Analysis Of No_X Emission Characteristics Of Heavy-duty Vehicles Based On Monitoring Platform

With the continuous development of society,motor vehicles have become an indispensable part of our daily lives,and it has inevitably brought about environmental pollution.In recent years,China’s motor vehicle emission test standards have been continuously updated,but there is still much room for development and improvement in terms of emission supervision.Current motor vehicle emission test regulations basically use fixed cycle conditions for engine and vehicle emissions test methods,which can easily cause a large difference in pollutant emissions between actual road conditions and type certification conditions.The emission of motor vehicle pollutants plays a regulatory role,and it largely depends on the correlation between test conditions and actual conditions.Based on the above problems,this article builds a monitoring platform that can remotely monitor vehicle conditions and emissions in real time.Monitor and store vehicle operating conditions and emissions data to achieve precise positioning of "one vehicle,one condition",and design algorithms to automatically query and record vehicles with higher emissions for automatic monitoring.This study first designed a test to verify the accuracy of the platform data.A heavy-duty diesel vehicle with a national V emission standard was used as the test object.The vehicle was subjected to a chassis dynamometer discharge test and a PEMS based on actual road conditions.At the same time of testing and testing,the monitoring platform synchronously collected real-time operating condition information and nitrogen oxide emissions data of the vehicle.The test results showed that the error between the nitrogen oxide emissions monitored by the monitoring platform and the standard test and testing equipment was small.During the cycle,the nitrogen oxide emission has an error of less than 10 % twice.In the PEMS test,the nitrogen oxide emission correlation coefficient is0.936.Therefore,this study believes that the data of the monitoring platform can be used as valid data.Based on the monitoring platform,the speed,acceleration,SCR system temperature,and nitrogen oxide emission rules of the heavy-duty vehicles in the fifth and sixth emission phases are analyzed.The results show that the heavy-duty vehicles in the fifth and sixth emission phases have higher exhaust temperatures than The conversion efficiency can reach more than 90 % at 300 ℃ and 180 ℃.The fitting curve of SCR conversion efficiency and exhaust temperature of heavy-duty vehicles in the fifth emission stage is parabolic;as the speed increases,nitrogen oxide emissions increase first and then decrease.The acceleration of vehicles in the fifth emission stage has a greater impact on nitrogen oxides emissions in the high,medium and low speed ranges,and the impact of nitrogen oxide emission rates in the low speed range of the sixth emission phase is greater.At the same time,based on the operating conditions and emissions data of a city’s bus,the nitrogen oxide emissions of diesel and natural gas buses in the fifth emission stage during actual operation are analyzed with the change of road traffic conditions.The results show that the two types of fuel.The nitrogen oxide emissions of buses are greatly affected by traffic conditions;the correlation coefficients between nitrogen oxide emissions and speed of diesel buses and natural gas buses are 0.71 and 0.24,respectively.The impact of acceleration on diesel buses is greater than that of natural gas buses.The nitrogen oxides emission rules of buses put forward their own reasonable suggestions.