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In a motorcycle gasoline engine, the port fuel injection system is rapidly spread. Compared to an automotive engine, the injected fuel does not impinge on the intake valve due to space restriction to install the injector. In addition, as the air flow inside the intake pipe may become very fast and has large cycle-to-cycle variation, it is not well found how the injector should be installed in the intake pipe to prepare “good” fuel-air mixture inside the intake pipe. In this study, the formation process of the fuel-air mixture is measured by using ILIDS system that is a 2-D droplets' size and velocity measurement system with high spatial resolution. Experiments with changing conditions such as flow speed and injection direction are carried out. As a result, the effects of injection direction, ambient flow speed and wall roughness on the fuel-air mixture formation process was examined, considering the three conditions of cold start, light to medium load operation and high load operation.

The objective of this study is to develop a practical technique to achieve HCCI operation with wide operation range. To attain this objective, the authors previously proposed the blowdown supercharge (BDSC) system and demonstrated the potential of the BDSC system to extend the high load HCCI operational limit. In this study, experimental works were conducted with focusing on improvement of combustion stability at low load operation and the reduction in cylinder to cylinder variation in ignition timing of multi-cylinder HCCI operation using the BDSC system. The experiments were conducted using a slightly modified production four-cylinder gasoline engine with compression ratio of about 12 at constant engine speed of 1500 rpm. The test fuel used was commercial gasoline which has RON of 91. To improve combustion stability at low load operation, the valve actuation strategy for the BDSC system was newly proposed and experimentally examined.

The variable valve lift and duration (in the following: VVLD) devices, some have been mass-produced already in the world, are necessary to be assembled with the variable cam phaser (in the following: VCP) to optimize open and close valve timing. On the other hand, with the variable valve phase and lift (in the following: VVPL) mechanism, the valve event is advanced with decreasing the valve lift and duration. Hence, no additional VCP is required when using the VVPL for throttle-less operation. A new VVPL has been developed as a mechanical, swing-cam actuation mechanism. The mechanisms of the conventional production VVLD devices are investigated and the functional analysis of the possible mechanisms is carried out to identify and design a simple mechanism for the new VVPL. The designed VVPL system is capable of continuously varying the valve lift from 0 mm to 10 mm, with the higher valve lift for any of the given duration.

Research into HCCI technology has been based on gasoline or diesel engines, using a large amount of EGR and supercharging(1). In this paper, a new method is introduced, which realizes heavy internal EGR and supercharging simultaneously using exhaust blow down pressure without a super charger. A four cylinder HCCI gasoline engine is initially introduced with a BDSCac (Blow Down Super-Charging by accumulation) system which achieves a large amount of EGR and simultaneously supercharging without a supercharger. This is brought about by accumulating the exhaust blow down pressure in one of two separate exhaust systems, and its characteristics are explained. Further research has been made into a new method to achieve a similar effect as BDSCac by using a common exhaust system and a simple mechanical cam-driven variable valve actuation system. The system is called BDSCpw (Blow Down Super-Charging by pressure wave).

In this study, the characteristics of diesel spray droplets, such as the velocity and the diameter were simultaneously measured by using an improved ILIDS (Interferometric Laser Imaging for Droplet Sizing) method on a 2D plane to evaluate the droplet breakup modeling. In numerical analysis, DDM (Discrete Droplet Model) was employed with sub-models such as droplet breakup, droplet drag force and turbulence. Experiments have been performed with an accumulator type unit-injector system and a constant-volume high-pressure vessel under the condition of quiescent ambient gas. The injection pressure and ambient gas pressure were set up to 100 MPa and 0.1 / 1 MPa, respectively. The nozzle orifice diameter was 0.244 mm with a single hole. The measurement region was chosen at 40 ∼ 60 mm from the nozzle-tip. Numerical analysis of diesel sprays was conducted and the results were compared to the measured results.

Reduction of transmission error by gear tooth profile optimization and tuning of gear resonance modes are known as effective methods for gear noise reduction. This paper concentrates on structuring a process for reducing gear noise using the latter method. The procedure comprises a study of gear noise mechanism from transmission error to radiation noise, an application of Steyer's method in gear frequency analysis and implementation of an invented device called “noise reduction ring”. This inexpensive and practical ring reduces gear noise drastically by 10dB, which is predicted by the simulation and verified by the experiment.

In order to minimize power train length, it is required for transmission components to layout compact. The requirement results in thinner and larger transfer gears, which are disadvantageous for gear noise. On the other hand, improvement of gear accuracy and/or vehicle interior noise increases sensitivity to manufacturing variation. It tends to appear noisiness by transmission unit variation. To prevent such gear noise problem, we made detailed investigation by both several tests and simulation, i.e. noise measurement, shaker test, running gear vibration measurement and FE Model analysis. This paper describes the experimental analysis of gear noise generation mechanism of transmission with thin and large diameter gear and its prediction method. It was found that gear web out-of-plane vibration modes are closely related to vibration transfer to the mission case. Planarly non-symmetric modes have dominant effect for case dynamic excitation by gear engagement.

To clarify the fuel spray formation process for a swirl-type injector, numerical analyses using both VOF (Volume Of Fluid) model and DDM (Discrete Droplet Model) method are carried out. VOF model is used to simulate the two-phase flow inside the injector and also the liquid film formation process outside the nozzle, while DDM is used to simulate a free fuel spray in a constant-volume chamber using initial conditions deduced by empirical equations or calculated results of VOF model. As a result, fairly good agreement of spray characteristics, such as the spray shape and the tip penetration between the experiment and calculation can be obtained by adopting initial conditions calculated by VOF model. However, improvements of droplet breakup models and of two-phase flow calculation method would be required to achieve quantitatively good agreement.

A gasoline engine with an entirely new combustion cycle deriving from Miller Cycle is developed. By delaying closing timing of intake valve and with new Lysholm Compressor which provides higher boost pressure, engine knocking is avoided while high compression ratio is maintained and approximately 1.5 times larger toque than that of a naturally aspirated(NA) engine of the same displacement is realized. This V6 Miller Cycle gasoline engine can be the alternative to a larger displacement NA engine because of its equivalent torque performance and its lower fuel consumption by the effect of smaller displacement.

High performance automotive engines are required to overcome the environmental problems and to achieve less fuel consumption. For the realization of such engines, the high efficiency Lysholm (screw type) compressor was developed and its mass-production has been started, which can produce high pressure boost for the engine in whole engine speed range. This compressor has achieved high volumetric efficiency and the adequate durability for automotive use has also been confirmed through various kinds of tests.

The analysis of spray characteristics is important to examine the combustion characteristics of DI (Direct Injection) gasoline engines because the fuel-air mixture formation is controlled by spray characteristics and in-cylinder gas motion. However, the mixture formation process has not been well clarified yet. In this study, the characteristics of a fan-shaped spray caused from a slit-type injector, such as the droplet size, its velocity and the droplet distribution were simultaneously measured on a 2D plane by using improved ILIDS (Interferometric Laser Imaging for Droplet Sizing) method. ILIDS method is an optical measurement technique using interference fringes by illuminating a transparent spherical particles with a coherent laser light. In the measurement of the wall-impinging spray, effects of the distance to the wall and the wall temperature on the spray characteristics were investigated.

Post-oxidation has been used to enhance the chemical reactions in the exhaust gas pipes, leading to the activations of the turbocharger and catalyst at cold state. In this research, a detailed study of the various mechanisms for post-oxidation is performed. For the post-oxidation activation, the unburned gas species (CO, THC, H2) in the exhaust manifold must be produced by some methodologies, such as scavenging, lambda-split, and post-injection. The required amount of O2 concentration can be either supplied by the scavenging (valve overlap tuning) or the secondary air injection (SAI) system. Mixing the species is also an important key to promoting post- oxidation, and an internal bypass adapter with a modified exhaust adapter shape was developed and evaluated.