Abstract:

In order to obtain the reactor temperature of the diesel selective catalytic reduction （SCR） system of the diesel engine in real time， based on analysis of the heat transfer process of the SCR system， the Matlab/Simulink model of temperature estimating algorithm is established. RTW is used to convert the temperature estimating algorithm into executable embedded codes of single chip microcomputer ， which are downloaded to the SCR control unit. The test results show that the proposed model is suitable for the SCR control unit and can predict the catalyst internal temperature and downstream temperature on line. The relative error between the calculated value of the model and the measured value is less than 5% under steady and continuous conditions； the maximum relative error is 5.2% under step conditions； under the vehicle test condition， the maximum relative error is 9.3% and the probability distribution with a relative error of less than 6% reaches 91%. The algorithm can be used to guide urea injection， and improve urea injection accuracy of the SCR system.

Key words: diesel engine, selective catalytic reduction, temperature estimating model, control algorithm, injection control unit