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A direct fuel-injection two-stroke cycle engine operated with neat methanol was investigated. The engine performance, combustion and exhaust-gas characteristics were analyzed experimentally and compared for operation with a carburetor, EFI injection at the intake manifold, and EFI injection at the scavenging port. The power and the brake thermal efficiency of the direct fuel-injection engine were higher than those of engines operated with a carburetor and either of the two EFI methods. The exhausted unburnt fuel of the direct fuel-injection engine was lower than that for operation with a carburetor, and formaldehyde and the CO concentration were of the same level as for operation with the carburetor and EFI methods. The NOx concentration of the direct fuel-injection was half the level of the result of carburetor operation.

Under accelerating or decelerating operation, it is demanded to improve the performance and to reduce the exhaust smoke of diesel engines. Regarding the exhaust smoke regulation for a vehicle engine under transitional operation, the so-called free or controlled accelerating operation, are adopted as the simple measuring method. And the engine applied the construction or agricultural use is always operating under the load conditions of stepwise or periodical changes. For two-stroke cycle engines, in particular, the effects of operating conditions on the engine performance and the smoke character are unclear. In order to meet such demand, it is necessary to make clear the transitional character of each transfer element, i.e., the fuel injection system, the combustion process and the frictional loss.

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.

Under the accelerating or decelerating operation, it is demanded to improve the performance and reduce the exhaust smoke of diesel engines. Regarding the exhaust smoke regulation for a vehicle engine under transitional operation, the so-called free or controlled accelerating operation, are adopted as the simple measuring method. And the engine applied for the construction or agriculture is always operating under the load conditions of stepwise or periodical changes. For two-stroke engines, in particular, the effects of operating conditions on the engine performance and the smoke character are unclear. In order to meet such demand, it is necessary to make clear the transitional character of each transfer element, i.e., the fuel injection system, the combustion process and the frictional loss.

A two-stroke engine has various advantages. It is simple in structure, light in weight, high in mechanical efficiency, superior in accelerating ability, etc. However, its fuel consumption is bad, its combustibility under partial load is poor and it is usually accepted that its exhaust gas is problematic. With increasing traffic flow volume, it has become recently necessary to operate transiently each vehicle with frequent stops and starts, as well as decelerations and accelerations. From this standpoint, the authors have formed a simple dynamic model of two-stroke engine, and by means of simulation investigated how its performance can be improved while it is transiently operated, in combination with experiment. The results confirm that the calculations from the model coincide approximately with experiment. The influences of various factors on the performance have been revealed.

In this study, accordingly, methanol fuel was supplied in suction pipe with carburetor and with electronically-controlled fuel injector (EFI), which located in front of the suction valve, to clear experimentally the influence of various factors, such as the methanol-gasoline ratio (M/F), the difference in fuel feed system, the number of times of injection [ni], the injection timing (θinj), the engine speed (N), the volumetric efficiency (η v), the suction pipe wall temperature (tw), the water content in fuel (yw) etc., on the engine performance (the output and the thermal efficiency), the exhaust characteristics (NOx, CO, UBF and HCHO concentrations) and combustion variation as well as obtaining a guideline to establish the optimum condition. The authors will be report about the results of above-mentioned.

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.