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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.

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.

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

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.

In this experimental study, measurements were made on the characteristics of evaporating steady-state fuel spray injected into a high pressure and temperature cylindrical vessel by means of an electronically controlled common rail injection system. A fuel consisting of two components, n-octane and n-hexane, having different boiling points was used to investigate the characteristics of evaporation and mixing with the surrounding gas. Fluorescence characteristics of dopants excited by the YAG laser were calibrated by means of a spectroscope having an optical fiber. From the measurement of fluorescence wavelength, we decided that fluorobenzene and diethy-methyl-amine (DEMA) in a solution of fuel. Then, two-dimensional images were analyzed for each fuel component at liquid and gas phases, simultaneously. The results show that the density and temperature of the surrounding gas are two dominant factors influencing the penetration and evaporation of the spray.

An experimental study was carried out to verify the feasibility of a quantitative analysis of fuel droplet diameter at high pressures and temperatures in combustion systems. A fueling system was developed to atomize fuel into droplets of the same diameter. Using this system, fueling was made into a visualized device where high pressure and temperature nitrogen flowed under steady-state conditions. The laser induced fluorescence method was utilized to determine n-dodecane fuel and iso-octanefuel droplet behavior and the phase Doppler particle analyzer was used to measure the diameter and velocity of the droplets. As a result, it was confirmed that a quantitative analysis of fuel droplets is possible. The results indicate that due to its lower boiling point, iso-octane droplets tend to evaporate much faster the n-dodecane droplets.

A numerical model has been developed for predicting exhaust gas emissions including NOx HCHO, CH3OH 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 NO2 during the expansion stroke.

An experimental study was carried out to make a quantitative analysis of fuel droplet diameter at a high pressure and temperature occurring in combustion systems. A fueling system was developed to atomize fuel into droplets having a single small diameter. By using this system, fueling was made into a visualized device where high pressure and temperature nitrogen flew under steady-state conditions. The laser induced fluorescence method was utilized to determine the n-dodecane fuel and iso-octane fuel droplet behavior and the phase doppler particle analyzer to measure the diameter and velocity of the droplets. As a result, quantitative analysis of a fuel droplet got possible. The results indicate that due to its lower boiling point, iso-octane droplets tend to evaporate much faster then dodecane droplerts.

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 O2 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.

In this study, the effect of town gas composition on gas engine rating is evaluated. Engine test work was carried out using a range of gases to characterize the tendency for knocking combustion to occur under stoichiometric and lean conditions. A matrix of 133 gases at a stoichiometric mixture ratio and that of 100 gases under a lean condition were used to allow in the statistical analysis of test results. Analyzing the test results, it is identified that efficacy on gas engine rating is n-C4H10, i-C4 H10, C3H8, C2H6 and H2 in a descending order. It is also clarified that the hydrocarbons have almost the same effect on gas engine rating under stoichiometric and lean conditions, whereas hydrogen greatly affects the rating under the lean condition.

An experimental study has been carried out to investigate the effects of supercharging on diesel spray dynamics and combustion characteristics. A rapid compression and expansion machine has been developed to reproduce diesel sprays and combustion. A copper vapor laser is used as a light source to visualize the spray. By synchronizing the laser output to a high speed 16 mm camera, instantaneous photographs of the spray can be taken. It is shown that supercharging can increase air entrainment in the spray and its evaporation. As a result, ignition lag can be reduced while the early part of diffusion combustion is increased.

This paper presents the results of analysis into the adverse effects on vehicle performance caused by the deterioration in capacity and increase in resistance of lithium-ion batteries installed in hybrid electric vehicles (HEVs). Detailed evaluations were conducted based on simulations to determine the adverse effects on HEV performance. It was concluded that the battery resistance at which the CO2 emissions rate and the Fuel Consumption reaches 120% of the level of a new vehicle is approximately 350% of the initial battery resistance value.

The Waseda Advanced Electric Micro Bus (WEB) has been developed and tested for convenient regional public transportation. By adopting an advanced hybrid electric power supply system (Nickel Sodium Chloride Battery &amp, Super capacitor for WEB-1, Nickel Sodium Chloride Battery &amp, Li-ion Battery for WEB-2) and related key components, significant improvements in energy consumption and CO2 emissions have been achieved, compared to that of an equivalent diesel micro bus.

This paper describes a dynamic simulation model built to assess Plug-in Hybrid Electric Vehicles (PHEVs) performance and lithium-ion battery performance installed in PHEVs. First, we examine vehicle performance. In particular, the effects of engine on/off controls and the effects of drive distance are evaluated, because they have significant impact on PHEVs environmentally friendly performance. A study of cycle life test methods for batteries installed in PHEVs is also examined. Here, we discuss the establishment of a common PHEV battery charge/discharge test profile for Japan, the US, and Europe.

A numerical simulation model has been developed to predict the direct-injection stratified charge combustion in a constant-volume vessel. Important factors such as local fuel concentrations, their fluctuations and turbulent flow characteristics were measured throughout the vessel as functions of time. These data were utilized to estimate the burning rate composed of the turbulent fuel-air mixing rate and chemical reaction rate. The model can predict the combustion pressures and heat release rates measured for different ignition timings and spark locations.

Two conventional combustion chamber types and a re-entrant type of direct-injection diesel engine were compared in order to investigate the effects of heat transfer and in-cyliner flow associated with the combustion chamber geometry on combustion itself, engine performance and exhaust gas emissions. Heat transfer calculation and heat release analysis have shown that the re-entrant chamber tends to reduce ignition lag due to the higher chamber wall temperatures. In-cylinder flow measurements using hot wire anemometry have indicated that the re-entrant chamber generates a higher turbulence level, particularly around the top dead center, causing an increase in the rate of heat release. Thus, the re-entrant chamber can favorably improve both fuel economy and smoke, even though fuel injection timing is retarded to reduce NOx emission.

An experimental study has been made on stratified charge combustion which may possibly realize lean combustion in a speak ignition engine. In order to simulate charge stratification, methane was injected into a constant volume vessel, and its temporal and spatial concentrations were measured using a hot wire probe. Thus, fuel distribution maps were drawn throughout the vessel for successive timings after fuel injection. Then, ignitability was determined for various spark plug locations and related to the measured stratified charge. The results have shown that a local mixture exceeding its flammable limit for mean fuel-air ratio can be ignited with a proper turbulence of fuel concentration and that for fast burning of the whole charge, spark ignition should be made at a downstream point of the fuel jet.

本研究では、予燃焼室ディーゼル機関を対象とし、主・副両室内の燃焼ガスを高速電磁弁によって採取・分析し、燃焼過程におけるNOx生成の時間的変化を追跡した。その結果、NOxは予燃焼室内での生成は比較的少なく、噴孔を通過した後の主燃料室内での燃焼により、多く発生することが確認された。また、各種の運転条件や予燃焼室の設計因子がNOxの生成過程に及ぼす影響についても明確にされた。