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Hydrogen ICE can achieve carbon neutrality and is adaptable to medium and heavy-duty vehicles, for which electricity is not always a viable option. It can also be developed using high-quality conventional diesel/gasoline engine technology. Furthermore, it allows for the conversion of existing engines to hydrogen ICE, making it highly marketable. The reliability and durability of MPI hydrogen ICE is better than that of DI, and MPI has an advantage over DI in terms of cruising range because the low-pressure injection of hydrogen reduces the remaining hydrogen in the tank. Improving MPI output is, however, an important subject, and achieving this requires suppressing abnormal combustion such as pre-ignition. In this study, an inline four-cylinder 5L turbo-charged diesel engine was converted to a hydrogen engine. Hydrogen injectors were installed in the intake ports and spark plugs were installed instead of diesel fuel injectors.

The mechanism of lubricant dilution by post injection fuel in a diesel engine was investigated. The operating conditions of the engine were changed, and oil was sampled from each part of the piston and the crankcase, and the dilution ratio was analyzed. Also, photochromism was used to visualize the oil and fuel flow. Dilution ratios obtained from oil sampling and photochromism showed the same tendency.

Honda has developed a new hybrid system targeting the C and D segments that aims for the latest environmental performance, high fuel economy, and enhanced acceleration feeling in driving. The new engine to be applied to this new hybrid system has been developed with the goal of expanding the high thermal efficiency range, realizing the latest environmental performance, and high quietness. The new engine has adopted the Atkinson cycle and cooled exhaust gas recirculation (EGR) carried over from the previous model [1], and employed an in-cylinder direct fuel injection system with fuel injection pressure of 35 MPa. The combustion chamber and ports have been newly designed to match the fuel system changes. By realizing high-speed combustion, the engine realized a high compression ratio with the mechanical compression ratio of 13.9.

According to some papers, the label fuel economy and the actual fuel economy experienced by the customers may exhibit a gap. One of the reasons may stem from the aerodynamic drag variations due to the natural wind. The fuel consumption is measured through bench test under several driving modes by using the road load as input condition. The road load is measured through the coast down test under less wind ambient conditions as determined by each regulation. The present paper aims to analyze the natural wind conditions encountered by the vehicle on public roads and to operate a comparison between the fuel consumptions and the driving energy. In this paper, the driving energy is calculated by the aerodynamic drag from the natural wind specifications and driving conditions. This driving energy and the fuel consumptions show good correlation. The fuel consumption is obtained from the vehicle Engine control unit(ECU) data.

The reduction of cycle-to-cycle variations (CCV) is a prerequisite for the development and control of spark-ignition engines with increased efficiency and reduced engine-out emissions. To this end, Large-Eddy Simulations (LES) can improve the understanding of stochastic in-cylinder phenomena during the engine design process, if the employed modeling approach is sufficiently accurate. In this work, an inhouse code has been used to investigate CCV in a direct-injected spark ignition (DISI) engine under fuel-lean conditions with respect to a stoichiometric baseline operating point. It is shown that the crank angle when a characteristic fuel mass fraction is burned, e.g. MFB50, correlates with the equivalence ratio computed as a local average in the vicinity of the spark plug. The lean operating point exhibits significant CCV, which are shown to be correlated also with the in-cylinder subfilter-scale (SFS) kinetic energy.

Recent trends to downsize engines have resulted in lighter weight and greater compactness. At the same time, however, power density has increased due to the addition of turbocharger and other such means to supplement engine power and torque, and this has increased the thermal and mechanical load. In this kind of environment, corrosion of the copper alloy bushing (piston pin bushing) that is press-fitted in the small end of the connecting rod becomes an issue. The material used in automobile bearings, of which the bushing is a typical example, is known to undergo sulfidation corrosion through reaction with an extreme-pressure additive Zinc Dialkyldithiophosphate (ZnDTP) in the lubricating oil. However, that reaction path has not been clarified. The purpose of the present research, therefore, is to clarify the reaction path of ZnDTP and copper in an actual engine environment.

The cooling performance and the heat resistance performance of commercial vehicle are balanced with aerodynamic performance, output power of powertrain, styling, cost and many other parameters. Therefore, it is desired to predict the cooling performance and the heat resistance performance with high accuracy at the early stage of development. Among the three basic forms of heat transfer (conduction, convection and radiation), solving thermal conduction accurately is difficult, because modeling of “correct shape” and setting of coefficient of thermal conductivity for each material need many of time and efforts at the early stage of development. Correct shape means that each part should be attached correctly to generate the solid mesh with high quality. Therefore, it is more efficient and realistic method to predict the air temperature distribution around the rubber/resin part instead of using the surface temperature at the preliminary design stage.

The dynamic performance of battery electric vehicles (BEV) is affected by battery output power, which depends on state of charge (SOC) and the temperature of battery cells. The temperature of the batteries varies in particular with the environment, in which the user stores the vehicle, and the battery output power. It is therefore necessary to employ thermal management systems that can control the battery temperature within the optimal range under severely hot and cold conditions in BEVs. A highly sophisticated thermal management system and its operation strategy were developed to fulfill the above requirements. The powertrain components to be thermo-controlled were located into two coolant circuits having different temperature range. The compact and efficient front-end heat exchangers were designed to optimally balance the cooling performance of powertrain, cabin comfort, vehicle aerodynamics and the vehicle design.

Downsizing and slowing down of engine speed reduce mechanical losses and improve fuel economy. However, they exacerbate lubrication condition. The oil film thickness of the bearing of the small end of the connecting rod, which was one of the sliding surfaces with the severest lubrication condition in a diesel engine, was measured in this study to clarify the lubrication condition. Optical fibers were embedded in the bearing, and oil film was measured by means of the laser induced fluorescence method. It was found that oil film thickness was affected combustion gas pressure and distortion of the piston pin.

Clarifying the mechanism of oil transporting upward at around an oil ring of a piston is necessary for calculating engine oil consumption. This study aimed to clarify the function of oil drain holes in the oil ring groove of a piston. The effect of the oil drain holes in the groove on oil consumption was investigated. Also the pressure balance around the oil ring was measured. It was found that the drain holes in the groove lowered oil consumption. It was assumed that lower pressure in the groove with the drain holes caused less oil flow into the third land.

The authors have previously proposed a plume ignition and combustion concept (i.e., PCC combustion), in which a hydrogen fuel is directly injected to the combustion chamber in the latter half of compression stroke and forms a richer mixture plume. By combusting the plume, both cooling losses and NOx formation are reduced. In this study, thermal efficiency was substantially improved and NOx formation was reduced with PCC combustion by optimizing such characteristics as direction and diameter of the jets in combination with combustion of lean mixture. Output power declined due to the lean mixture, however, was recovered by supercharging while keeping NOx emissions at the same level. Thermal efficiency was further improved by slightly re-optimizing the jet conditions.

The friction reduction of a piston/piston-ring assembly is effective for fuel economy of an engine, and a friction measurement method is required for developing low friction pistons, piston-rings and lubricants. Most suitable method for friction measurement for piston assemblies is “floating liner method”. It has load sensors between a floating cylinder liner and cylinder block, and the sensors can detect friction force acting on the liner. Many apparatuses using floating liner method are developed. They are roughly divided to two categories. In one of them, floating liner is supported by load-washers which axis is set parallel to the center line of the cylinder liner. In another type, floating liner is supported by three-component force sensors installed on the side face of the cylinder. In this paper, five types of floating liner devices were compared.

Turbine housings in car engine turbochargers, which use costly stainless steel castings, account for nearly 50% of the parts cost of a turbocharger. They are also the component which controls the competitiveness of the turbocharger, in terms of both function and cost. In this research, focusing on thermal fatigue resistance which is one of the main functions demanded of a turbine housing, achieving reduction in wall thickness while securing sufficient thermal fatigue resistance, it is possible to reduce the amount of material used in the turbine housing and aimed for cost reduction. Therefore, we built a method to quantitatively predict, using 3D FEM, the lifespan from the initiation of thermal fatigue cracking to the formation of a penetrating crack which leads to gas leakage.

In engines having an inline four cylinder DOHC configuration, the rotational vibrations of camshaft increase at high engine speeds above 10000 rpm, causing an increase of tension in the cam chain. It is therefore difficult to realize an optimum designing of a cam chain system when the durability has to be taken into considerations. Using the simulation we analyzed in this research how the rotational vibrations and tension increase at high engine speeds in an inline four cylinder DOHC engine. As its consequent, it is understood that the increases of rotational vibrations and tension caused by the resonance of the spring mass vibration system in which the cam chain serves as springs and the camshafts as the equivalent masses. Also it is found out that the vibration system is of a unique non-linear type in which the resonance of the fourth order frequency is also excited by the crankshaft torque fluctuations of the second order frequency.

In order to verify cooling loss reduction effect of internal combustion engine, method for measuring wall surface temperature and heat flux with high accuracy is required. Various methods have been proposed for measuring the cooling loss from the combustion gas to the combustion chamber wall, newly coaxial type thin-film temperature sensor was developed for wall temperature and heat flux measurement by the authors. This sensor consists of thin-film and body and center wire have three junction positions in the case where three materials are different. Therefore, it is necessary to use the same materials for thin-film and body or thin-film and center wire to make two junction points. In this study, sputtering method that can be formed various kinds of alloy materials and film thickness of 0.1~1μm on the sensor surface was chosen.

We studied a simple and cost effective controlled auto ignition (CAI) combustion engine in order to achieve simultaneous reduction of NOx and soot, which are issues in diffusion combustion. The engine type was a uniflow scavenging 2-stroke engine, and the fuel used was diesel, as is common in diesel engines. We examined the position of the injector that effectively forms the premixture and realized stable operation with diesel fuel by the low pressure fuel injection device for port fuel injection (PFI), and it was found that the CAI combustion ignition timing can be controlled through setting the air/fuel ratio that obtains the optimal ignition timing per operation conditions.

The piston rings, the engine sliding parts, are required to further contribute on mechanical loss reduction in order to improve fuel efficiency. However, many cases of the abnormal combustion due to oil upward flow, as well as the increase in oil consumption have been reported. Therefore, elucidation of the mechanism of those phenomena is still an urgent task. It is widely known that the distribution of the sliding face pressure in between the piston ring and the cylinder bore largely influence the oil flow via the sliding face of the piston ring. However, there are many unknown aspects in this field. Therefore, verification of the sliding face pressure during the actual operation is necessary in order to elucidate the mechanism of oil consumption. The thin-film sensor, since it has little influence on shape, is widely used as a measurement method of the sliding face pressure between two different faces, however this method has never been applied to the piston ring in the past.

The purpose of this research was to predict the amount of wear on exhaust valve seats in durability testing of gasoline engines. Through the rig wear test, a prediction formula was constructed with multiple factors as variables. In the rig test, the wear rate was measured in some cases where a number of factors of valve seat wear were within a certain range. Through these tests, sensitivity for each factor was determined from the measured wear data, and then a prediction formula for calculating the amount of wear was constructed with high sensitivity factors. Combining the wear amount calculation formula with the operation mode of the actual engine, the wear amount in that mode can be calculated. The calculated wear amount showed a high correlation with the wear amount measured in bench tests and the wear amount measured in vehicle tests.

Increasing the strength of materials is effective in reducing weight and boosting structural part performance, but there are cases in where the residual strain generated during the process of manufacturing of high-strength materials results in a decline of durability. It is therefore important to understand how the residual strain in a manufactured component changes due to processing conditions. In the case of a connecting rod, because the strain load on the connecting rod rib sections is high, it is necessary to clearly understand the distribution of strain in the ribs. However, because residual strain is generally measured by using X-ray diffractometers or strain gauges, measurements are limited to the surface layer of the parts. Neutron beams, however, have a higher penetration depth than X-rays, allowing for strain measurement in the bulk material.

Along with the suspension improvement in these two decades, it is well known that the suspension friction force became one of major parameters to affect ride comfort performance. However, it was difficult to carry out quantitative prediction on ride comfort improvement against friction force change with high correlation. It was difficult to analyze correlation between actual vehicle performance and simulation since there were difficulties in controlling damping force and friction individually. On the other hand, magneto-rheological shock absorber (MR Shock) has had several applications and widely spread to passenger vehicles. The large variation and high response of damping force especially in slow piston speed region contributes to achieve an excellent vehicle dynamics performance. However, MR Shock shows the high friction characteristics, due to the unique sliding regime of internal parts. It is said that this high friction characteristic is causing obstacles in ride-comfort.