【作者】 未建飞；

【导师】 汤东；

【作者基本信息】 江苏大学 ， 动力工程及工程热物理， 2017， 硕士

【摘要】 与汽油机相比,柴油机具有热效率高,动力性强,经济性好等优点,应用领域越来越广泛。尤其是对于非道路移动机械,柴油机已成为重要的动力来源。但随着环境污染的日益严重,人们对环境问题愈发关注,各国也相继制定了日益严格的排放法规。柴油机的主要排放污染物为NOx和PM,其中NOx会对人体健康产生危害,而PM则是造成空气污染的重要原因之一。因此如何有效地降低柴油机的有害污染物,是当前迫切需要解决的问题,对于改善环境问题有着重要的意义。本文以一台非道路增压中冷柴油机为研究对象,通过模拟计算与试验相结合的方法,对电控单体泵系统参数进行优化研究以改善柴油机排放和经济性能,使其达到国家排放法规的标准。首先,利用Pro-E与Hypermesh软件建立该柴油机燃烧室的几何模型和网格模型,通过柴油机台架试验和经验值确定初始条件和边界条件,对仿真模型的各个子模型进行论述和选择,利用AVL FIRE软件,建立该柴油机的三维计算模型,并通过模拟示功图与实测示功图的对比验证仿真模型的准确性。其次,采用单一变量法分别研究喷孔直径、喷油提前角、EGR率等参数对柴油机燃烧过程的影响,主要分析气缸内湍动能、燃空当量比分布、气缸压力、缸内平均温度、温度场分布的变化情况。最后,结合仿真计算结果提出优化改进方案,搭建排放试验台架并进行排放试验,研究油嘴伸出量、喷孔直径、喷油正时、EGR率等参数对排放性能和燃油消耗率的影响,根据试验结果确定柴油机的油嘴伸出量为3.2 mm,喷孔直径为0.24 mm,并确定各工况下使柴油机性能最优的喷油正时和EGR率。在某国家认证排放实验室对优化改进后的柴油机进行八工况稳态循环试验,试验测得的NOx、CO、HC和PM排放物的结果分别为:4.179 g/(kW·h)、0.494g/(kW·h)、0.238 g/(kW·h)和0.159 g/(kW·h),整机满足非道路国III排放标准。更多还原

【Abstract】 Compared with the gasoline engine,diesel engine is more and more widely used for its advantages of high thermal efficiency,strong power output and better fuel economy.For non-road mobile machinery especially,their main power supply sources are normally from diesel engine.Nevertheless,with environmental pollutants on the rise,more attention is paid globally towards environmental protection currently.This attention has resulted in the enactment of stringent emission regulations in many countries.The main emissions of diesel engines are NOx and PM(particulate matter).NOx is harmful to human health and PM is one of the main causes of air pollution,hence the need to effectively reduce these harmful pollutants has become issues of global concern,which will contribute significantly to improving the environment.In this paper a non-road turbocharged intercooled diesel engine for mobile machinery is used as the research object.Through the combination of simulation and experiment,the parameters of the combustion system are optimized while the emission and economic performances are also improved to meet the national emission regulations standards.Firstly,the geometrical and grid models of the diesel engine combustion chamber are built by using Pro-E and Hypermesh softwares.The initial conditions and boundary conditions are determined from diesel engine experimental test bench and empirical values.After the various submodels of the simulation model are discussed and selected,AVL FIRE software is used to establish the three-dimensional calculation of the diesel engine.The simulation results are compared with the diesel engine’s experimental data to verify the accuracy of the simulation model.Secondly,the effect of nozzle diameter,injection timing and EGR rate on the combustion process of the engine is studied based on single variable method.Turbulence kinetic energy,fuel/air equivalence ratio distribution,average pressure,average temperature and temperature distribution are mainly analyzed.Lastly,the test bench is set up to carry out the emission experiment according to the simulation optimized program.The effects of nozzle protrusion,nozzle diameter,fuel injection timing and EGR rate on emission and fuel consumption are investigated.From experimental results,the nozzle protrusion of 3.2 mm and nozzle diameter of 0.24 mm are determined as the optimum parametric choice.The fuel injection timing and EGR rate for the diesel engine optimum performance under each working condition are also determined.The eight condition ESC test is operated on the optimized diesel engine in a national certification emission laboratory,and the result of NOx、CO、HC、PM are 4.179 g/(kW·h)、0.494 g/(kW·h)、0.238 g/(kW·h)and 0.159 g/(kW·h)respectively.The diesel engine can meet the non-road national stage Ⅲ emission regulation.更多还原