柴油甲醇组合燃烧对机车柴油机排放性能的影响

对一台应用于机车的中速大型柴油机，按照柴油/甲醇组合燃烧(DMCC)的要求,进行了相应的改造，以探究DMCC燃烧模式对其排放性能的影响。结果表明:在800 r/min@9 600 N·m工况下，掺烧甲醇后，NO_x比排放大幅降低，但过分提高甲醇替代率，则NO_x比排放会有所升高；CO₂比排放、燃料费用随甲醇替代率的升高而降低；当量油耗则先随甲醇的替代率提高而升高，随后降低;HC比排放随甲醇替代率提高有所升高。相比于原机，在800 r/min、9 600 N·m、-4° ATDC、35.9%替代率工况, NO_x比排放仅为3.15 g/(kW·h),最大降幅达到56.5%；DMCC模式，640 r/min@6 850 N·m工况下，随着供油提前角的推迟，NO_x、HC比排放降低，排气温度逐渐升高；中等替代率下最低油耗对应的供油提前角推迟，高替代率下供油提前角提前。

The Impacts of Diesel/Methanol Compound Combustion on theEmissions of Locomotive Diesel Engines

The modification of a large medium-speed locomotive diesel engine was carried out according to the requirements of implementing diesel/methanol compound combustion (DMCC), and the impacts of DMCC combustion mode on the emissions were explored. The experimental results showed that at working condition of 800 r/min@9 600 N·m, the NO_x emission was greatly reduced after injecting methanol, but the NO_x emission would increase once the methanol-substitution rate was beyond the limitation. And under the same working condition, with the increasing of methanol-substitution rate,both the CO₂ emi-ssions and the fuel cost decreased,and the BSFC increased first and a then decreased,the HC emi-ssions increased. Under the working condition of 800 r/min,9 600 N·m,-4°CA ATDC,35.9% subs-titution rate,the NO_x emissions, which was only 3.15 g/(kWh), had a maximum reduction of 56.5% compared to the original engine. Under the working condition of 640 r/min@6 850 N·m of DMCC mode, with the delay of the fuel supply advance angle, both NO_x emissions and HC emissions decreased, exhaust gas temperature increased.The fuel supply advance angle corresponding to the minimum BSFC was delayed under medium substitution rate and advanced under high substitution rate.