Study On Controlling Exhaust Emissions From Non-road DI Diesel Engine

Energy and environmental protection have become two main themes of the contemporary world.As society and economy developing,the problem caused by non-road diesel engine emission has been widely drawing people's attention,and lots of countries have established non-road diesel engine emission regulations.For small non-road diesel engines,optimized matching among the fuel injection,in-cylinder air movement and the combustion chamber is a most important means to reduce exhaust emissions.Taking 395E non-mad diesel engine as a target prototype,emission controlling methods and approaches are discussed in this dissertation in order to make non-road diesel engine meet EPA Tier4 standards.Firstly,the main parameters,test devices and exhaust test method of the target diesel engine are introduced.Adopting supercharging inter-cooler technology is confirmed as the technical means and testing scheme by basically conducting performance and exhaust experiments of 395E diesel engine and analyzing its emission characteristics.Secondly,the influences to the diesel performance and emission which brought by the variation of intake air pressures due to three different types of turbocharger and the variation of intake air temperatures due to the inter-cooler are analyzed.The results show that the diesel power performance and fuel economy are apparently improved with a reduction of PM through turbocharger.However,there is some increase for NO_X emission.Judging by the operating conditions of the diesel engine after matching,it is concluded that HP48 turbocharger is better than HP45 and SJ44Q turbochargers.Also,the reduction of the air temperature after inter-cooler is also a benefit for improving the diesel exhaust,the power performance and the fuel economy.Thirdly,three types of combustion chamber are designed.The matching of the diesel engine with three kinds of combustion chambers was investigated and the diesel power,the fuel consumption rate and the exhaust under different combustion chambers parameters were compared.The results show that the re-entrant dumbbell-shaped chamber adapts better with 395E engine.The Maxican-hat dumbbell-shaped chamber is good to greatly reducing NO_X emission while it shows no obvious effect on reducing PM exhaust.The No2 combustion chamber matches best with 395E engine.Additionally,the influences of the fuel supply system parameters on the diesel power performance,the fuel economy and the exhaust were investigated,including fuel supply advanced angle,nozzle spray-hole diameter,opening injection pressure,the inclined angle of injector installation,injector extending height,etc.The results show that increasing the fuel supply advanced angle appropriately can reduce PM exhaust effectively,while with an overfull angle the NO_X emission will be increased.As for 395E,it is better for the overall parameter matching to make the injector nuzzle smaller and appropriately boosting the injector opening pressure.The emission can be further improved through choosing a reasonable injector installing inclination angle and injector extending height.Finally,among all experimental parameters,a group of matching parameters was selected, which can make the exhaust emissions of 395E diesel engine to meet the emission limits of EPA Tier4 exhaust emissions standards for non-road diesel engines of US,which were executed from 2008.Meanwhile,the power performance and economy of 395E have been also improved.