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

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. © 2016, Zhejiang University Press. All right reserved.