柴油机暖车阶段未燃碳氢排放影响因素的研究

通过在一台高速直喷式柴油机上的试验,得出了在暖车阶段柴油机未燃碳氢(HC)排放与冷却液温度之间的变化规律以及发动机转速与负荷对未燃HC排放的影响,试验结果表明,暖车时柴油机采用的负荷和转速大小决定了未燃HC排放的多少,当转速一定时,存在一个决定未燃HC排放随冷却液温度变化而有不同趋向的临界负荷,低于此负荷,随着冷却液温度的升高,HC排放浓度趋于下降或基本不变;超过此负荷后,HC排放浓度会随着冷却液温度的升高而增大,另外,研究表明,在负荷相同时,柴油机的未燃HC排放量随着转速的升高而下降,就未燃HC排放总量而言,存在一个未燃HC排放最少的暖车转速和负荷区间。在该区间内,要求发动机应采用较高转速,较低的负荷。

Study on Unburned Hydrocarbon Emissions from Diesel Engine During Warm-up Period

When direct injection (DI) diesel engi ne s run at the period of warm-up, they will emit a lot of blue-smoke containing unburned hydrocarbons (HC) which are harmful to environment, so it is very impor tant to reduce HC emission. This paper reports a study on the effect of the temp erature of cooling water on HC emission from DI diesel engine running after cold -start. The tests were carried out on a naturally aspirated DI diesel engine. T he results of the test unveiled that the temperature of cooling water had much i nfluence on HC emission while the engine was running at low load or at the perio d of warm-up. In the case of the constant engine speed,there is a critical load range for warming up. Lower than that load,the HC emission decreased or remaine d unchanged as the temperature of cooling water increased; higher than that, the HC emission would increase as the temperature went up. Additionally, there exis ts a relationship between the HC emissions and the engine speed as well as the e ngine load. HC emissions were reduced as the engine speed went up at the same en gine load, and the higher the load is, the more the HC emissions are,while the s peed remained unchanged. As for the concentration and the total amount of HC emi ssions during the period of warm-up, there exists a range in which the total am ount of HC emitted to environment will be the least. In the range, the engine sp eed is required to be set higher and the load should be set lower.