Experimental and simulation investigations of the effects of charge density, temperature and oxygen concentration on emissions and thermal efficiency were conducted in a high brake mean effective pressure (BMEP)diesel engine. Experimental investigation was carried out in a modified single cylinder engine equipped with variable mechanisms of boost, exhaust gas recirculation (EGR), intake valve closing timing (IVCT)and a flexible fuel injection system to regulate charge density, oxygen concentration and temperature. Simulation of engine combustion processes was performed using an ECFM-3Z combustion model-based three-dimensiunal code. Combustion-paths analysis based on the calculated mass-phi-Thistory was proposed and employed for the study. It is found that higher charge density leads to lower overall equivalence ratio, will enhance the rates of mixing and chemical reaction and improves thermal efficiency. The role of lower oxygen concentration essentially reduces the chemical reaction rate and lowers the combustion temperature and the NOx emissions. Higher charge density, combined with moderatelow oxygen concentration and retarding IVCT are found to be effective control-strategies for high BMEPclean diesel engines.%采用试验和数值模拟方法研究了充量密度、温度和氧浓度对柴油机高负荷工况下的热效率和排放的影响.试验是在一改装的单缸柴油机上进行,装有进气增压、废气再循环、进气门晚关和可调节的燃油喷射系统等回路,在该试验台上充量密度、温度和氧浓度可自由调节.三维模拟采用ECFM-3Z燃烧模型.提出并应用了质量-φT-θ燃烧路径分析方法.研究结果表明,高充量密度降低全局当量比,增强燃空混合率和化学反应率,有利于提高热效率.适当低的氧浓度降低化学反应率,燃烧温度降低,有利于降低NOx排放.高充量密度、适当氧浓度和进气门晚关3种技术相互优化耦合是柴油机高负荷下实现高效清洁燃烧的有效控制方法.
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