双燃料发动机的燃烧和排放特性研究

Study on combustion and emission characteristics of dual fuel engine

为了解决双燃料发动机的CH4与NOX排放的trade-off关系,利用实验和模拟结合的方法,研究了喷油压力和EGR率对柴油/天然气双燃料发动机的燃烧和排放的影响。结果表明,随着喷油压力的上升,甲烷的火焰传播速度增加,热效率(BTE)上升;汽缸壁和狭隙区域的甲烷由于低温未能燃烧,成为甲烷排放的主要来源。当EGR率上升时,BTE呈现出先上升后下降的趋势;在EGR率较小(0~10%)时,CO和CH4排放对喷油压力不敏感,在大EGR率工况(30%~40%)下,提高喷油压力可明显降低CO和CH4排放。因此,当喷油压力为120 MPa并且EGR率为20%时,柴油/天然气双燃料发动机可获得较高的热效率和较低的排放。

In order to solve the trade-off relationship between CH4 and NOX emissions of the dual fuel(DF)engines,the effects of injection pressure(IP)and EGR ratio on combustion and emission of diesel/natural gas(NG)dual fuel engines were studied by combining experiments and simulations.The results showed that the flame propagation speed of methane increased and the brake thermal efficiency(BTE)increased while the IP increases.The methane in the crevice region and the cylinder wall can not be ignited due to low temperature,which became the main source of methane emissions.When the EGR rate increases,BTE tends to increase first and then decrease.When the EGR rate is small(0~10%),CO and CH4 emissions were not sensitive to IP.Under the condition of large EGR rate(30%~40%),the CO and CH4 emissions significantly decreased by increasing the IP.Therefore,when the IP is 120 MPa and the EGR rate is 20%,the diesel/NG DF engine can achieve higher BTE and lower emissions.