Abstract: In order to solve the boost pressure control problems of regulated two-stage turbocharged diesel engine under whole operating conditions at varying altitudes, the working process model of a two-stage turbocharged diesel engine at high altitudes is established by GT-POWER and verified by experimental data. The control scheme of the regulated two-stage turbocharging system at different altitudes is designed, and the optimal opening of high-pressure turbo-valve, low-pressure turbo-valve and boost pressure are obtained by optimization calibration. The effect of PID closed-loop control based on boost pressure and open-loop control based on turbo by-pass valve opening on the transient performance of diesel engine at high altitude is compared by simulation and test. The results show that, compared with the plain, the time when the boost pressure first reaches 90% of the target value at the altitudes of 3 000 and 5 000 m increases by 0.11 and 0.19 s respectively based on PID closed-loop control. Compared with PID closed-loop control, the time when the boost pressure first reaches the target value under open-loop control shortens by 0.09,0.197 and 0.14 s at the altitudes of 0,3 000 and 5 000 m, but there exists a certain deviation between actual boost pressure value and target boost pressure value. Based on this, the control algorithm combining the PID closed-loop feedback control of boost pressure with the open-loop control of turbo bypass valve can take into consideration of the robustness and accuracy of the transient process of the two-stage boost system at the same time. It is an ideal control algorithm for the transient process of the two-stage boost system at high altitude in the future

Key words: diesel engine, variable altitudes, regulated two-stage turbocharging system, turbo bypass valve, electronic-controlled pneumatic, control strategy