Experimental investigation of gasoline fumigation for different compression ratios in a diesel engine

Abstract

In this study, the effects of gasoline injection into intake air (gasoline fumigation, GF) on the brake specific fuel consumption (bsfc), combustion characteristics such as excess air coefficient and exhaust temperature (Tex), nitrogen oxides (NOx) and opacity were experimentally investigated in an automotive diesel engine. One of the main objectives of this study is to experimentally investigate the effects of GF at the same engine for different compression ratios (CRs). The original CR of the engine is 18.25 (high CR, HCR). Here, CR of the engine was changed to 17 (low CR, LCR) by changing the cylinder head gasket thickness. Thus, experiments were performed for two different CRs such as 18.25 and 17 under five different loads such as 150, 135, 120, 105, and 90 Nm at 2000 rpm and under five different load such as 120, 105, 90, 75, and 60 Nm at 4000 rpm for various gasoline fumigation ratios (GFs). In this study; approximately 5, 10, 15 and 20 %, (by vol.) gasoline was injected into intake air by using an adapted carburetor. The test results showed that GF decreases bsfc for all of the working conditions. NOx emissions decrease with GF for high CR at 2000 rpm, but it generally increases for low CR (17) under high loads. NOx emissions increase significantly with GF for both CRs at 4000 rpm. Opacity decreases at low GFs, but it increases at high GFs. In general, the results of GF at the original CR (HCR) are better than the LCR. However, in the present study, no arrangement has been made in the electronic control unit (ECU) of the engine for changed CR.