| Small power non-road diesel engine plays an important role in the fields of industry,agriculture,forestry,animal husbandry and fishery,the problem of whose exhaust pollution and noise is becoming more and more serious.As the emission and noise restriction of non-road diesel engine become stricter,a method that includes internal purification to optimize combustion process and external optimization by designing purifier muffler was used to reduce the emission and noise of small power non-road diesel engine,which has important academic value and practical significance.R180 diesel engine was used as the prototype,whose fuel injection process was optimized by using the method of simulation calculation and experimental study,including based on the diesel engine cylinder working volume and fuel injection quantity to design nozzle flow area,reduce the delivery valve retraction volume of fuel injection pump and volume of high-pressure oil pipeline.By optimal designing,the maximum nozzle pressure at rated working condition was increased by 53.2% and the fuel injection duration was 20.1°CA.The intersecting line of injector mounting hole and swirl chamber spherical surface became more regular by reducing the long size short structure nozzle head diameter from 14 mm to 8mm;the gas flow in the swirl chamber was enhanced,which was helpful for the mixing of the fuel and the air,and the heat load of the nozzle was reduced.By using the optimized fuel injection system,the combustion process of diesel engine has been improved.Compared with the original engine,the brake specific fuel consumption was decreased by 4.4% at rated condition.After optimization,the carbon monoxide(CO),hydrocarbon(HC),nitrogen oxide(NOX)and particulate matter(PM)of 8-mode emission test cycle were 3.11 g/(kW·h),0.65 g/(kW·h),4.62 g/(kW·h)and 0.55 g/(kW·h)respectively.Compared with results of the original engine,the values of CO,HC,NOX and PM were reduced by 72.2%,75.9%,27.8% and 54.2% respectively.At the same time,the maximum cylinder pressure rise rate of optimized engine was decreased by 48.5% compared with the original engine.Experimental result showed that the sound power level of optimized engine was 103.9 dB(A),which was reduced by 1.4 dB(A)compared with the original engine.A purifier muffler that has an oxidation catalyst carrier used as a muffler element was designed by the way of simulation,and the internal structure of purifier muffler was optimized and coupled to make the air flow in the catalyst carrier homogeneous as well as improve the anechoic performance.The uniform flow field of purifier muffler carrier improved the conversion efficiency of oxidation catalyst,and the service life of catalyst was prolonged.Compared with the results of the diesel engine that only adopted engine internal purification,the CO,HC and PM of the diesel engine with purifier muffler were decreased by 88.4%,70.8% and 23.6% respectively.Compared with the result of the diesel engine with original muffler,the sound power level of the diesel engine with purifier muffler was declined by 0.7 dB(A).Compared with the results of the prototype diesel engine,the CO,HC,NOX and PM of the diesel engine that adopted the way combined internal purification to optimize combustion with external optimization by designing purifier muffler were 0.36 g/(kW·h),0.19 g/(kW·h),4.35 g/(kW·h)and 0.42 g/(kW·h)respectively,which were reduced by 96.8%,93.0%,32.0% and 65.0% respectively.The sound power level of optimized diesel engine was 103.2 dB(A),which was declined by 2.1 dB(A)compared with the prototype diesel engine.Research shows that the fuel injection system is important to the performance of swirl diesel engine;and the way combined internal purification to optimize combustion with external optimization by designing purifier muffler is one of the effective technical way to improve the performances of small power non-road diesel engine and meet the strict emission and noise standards. |
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