| With the increasingly strict emission standards of vehicles in China,the pollution weight of non-road mobile machinery was increasing.At present,the emission limits of non-road mobile machinery could no longer meet the increasingly strict policy requirements for environmental pollution control.Therefore,it was urgent to strengthen the emission control of non-road mobile machinery.In this paper,a four-cylinder diesel engine produced by an enterprise was taken as the research object.The diesel engine used high pressure common rail system,turbocharged intercooling technology,exhaust gas recirculation technology（EGR）,and four valve structure to optimize the combustion process and reduce pollutant emission.Moreover,a suitable DOC+DPF（Diesel Oxidation Catalyst + Diesel Particulate Filter）aftertreatment system was selected to further reduce pollutant emission.So that it at least met China’s phase IV non-road emission regulations.On this basis,the diesel engine was applied to agricultural tractor,and the regeneration of the aftertreatment system in the field was further studied through experiments.This study has obtained some academic and practical results in the following:（1）The eight-condition steady-state cycle（NRSC）test was carried out on the diesel engine without aftertreatment system,and the technical path that could meet the requirement of China’s phase IV non-road emission regulations was determined.The PM value obtained by NRSC test was 0.0715g/（k W·h）,which was much lower than the emission limit of 0.025g/（k W·h）,and the emission result of HC was also lower than the emission limit.However,both CO and NOx could meet the emission limit and leave enough margin.Therefore,a technical path to remove HC and PM by installing DOC and DPF aftertreatment equipment was proposed,which could effectively reduce HC and PM emission and meet the requirement of China’s phase IV non-road emission regulations.（2）The electronic control parameters such as rail pressure,EGR and timing were calibrated and optimized to further improve the emission performance of the diesel engine.The emission characteristics of the diesel engine were obtained through steady-state test cycle,control area test and transient test cycle（NRTC）,and it was found that the degraded emission result could meet China’s phase IV non-road emission regulations and the next-stage emission regulations.NRSC cycle,NOx = 2.627/g/k Wh,PM = 0.0066g/k Wh,the removal rate of PM reached 90%;NRTC cycle,NOx = 2.543g/k Wh,PM = 0.0041g/k Wh,PN = 2.4949 × 1010#/k Wh;the emission results of CO and HC were far less than the limit of current emission regulations.（3）Field tests were carried out on tractor equipped with this diesel engine,and the DPF regeneration conditions in different working environment were studied.The active regeneration test was carried out when the tractor was tilling,plowing and walking.During the regeneration process,the diesel engine injected a small amount of fuel in the near and far back spray,and the temperature control effect was better.There was no fluctuation of diesel engine speed and power shortage,and the tractor could work normally.When the tractor was tilling,the load was large.There was basically no carbon deposits,and passive regeneration effect was good.When the tractor was plowing and walking,the exhaust temperature was relatively low.DPF accumulated carbon quickly,and the passive regeneration effect was poor.The user should try to avoid the tractor continuously plowing and walking for a long time while working. |
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