Study On Optimal Control For Diesel Engine Air Path With Electrically Assisted Turbocharger Based On Model Prediction

Exhaust gas turbocharging technology can use exhaust energy recovered by turbine to drive compressor,thereby increasing intake pressure and engine power density,realizing downsizing of engine and reducing fuel consumption.During transient conditions,due to the mechanical inertia of the turbocharger and the volume effect of intake and exhaust pipelines,the lag response of intake pressure leads to the increase of engine pumping loss,the decrease of economy and the slow response of torque.The electrically assisted turbocharger(eTurbo)is an effective technique to alleviate the turbo lag.However,the motor increases the complexity and coupling of the diesel engine air system.The power distribution between turbine and motor will change the turbine efficiency,pumping loss,high pressure exhaust gas recirculation(HPEGR)mass flow and power consumption,thereby affecting the engine fuel consumption,electric consumption and emissions.To solve this problem,a two level control architecture based on model prediction is proposed for the multi-objective optimal control of the heavy-duty diesel engine air system equipped with eTurbo.First,the experiment and simulation platforms of eTurbo and diesel engine with it are established.The independent experimental platform of eTurbo is built,and the power closed-loop control algorithm of the high-speed motor of eTurbo is developed by Simulink and verified by experiment.Integrating eTurbo with a 6.7L heavy diesel engine.The effective running of the engine is realized based on the independent development of ECU.The GT-SUITE one dimension simulation platform for the engine is built and calibrated,which is used to verify the eTurbo control algorithm and evaluate the performance of the eTurbo diesel engine.Second,the mean value model of diesel engine with eTurbo is established,and calibrated and verified by the experimental data.A two level control algorithm is developed for eTurbo system,which consists of a transient tracking controller for boost pressure and intake oxygen concentration and a power optimization distribution control between turbine and high-speed motor.The influence of VGT nozzle opening and motor power on boost pressure,HPEGR mass flow(intake oxygen concentration)and engine fuel consumption is systematically analyzed.The active disturbance rejection control(ADRC)algorithm is adopted to achieve transient tracking control of target intake oxygen concentration and boost pressure by adjusting HPEGR valve opening and compressor power demand.By the model predictive control(MPC)algorithm,the optimal VGT nozzle opening is calculated in real time,and the optimal distribution of turbine power and motor power is achieved.The best compromise among engine fuel consumption,power consumption and intake oxygen concentration tracking error is achieved.Finally,the effectiveness of the control algorithm is verified and the performance of the diesel engine equipped with eTurbo is evaluated on the GT-SUITE/Simulink simulation platform.Simulation results show that under the FTP-75 driving cycle,compared with the traditional turbocharged diesel engine,the boost pressure tracking error of the diesel engine equipped with eTurbo decreases by 87.2%,and the intake oxygen concentration tracking error increases by 1.93% and the fuel economy is improved by 0.82%.To sum up,this paper designs a two level control architecture for the optimal control of the diesel engine air system with eTurbo,which realizes the tracking control and energy optimization management of the intake components in the transient process,and quantitatively evaluates the potential of fuel saving the technology under FTP75 road conditions.The research work has theoretical and engineering value for the engineering application of eTurbo technology.