二甲醚发动机燃烧特性的试验与数值模拟研究

Experimental and Modeling Study of Dimethyl Ether Combustion in Compression Ignition Engine

在一台直喷式压燃发动机上开展了二甲醚燃烧与排放特性的试验与数值模拟研究。测量了二甲醚在高压燃油泵内的泄漏量及其与发动机转速之间的定量关系,并就发动机分别燃用二甲醚和柴油的运转性能进行了对比试验研究,结果表明,发动机燃用二甲醚要比燃用柴油具有更好的性能与排放水平;另从二甲醚低温着火的化学反应机理入手,开展了其自燃着火过程的数值模拟研究,进而建立了计及温度、压力和燃空当量比因素的DME滞燃期数据库;通过将该数据库与发动机循环模拟程序相耦合,对DME发动机的运转性能进行了变参数预测分析,预测结果与试验结果吻合较好。

This paper presents an experimental and computational study on the combustion and exhaust emissions in a direct injection compression ignition engine operated on dimethyl ether (DME). The fraction of the fuel leakage from the fuel pump to the supplied fuel and the relationship between the leaked fuel quantity and engine speed were determined with fuel injection experiment under engine motored conditions. Experimental studies were also conducted on performance and emissions between DME and conventional diesel fueled engine. The experimental results showed that engine performance and exhaust emissions of DME engine were superior to the original diesel engine. In addition, an auto-ignition model based on the multi-step DME/air chemical kinetic mechanism was developed and an ignition delay data library was generated using the computational results of DME ignition delay correlated against temperature, pressure and fuel/air equivalence ratio. In order to seek significant reductions in both computer space and computation time the coupling method of this library with the engine thermodynamic model was given and the simulation of the combustion process in the DME fueled engine was carried out. It is found that the predictions of ignition delay and engine pressure history were in good agreement with the experimental observations.