甲醇-汽油双燃料发动机分层稀燃与均质稀燃特性对比分析
鲁伟，蒋炎坤*，韩荣，陈烨欣
华中科技大学能源与动力工程学院，湖北 武汉 430074
摘要：为研究稀薄燃烧方式对甲醇进气道喷射（methanol port injection, MPI)-汽油缸内直喷(gasoline direct, GDI)双燃料发动机的影响，在缸内直喷光学发动机上加装甲醇进气道喷射装置实现MPI-GDI发动机双燃料复合喷射功能；基于Converge软件建立仿真模型，利用试验喷雾图像和缸压试验结果验证模型的准确性，研究分层稀燃和均质稀燃对双燃料复合喷射发动机燃烧及排放特性的影响。结果表明：MPI-GDI双燃料发动机的甲醇替代比较低时，相比分层稀燃，均质稀燃缸内峰值压力更大且对应的相位提前，靠近上止点燃烧放热，燃烧定容度更好；随着甲醇替代比增加，分层稀燃情况改善，2种方式燃烧差距减小；相同工况下，均质稀燃时CO和碳烟排放比分层稀燃低，分层稀燃时NOx排放较低；过量空气系数为1.3时，均质稀燃THC排放较低；过量空气系数为1.5时，分层稀燃时THC排放更低。该研究可为降低甲醇-汽油双燃料发动机在不同燃烧方式下的排放提供参考。
关键词：复合喷射；均质稀燃；分层稀燃；燃烧特性；排放特性
Comparative analysis of stratified and homogeneous lean combustion of methanol-gasoline dual-fuel engine
LU Wei, JIANG Yankun*, HAN Rong, CHEN Yexin
School of Energy and Power Engineering,Huazhong University of Science and Technology,Wuhan 430074,China
Abstract：In order to investigate the influence of lean combustion mode on MPI-GDI(methanol port injection and gasoline direct injection) dual-fuel engine, the MPI-GDI dual-injection function is established by adding a methanol intake port injection device to a direct-injection optical engine. Establishing a simulation model based on the Converge software and verifying its accuracy by the experimental spray image and cylinder pressure test data, the effects of stratified and homogeneous lean combustion on combustion characteristics and emission characteristics of dual-injection engine are studied. The results show that, for MPI-GDI methanol-gasoline dual-fuel engine, the peak pressure in the homogeneous lean combustion cylinder is larger and the corresponding phase is advanced, combustion is close to TDC, and the combustion constant volume is better than that of stratified lean combustion at a low methanol substitution ratio, with the increase of methanol substitution ratio, the combustion performance of stratified lean combustion is improved and the difference between the two modes is reduced. For emission characteristics under the same conditions, CO and carbon soot emissions of homogeneous lean combustion are generally lower than that of stratified lean combustion, but the NOx emission of stratified lean combustion is lower, the THC emission of homogeneous lean combustion is lower than that of stratified lean combustion when excess air coefficient is 1.3, but the THC emission of stratified lean combustion mode is lower when excess air coefficient is 1.5. This study can provide a reference for reducing the emissions of methanol-gasoline dual fuel engine under different combustion modes.
Keywords:compound injection;homogeneous lean combustion;stratified lean combustion;combustion characteristics; emission characteristics
