Development Of Model Based Virtual Calibration Platform For Diesel Engine Emission

With the increasingly stringent emission regulations,the emission limits of diesel engines are required to be further stringent.Compared with National V,National VI decreases the emission limits of NOx by 78%,THC by 70%,PM by 50%,and increases the requirements of PN,NH3 measurements and limits.Significant changes have also taken place in the emission testing cycle.In order to meet the stringent requirements of emission regulations,it is necessary to carry out multi-scheme design of diesel engine aftertreatment system and other components,and optimize a large number of calibration parameters of electronic control unit(ECU).In order to reduce the workload of be nch test,save cost and improve efficiency,it is of great significance to optimize the calibration parameters of ECU based on dSPACE hardware-in-the-loop simulation platform through simulation technology for diesel engine and post-processing system.In this paper,the bench test and simulation analysis of a diesel engine are carried out.Based on the test data,the intake and exhaust system and the original exhaust model of the diesel engine are built for hardware-in-the-loop simulation calculation.Firstly,the performance characteristics of a diesel engine are analyzed by DOE(design of experiment)test,and the calibration parameters of the diesel engine are initially calibrated.Then the cylinder model of diesel engine is built based on steady DOE test data to predict the combustion and emission characteristics of diesel engine.The intake and exhaust system model of diesel engine is built by thermodynamic analysis software to simulate turbocharging,EGR and intercooler.The accuracy of the model is verified by the WHTC cycle test.The diesel engine performance model can accurately predict the power and emission characteristics of the diesel engine.The overall error is less than 5%,and it meets the real-time requirements.After the real-time model is built,the model is compiled by Simulink automatic code generation and downloaded to the dSPACE platform for hardware-in-the-loop simulation.Depending on the abundant I/O interface of dSPACE,the communication between the model and the real actuator and the real ECU is completed,and the ControlDesk interface is designed,and the hardware-in-the-loop simulation platform is developed.The performance of diesel engine is optimized on the hardware-in-the-loop simulation platform.By optimizing calibration parameters,the NO,emission of diesel engine is optimized,and the NO,emission data of transient WHTC cycle is obtained for the simulation of post-processing system.According to the exhaust parameters of diesel engine calculated by hardware-in-the-loop simulation,the aftertreatment system of diesel engine is designed and optimized.This paper mainly focuses on the development and design of urea injection strategy for diesel engines.After the exhaust parameters of diesel engine are obtained by hardware-in-the-loop simulation,the off-line simulation of the Aftertreament system of diesel engine is carried out.According to the space layout of the real vehicle and the original exhaust of the diesel engine,the initial layout of the Aftertreament system is selected.The DOC+cDPF+SCR(ASC)Aftertreament system is adopted for the engine used in the test.Then,a Aftertreament model based on detailed chemical reaction kinetics is built.On this basis,the control strategy of urea injection is designed and optimized,focusing on the emission of NOx.Through the optimization of SCR closed-loop control strategy,the NOx emission of diesel engine meets the requirements of the national VI regulation.The simulation results of the virtual calibration platform for diesel engine are verified by the diesel engine bench test to meet the accuracy requirements,and can be used to optimize the development of the national VI project.