Abstract

This paper presents a numerical investigation carried out to determine the effects of second and third injection timing on combustion characteristics and mixture formation of a GDI (gasoline direct injection) engine by comparing conical spray against multi-hole spray. The results showed that at 80% of the engine full load for 2000 r/min, the difference in mixture distribution between the two sprays was obvious with double and triple injection strategies. With the second injection timing from 140° CA delay to 170° CA, the in-cylinder pressure, the in-cylinder temperature, and the heat release rate of the conical spray increased by 20.8%, 9.8%, and 30.7%. That of the multi-hole spray decreased by 30.7%, 13.6%, and 37.8%. The delay of the injection time reduced the performance of the engine with the multi-hole spray, and the performance of the multi-hole spray was obviously in the simulation of the triple injection strategy. However, for the conical spray, the application of the triple injection strategy increased the temperature and pressure compared with the double injection strategy.

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