Study on optimal control strategy for regulated two-stage turbocharged diesel engine during transient process

Controlling the turbo bypass valve is valid to enhance transient characteristic of turbocharging system. Appropriate fuel delivery is beneficial to transient performance of diesel engine. Researches on transient performance improvement depends on plenty of calibration or focus on special operation condition so that investigation result is not universal. This paper discusses optimization method and control strategy for turbocharged diesel engine. An optimum control model is established. Mathematical model describes the optimization issue and solution method is proposed, and a co-simulation model of GT-Power and MATLAB/Simulinke calculates transient performance of diesel engine. Optimal control strategies of bypass valves and fuel flow rate are acquired with this model. Experiments are carried out to investigate the effect of different control strategy on transient performance. Bypass valve should be fully closed rapidly to improve responsiveness during low-speed loading and acceleration process, while early turned down bypass valve arouses unacceptable overshoot of boost pressure under high-speed loading condition. Fuel supply increases fast and insures sufficient combustion initially. Experiment results shows the optimal control strategies reduce response time and limit the overshoot. Optimal control strategies achieve the minimal weighted error of 0.0286 at 1100 r/min and 0.0416 at 1600 r/min during loading process, and minimal weighted error reaches 0.00835 in acceleration process.