An incidence loss model for wave rotors with axially aligned passages

AN INCDENCE LOSS MODEL FOR WAVE ROTORSWITH AXIALLY ALIGNED PASSAGESDaniel E. Paxson tNASA Lewis Research CenterCleveland, Ohio, USAAbstractA simple mathematical model is described to accountfor the losses incurred when the flow in the duct (port)of a wave rotor is not aligned with the passages. Themodel, specifically for wave rotors with axially alignedpassages, describes a loss mechanism which is sensitiveto incident flow angle and Mach number.Implementation of the model in a one-dimensional CFDbased wave rotor simulation is presented. Comparisonswith limited experimental results are consistent with themodel. Sensitivity studies are presented which highlightthe significance of the incidence loss relative to otherloss mechanisms in the wave rotor.IntroductionInlet flowfields of nearly any wave rotor typicallycontain significant velocity non-uniformities. This istrue for both on and off-design operation. The non-uniformities arise from, among other causes, mis-timedwaves in the passages, and reflected expansion waves offinite width. From the reference frame of the rotorpassages, the non-uniformities result in inflow incidenceangles which can be severe, and can in turn result inlarge relative total pressure losses. Despite the largelosses in the relative frame however, incidence canresult in work being done on (or by) the entering flow,which can affect the overall performance of themachine. Thus, accurate predictions of wave rotorperformance requires adequate accounting of theseeffects. In the case of two and three-dimensionalunsteady CFD calculations they are computed directly)For unsteady one-dimensional, and steady . two-dimensional calculations however, they must bemodeled. 2_ Unfortunately, little has been found in theliterature, either theoretical or experimental, to shedlight on an appropriate modeling approach.This paper presents a model which has beenimplemented in a one-dimensional CFD based waverotor simulation 4. It applies specifically to wave rotorconfigurations in which the passages are aligned witht Member AIAA