No_x Emission Characteristics Of Diesel Bus Under Real-World Driving Conditions

With the increase in the amount of public buses and the pollutant emissions impact on the environment is more and more big.Taking a serious literature analysis about the NOx emission problem that everybody pay close attention,found that NOx emissions is far beyond the limits of type approval in the actual operation of the diesel buses,resulting in a lot of NOx emission of pollutants.According to the test requirements,making the portable emission measurement system(portable emission measurement system using GPRS wireless transmission technology,GPS technology and web server technology,PEMS),system acquisition GPS data,nitrogen oxide sensor data and engine load data,using GPRS wireless transmission technology to the acquisition data is sent to the lab server,received by the server,processing and save.Through the test,the system can well meet the test requirements.Then using PEMS collect the real road emission data of diesel buses that meet different emission standard stage(?,?)in Beijing's real-world conditions,using average method to study on the emission characteristics of the bus.Study found that the NOx emissions of bus has a great relationship with speed,power and exhaust temperature,as the basic decreases with the increase of the speed,power,and exhaust temperature.There are only 2 cars in 10 bus vehicles reached the limit value in ESC and ETC test,the emissions of a foreign brand engine is significantly better than a domestic brand engine.The exhaust temperature of a domestic brand engine is significantly lower than the foreign engine exhaust temperature.SCR system cannot do well,especially in low speed ?low load or low exhaust temperature,cannot effectively reduce the NOx emissions of diesel engine,then the effective thermal management are needed to improve the effect of low load of SCR work at low speed.