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Significant advancements have been made in recent years in the development of combustion system for spark-ignition direct-injection engine (SIDI) engine, which have resulted in fuel economy saving, low exhaust emission and a significant power advantage under homogeneous fuel operation, compared to equivalent PFI (Port Fuel Injection) engines. Key challenge for small-displacement SIDI engine, which has short path lengths between the injector and piston and is therefore prone to increase wall wetting, is minimizing or eliminating the amount of wall wetting to reduce smoke emission. A side-injection system also requires sufficient spray penetration to fully transport fuel to the centrally mounted spark plug at the desired injection timing event.

To suppress knock in small gasoline engines, the coolant flow of a single-cylinder engine was improved by using two methods: a multi-dimensional knock prediction method combining a Flamelet model with a simple chemical kinetics model, and a method for predicting combustion chamber wall temperature based on a thermal fluid calculation that coupled the engine coolant and the engine structure (engine head, cylinder block, and head gasket). Through these calculations as well as the measurement of wall temperatures and the analysis of combustion by experiments, the effects of wall temperature distribution and consequent unburnt gas temperature distribution on knock onset timing and location were examined. Furthermore, a study was made to develop a method for cooling the head side, which was more effective to suppress knock: the head gasket shape was modified to change the coolant flow and thereby improve the distribution of wall temperatures on the head side.

The purpose of this study was to examine the cause of fluctuations in combustion. It is important to understand the changes that occur in flame kernel development and in flame propagation during cyclic variation. In this study, a comparison was made between time-series variations in OH emission with THC concentration, and the intensity of the combustion reaction and the direction of flame propagation are also discussed. Early flame development and cyclic variation at an early stage of combustion were demonstrated by simultaneously measuring a two-dimensional image of flame emission and the time-series variation of local flame emission. The instantaneous intensity at Cassegrain measurement point agreed with the intensity of time-series variation in local flame propagation at CCD recorded timing. Variations in THC concentration in the cylinder were compared with time-series variations in local flame emission.

To improve the accuracy of engine vibration analysis, the bolt model which fastens an engine head and an engine block had been developed. In the conventional method of engine vibration analysis, the bolt was modeled with a rigid bar. However, it is seen that the power plant rigidity becomes higher in proportion to the rigid bar bolt length. So, to precisely predict the vibration property of engine parts, the elastic deformation of the bolt was considered in this paper. It is known that the parameters, which are Young's modulus, the length of bolts, the distance between bolts, the area of contact plane, the tightening torque and so on, have a great influence on the performance of the engine vibration model. This paper describes a study of FE bolt model to correlate eigenvalue and mode shapes with the test result. The effects of following parameters were investigated: 1) Bolt model with elastic material 2) Rigidity of bolted-connection in tightening plane.

Superior fuel economy was achieved for a small-displacement spark-ignition direct-injection (SIDI) engine by optimizing the stratified combustion operation. The optimization was performed using computational analyses and subsequently testing the most promising configurations experimentally. The fuel economy savings are achieved by the use of a multihole injector with novel spray shape, which allows ultra-lean stratification for a wide range of part-load operating conditions without compromising smoke and hydrocarbon emissions. In this regard, a key challenge for wall-controlled SIDI engines is the minimization of wall wetting to prevent smoke, which may require advanced injection timings, while at the same time minimizing hydrocarbon emissions, which may require retarding injection and thereby preventing over-mixing of the fuel vapor.

An oil-cooled engine has been developing to achieve better warm-up performance. The oil-cooled engine has an oil jacket that pass through around the exhaust port and the cylinder liner. Fins were installed inside the oil jacket to enhance cooling performance. The result of a bench test shows that the fins enhance the cooling performance with slight loss of warm-up performance. The aim of this study is to clarify effects of the fins. This study conducted two simulations. One is a cooling simulation that was conducted to clarify the reason why the fins enhanced the cooling performance. The other is a warm-up simulation that was conducted to clarify the reason why the fins almost maintained the warm-up performance. The cooling simulation was conducted by steady flow simulation. It simulated a full-load operation of the bench test. It compared converged temperature between the engines with/without the fins. The warm-up simulation was conducted by unsteady flow simulation.

One issue of Homogeneous Charge Compression Ignition (HCCI) engines that should be addressed is to suppress rapid combustion in the high-load region. Supercharging the intake air so as to form a leaner mixture is one way of moderating HCCI combustion. However, the specific effect of supercharging on moderating HCCI combustion and the mechanism involved are not fully understood yet. Therefore, experiments were conducted in this study that were designed to moderate rapid combustion in a test HCCI engine by supercharging the air inducted into the cylinder. The engine was operated under high-load levels in a supercharged state in order to make clear the effect of supercharging on expanding the stable operating region in the high-load range. HCCI combustion was investigated under these conditions by making in-cylinder spectroscopic measurements and by analyzing the exhaust gas using Fourier transform infrared (FT-IR) spectroscopy.

This paper discusses the prediction method of engine mount vibration using multi body simulation (MBS) with FE models in power plant assembly. In this analysis, some parts of the power plant were modeled with shell type elements and solid type elements, and modal parameters from FEA were imported into MBS, which method is called “Component Mode Synthesis”. For this analysis, the computational models of Suzuki 660cc in-line 3-cylinder engine with 4-speed automatic transmission were used. The flexibility of some engine parts was considered using FE models regarding the cylinder block, the crankshaft, the transmission case, etc. Also the properties of stiffness and viscous damping of the engine mount bushings were considered and the properties of the hydrodynamic oil film at the journal bearings were modeled with “Enhanced Short Bearing Model”. Accelerations at each engine mount were calculated.