A Research On The Characteristics Of NO₂Emission Of High Pressure Common Rail Diesel Engine

With the rising of car ownership, the environment is more and more seriouspollution caused by car. The motor vehicles pollution report of environmental protectiondepartment in2011shows that, the air quality of environment is getting worse caused bythe rising car ownership and low penetration rate of emission standards during “EleventhFive-Year” period. With the development of society, the high-power and good-fueleconomy of diesel engine is more and more attention. So as to the atmosphericenvironment is growing concern caused by the pollution from diesel engine. The pollutionof diesel engine is researching topic in recent years. A large number research resultsshowed that NO2is the most toxic pollutant in the emissions (NO, NO2) of diesel engine.In order to solve fundamentally the toxic of emission from diesel engine and theserious harm on environment, the main task of the diesel engine workers is studying theformation mechanism of NO2pollution and the emission characteristics of NOx. In thispaper an experimental study is conducted on the emission characteristics of NOx, andcoupling SCR in a high-pressure common-rail diesel engine. Finally, this paper establisheda forecast model of NOxemission on high-pressure common-rail diesel engine.First, the diesel engine without after-treatment is tested in the new European test cycleconditions (ETC). The test results show that the maximum emission of NO and NOxappear in low-speed and medium-torque operating conditions; the maximum emission ofNO2appear in low-speed and high-torque. The test data also show that the relationshipbetween NO2/NOxemission and torque is a linear transformation trend under a certainspeed. When the load is constant, NO2/NOxwill transform in “V” way with the speedchange.Secondly, the with after-treatment experimental study show that with the raising ofSCR’s pre-temperature, the rate of NO2/NOxwill reduce. When the pre-temperaturecontinues to rise, the dropping trend of NO2/NOxwill come down. The effect’s volatility ofNO2/NOxon the rate of SCR will enlarge in low temperature zone. In high temperaturezone, the effect will going steady.After that, in order to better study the mechanism of NO2emission on high-pressure common-rail diesel engine, this paper gives a simplified combustion mechanism of dieselwhich contains40reactants and72response equations. The verified simulation resultsshow that the new mechanism’s pressure and temperature increase earlier than the Patel’smechanism in low temperature zone. As same time, the trend of pressure and temperatureincreasing are more significant than Patel’s mechanism. This makes the in-cylinder’spressure and temperature is more accurate. The pressure of in-cylinder and heat release rateare basic anastomotic with the results of FIRE’s, it is the same with the characteristics ofNO, NOx, CO2, H2O.Finally, this paper verified the prediction model of NO2emission, and the emission ofNO. The results show that, the trend of simulation is good, as well as the test results. Thedeviation is also less than16%, so this model of NO2can describe the emission of NO2emission of high pressure common rail diesel engine.