二甲醚-柴油预混压燃柴油机燃烧与排放特性的研究

Study on Combustion Processes and Emission Characteristics of a DME/Diesel Premixed Charge Compression Ignition Engine

摘要: 以一台2105柴油机为原型机，增加二甲醚(DME)预混合系统，实现进气道预混二甲醚—缸内直喷柴油预混充量压缩燃烧模式，对二甲醚-柴油预混压燃柴油机在不同DME预混率下的燃烧过程和排放特性进行深入研究。试验结果表明，进气道预混DME后，燃烧过程呈现3阶段放热。随DME预混率的增大，缸内压力和温度峰值逐渐增大，对应相位逐渐前移；DME低温反应对应的相位基本不变，DME高温反应和柴油扩散燃烧逐渐前移；33%负荷工况下NOx排放逐渐减小，66%负荷工况下NOx排放先减小后增大；HC和CO排放均逐渐增多；颗粒物的数量浓度和质量浓度均逐渐下降，DME预混率PR = 40%时降低幅度较大。研究结果为二甲醚-柴油双燃料预混压燃发动机的燃烧过程优化和污染物排放控制提供了参考。

Abstract: Based on a 2105 diesel engine, it was modified into dual-fuel engine which was added DME (di-methyl ether) pre-mixing system for realizing premixed charge compression ignition (PCCI) com-bustion mode. The combustion processes and emission characteristics of a DME/diesel dual-fuel PCCI engine under different DME pre-mixing ratio were studied deeply. The results show that the combustion process exhibits a three-stage heat release with port DME induction. With an increase in DME pre-mixing ratio, the peak values of in-cylinder pressure and temperature increase and the corresponding phases advance. The crank-angle position corresponding to the DME low-temperature reaction (LTR) stage was almost kept constant, but the crank-angle position corresponding to the DME high-temperature reaction (HTR) and diesel diffusion combustion stage advanced; at the condition of 33% load, NOx emission was a little lower; at the condition of 66% load, NOx emission decreased at first and then increased; both HC and CO emission increased; both particle number concentration and mass concentration decreased; the effects of DME introduction on the reduction of particle number concentration and mass concentration were most pronounced for PR = 40%. The results will provide references for the combustion process optimization and emission control of a DME/diesel dual-fuel premixed charge compression ignition engine.