Effect of the Injection Method in DI CNG Engine on the Flame Propagation Process and Engine Performance

Abstract

Test with optical single cylinder engine, in-cylinder with twin jet layout, dual spark plug ignition conditions, with the combination of calculation of 3D simulation software and experiment, analyzed the effect of different mixture concentration distribution characteristics of different jet and different ignition on the flame propagation, the temperature field, the lean combustion process and NOx emission characteristics. The result showed that the mixture concentration gradient near the spark plug in the organized lean combustion process had a great effect on the flame propagation and combustion stability. The greater the concentration gradient was, the circulation changes would be smaller, the combustion would be more stable, but the NOx emissions would increase; With the use of dual-point ignition, the air flow movement in the cylinder had a “traction” of the incipient flame, the difference moment of formation and of two flame and the interaction of the two flame affected the whole flame propagation; The NO was generated first when the temperature of cylinder was greater than 2,000 K and equivalence ratio was at the range of 0.8–1, within the range of the concentration of the mixture, the increasing of the temperature led to the significantly improving of the NO formation rate, and the maximum NO production rate appeared after the peak of the heat release rate. The thin out mixture led to the decreasing of the peak of heat release rate and the lag of the crank angle corresponding to the position led to the decreasing of NO formation rate.

F2012-A01-027