船用柴油机应用柴油/甲醇二元燃料的性能特性研究

Performance Study About Marine Engines With Diesel-Methanol Dual Fuel

在柴油/甲醇二元燃料(DMDF)燃烧模式下,研究了不同负荷下甲醇替代率对船用柴油机性能的影响,以及不同喷油时刻对DMDF燃烧的影响。试验结果表明:不改变原机喷油定时的情况下,发动机25%负荷率时最大替代率为57. 8%,50%负荷率时最大替代率为59. 6%,100%负荷率时最大替代率为36. 7%;受喷醇流量的限制,在75%和90%负荷率时,甲醇替代率分别只做到49. 1%和39%。据试验情况分析,限制甲醇替代率提高的因素有发动机失火和发动机最高燃烧压力过高等,因此,除受试验条件限制的负荷区域(50%～90%负荷率)外,将DMDF在船用柴油机上的非稳定运行的区间分为失火限制区和最高燃烧压力限制区,分别对应的负荷率范围大致为0～50%和90%～100%。另,喷油时刻太靠后会限制甲醇替代率提升,其主要原因是发动机易失火;而喷油时刻太靠前则因最高燃烧压力升高限制了甲醇替代率的提升。

Under the combustion mode of diesel-methanol dual fuel,researches were carried out on the influence of methanol substitution rate to marine engine performance at different load factors and the influence of different injection timing to DMDF combustion.The test results show that,the maximum methanol substitution rate is 57.8% on 25% load factor,59.6% on 50% load factor,36.7% on 100% load factor without changing the injection timing of original engine,and due to the limitation of methanol flow,the number is 49.1% and 39% on 75% and 90% respectively.According to the test date analysis,there are several reasons which limit the increase of methanol substitution rate,including fire-missing,excess peak pressure,etc.Therefore,except the load range (50%~90%) limited by test conditions,the unstable operation areas are divided into fire-missing restriction area and peak pressure restriction area,corresponding respectively to 0%~50% load factor and 90%~100% load factor.When injection timing is too late,fire-missing limits the increase of the substitution rate,while the limiting factor is peak pressure when injection timing is too early.