燃料特性对HCCI发动机燃烧和工况范围影响

The Influence of Fuel Property on Combustion and Operating Range of a HCCI Engine

在一台改装的4缸直喷柴油机上进行燃料特性对均质压燃(HCCI)燃烧和工况范围影响的试验研究。试验选用6种不同燃料:基础燃料(PRF)、汽油以及基础燃料与乙醇混合物。控制6种发动机运转条件:不同进气温度(tin)、进气压力(pin)和转速。结果表明:在某些运转条件下,汽油着火时刻最早,而在另一些运转条件下,PRF着火时刻最早,这就表明燃料特性对HCCI燃烧过程的影响依赖于发动机运转条件。选用敏感性燃料协同合理的运转条件控制,对于运行工况范围的拓展具有更大潜在优势。CA50(放热完成50%所对应的曲轴转角)与辛烷值指数(OI)具有很好的相关性,OI越高,着火越晚。然而,使用基础燃料与乙醇的混合物时,OI与着火时刻不具有相关性。

The influence of fuel property on combustion characteristics and operating range of a homogeneous charge compression ignition （HCCI） engine was investigated in a modified four-cylinder direct injection diesel engine. Six fuels were used including the primary reference fuel （PRF） , the gasoline, and the mixture of PRF and ethanol. Six operating conditions were considered, including different intake temperatures （tin） , intake pressures （Pin） and engine speeds （n）. The test results show that, under some operating conditions, the gasoline gives the earliest auto-ignition among all fuels, while under some operating conditions, the PRF shows the earliest auto-ignition at others conditions. That reveals that the effect of fuel property on the HCCI combustion process is depended on operating conditions. By using the sensitive fuels and properly controlling engine operating conditions, the operating range can be extended. CA50 （ crank angle at 50% accumulated heat release） has good correlation with the octane index （OI）. High OI corresponds to late auto-ignition. However, no correlation is found between OI and auto-ignition timing for the mixtures of PRF and ethanol.