Abstract
Experimental research was conducted on a rapid compression and expansion machine (RCEM) that has characteristics similar to a gasoline compression ignition (GCI) engine, using two gasoline–biodiesel (GB) blends—10% and 20% volume—with fuel injection pressures varying from 800 to 1400 bar. Biodiesel content lower than GB10 will result in misfires at fuel injection pressures of 800 bar and 1000 bar due to long ignition delays; this is why GB10 was the lowest biodiesel blend used in this experiment. The engine compression ratio was set at 16, with 1000 µs of injection duration and 12.5 degree before top dead center (BTDC). The results show that the GB20 had a shorter ignition delay than the GB10, and that increasing the injection pressure expedited the autoignition. The rate of heat release for both fuel mixes increased with increasing fuel injection pressure, although there was a degradation of heat release rate for the GB20 at the 1400-bar fuel injection rate due to retarded in-cylinder peak pressure at 0.24 degree BTDC. As the ignition delay decreased, the brake thermal efficiency (BTE) decreased and the fuel consumption increased due to the lack of air–fuel mixture homogeneity caused by the short ignition delay. At the fuel injection rate of 800 bar, the GB10 showed the worst efficiency due to the late start of combustion at 3.5 degree after top dead center (ATDC).
Highlights
In recent years, economic improvements have increased consumer purchasing power, leading to increased demand for vehicles and electric devices around the world, which will significantly increase the use of fossil fuels
It injects fuel near the top dead center (TDC: the position of an engine’s piston when it is at the very top of its stroke), which means that only compressed air is used in the compression step
The experiment was carried out on an rapid compression and expansion machine (RCEM) that was designed to replicate the phenomena in one cycle of a compression ignition (CI) system
Summary
Economic improvements have increased consumer purchasing power, leading to increased demand for vehicles and electric devices around the world, which will significantly increase the use of fossil fuels. Gasoline compression ignition (GCI) engines are promising because of their low emissions and high thermal efficiency characteristics, attracting considerable research interest [5,6]. Adams et al [13] investigated the combustion behavior of GCI engines, using a mixed fuel of gasoline and biodiesel They demonstrated that adding biodiesel to conventional petroleum diesel increases the combustion stability and decreases the required intake temperature. This enhances the vapor capability of the fuel and produces more complete combustion This experiment analyzes the effect of high injection pressure on a GCI engine that uses gasoline as the main fuel. By varying the injection pressure for the two different fuel mixtures, the combustion characteristics could be analyzed
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