of one-dimensional adiabatic laminar burning velocity and 3D-CFD well predicts thermodynamics analysis of pressure-time and rate of heat release-time history and visualizations of flame front positions. Temperature and chemical species distributions of flame reaction zone are reported in comparison to that of experiments.

This paper aims to improve thermal efficiency of spark ignition engine by numerical calculation with detailed chemistry. Experimental results from a four-stroke-single-cylinder engine are compared with that of simulations. It is experimentally found that peak efficiency is achieved at lean-limit combustion under excess air ratio λ=1.6. Due to engine output power loss, further investigations are conducted under lean-boost operations. The best condition of the lean-boost mode is at λ=1.3 and 150 kPa boosted pressure (abs). To further improve the efficiency without power loss, simulations are conducted under lean-boost combustion with dilution rate, high engine swirl, and high knock resistant fuel.

The fuel efficiency and emission reductions are the two consistent drivers for diesel engine development. Although many control devices mounted in diesel engine and in addition to the development of individual emission control methods, optimization techniques are required to utilize these methods in finding optimal engine operating conditions efficiently. This research was focused on the minimization of nitrogen oxides (NOx) emission and soot emission, as well as improving brake specific fuel consumption (BSFC) and power in a single cylinder diesel engine, which can be modeled as a multi-objective optimization problem. Many approaches have been applied to multi-objective optimization problems. In recent years, particle swarm optimization (PSO) method has been successfully applied to different areas since its advent. It has been demonstrated that PSO is an effective method for optimization problem. © 2012 IEEE.

With the problem of environmental pollution and energy depletion in recent years, a control technology which improves the performance of automobile engine has been demanded. This paper presents a method for construction of response surface model and a control parameter optimization method for automobile diesel engine in order to develop a model-based control system and the early development technique based on the model. The proposed method for construction of response surface model is able to efficiently-develop the response surface model that describes the multiple control parameters in relation to the characteristic value such as fuel consumption and emission. The proposed control parameter optimization method is able to quickly and efficiently calculate optimal control parameters to optimize evaluation item such as fuel consumption and emission based on the model.

This paper describes the development of a High Speed Calculation Diesel Combustion Model that predicts combustion-related behaviors of diesel engines from passenger cars. Its output is dependent on the engine's operating parameters and on input from on-board pressure and temperature sensors. The model was found to be capable of predicting the engine's in-cylinder pressure, rate of heat release, and NOx emissions with a high degree of accuracy under a wide range of operating conditions at a reasonable computational cost. The construction of this model represents an important preliminary step towards the development of an integrated Model Based Control system for controlling combustion in diesel engines used in passenger cars. © Copyright 2011 Society of Automotive Engineers of Japan, Inc. and SAE International.

Model based control design is an important method for optimizing engine operating conditions so as to simultaneously improve engines' thermal efficiency and emission profiles. Modeling of intake system that includes an intake throttle valve, an EGR valve and a variable geometry turbocharger was constructed based on conservation laws combined with maps. Calculated results were examined the predictive accuracy of fresh charge mass flow, EGR rate and boost pressure. © Copyright 2011 Society of Automotive Engineers of Japan, Inc. and SAE International.

This study examines the effects of ethanol content on engine performances and the knock characteristics in spark ignition gasoline engine under various compression ratio conditions by cylinder pressure analysis, visualization and numerical simulation. The results confirm that increasing the ethanol content provides for greater engine torque and thermal efficiency as a result of the improvement of knock tolerance. It was also confirmed that increasing the compression ratio together with increasing ethanol content is effective to overcome the shortcomings of poor fuel economy caused by the low calorific value of ethanol. Further, the results of one dimensional flame propagation simulation show that ethanol content increase laminar burning velocity. Moreover, the results of visualization by using a bore scope demonstrate that ethanol affects the increase of initial flame propagation speed and thus helps suppress knock. © 2008 SAE Japan.

With the problem of environmental pollution and energy depletion in recent years, a control technology which improves the performance of automobile engine is demanded. Therefore, there is a real need for cultivating human resources capable of understanding both the automobile engine and the control technology. This paper presents the development of teaching materials for Spark Ignition (SI) engine control exercise. The purpose of this work is for students to understand the engine characteristics and the actual engine control system using an engine simulator and hardware in the loop simulator (HILS). These teaching materials consist of a personal computer for designing control logic, a real-time arithmetic board, an experimental ECU, and an engine test bench. This work developed a simulation system in order to understand the engine characteristic of relation between the engine revolution, the ignition timing, and the throttle angel. Moreover, an engine starting control system of design base with ignition timing controller that changes the integral action parameter of PID controller is designed, and a real-time environment for engine is developed. The engine real-time simulation environment can load the designed control logic and the engine model into the real-time arithmetic board to run the real-time simulation and to confirm the characteristics of control parameters. In the future, when the engine simulator is connected with engine test bench and ECU, engine real-time simulation can be realized.

In this study, fuel ignition timing parameters, in-cylinder pressure and heat release rates, and quantities of major exhaust gas emissions from a diesel engine were calculated using multi-dimensional CFD codes coupled with complex chemistry analysis. In addition, a sensitivity analysis of parameters was conducted to identify the major variables affecting these diesel combustion parameters. Firstly, diesel combustion analysis under typical operating conditions was carried out to validate the analytical methods used in the study, and then the effects of intake gas variables (e.g. temperature, and pressure) were investigated in detail in the sensitivity analysis. The results show that the main determinant of ignition timing in the engine is the spatial density of oxygen in the cylinder. This finding indicates that diesel combustion with high EGR and high boost pressure can provide both high thermal efficiency and low emissions. © 2008 SAE International.

This paper presents an introduction of engine control education system. The education system is composed of PC hardware, high-speed arithmetic processing board, ECU, and engine test bench. This system can realize following functions: familiarize people with gasoline engine properties, do engine control simulation, design engine control system, and realize engine real-time simulation. In this paper, we designed basic engine control system and got simulation results, developed real-time simulation system, and realized real-time simulation by adjusting PID parameters. Further more, we can design new control system by improving the basic ones. When we connect engine control model to engine test bench and ECU, this system can realize virtual engine real-time simulation.

We report here a numerical and experimental study on particulate matter (PM) formation in fuel-rich HCCI combustion. In the experiments particulate emissions and particle size distributions obtained at various excess air ratios were measured, while in the simulations a phenomenological soot particle formation model based on sequential particle formation processes (including nucleation, surface reactions and coagulation) and a detailed chemistry precursor formation model were implemented in a multidimensional CFD code. Experimental data including particulate emissions, particle size distributions etc. were predicted reasonably well by the code, and the main processes that determine the mass and number density of the PM were identified.

In a Diesel Oxidation Catalyst (DOC) and Catalyzed Soot Filter (CSF) system, the DOC is used to oxidize additional fuel injected into the cylinder and/or exhaust pipe in order to increase the CSF's inlet temperature during soot regeneration. The catalyst's hydrocarbon (HC) oxidation performance is known to be strongly affected by the HC species present and the catalyst design. However, the engine operating conditions and additive fuel supply parameters also affect the oxidation performance of DOCs, but the effects of these variables have been insufficiently examined. Therefore, in this study, the oxidation performance of a DOC was examined in experiments in which both exhaust gas recirculation (EGR) levels and exhaust pipe injection parameters were varied. The results were then analyzed and optimal conditions were identified using modeFRONTIER. In addition, the HC species supplied by exhaust pipe injection were investigated using gas chromatography-mass spectrometry (GC-MS) and two gas analyzers. The results show that increasing the level of EGR and platinum group metals (PGM) loading, and decreasing the assist air pressure, can increase the uniformity of the DOC outlet gas temperature, while keeping it sufficiently high. In addition, various HC species - including C8-C21 alkanes, benzene-derived methyl and/or ethyl radicals, and acetaldehyde (CH 3CHO) - were detected in the exhaust pipe injections. Copyright © 2007 SAE International.

To suppress knock in small gasoline engines, the coolant flow of a single-cylinder engine was improved by using two methods: a multi-dimensional knock prediction method combining a Flamelet model with a simple chemical kinetics model, and a method for predicting combustion chamber wall temperature based on a thermal fluid calculation that coupled the engine coolant and the engine structure (engine head, cylinder block, and head gasket). Through these calculations as well as the measurement of wall temperatures and the analysis of combustion by experiments, the effects of wall temperature distribution and consequent unburnt gas temperature distribution on knock onset timing and location were examined. Furthermore, a study was made to develop a method for cooling the head side, which was more effective to suppress knock: the head gasket shape was modified to change the coolant flow and thereby improve the distribution of wall temperatures on the head side.

Three types of combustion chamber configurations (Types A, B, and C) with compression ratio lower than that of the baseline were tested for improved performance and exhaust gas emissions from an inline-four-cylinder 1.7-liter common-rail diesel engine manufactured for use with passenger cars. First, three combustion chambers were examined numerically using CFD code. Second, engine tests were conducted by using Type B combustion chamber, which is expected to have the best performance and exhaust gas emissions of all. As a result, 80% of NOx emissions at both low and medium loads at 1500 rpm, the engine speed used frequently in the actual city driving, improved with nearly no degradation in smoke emissions and brake thermal efficiency. It was shown that a large amount of cooled EGR enables NOx-free combustion with long ignition delay. In addition, the low compression ratio piston led to 22% improvement on maximum torque at the same engine speed without increasing maximum cylinder pressure. Copyright © 2006 SAE International.

This paper describes with internal combustion engines and fuel technologies trends toward reduction of both exhaust gas emissions and fuel consumption. The improvements of fuel consumption in gasoline engines will be achieved by the use of VVT (Variable Valve Train) system and homogeneous charge compression ignition combustion regime. The flexible common-rail injection system combined with advanced supercharging system can favorably reduced exhaust gas emissions of diesel engines without fuel penalty. Moreover, the new flexible combustion system must be developed for future automobiles. These engine technologies will be combined with future renewable fuels including GTL and biomass fuels, which lead to the reduction of CO_2 emission drastically.

To facilitate research and development of diesel engines, the universal numerical code for predicting diesel combustion has been favored for the past decade. In this paper, the finite-rate elementary chemical reactions, sometimes called the detailed chemical reactions, are introduced into the KIVA-3V code through the use of the Partially Stirred Reactor (PaSR) model with the KH-RT break-up, modified collision and velocity interpolation models. Outcomes were such that the predicted pressure histories have favorable agreements with the measurements of single and double injection cases in the diesel engine for use in passenger cars. Thus, it is demonstrated that the present model will be a useful tool for predicting ignition and combustion characteristics encountered in the cylinder.

Fuel temperature in the injector of direct injection gasoline engine is high. On some conditions it exceeds over 410 K. In order to understand spray behavior and mixture processes on these conditions, the effects of fuel temperature on spray characteristics injected by a swirl type injector for direct injection gasoline engines were investigated; In experiments, a constant volume chamber is used to visualize spray and mixture formation processes by LASER sheet, shadow graph and schlieren techniques. In addition Sauter mean radius (SMR) were measured. As these results, increasing fuel temperature over saturated temperature roll up didn't exist, the spray width was narrow and the penetration length was extremely long. Moreover although evaporation occurred quickly, the fuel vapor mixed with the surrounding air incompletely. This is because spray gathered near the nozzle axis and roll up didn't exist.

Natural gas pre-mixture is ignited by a small amount of pilot fuel in the dual fuel engine. In this paper, numerical studies were carried out to investigate the combustion and exhaust gas emissions formation process of this engine type by using a multi dimensional model combined with the detailed chemical kinetics including 57 chemical species and 290 elementary reactions. In calculation, the effect of the pre-mixture concentration on combustion was examined. The result indicated that the increased concentration of natural gas could improve the burning fraction and THC, CO emissions due to the increased pre-mixture consumption rate and the cylinders gas temperature. Copyright © 2003 Society of Automotive Engineers of Japan, Inc.

A dual fuel natural gas diesel engine suffers from remarkably lower thermal efficiency and higher THC, CO emissions at lower load because of its lower burned mass fraction caused by the lean pre-mixture. To overcome this inevitable disadvantage at lower load, two methods of reducing the number of operating cylinders were examined. One method was to use the two cylinders operation while the second one was to use the quasi-two cylinders operation. As a result, it was found that the unburned hydrocarbons and CO emissions could be favorably reduced with the improvement of thermal efficiency by reducing the number of cylinders to half for a dual fuel natural gas diesel engine. Moreover, it was also found that the quasi-two cylinders operation could improve the torque fluctuation more compared to the two cylinders operation. Copyright © 2003 Society of Automotive Engineers of Japan, Inc.

Fuel temperature in the injector of small direct injection gasoline engine is high. On some conditions it is higher than saturated temperature. Over saturated temperature spray characteristics greatly change. In order to predict in-cylinder phenomena accurately, it is important to understand spray behavior and mixture process above saturated temperature. Therefore spray shape, mixture formation process and Sauter mean radius were (SMR) measured in a constant volume chamber. And based on the measurement result initial spray boundary conditions were arranged so that spray characteristics over saturated temperature could be represented by using CFD code KIVA-3[1]. Moreover KIVA-3 code was combined with detailed chemical kinetics code Chemkin II to predict combustion products. [2] Calculated combustion process was validated with visualization of chemiluminescence. As a result, spray shape and penetration length have good agreement with measured ones for each fuel temperature. And also, tendencies of calculated flame propagation have roughly agreement with measured results and some species were predicted. Copyright © 2003 Society of Automotive Engineers of Japan, Inc.

Experimental and numerical studies are conducted on the formation of soot and Polycyclic Aromatic Hydrocarbons (PAHs), regarded as precursors of soot, during the combustion of fuel-rich homogeneous n-heptane mixtures. In-cylinder gases are sampled directly through a high-speed solenoid valve in engine tests, to be analyzed by GC/MS for qualifying PAHs. Smoke concentration is also measured. A numerical study is carried out by using a zero-dimensional model combined with detailed chemical kinetics. The experiments and computations show that PAHs can be predicted qualitatively by means of the present kinetic model. Copyright © 2003 Society of Automotive Engineers of Japan, Inc.

To improve urban air pollution, stringent emissions regulations for heavy-duty diesel engines have been proposed and will become effective in Japan, the EU, and the United States in a few years. To comply with such future regulations, it is critical to investigate the effects of intake and injection parameters and fuel properties on engine performance, efficiency and emissions characteristics, associated with the use of aftertreatment systems. An experimental study was carried out to identify such effects. In addition, the KIVA-3 code was used to gain insight into cylinder events. The results showed improvements in NOx-Smoke and BSFC trade-offs at high-pressure injection in conjunction with EGR and supercharging. Copyright © 2003 Society of Automotive Engineers of Japan, Inc.

An experimental ultra lightweight compact vehicle named "the Waseda Future Vehicle" has been designed and developed, aiming at a simultaneous achievement of low exhaust gas emissions, high fuel economy and driving performance. The vehicle is powered by a dual-type hybrid system having a SI engine, electric motor and generator. A high performance lithium-ion battery unit is used for electricity storage. A variety of driving cycles were reproduced using the hybrid vehicle on a chassis dynamometer. By changing the logics and parameters in the electronic control unit (ECU) of the engine, a significant improvement in emissions was possible, achieving a very high fuel economy of 34 km/h at the Japanese 10-15 drive mode. At the same time, a numerical simulation model has been developed to predict fuel economy. This would be very useful in determining design factors and optimizing operating conditions in the hybrid power system. Copyright © 2003 Society of Automotive Engineers of Japan, Inc.

It has been recognized that alternative fuels such as liquid petroleum gas (LPG) has less polluting combustion characteristics than diesel fuel. Direct-injection stratified-charge combustion LPG engines with spark-ignition can potentially replace conventional diesel engines by achieving a more efficient combustion with less pollution. However, there are many unknowns regarding LPG spray mixture formation and combustion in the engine cylinder thus making the development of high-efficiency LPG engines difficult. In this study, LPG was injected into a high pressure and temperature atmosphere inside a constant volume chamber to reproduce the stratification processes in the engine cylinder. The spray was made to hit an impingement wall with a similar profile as a piston bowl. Spray images were taken using the Schlieren and laser induced fluorescence (LIF) method to analyze spray penetration and evaporation characteristics. Combustion characteristics were examined visually by taking simultaneous images of the flame and OH radical formed during combustion. Numerical calculations using the KIVA-3 code was performed to predict mixture formation and combustion of LPG. The results showed that the LPG mixture moved along the impingement wall eventually reaching the spark plug location. The OH radical rose sharply and decreased gradually when combustion occurred vigorously. The predicted results from numerical calculations showed favorable agreement with measurements. Copyright © 2003 Society of Automotive Engineers of Japan, Inc.

A numerical study was carried out to investigate auto-ignition characteristics during HCCI predicted by using zero and multi-dimensional models combined with detailed kinetics including 116 chemical species and 689 elementary reactions involving iso-octane. In the simulation, homogeneous charge compression ignition of the fuel was analyzed under the same conditions as encountered in internal combustion engines. The results elucidated the combustible region and oxidation process of iso-octane with the formation and destruction of various chemical species in the cylinder. Copyright © 2003 Society of Automotive Engineers of Japan, Inc.

A CFD code combined with detailed chemical kinetics has been developed, linking with KIVA-3 and subroutines in CHEMKIN-II directly with some modifications. By using this CFD code, formation processes of combustion and exhaust gas emission for a turbo-charged DI diesel engine with common rail fuel injection system were simulated. As a result, formation processes of pollutant including NOx and soot were also considered according to the calculation results. The results show that NO caused by the extended Zeldvich mechanism accounted for about 88% of all NO, and it was found that there is a possibility to predict where and when soot will be formed by considering a simplified soot formation model. Copyright © 2003 Society of Automotive Engineers of Japan, Inc.

In this study, we selected four unregulated emissions species, formaldehyde, benzene, 1,3-butadiene and benzo[a]pyrene to research the emission characteristics of these unregulated components experimentally. The engine used was a water-cooled, 8-liter, 6-cylinder, 4-stroke-cycle, turbocharged DI diesel engine with a common rail fuel injection system manufactured for the use of medium-duty trucks, and the fuel used was JIS second-class light gas oil, which is commercially available as diesel fuel. The results of experiments indicate as follows: formaldehyde tends to be emitted under the low load condition, while 1,3-butadiene is emitted at the low engine speed. This is believed to be because 1,3-butadiene decomposes in a short time, and the exhaust gas stays much longer in a cylinder under the low speed condition than under the high engine speed one. Benzene is emitted under the low load condition, as it is easily oxidized in high temperature. Benzo[a]pyrene exists in the gas phase, because its boiling point is about 750K (at 128kPa). Once gaseous benzo[a]pyrene condenses, it is trapped by a filter with soot or sulfate. If it stays in the high temperature area, large part of it is oxidized. Consequently, benzo[a]pyrene is not emitted in great quantity under the high load condition. Copyright © 2003 SAE International.

Experimental and numerical studies on PAHs (Polycyclic Aromatic Hydrocarbons) and PM (Particulate Matters) formed in the fuel rich mixture have been conducted. In the experiment, neat n-heptane and n-heptane with benzene 25 % by weight were chosen as test fuels. In-cylinder gases produced by the fuel-rich HCCI (Homogeneous Charge Compression Ignition) combustion were directly sampled and analyzed by the use of GC/MS (Gas Chromatograph/Mass Spectro- metry), and PM emission was also measured by PM sampling system to reveal characteristics of PM formation. Numerical study has been also carried out using a zero dimensional combustion model combined with detailed chemistry. Furthermore, simple surface growth of soot particles was integrated into a detailed chemical kinetic model, and validated with the experimental data. Copyright © 2003 SAE International.

Natural gas pre-mixture is ignited by a small amount of pilot fuel in the dual fuel engine. In this paper, numerical studies were carried out to investigate the combustion and exhaust gas emissions formation process of this engine type by using a multi dimensional model combined with the detailed chemical kinetics including 57 chemical species and 290 elementary reactions. In calculation, the effect of the pre-mixture concentration on combustion was examined. The result indicated that the increased concentration of natural gas could improve the burning fraction and THC, CO emissions due to the increased pre-mixture consumption rate and the cylinders gas temperature. Copyright © 2003 Society of Automotive Engineers of Japan, Inc.

It is recognized that alternative fuels such as liquid petroleum gas (LPG) have less polluting combustion characteristics than diesel fuel. In this study, LPG was injected into a high pressure and temperature chamber to reproduce the stratification processes in an engine. The spray images were taken by the use of a PLIF method with Nd:YAG laser to analyze their penetration and evaporation characteristics. Also the characteristics of combustion were investigated by simultaneous visualization of OH radical and flames.
The results show that the mixture moves along the impingement wall that reproduced the piston bowl and reaches the ignition spark plug. Also, OH fluorescence rises sharply and then decreases gradually when the combustion is carried out actively. (C) 2002 Society of Automotive Engineers of Japan, Inc. and Elsevier Science B.V. All rights reserved.

Fuel properties play a dominant role in the spray, mixture formation and combustion process, and are a key to emission control and efficiency optimization. This paper deals with the influence of the fuel properties on the spray and combustion characteristics in a high-pressure and temperature chamber. Light diesel fuel spray and combustion images were taken by using a high-speed video camera and analyzed by their penetration and evaporation characteristics in comparison with current diesel fuel. Then, a single-cylinder DI engine was used to investigate combustion and exhaust characteristics. The mixture formation of the light diesel fuel is faster than that of the current fuel depending on physical properties like boiling point, density, viscosity and surface tension. Engine test results show that smoke is reduced without an increase in other emissions. © 2002 Society of Automotive Engineers of Japan, Inc. and Elsevier Science B.V. All rights reserved.

This paper deals with a diesel engine dual-fueled with natural gas. This system can achieve a high thermal efficiency at higher loads by utilizing the premixed lean natural gas mixture ignited by pilot-injected diesel fuel. At low loads, however, high THC emission and low thermal efficiency were observed. To resolve these problems, effects of EGR and intake heating with an exhaust to intake heat exchanger on engine performance and exhaust gas emissions were investigated, especially at low loads. In addition, 3-CFD simulations were conducted to analyze the combustion process in the combustion chamber, using the KIVA-3 code. The result indicates that thermal efficiency and THC emission at lower loads can be improved by intake air heating combined with EGR. (C) 2000 Society of Automotive Engineers of Japan, Inc. and Elsevier Science B.V. All rights reserved.

This paper deals with a diesel engine dual-fueled with natural gas. This system can achieve a high thermal efficiency at higher loads by utilizing the premixed lean natural gas mixture ignited by pilot-injected diesel fuel. At low loads, however, high THC emission and low thermal efficiency were observed. To resolve these problems, effects of EGR and intake heating with an exhaust to intake heat exchanger on engine performance and exhaust gas emissions were investigated, especially at low loads. In addition, 3-CFD simulations were conducted to analyze the combustion process in the combustion chamber, using the KIVA-3 code. The result indicates that thermal efficiency and THC emission at lower loads can be improved by intake air heating combined with EGR.

The homogeneous charge compression ignition (HCCI) combustion has been attracting growing attention in recent years due to its potential for simultaneous improvement of exhaust gas emissions and fuel consumption in diesel engines. For practical application of HCCI to internal combustion (IC) engines, precise control of auto-ignition of pre-mixtures during the compression stroke is inevitable. This paper discusses the auto-ignition processes in an HCCI engine operated with n-heptane/air mixtures using a zero-dimensional combustion model including a detailed kinetics. The model proposed is validated first by a comparison between calculated and experimental pressure diagrams, and then the effects of initial charge conditions, compression ratio and excess air ratio on ignition and combustion are investigated. It was found from the parametric study that HCCI combustion of n-heptane/air mixtures is classified into three types of combustion: complete combustion, only low-temperature reaction and misfire, depending on the compression ratio and excess air ratio at which the engine is operated. Finally, the major paths of the HCCI reaction occurring in the engine cylinder were clarified by a sensitivity analysis of chemical reactions involved in the HCCI reaction scheme. © 2000, Institution of Mechanical Engineers. All rights reserved.

Combustion and exhaust gas emissions characteristics of natural gas injected into the cylinder of a four-stroke-cycle diesel engine and ignited by pilot injection of liquid diesel fuel have been investigated numerically and experimentally. A 3D-CFD simulation has been conducted to examine the effect of natural gas injection timing on the behavior of natural gas mixture. As a result, the optimum injection timing of natural gas was examined for an engine operating condition, which led to improved THC emissions and thermal efficiency. This can be explained by the fact that the distribution of natural gas at ignition plays an important role in combustion and exhaust gas emissions.

An experimental and numerical study of HCHO (Formaldehyde) and other pollutant species formation in the cylinder of a direct-injection diesel engine fueled with methanol has been conducted. Engine tests were carried out under variety of intake conditions including throttling, heating and EGR for the purpose of changing gas composition, temperature in the post-combustion zone. Moreover, the relative importance and influence of individual reactions on HCHO formation and mechanism were assessed with aid of sensitivity analysis.

A numerical model has been developed for predicting exhaust gas emissions including NO_x HCHO, CH_3OH and other chemical species in a direct injection diesel engine fueled with methanol. In this model, 39 species with related 157 elementary reactions are taken into account. The effects of air excess ratios and load conditions on the exhaust gas emission characteristics were investigated based on this kinetic model. The model can predicts the formation and destruction of chemical species in the combustion process and the formation of formaldehyde and NO_2 during the expansion stroke.

An experimental and numerical study has been conducted on the emission and reduction of HCHO (formaldehyde) and other pollutants formed in the cylinder of a direct-injection diesel engine fueled by methanol. Engine tests were performed under a variety of intake conditions including throttling, heating, and EGR (exhaust gas recirculation) for the purpose of improving these emissions by changing gas compositions and combustion temperatures in the cylinder. Moreover, a detailed kinetics model was developed and applied to methanol combustion to investigate HCHO formation and the reduction mechanism influenced by associated elementary reactions and in-cylinder mixing.

A methanol-fueled direct-injection diesel engine with a glow-assisted ignition system tends to suffer from poor ignitability under low load conditions. Chemical delay phenomena associated with methanol mixture ignition were investigated to improve ignitability. The effects of the vaporization heat of liquid methanol, the surface temperature of the glow-plug, the heat created by the glow-plug and the Oz excess ratio of methanol-air mixtures on the ignition characteristics were examined. Our numerical model considers these parameters, and a detailed chemical kinetic scheme, including 39 chemical species and 157 elementary reactions, was used to predict the delay in methanol mixture ignition.

An experimental and numerical study has been conducted on the emission and reduction of HCHO (formaldehyde) and other pollutants formed in the cylinder of a direct-injection diesel engine fueled by methanol. Engine tests were performed under a variety of intake conditions including throttling, heating, and EGR (exhaust gas recirculation) for the purpose of improving these emissions by changing gas compositions and combustion temperatures in the cylinder. Moreover, a detailed kinetics model was developed and applied to methanol combustion to investigate HCHO formation and the reduction mechanism influenced by associated elementary reactions and in-cylinder mixing. © 1997 Society of Automotive Engineers, Inc.

An experimental and numerical study has been conducted on the emission and reduction of HCHO (formaldehyde) and other pollutants formed in the cylinder of a direct-injection diesel engine fueled by methanol. Engine tests were performed under a variety of intake conditions including throttling, heating, and EGR (exhaust gas recirculation) for the purpose of improving these emissions by changing gas compositions and combustion temperatures in the cylinder. Moreover, a detailed kinetics model was developed and applied to methanol combustion to investigate HCHO formation and the reduction mechanism influenced by associated elementary reactions and in-cylinder mixing. © 1997 Society of Automotive Engineers, Inc.

A numerical model has been developed to predict the formation of NOx and formaldehyde in the combustion and post-combustion zones of a methanol DI engine. For this purpose, a methanol-air mixture model combined with a full kinetics model has been introduced, taking into account 39 species with their 157 related elementary reactions. Through these kinetic simulations, a concept is proposed for optimizing methanol combustion and reducing exhaust emissions. © 1996 Society of Automotive Engineers, Inc.

A new type of fuel injection nozzle, called a "slit nozzle," has been developed to improve poor ignitability and to stabilize combustion under low load conditions in direct-injection methanol diesel engines manufactured for medium-duty trucks. This nozzle has a single oblong vent like a slit. Engine test results indicate that the slit nozzle can improve combustion and thermal efficiency, especially at low loads and no load. This can be explained by the fact that the slit nozzle forms a more highly concentrated methanol spray around the glow-plug than do multi-hole nozzles. As a result, this nozzle improves flame propagation. © Copyright 1994 Society of Automotive Engineers, Inc.