Effect of Injector Type and Intake Boosting on Combustion, Performance, and Emission Characteristics of a Spray-Guided Gasoline Direct Injection Engine—A Computational Fluid Dynamics Study

Abstract

In general, GDI engines operate with stratified mixtures at part-load conditions enabling increased fuel economy with high power output, however, with a compensation of increased soot emissions at part-load conditions. This is mainly due to improper in-cylinder mixing of air and fuel leading to a sharp decrease in gradient of reactant destruction term and heat release rate (HRR), resulting in flame quenching. The type of fuel injector and engine operating conditions play a significant role in the in-cylinder mixture formation. Therefore, in this study, a CFD analysis is utilized to compare the effect of stratified mixture combustion with multi-hole solid-cone and hollow-cone injectors on the performance and emission characteristics of a spray-guided GDI engine. The equivalence ratio (ϕ) from 0.6 to 0.8 with the constant engine speed of 2000 rev/min is considered. For both injectors, the fuel injection pressure of 200 bar is used with 60° spray-cone angles. For lean boosting conditions, intake pressures of 1 bar, 1.2 bar, and 1.4 bar are maintained for 0.8 equivalence ratio cases for both injectors. Results from the CFD analysis are compared with those of the available experimental results with good agreement. Analyzing the results, naturally aspirated and intake boosting conditions for ϕ of 0.8, mixture distribution and flame propagation for the multi-hole solid injector are better than hollow-cone injector. Also, for the ϕ of 0.8, naturally aspirated mode, the soot emissions by the hollow-cone injector are higher by about 90%, and the NOx emissions are higher by about 19% compared to that of the multi-hole solid-cone injector. Under boosted intake pressure conditions, for the hollow-cone injector, the soot emissions are higher by about 97%–99%, and NOx emissions are higher by about 7%–6% compared to the multi-hole solid-cone injector. Also, HC and CO emissions are considerably lower for the hollow-cone injector than that of the multi-hole solid-cone injector.