Study on transient flow characteristics and measurement method for multi-point injection system of natural gas engine

Abstract

This paper presents an innovative measurement method of injection characteristics for the multi-point injection (MPI) system of the natural gas engine. The gas injection rate of different nozzle structures can be obtained by measuring the change of gas pressure in the measurement chamber. Base on this, the gas injection characteristics and their variations under different nozzle structures were studied. The results show that, with the increase of injection pressure, the beginning injection moment hysteresis and the end injection moment advances. When the energizing time is less than 6 ms, the injection mass decreases with the increase of injection pressure, and the injection pressure becomes the dominant hindering factor affecting the increase of injection mass. Due to the circumferential open-hole injection tube structure can not directly use the axial momentum of the gas flow along the tube, the injection duration is longer than that of the straight-through injection tube structure.