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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 H2 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.

A mixed time-scale subgrid large eddy simulation was used to simulate mixture formation, combustion and soot formation under the influence of turbulence during diesel engine combustion. To account for the effects of engine wall heat transfer on combustion, the KIVA code's standard wall model was replaced to accommodate more realistic boundary conditions. This were carried out by implementing the non-isothermal wall model of Angelberger et al. with modifications and incorporating the log law from Pope's method to account for the wall surface roughness. Soot and NOx emissions predicted with the new model are compared to experimental data acquired under various EGR conditions.

Electric buses have superior environmental performance because they emit no CO2 and other exhaust gases while driving. However, in terms of more popularization of electric buses, it is essential to improve battery performance and realize user-friendliness of charging. To resolve these issues, a concept “short range running and frequent charging” was formulated. Under this approach, the authors have studied methods of greatly reducing the amount of large, heavy, and expensive battery. Research on non-contact inductive power supply (IPS) system has also been conducted as a way of improving charging convenience. A longterm operation test of electric buses was performed in Nagano prefecture as part of a project organized by the Japan Ministry of the Environment from 2011 to 2014. For this project the short-range frequentcharging type electric buses, “Waseda Electric Buses (WEBs)” were developed and tested on public roads to make clear the environmental performance and energy costs. WEB-3, one of the test vehicles, was driven for 41,724 km without any major problems and had advantages to reduce 28 - 42 % of CO2 emissions and 57 – 64 % of energy costs, compared to conventional diesel buses. And it was estimated on Matlab simulation model that total energy consumption could be reduced by 11 % with vehicle weight reduction, modifications of drivetrain and other components.

Plug-in hybrid vehicles (PHVs) have two driving modes, which are known as charge-depleting (CD) mode and charge-sustaining (CS) mode. The environmental performance of a PHV differs greatly based on the travel distance when the PHV switches from the CD mode to the CS mode. This paper focuses on the low-carbon effect and energy cost reduction effect of PHVs and numerically describes the dependence of the effects on the distance traveled. It also accounts new knowledge obtained through a detailed analysis and examination of the mathematical equations.

The two opposite concepts of BE bus (battery-electric bus) which were “Short-range Frequent-charging-type” and “Night-charging-type” low-floor buses, were designed and evaluated. Firstly, the current technical level of battery and charging equipment had taken into account to conduct the vehicle design of both BE buses. In additional, the ideal performances of battery and charging equipment for fully substituting the highly used diesel buses in the very densely packed city transportation routes would be clarified in the paper.

The degradation mechanisms of lithium iron phosphate battery have been analyzed with 150 day calendar capacity loss tests and 3,000 cycle capacity loss tests to identify the operation method to maximize the battery life for electric vehicles. Both test results indicated that capacity loss increased under higher temperature and SOC conditions. And also, large increase of internal resistance on the high temperature and high SOC conditions was confirmed by AC impedance tests. The real cycle capacity loss characteristic was derived by subtracting the capacity decrease due to calendar capacity loss during the cycle test from the overall capacity loss characteristic obtained from the cycle test. As a result, it is found that the real capacity loss contains not only structural disorders of electrode but also degradation factors due to the chemical reactions. Characteristics of degradation were quantified with equations based on the chemical kinetics. With this degradation prediction, an operation method was proposed that is compatible with the long life of batteries and the safety driving of a vehicle. As a result, with optimizing the SOC range used in the operation as follows: 30-10% in the warm seasons, 45-25% in the cold seasons, it was found that batteries can last 4 times longer than it used with high SOC range in every season.

A long-term operation test in cold region of electric buses on public roads was performed in Nagano prefecture as a project of the Japan Ministry of the Environment from 2011 to 2014. For this project, the short-range frequent-charging type electric buses, “Waseda Electric Buses (WEBs)” were developed. WEB-3, one of the test vehicles, was driven for 42,114 km over 902 days and charged 4,298 times. In this paper, the following was obtained. (1) The battery performance deterioration is measured and proofed to be predictable. (2) One strategy is advised for expanding battery lifetime. (3) Even started the operation at sub-zero environment, the performance of vehicle was not affected.

A variable valve timing mechanism has been applied in a high-speed direct injection diesel engine. The effective compression ratio ( εeff) is lowered by means of late intake valve closing, while keeping the expansion ratio constant. Premixed charge compression ignition (PCCI) combustion, adopting the Miller cycle, was experimentally realized and numerically analysed. Significant improvements in NO x (nitrogen oxides) and soot emissions were achieved for a wide range of engine speeds and loads frequently used in a transient mode test. The operating range of the Miller-PCCI combustion has been expanded up to an indicated mean effective pressure of 1.3 MPa.

A variable valve timing (VVT) mechanism is applied to achieve premixed diesel combustion at higher load for low emissions and high thermal efficiency in a light-duty diesel engine. By means of late intake valve closing (LIVC), compressed gas temperatures near the top dead centre are lowered, thereby preventing too early ignition and increasing ignition delay to enhance fuel-air mixing. The variability of an effective compression ratio has significant potential for ignition timing control of conventional diesel fuel mixtures. At the same time, the expansion ratio is kept constant to ensure thermal efficiency. Combining the control of LIVC, exhaust gas recirculation (EGR), supercharging systems, and high-pressure fuel injection equipment can simultaneously reduce NO x and smoke. The NO x and smoke suppression mechanism in the premixed diesel combustion is analysed using a three-dimensional computational fluid dynamics (3D-CFD) code combined with detailed chemistry. LIVC can achieve a significant NO x and smoke reduction due to lowering combustion temperatures and avoiding local overrich regions in the mixtures respectively.

A long-term operation test of electric buses on public roads was performed in Nagano as part of a project of the Japan Ministry of the Environment from 2011 to 2014. For this project the short-range frequent- charging type electric buses, "Waseda Electric Buses (WEBs)" were developed. WEB-3, one of the test vehicles, was driven for 41,724 km without any major problems and had advantages to reduce 28-42% of CO2 emissions and 57-64% of energy costs, compared to conventional diesel buses. The battery performance deterioration is also confirmed to be predictable, therefore two suitable strategies is advised for expanding battery lifetime.

Degradation mechanisms of lithium iron phosphate battery have been analyzed with calendar tests and cycle tests. To quantify capacity loss with the life prediction equation, it is seen from the aspect of separating the total capacity loss into calendar capacity and real cycle capacity loss. The real cycle capacity loss of total capacity loss was derived by subtracting the calendar capacity loss parts during cycle tests. It is considered that calendar capacity loss is dominated by SEI formation. On the other hand, real cycle capacity loss includes structure disorder of electrodes and promotion of SEI growth such as delamination and regrowth. Generally, the test results indicated that capacity loss increases under high temperature and SOC condition, and SOC range (ΔSOC) is not related to the loss. However, we founded that the test results under 5℃ condition do not exactly show the same tendency of degradation. As a result, the life prediction equation is based on the chemical kinetics and it can only be adopted only beyond the 15℃ temperature limitation. At this time in life prediction equation, to take ΔSOC into consideration and describe the real cycle capacity loss specifically with amounts of lithium-ion intercalation/deintercalation, the processing amount of current is adopted as the standard of capacity degradation instead of the cycle number. Finally, it is considered to be possible that certain reactions such as further structure disorder or lithium plating caused under low temperature. However, we also founded that DC internal resistance tests results indicated that only calendar capacity loss can apply to chemical kinetics. It is necessary to consider the other construction method of the life prediction equation in the future

NOx conversion performance of a urea-selective catalytic reduction (SCR) system comprising V2O5/TiO2 catalyst under steady state operating conditions of an 8-litre, common-rail turbo direct injection (TDI) diesel engine was investigated. It was shown that the urea-SCR system achieves 70–90 per cent NOx conversion under medium and high load conditions at 1440 r/min and that NOx conversion is low under low load conditions because of the low catalyst temperatures and the NO/NO2 ratio being higher than unity. It was also shown that NOx conversion exceeds 90 per cent when the catalyst temperature is higher than 530 K. To investigate the details of the chemistry and thermofluid dynamics within the urea-SCR system, a computational fluid dynamics (CFD) code that incorporates detailed surface chemistry was developed based on the modified subroutines of CHEMKIN-II. The spatial variations of chemical species including NO and NH3 in a thin catalyst channel was calculated using the model. The calculated result of NO conversion showed relatively good agreement with experimental results.

Dimethyl ether (DME) has been recognized as an alternative fuel for better combustion and less pollutant formation than diesel, even though they have a cetane number. In this study, characteristics of DME spray were observed experimentally under various ambient conditions in a constant-volume chamber with a common-rail injection system. To understand the combustion characteristics of DME, radicals from the flame and exhaust gases were also investigated. Radicals from DME combustion were measured by a high-speed camera with stereoscope. Flame spectra were taken near 310 and 400-530 nm emitting from OH and CH or C2 radicals respectively. Flames of diesel were found to be much stronger than those of DME because of the smoke emitted from CH and C22 radicals. Moreover, NOx emission is substantially decreased without increasing in the smoke emission with a high exhaust gas recirculation (EGR) rate in DME combustion. It was confirmed from these results that DME has the potential for a low emission fuel alternative to diesel.

Swirl injector spray at high fuel temperature has features of rapid atomization and evaporation, compared to those at normal fuel temperature. These have a possibility to improve fuel consumption and emissions under cold start condition. The purpose of this study was to reveal the feasibility of improving cold start emissions of a DI engine by using high temperature fuel spray, to make a simulation procedure which can reproduce the spray formation process at high gasoline temperature and to incorporate it with a 3-D in-cylinder calculation of the mixture of in-cylinder gas and the spray. Results show that heating fuel was an affect to reduce the mass of wall-film. Thus using high temperature fuel has the possibility to improve fuel consumption and exhaust emissions under cold start condition.

This paper investigates the effects of combustion system and fuel properties on spray, mixture formation, combustion process, and emissions, using a constant volume chamber and single- cylinder engine. In a combustion system, high-pressure injection, exhaust gas recirculation (EGR), and impingement spray are applied while visualizing and analysing exhaust gas. Also, light diesel fuel, which has approximately the same cetane value as the diesel but has low values of PAHs, boiling point, density, viscosity, and surface tension, were used. Spray and combustion images were taken using a high-speed video camera and analysed by their penetration and evaporation characteristics in comparison with current diesel fuel. The results showed that the mixture formation of the high- pressure injection, impingement spray, and light diesel fuel is faster than that of diesel fuel, depending on physical properties. In the engine test, a considerable reduction of smoke emission was observed using the high-pressure injection with supercharging, due to the enhanced fuel atomization and air entrainment. In addition, a high reduction of NOx emission can be achieved with a high EGR rate, and with supercharging can achieve a reduction of NOx emission without deteriorating BSFC.

It has been recognized that alternative fuels, such as liquid petroleum gas (LPG), have less polluting combustion characteristics than diesel fuel. Furthermore, when LPG direct-injection, stratified-charge combustion can be adopted in the spark-ignition engine in place of the conventional premixed spark-ignition combustion, it will be possible to achieve less polluting and more efficient combustion characteristics. However, the physical properties of LPG, such as boiling point (—40-0°C) and viscosity, differ largely in comparison with current fuels. Therefore, there are many unknown phenomena in the behaviour of spray, mixture formation, and combustion of LPG in the cylinder. These issues make the development of a high-efficiency LPG engine difficult. Thus, in this study, a numerical method has been adjusted to predict the mixture formation and combustion of LPG. KIVA-3 code was used for this purpose, and tuning factors were adjusted by comparing them with the measurements. In the combustion model, the eddy-dissipation combustion model proposed by Magnussen and Hjertager [1] is adopted. The predicted results show favourable agreement with the measurements and the possibility of useful methods to improve engine performance.

The purpose of this study is to elucidate autoignition characteristics of HCCI of natural gas mixtures during the compression process in the engine. A rapid compression and expansion machine was used to reproduce and visualize autoiginition combustion. The test results show that initial temperature and density, and hydrocarbon contents other than methane, are important parameters influencing autoignition timing and the successive combustion. A detailed chemical kinetics model combined with a multi-dimensional CFD code supports these autoignition characteristics.

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.

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.