Study on Effect of Engine Operating Parameters on Flame Characteristics 2015-01-0749
In gasoline direct injection (GDI) engines, air-fuel mixture homogeneity plays a major role on engine performance, especially in combustion and emission characteristics. The performance of the engine largely depends on various engine operating parameters viz., start of injection, duration of injection and spark timing. In order to achieve faster results CFD is becoming a handy tool to optimize and understand the effect of these parameters. Therefore, this study aims on evaluating the two injection parameters viz., single and split injection to evaluate different flame characteristics. Novelty in this study is to define five different parameters which are called α, β, γ, δ and η the details of which are explained in the paper. In order to understand the flame characteristics, these five parameters are found to be very useful.
In the present study, a single-cylinder, two-valve, four- stroke engine which is used in two-wheelers in India is considered for carrying out the CFD analysis. An air-assisted direct in-cylinder fuel injection is considered for the analysis and experiments. Commercial software is used for carrying out the combustion analysis. For specifying the boundary conditions, pressure measurements were made in an actual engine. In order to study the effect of engine performance three different start of injection, duration of injection, spark timings, fuel split ratios are considered. In order to validate the CFD results, measurements of output power is made on the actual engine and is compared with the CFD predictions.
From the results obtained, it is concluded that for better mixing and good combustion, for single injection case, SOI of 198 CAD and 3 ms injection duration, with 20° spark advance found to be the best. Similarly for split injection case, fuel split ratios of 2:1 with SOI of 45 and 250 CADs for first and second injections respectively are found to be the best.