Research On Emission Characteristics Of Marine Diesel Engine In Durability Test

In recent years,with the increasing discharge of pollutants from ships,the public health and living environment of inland river and port cities have been seriously threatened.Countries around the world continue to upgrade marine diesel engine emission regulations.In order to prevent the pollution of marine pollutant emissions to the environment,China has promulgated the marine diesel engine pollutant emission regulations(GB15097-2016),it is required that both the engines and its post-processing devices shall undergo durability tests to determine the deterioration coefficient.With the implementation of GB15097,the problem of large change in environmental factors during the durability test of marine diesel engine is more prominent.If the test plan is not fully considered or adjusted in time,the deterioration coefficient has a great impact.Therefore,the research on the emission characteristics of the durability test has a certain reference for the formulation and implementation of the subsequent ship engine durability test plan.This subject takes the durability test of marine diesel engine as the background,and is based on the three groups of durability tests,aiming at the characteristics of large change in environmental factors,the pollutant emission characteristics of marine diesel engines are studied.Combined with the different NO_X humidity correction methods in various emission regulations,the key analysis of the NO_X humidity correction coefficient is carried out,which is greatly affected by environmental factors.The main research contents are as follows:(1)Combined with the requirements of regulations and the characteristics of marine diesel engine,the test models,test cycles,test methods and test nodes in the durability test plan are determined,build a test platform.The three groups of tests in this subject adopt the accelerated aging test method based on the principle of equal work,the total running time of the durability test is 1719 hours,the emission test is carried out at equal intervals at six nodes,and the emission deterioration trend is determined by the least squares method.The measurement of gaseous pollutants adopts the original gas direct sampling method,while the measurement of particulate matter adopts the method of partial flow dilution full flow sampling.(2)Due to the long time span of the durability test and the large changes in environmental factors during the test,the operating state of the diesel engine changes greatly.Therefore,the law of the emission concentration,correction coefficient,specific emission,etc.of each pollutant changing with the environment is analyzed.The results show that the specific emission and deterioration trend of NO_X are seriously affected by changes in environmental factors,it is related to the large change of NO_Xhumidity correction coefficient.The specific emission of PM has different sensitivity to changes in various environmental parameters.While the specific emissions of HC and CO are less affected by the correction factor.(3)Since the NO_X humidity correction coefficient in GB15097 is greatly affected by changes in environmental factors,and each marine diesel engine emission regulation has its own NO_X humidity correction method,the different correction formulas have a greater impact on the NO_X specific emissions.The three sets of test data were calculated according to different NO_X humidity correction calculation formulas.The conclusions are as follows:the NO_X humidity correction coefficient of the IMO standard has the strongest correction effect,and the fitting effect of the specific emissions of each model is better.The EU regulations and the US EPA regulations do not correct the intake air temperature,which is insufficient.While the NO_X humidity correction coefficient in GB15097 is generally lower than the correction result of the IMO standard,and there is insufficient or excessive correction in some test nodes.(4)During the valid life,the deterioration degree of HC+NO_X emissions of marine diesel engine models did not reach 15%,the deterioration degree of PM emissions was relatively gentle,only the deterioration degree of CO emissions of individual models was more serious,but the CO emission limit was very loose.Therefore,if the marine diesel engine learns from the practice of specifying the deterioration coefficient and follows the deterioration trend of the existing specified deterioration coefficient,it will not have a great impact on the first-stage emission certification work of GB15097.