Optimization of intense diffusive turbine nozzle guide vanes suitable for transonic outlet Rotating Detonation Combustors

Authors

Sergio Grasa  - Purdue University, United States of America
Guillermo Paniagua - Purdue University, United States of America

Abstract

In rotating detonation engines the turbine inlet conditions may be transonic with unprecedented unsteady fluctuations. To ensure an acceptable performance of the propulsion system, the turbine passages must be unchoked at subsonic and started at supersonic conditions. This paper focuses on the design and optimization of highly diffusive nozzle guide vanes that can operate at any transonic inlet Mach number, from subsonic into low supersonic conditions. First of all, the problem of unstarting is presented, concentrating on the effect of pressure loss on the accurate prediction of the starting limit. Afterwards, a multi-objective optimization with steady Reynolds Averaged Navier Stokes simulations is performed, including both the endwall and the vane design. Compared to previous research on stator passages with contoured endwalls, significant reductions in pressure loss and rotor forcing are obtained. Furthermore, the inlet Mach number working range is extended while preserving a high level of turning. Additional guidance is provided on the vane and endwall design through the analysis of the isentropic Mach number plots and the visualization of regions of separated flow. Finally, the impact of the inlet boundary layer thickness on the design and performance of the nozzle guide vane is quantified.