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Blended fuels of turpentine oil and castor oil, palm oil, and sunflower oil have been used as alternative fuels in compression ignition, pre-combustion chamber CI engines. The effect of these blended fuels on engine performance, exhaust emissions, and combustion process have also been investigated. Here, the effect of higher injection valve opening pressures with blended fuels was investigated, and the behavior of the fuel spray at the higher injection valve opening pressure were observed by a Liquid-Liquid Injection Technique. The fuel injection rate at the higher injection valve opening pressure was measured by the Bosch method.

The engine performance, combustion characteristics and the effect of injection timing differences of a prechamber-type diesel engine operated by Diesel-fuel and methanol were investigated. When the Diesel-fuel is used as a pilot fuel, the ignition lag was mainly controlled by the Diesel-fuel. The maximum thermal efficiency occurs with the optimum main methanol injection timing. The optimum methanol injection timing is about 2 to 3 degrees crank angle before the ignition, as methanol vapor is required for smooth combustion. This was determined from results showing that the methanol combustion was initiated by flame propagation from the combustion of Diesel-fuel. It is advantageous that parts of the Diesel-fuel and methanol sprays be mixed.

The engine performance, combustion characteristics and exhaust emission of pre-chamber type compression ignition engine operated by various biomass fuels were investigated experimentally. The biomass fuel investigated in this report are an emulsified fuel made with gas oil and hydrous ethanol or hydrous methanol, an emulsified fuel made with hydrous methanol and rape-seed oil, and neat rape-seed oil, and gas oil. There are small deviations of the experimental results between the biomass fuels, however, the general tendencies of the engine performances and exhaust gas characteristics operated by biomass fuels are as follows: The brake thermal efficiency during biomass fuel operation becomes maximum at a certain injection timing as well as those of the gas oil operation. And this injection timing is advanced with increasing the biomass content in the fuel.

So far the studies on the dynamic characteristic of internal combustion engines have been mainly carried out on the governor system and have led to development of a mathematical model more efficient for simulation and control purpose. But, there are still uncertain dynamic behaviors of the engine. The experiment and analysis on the transfer characteristic of effective torque and engine speed under a changing fuel feed quantity or brake load were carried out by using the frequency response and step response methods. Consequently, it was confirmed that the transfer response of effective torque and engine speed to the changes in fuel feed quantity or brake load comprises a response time lag and its time constant is variable with the operating condition of the engine.

If the water/gas-oil-emulsion fuel is to be used in a compression ignition engine, it is necessary not only to carry out directly engine experiment but also to determine the characteristics of so-called mixture formation process, including those of fluidity, spray mode, injection rate and evaporation in high-temperature environment and on high-temperature wall as well as the influence of these characteristics on engine performance. In this report, the authors have experimentally investigated on the physical properties and injection characteristics of water/gas oil-emulsion fuel (W/O).

To determine definitely the transient characteristics of smoke emission on a Diesel engine, it is necessary to know those of each power transmission elements including its fuel injection system, combustion process, engine rotating system and its friction losses. Nevertheless, have been so far studied, it is unclearly about the relations the engine performance, smoke characteristics and influence of operating conditions, especially on the two-cycle engine. Therefore, the authors carried out the experiments while stepwise changing its brake load and fuel pump rack, respectively, to examine the effects of the operating conditions on the exhaust smoke density under transient operations.

In a small-type spark ignition engine with a carburetor, the mixture strength charged into a cylinder, that is, the combustion state and the exhaust emissions are remarkable influenced by instantaneous behavior of the fuel liquid-film flow on the inner wall of intake pipe, during transient running. Accordingly, the authors carried out some experiments in order to explicate the instantaneous mixture formation in cylinder, and go a step further, they had numerically analysed on the model of fuel supply system during the transient operation as the carburetor's throttle valve is stepwise changed.

In a two-stroke cycle engine, it is impossible to except the effect of engine brake, owing to its structure. However, since the necessity of engine brake has increased with increasing the vehicle speed, and with increasing the complexity of traffic problems, it is demanded to solved. For this reason, the authors investigated the mean frictional loss pressure of engine, and the effect of releasers on the engine brake with a crankcase-compression two-stroke cycle engine. The results, one of the weak points on a two-stroke cycle engine be solved completely by the application of releaser.

In a gasoline engine, it is most important to recognize the behavior of fuel liquid-film flow in the intake pipe. Accordingly, the authors have tried to measure directly the amount of fuel liquid-film flow by means of the each separator inserted in the intake manifold and at the same tine to record the instantaneous behavior of liquid-film thickness from the change in electric conductivity. Especially, the experimental results on the measuring method of fuel liquid-film thickness will be described in this paper.

Taking note of the value of the maximum delivery ratio Km produced by the inertia effect, the authors qualitatively considered the influences of the atmospheric conditions and the engine factors to compare them with the experimental. It is ascertained that the value od maximum delivery ratio depends on the inertia effect and the theoretical results correspond fairly well with those of the experimental value.