Alternative Testing Method For In-Use Compliance Of Heavy-Duty Diesel Vehicles And Engines In China

It demands10%reduction in NOx emissions in"12th Five-Year Plan" of the National Economic and Social Development.Motor vehicle is the key to reduce NOx emissions, and heavy-duty diesel vehicle is dominant in vehicular NOx emissions. In order to control the vehicle pollution, the environmental protection department is promoting in-use compliance besides the strict vehicle emissions standards. Only the in-use vehicle emission can be controlled effectively is the fundamental way of pollution control from all the experience. The compulsory on-board vehicle emission test regulations in United States and European Union is the key effective supervision in heavy duty diesel vehicle emissions control.In order to put forward heavy duty diesel vehicle emission test regulations.vehicle emission test regulations, it needs comprehensive researching before bring in the emission test regulations because of the defference between China and abroad in fuel quality, vehicles technology, and road condition.This study carry out real road emission test of20trucks and city buses which equipped with China Ⅳ diesel engines (including a few China Ⅲengines and CNG EEV) in the key areas,and choose the typical model engines to laboratory bench test under different conditions, and test equipments. then analyze the emissions characteristic and the influencing factors of China IV diesel engines (including a few China Ⅲengines and CNG EEV), evaluate the applicability of US NTE and EU AWM and propose a proper method for China,as well as the flexibility factor and allowance of on-board test.Through the work above, we have these main conclusions and recommendations:(1) The representative of ETC/ESC is not enough in our heavy duty vehicle engine emission standards regulations. The difference between heavy duty truck real road condition and ETC mainly embodies in the dislocation of the engine speed, the difference between city bus real road condition and ETC mainly embodies in the dislocation of the engine load.13steady-state points of ESC can’t reflect transient changes of real road engine operatio. These dislocation of engine speed and load lead to great influence on NOxemissions:the NOx emissions of in-use heavy trucks is1.5to2times more than value of the engine bench test regulation,and3to5times to city bus.(2) It must strictly in accordance with the test procedures when using the portable emission measurement system (PEMS) for heavy duty diesel vehicles emission test, including the test vehicle preparation, the environmental condition, test equipment operation procedures and the acquisition and processing of test data, etc. Based on the consideration of effective availability and use of the efficiency of emissions data, we suggest the Main reference of EU AWM emission standard methods and take US NTE as auxiliary method when establishing heavy duty vehicle emissions test standard in China.(3) The data analysis method can be EU AWM For heavy duty trucks (and long distance busES), and the minimum engine load demand can be changed from30%to20%when using US NTE method, at the same time the minimum NTE events last time requirement can be changed from30seconds down to10to20seconds. The average engine load could be expanded to the10%-20%for the city buses when using EU AWM. For buses not able to obtain enough valid data, they could use the data with10%～20%average engine load for compliance check, and the flexibility of emission limits would be increased.(4)Relatively stringent NOX limit setting:flexibility factor×1.5-2.0, allowance0.5～1.0g/kW·h, then up-rounded to the multiples of0.5. The flexibility factor of relatively lowered NOX limit is×2.0-2.5, the allowance is same to relatively stringent NOx limit.