Effect of intake temperature and coolant temperature with injection strategy on gasoline compression ignition combustion stability under the idle condition

Abstract

The gasoline compression ignition (GCI) is deemed to be one of the effective ways to achieve efficient and clean combustion. However, the low in-cylinder temperature under idle and low-load conditions leads to certain problems, such as difficulties in the ignition and unstable combustion. In this paper, based on a refitted single-cylinder diesel engine, the combustion stability of the GCI mode under idling speed and low-load conditions was studied. The combustion stability and thermal efficiency were improved by adjusting the intake temperature, the coolant temperature and the injection strategy. During the test, the engine speed was set to 800 rpm at the idle condition and 1300 rpm at the low-load condition, and the gross indicated mean effective pressure was 5.5 bar. The injection mode of the fuel was direct injection with one injector. The results indicated that when the injection timing was −15°CA ATDC, and the intake temperature was increased from 50°C to 60°C under the idle condition; the gross indicated thermal efficiency (ITEg) was 39.7%, an increase of 8.5%. Under the low-load condition, increasing the coolant temperature can improve the combustion stability. Specifically, when the coolant temperature was increased from 70°C to 90°C and the injection timing was −27°CA ATDC, an ITEg of 52.1% can be realized.