Characterizing the Oscillatory Unstart/Restart of a Supersonic Stator in Unsteady Conditions

This paper presents a numerical investigation of an undesirable mode of unsteady supersonic turbine operation that may arise under off-design conditions. Two-dimensional unsteady Reynolds-averaged Navier–Stokes simulations of a supersonic stator operating in unsteady conditions were performed to characterize the oscillatory unstart/restart behavior that was observed in cases where inlet Mach numbers fluctuated between the unstarted and self-started conditions of the stator. Oscillatory unstart/restart at higher reduced frequencies corresponded to shorter unstart/restart durations, which resulted in lower stator total pressure losses and higher outlet tangential velocities. It was observed that supersonic stator operation at sufficiently high reduced frequencies resulted in a mitigation of unstarting in unsteady conditions.