Thermodynamic analysis was conducted on a regulated two-stage turbocharging system of a heavy-duty vehicle.An adiabatic efficiency function of the turbine stage was deduced.A calculation method for mass flow and expansion ratio of high pressure and low pressure turbine was established.Calculation results show that mass flow and expansion ration of high pressure turbine increase as regulated valve closing when the inlet pressure and temperature is fixed,whereas mass flow and expansion ration of low pressure ...