To improve the matching between the turbine and engine

computational fluid dynamics(CFD) methods were adopted to investigate the unsteady performance of variable nozzle turbine influenced by pulsating flow frequency

pulsating flow amplitude

nozzle vane angle and turbine rotating speed.Results show that the turbine instantaneous minimum mass flow rate under 80Hz condition is 10.4% higher than that under 40Hz condition

and the lowest efficiency increases by 4.7%.At high pulsating frequency

the unsteady efficiency apparently lags behind velocity ratio.Under pulsating amplitude of 25kPa condition

the swallow capacity and efficiency recover rapidly

indicating that it is possible to design turbines by steady flow hypothesis under low amplitude conditon.For nozzle angle of 32 degree

the mass flow difference between pulsating inlet flow condition and steady inlet flow condition is 3.3% more than that of 10 degree

and the efficiency difference is 6.6% more.Higher nozzle angle makes turbine flow field more pulsative and results in mass flow rate and efficiency dropping significantly.Under turbine rotating speed of 47256r/min condition

the mass flow rate and efficiency variation caused by pulsating inlet flow is 2.9% and 0.8% more compared to that of 30000r/min.The turbine flow field is more sensitive to turbine inlet condition when rotating speed is high

and the mass flow rate

efficiency and attacking angle deviate from equivalent steady values.