Effect of Fuel Injector Location and Nozzle-Hole Orientation on Mixture Formation in a GDI Engine: A CFD Analysis 2018-01-0201

Gasoline direct injection (GDI) engines have gained popularity in the recent times because of lower fuel consumption and exhaust emissions compared to that of the conventional port fuel injection (PFI) engine. But, in these engines, the mixture formation plays an important role which affects combustion, performance and emission characteristics of the engine. The mixture formation, in turn, depends on many factors of which fuel injector location and orientation are most important parameters. Therefore, in this study, an attempt has been made to understand the effect of fuel injector location and nozzle-hole orientation on the mixture formation, performance and emission characteristics of a GDI engine. The mixture stratification inside the combustion chamber is characterized by a parameter called “stratification index” which is based on average equivalence ratio at different zones in the combustion chamber. The analysis is carried out on a four-stroke wall-guided GDI engine by computational fluid dynamics (CFD) analysis using CONVERGE software. The spray breakup model used, in this study, is validated with the available experimental results from the literature to the extent possible. The analysis is carried out for four nozzle-hole orientations at two different fuel injector locations. All the CFD simulations are carried out at an engine speed of 2000 rpm, with an overall equivalence ratio of about 0.65±0.05. The results show that at the original injector location, with smaller nozzle-hole diameter, for all the nozzle-hole orientations better mixture formation, higher Indicated mean effective pressure (IMEP) and lower HC emissions are obtained. But, at the new fuel injector location, better mixture formation, higher IMEP, and lower HC emissions are obtained with the larger nozzle-hole diameter with the which is also indicated by stratification index closer to 1.