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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.

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 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.

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.

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.

Various studies were conducted from the aspects of both the battery cells and the module with the aim of making more effective use of the battery capacity. As a result, after 77 cycles of driving and rapid charging, the capacity degradation of the battery module as a whole was 7.7 % and it was determined that the cause of this additional 0.7 % degradation of the capacity was the loss of cell balance. In addition, by adopting module balance coefficient (945;) that was proposed as an indicator to show the available percentage of the lowest capacity cell in the module, new cell balancing rules were created that do not significantly affect the convenience of vehicle operation.

It has been recognized that alternative fuels such as dimethyl ether (DME) and liquefied petroleum gas (LPG) have less polluting combustion characteristics than diesel fuel. In this study, such alternative fuels were injected into a high pressure and temperature chamber by means of an electronically controlled common rail injection system to reproduce their charge stratification processes in the engine. Their spray images were taken by using a high-speed video camera and copper-vapor laser to analyze their penetration and evaporation characteristics in comparison with normal-dodecane (n-dodecane) which represent the physical and chemical characteristics as a replacement for diesel fuel. The mixture formation of DME and LPG sprays is faster than that of n-dodecane due to their flash boiling characteristics at high pressures and temperatures.

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.

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.

An experimental study was carried out to measure the evaporating processes of fuel sprays having different boiling points. n-dodecane was used as the higher boiling point fuel, and iso-octane as the lower boiling point fuel. A laser induced fluorescence method was used to separate vapor and liquid-phases of the spray. The measurement of fluorescence wavelength indicates that dimethyl-anilene (5 wt%)+naphthalene (5 wt%) should be added to each fuel. As a result, it was confirmed that n-dodecane in a spray consisting of n-dodecane and iso-octane evaporates more rapidly than an n-dodecane 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.

A lithium iron phosphate battery has superior rapid charging performance and is suitable for electric vehicles designed to be charged frequently and driven short distances between charges. This paper describes the results of testing conducted to evaluate the capacity loss characteristics of a newly developed lithium iron phosphate battery. These results confirmed that, in the assumed use temperature range of the battery, the degree of storage capacity loss (referred to below as “calendar capacity loss”) over 120 days was approximately 4% and the degree of capacity loss on cycle test over 500 cycles was approximately 6%.

1. (1) Slit nozzles which concentrate methanol spray around the glow-plug improve combustion at low load although ignition delay was slightly long, which can favorably reduce unburned methanol emissions. At high load, there is room for improvement in utilizing air after ignition. 2. (2) At low load, the glow-plug temperature must be kept at more than 900°C to avoid misfire.

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.

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.

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. 3 refs., 12 figs., 4 tabs.

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.

Influence de la geometrie de la chambre de combustion sur la combustion dans un moteur diesel

From the viewpoint of utilizing methanol fuel in an automotive turbocharged direct-injection diesel engine, an intercooling system supplying liquid methanol has been devised and its effects on engine performance and exhaust gas emissions have been investigated. With an electronically controlled injector in this system, methanol as a supplementary fuel to diesel fuel can be injected into the intake pipe in order to intercool a hot air charge compressed by the turbocharger. It has been confirmed that especially at heavy load conditions, methanol-intercooling can yield a higher thermal efficiency, and lower NOx and smoke emissions simultaneously, compared with three other cases without using methanol: natural aspiration and the cases with and without an ordinary intercooler. However, methanol fueling must be avoided at lower loads since sacrifices in efficiency and hydrocarbon emissions are inevitably involved.