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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.

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.