Numerical study on the injection strategy on combustion and emission characteristics of a non-road diesel engine under different altitude conditions

Abstract

The combustion and emission characteristics in internal combustion engine were found to deteriorate due to poor spray atomization in the cylinder at high altitude conditions. Improving the fuel mixing efficiency method like two-stage injection strategy could elevate engine power output and reduce harmful substance emissions. A non-road diesel engine operating at different altitudes were investigated. Meanwhile, a two-times orthogonal experiment optimization was proposed to optimize the injection strategy for improving the combustion and emission characteristics. Results showed that the combustion phase can be advanced, the equivalence ratio in the cylinder becomes uniform, and the combustion was more sufficient, which was conducive to improving the power performance and fuel economy of the engine at high altitude. The emissions of HC, SOOT, and CO, especially carbon smoke emissions, were effectively reduced after two times of OED optimization, with only a small increase in NOx emissions, indicating that, the traditional trade-off between carbon smoke and NOx were broken to a certain extent by using two OED optimizations. The conclusion of the present study states that the two-stage injection strategy combining with two OED can solve the problems of power reduction and increased pollution emissions caused by insufficient intake of air in the engine.