进气温度对汽油直喷压燃发动机燃烧及排放性能影响的试验

Experiment of the Effects of Intake Temperature on GCI Engine Combustion and Emission Characteristics

通过一台改装的单缸直喷式柴油机,在不同进气温度条件下实现汽油直喷压燃(GCI)燃烧方式的燃烧特性、工况范围以及排放特性的试验.结果表明:在进气温度为323 K时,汽油GCI燃烧方式即可实现稳定运转,燃烧表现为单阶段放热,整体放热集中,燃烧持续期短;在保持过量空气系数一定、发动机正常运转条件下,随着进气温度提高,着火时刻提前,最高爆发压力和峰值放热率均升高,指示热效率提高,HC和CO排放降低,NO排放升高;同一进气温度下,随着过量空气系数的增大,缸内混合气变稀,平均指示压力减小,指示热效率减小,CO排放先升高后降低,HC排放显著增大,NO排放减小;进气温度对汽油GCI燃烧方式正常工况范围影响很大,随着进气温度升高,负荷上限和下限均明显下降,表明进气温度是向小负荷范围拓展的重要边界条件.

Bench test was carried out on a modified single-cylinder direct-injection diesel engine with gasoline fuel to investigate the effects of intake air temperature on the combustion and emissions character- istics and operating range of gasoline compression ignition （GCI） combustion concept. Results show that at 323 K of intake temperature, gasoline compression ignition engine can be successfully operated, and single-stage heat release, fast combustion rate and relatively short combustion duration are clearly ob- served. When excess air ratio is kept constantly and engine operates steadily, with the increase of intake temperature, phase of ignition occurs earlier, and maximum cylinder pressure, peak of heat release and indicated thermal efficiency are increased, HC and CO emissions are decreased, but NO emission is increased. When intake temperature is kept constantly, with the increase of excess air ratio, the indicated mean effective pressure and indicated thermal efficiency are decreased, CO emission shows an increase and then a decrease, HC emission increases remarkably, NO emission decreases. The operating ranging of GCI combustion mode is remarkably affected by intake air temperature. When intake temperature is increased, both maximum load and minimum load are decreased obviously. Experimental results manifest that intake temperature is an important factor in controlling the combustion phasing and engine operating range.