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A development project for a hydrogen internal combustion engine (ICE) system for trucks supporting Japanese freightage has been promoted as a candidate for use in future vehicles that meet ultra-low emission and anti-global warming targets. This project aims to develop a hydrogen ICE truck that can handle the same freight as existing trucks. The core development technologies for this project are a direct-injection (DI) hydrogen ICE system and a liquid hydrogen tank system which has a liquid hydrogen pump built-in. In the first phase of the project, efforts were made to develop the DI hydrogen ICE system. Over the past three years, the following results have been obtained: A high-pressure hydrogen gas direct injector developed for this project was applied to a single-cylinder hydrogen ICE and the indicated mean effective pressure (IMEP) corresponding to a power output of 147 kW in a 6-cylinder hydrogen ICE was confirmed.

It is well known that lubricating oil consumption (LOC) is much affected by the cylinder bore deformation occurring within internal combustion engines. There are few analytical reports, however, of this relationship within internal combustion engines in operation. This study was aimed at clarifying the relationship between cylinder bore deformation and LOC, using a conventional in-line four-cylinder gasoline engine. The rotary piston method developed by the author et al. was used to measure the cylinder bore deformation of the engine’s cylinder #3 and cylinder #4. In addition, the sulfur tracer method was applied to measure LOC of each cylinder. LOC was also measured by changing ring tension with a view to taking up for discussion how piston ring conforms to cylinder, and how such conformability affects LOC. Their measured results were such that the cylinder bore deformation was small in the low engine load area and large in the high engine load area.

Due to increasing economic and environmental performance requirements of internal combustion engines, piston manufacturers now focus more on lower friction designs. One factor strongly influencing the friction behavior of pistons is the dynamic interaction between lubricating oil, cylinder bore and piston. Therefore, the dynamic effect of the oil film in the gap between the liner and piston has been studied, using a single cylinder engine equipped with a sapphire window. This single cylinder engine was also equipped with a floating liner, enabling real-time friction measurement, and directly linking the oil film behavior to friction performance of pistons.

Hydrogen is expected to be a clean and energy-efficient fuel for the next generation of power sources because it is CO2-free and has excellent combustion characteristics. In this study, an attempt was made to apply Homogeneous Charge Compression Ignition (HCCI) combustion to hydrogen with the aim of achieving low oxides of nitrogen (NOx) emissions and high fuel economy with the assistance of the di-methyl-ether (DME) fuel supplement. As a result, HCCI combustion of hydrogen mixed with 25 vol% DME achieved approximately a 30% improvement in fuel economy compared with HCCI of pure DME and spark-ignited lean-burn combustion of pure hydrogen under almost zero NOx emissions and low hydrocarbon (HC) emissions. This is attributed to control of the combustion process to attain the optimum onset of combustion and to a reduction of cooling losses.

The results of this study make clear the characteristics of electrode performance deterioration in terms of cell voltage reduction in polymer electrolyte fuel cells (PEFCs) caused by the presence of certain quantities of carbon monoxide and/or hydrogen sulfide in the anode feed. AC impedance measurements of the anode and cathode potentials revealed that both electrode potentials showed deterioration in the presence of each type of poisoning gas. This suggests that the poisoning gases permeated the electrolyte membrane and transferred to the cathode, causing performance deterioration by poisoning the catalyst. In addition, AC impedance measurements indicated that the presence of hydrogen sulfide in the anode feed increased the membrane impedance, thus implying some poisoning effect even on the electrolyte membrane.

Hydrogen can be readily used in spark-ignition engines as a clean alternative to fossil fuels. However, a larger burning velocity and a shorter quenching distance for hydrogen as compared with hydrocarbons bring a larger cooling loss from burning gas to the combustion-chamber wall. Because of the large cooling loss, the thermal efficiency of a hydrogen-fueled engine is sometimes lower than that of a conventionally fueled engine. Therefore, the reduction of the cooling loss is very important for improving the thermal efficiency in hydrogen-combustion engines. On the other hand, the direct-injection stratified charge can suppress knocking in spark-ignition engines at near stoichiometric overall mixture conditions. Because this is attributed to a leaner end gas, the stratification can lead to a lowered temperature of burning gas around the wall and a reduced cooling loss.

Although various factors affecting oil consumption of an internal combustion engine can be considered, a technique to predict the amount of oil consumed within a cylinder that passes across a running surface of a ring was developed in this study. In order to predict the effect of cylinder deformation on oil consumption, a simple and easy technique to calculate the oil film thickness in deformed cylinder was proposed. For this technique, the piston ring was assumed to be a straight beam, and the beam bends with ring tension, gas pressure, and oil film pressure. From the calculated oil film thickness, amount of oil passing across the running surface of the TOP ring and into the combustion chamber was calculated. The calculated results were then compared to the oil film thickness of the ring and oil consumption measured during engine operation, and their validity was confirmed.

A diesel fuel and air diffusion flame burner system has been designed for laboratory simulation of diesel exhaust gas. The system consists of mass flow controllers and a fuel pump, and employs several unique design and construction features. It produces particulate emissions with size, number distribution, and morphology similar to diesel exhaust. At the same time, it generates NOx emissions and HC similar to diesel. The system has been applied to test plasma discharges. Different design discharge devices have been tested, with results indicating the importance of testing devices with soot and moisture. Both packed bed reactor and flat plate dielectric barrier discharge systems remove some soot from the gas, but the designs tested are susceptible to soot fouling and related electrical failures. The burner is simple and stable, and is suitable for development and aging of plasma and catalysts systems in the laboratory environment.

This study analyzes the factors influencing the thermal efficiency of a homogeneous charge spark-injection (SI) engine fuelled with hydrogen, focusing on the degree of constant volume and cooling loss. The cooling loss from the burning gas to the cylinder walls is quantitatively evaluated by analyzing the cylinder pressure diagram and exhaust gas composition. The degree of constant volume burning and constant volume cooling are also obtained by fitting the Wiebe function to the rate of heat release calculated using the cylinder pressure diagram. A comparison of combustion and cooling characteristics of hydrogen and methane combustion reveals that cooling loss in hydrogen combustion is higher than that of methane combustion due to the short quenching distance and rapid burning velocity during hydrogen combustion. It is also suggested that the high cooling loss observed during hydrogen combustion reduces thermal efficiency.

Thermodynamic characteristics of premixed compression ignition combustions were clarified quantitatively by heat balance estimation. Heat balance was calculated from temperature, mole fractions of intake and exhaust gases, mass and properties of fuels. Heat balance estimation was conducted for three types of combustion; a conventional diesel combustion, a homogeneous charge compression ignition (HCCI) combustion; fuel is provided and mixed with air in an intake pipe in this case, and an extremely early injection type PREmixed lean DIesel Combustion (PREDIC). The results show that EGR should be applied for premixed compression ignition combustion to complete combustion at lower load conditions and to control ignition timing at higher load conditions. With an application of EGR, both HCCI and PREDIC showed low heat loss characteristics at lower load conditions up to 1/2 load.

Reformed fuel from hydrocarbons or alcohol mainly consists of hydrogen, carbon monoxide and carbon dioxide. The composition of the reformed fuel can be varied to some extent with a combination of a thermal decomposition reaction and a water gas shift reaction. Methanol is known to decompose at a relatively low temperature. An application of the methanol reforming system to an internal combustion engine enables an exhaust heat recovery to increase the heating value of the reformed fuel. This research analyzed characteristics of combustion, exhaust emissions and cooling loss in an internal combustion engine fueled with several composition of model gases for methanol reformed fuels which consist of hydrogen, carbon monoxide and carbon dioxide. Experiments were made with both a bottom view type optical access single cylinder research engine and a constant volume combustion chamber.

There have been strong demands recently for reductions in the fuel consumption and exhaust emissions of diesel engines from the standpoints of conserving energy and curbing global warming. A great deal of research is being done on new emission control technologies using direct-injection (DI) diesel engines that provide high thermal efficiency. This work includes dramatic improvements in the combustion process. The authors have developed a new combustion concept called Modulated Kinetics (MK), which reduces smoke and NOx levels simultaneously by reconciling low-temperature combustion with pre-mixed combustion [1, 2]. At present, research is under way on the second generation of MK combustion with the aim of improving emission performance further and achieving higher thermal efficiency [3]. Reducing heat rejection in the combustion chamber is effective in improving the thermal efficiency of DI diesel engines as well as that of MK combustion.

Accurate measurements of combustion gas temperature and the coefficient of heat transfer between the gas and the combustion chamber wall of internal combustion engine in cyclic operations are difficult at present. Hence the only method available for determination of states of thermal load and heat loss to the combustion chamber wall in a cycle is to measure the instantaneous temperature on the combustion chamber wall surface accurately and precisely using proper thin-film thermocouples, then to calculate the instantanenous heat flux flowing into the wall surface by means of numerical analysis. However, it is necessary to pay adequate attention to the effects of thermophysical properties of the thermocouple materials on the measured values, since any thermocouple consists of several kinds of materials which are different from those of portions to be measured.

Hybrid electric vehicle with internal combustion engine fueled with hydrogen can be a competitor to the fuel cell electric vehicle that is thought to be the ultimately clean and efficient vehicle. The objective in this research is to pursue higher thermal efficiency and lower exhaust emissions in a hydrogen-fueled engine for the series type hybrid vehicle system. Influences of compression ratio, surface / volume ratio of combustion chamber, and boost pressure on thermal efficiency and exhaust emissions were analyzed. Results showed that reduction of the surface / volume ratio by increased cylinder bore was effective to improve indicated thermal efficiency, and it was possible to achieve 44% of indicated thermal efficiency. However, brake thermal efficiency resulted in 35.5%. It is considered that an improved mechanical efficiency by an optimized engine design could increase the brake thermal efficiency largely.

Exhaust-gas recirculation (EGR) causes the piston ring and cylinder liners of a diesel engine to suffer abnormal wear. The present study aimed at making clear the mechanism of wear which is induced by soot in the EGR gas. The piston ring has been chrome plated and the cylinder was made of boron steadite cast iron. Detailed observations of the ring sliding surfaces and that of the wear debris contained in lubricating oil were carried out. As a result, it was found that the wear of the top ring sliding surfaces identify abrasive wear without respect to the presence of EGR by steadite on the cylinder liner sliding surface. In addition, it is confirmed in a cutting test that soot mixed lubricating oil improved in performance as cutting oil. Based on these results, we proposed the hypothesis in the present study that ring wear is accelerated at EGR because abrasive wear increases due to a lot of soot mixed into lubricating oil improving the performance of lubricating oil as cutting oil.

Nitrogen oxide (NOx) and particulate matter (PM) emissions of diesel vehicles are regarded as a source of air pollution, and there is a global trend to enforce more stringent regulations on these exhaust gas constituents in the early years of the 21st century. On the other hand, the excellent thermal efficiency of diesel engines is certainly a welcome attribute from the standpoints of conserving energy and curbing global warming. Recently, many research institutes around the world have been using high-efficiency direct-injection (DI) diesel engines to research emission control technologies. The authors have also been engaged in such research [1,2]. As a result of this work, we have developed a new combustion concept, called Modulated Kinetics (MK), that reduces NOx and smoke simultaneously due to low-temperature and premixed combustion characteristics, respectively, without increasing fuel consumption [3,4].

Exhaust-gas recirculation (EGR) causes the piston rings and cylinder liners of a Diesel engine to suffer abnormal wear on the sliding parts. The present study aimed at making clear such abnormal wear structurally by examining the state of lubrication of the piston with a floating liner method, observing directly a visualized cylinder and experimenting on a Diesel engine for wear. As a result, it was confirmed that soot in EGR gas would change a lot the characteristics of the piston friction force. There are two mechanisms: one directly enters the sliding surfaces, and the other enters the ring rear, applying more load to them. It was also confirmed that the level of wear on the piston ring would vary to a large extent as the state of lubrication changed.

This paper describes a measurement method using laser induced fluorescence we have developed for simple simultaneous measurements of piston ring oil film thickness at plural points for internal combustion engines. The findings obtained by the measurements of oil film thickness on both thrust and anti-thrust sides of the piston for a mono-cylinder compact diesel engine using this new measurement method are also discussed in this paper. One of main findings is that the oil film thickness of each ring on both sides differs markedly in terms of the absolute value and the stroke- to-stroke variation. It is found that this difference in oil film thickness is caused by the difference in the amount of lubricating oil supplied to the oil ring, and the effect is greater than that of engine speed or load.

It is a well-known fact that the exhaust emission characteristics of hydrogen fueled engines are extremely good. The external mixture formation - a hydrogen fuel supply method - has the merit of practically zero NOx emission level in the lean mixture range with the excess air ratio λ set at 2.0 or greater as well as the merits of simple mechanism and easy operation. However, the practical use of such engines has been impeded partly due to the occurrence of backfire where the excess air ratio λ is 2 to 3. In order to allow the practical use of the hydrogen fueled engines with external mixture formation, it is vital to determine the causes of backfire and to establish proper countermeasures. It is found through a recent study conducted on the mechanism of backfire that the abnormal electric discharge in the intake stroke is one of the causes of backfire.

The aim of this research was to analyze the lubrication conditions of piston pin boss bearings used in the press-fit piston pins of automobile gasoline engines. An original pin boss friction measuring device was developed and used to successfully obtain measurements. It was revealed that the friction force peaks twice every cycle at high engine loads, and non-fluid lubrication characteristics are displayed. The friction forces for various differing piston pins and pin boss bearings were analyzed, and it was shown that reducing piston pin length or thickness to reduce piston weight, or reducing the pin boss bearing clearance to reduce noise worsen the friction characteristics and increase the possibility of abnormal bearing friction as well as seizure.