缸内高压直喷天然气发动机的怠速排放特性

以一台缸内高压直喷天然气发动机为对象,在不同柴油轨压力及天然气喷射提前角条件下对CO、HC及NOx的排放量进行试验研究.结果表明:当发动机处于怠速运转,天然气在上止点附近喷入气缸时,3种轨压力下CO排放量的差异较小;当天然气喷射提前角推迟到上止点后一定角度时,CO的排放量随着柴油的轨压力升高而降低,当天然气喷射提前角提前到上止点前一定角度时,CO排放量则呈现出相反的变化趋势;随着天然气喷射提前角增大,3种轨压力下CO的排放量均降低;HC排放量随着柴油轨压力的升高而增加,随着天然气喷射提前角的增大而降低,且当柴油轨压力从18 MPa升到24 MPa时,HC的排放量增幅较大;NOx的排放量随着柴油轨压力的提高而升高,随着天然气喷射提前角的增大而升高,且当柴油轨压力从12 MPa升到18 MPa时,NOx的排放量增幅显著.

Idle Emission Characteristics of High-Pressure Direct-Injection Natural Gas Engine

Abstract： This paper studied the CO, HC and NOx emission characteristics of high-pressure direct-injection natural gas engine at different diesel rail pressures and gas injection timing by a series of experiments. The experimental results show that, at idle operation, diesel rail pressure has little influence on CO emissions when the gas is injected near top dead center (TDC). CO emissions decrease with the diesel rail pressure when the gas is injected at a certain angle after TDC and increase with the diesel rail pressure when the gas is injected at a certain angle before TDC. The advancing of gas injection results in lower CO emissions at three different diesel rail pressures. HC emissions increase with the rising of diesel rail pressure and reduce with the advancing of gas injection timing, both increasing significantly when the diesel rail pressure rises from 18 MPa to 24 MPa. NOx emissions increase with the advancing of gas injection, and increase markedly when the diesel rail pressure rises from 12 MPa to 18 MPa.