高压直喷天然气发动机HC排放

HC emissions of high pressure DI diesel pilot-ignited natural gas engine

为了研究直喷天然气发动机碳氢的排放规律和影响因素,以一台电控增压直喷天然气发动机为对象,在不同工况下进行实验测试.为了分析转速、负荷、轨压和燃料喷射时刻对碳氢生成的影响,分别设计3组对比实验,在实验过程中采集示功图和碳氢排放,结合燃烧参数和排放结果分析.试验结果表明:采用过高或者过低的喷射压力均会使碳氢排放增加.在燃料喷射较晚时,碳氢排放随转速的增加而增加,在燃料喷射较早时,低转速下碳氢排放高于中高转速下的碳氢排放;中高转速下,随燃料喷射的提前,碳氢排放总体呈减小趋势,在低转速下,随燃料喷射提前,碳氢排放呈增加小幅增加的趋势.低负荷时碳氢排放明显高于中高负荷时碳氢排放;当中低负荷时,碳氢排放随燃料喷射的提前而降低,当高负荷时,碳氢排放受燃料喷射时刻的影响较小.

Experiments and measurements were conducted on an electrically controlled supercharged direct injection（DI）natural gas engine at different operating conditions in order to investigate the characteristics and influencing factors of hydrocarbon（HC）emissions.Three sets of contrast experiments were designed to analyze the effects of engine speed,engine load,injection pressure as well as injection timing on HC formation.HC emissions together with indicator diagrams were collected during the experiments as the analysis of hydrocarbon emission characteristics should be combined with the analysis of combustion parameters.Results indicate that the adoption of over-high or over-low injection pressure leads to increased hydrocarbon emissions.At relatively retarded injection timings,HC emissions increase with the increase of engine speed while HC emissions of low engine speed are higher than that of medium and high engine speeds at relatively advanced injection timings.At medium and high engine speeds,HC emissions reduce with the advance of injection timing.At low engine speed,HC emissions slightly increase with the advance of injection timing.HC emissions are significantly higher at low engine load and decrease with the advance of injection timing at low and medium engine loads.At high engine load,HC emissions tend to be insensitive to injection timing.