The Effect of Bypass Valve Control on the Steady-State and Transient Performance of Diesel Engines with Regulated Two-Stage Turbocharging System

The concept of regulated two-stage turbocharging system is proposed to provide high boost pressure level over a wide range of engine speed by regulating the energy distribution of two turbochargers. However, the control strategy of turbine bypass valve becomes more complicated due to the frequently changing working of vehicle diesel engines. In this paper, a two-stage turbocharging system was matched for D6114 diesel engine to improve the low-speed torque. The effect of valve opening on the steady-state and transient performance was analyzed, and two different regulating laws were determined according to the different optimum aims. Then the transient response characteristics of two different regulating laws were studied and optimized at three speeds with the transient loading test. For steady-state performance, the output power and fuel efficiency were increased with the matched turbocharging system. The output power was increased by 21.4%, and the BSFC was decreased by 5.4% at 1100r/min. The economic and dynamic regulating laws were achieved for the purpose of minimizing the brake specific fuel consumption and maximizing the boost pressure. For transient loading performance, the transient response characteristic was improved with the control of turbine bypass valve, and the stable time of boost pressure was reduced with the matched turbocharging system.