Computational Analysis of Rotor-Stator Interaction in Turbomachinery Using Zonal Techniques

Abstract

IntroductionM OST techniques for the numerical prediction of flows in turbomachinery have been based on the approximation that the flow in each stator or rotor row is steady in the respective frames of reference; i.e., the spacing between adjacent stator and rotor rows is assumed to be far enough that there is no interaction between them. An extensive body of numerical results exists in the literature dealing with a wide variety of twoand three-dimensional cascade geometries, both planar and annular, stationary and rotating (see, for example, Refs. 1-5). Such analyses have gained widespread acceptance in the industrial community and are now being routinely used in the design process.In reality, however, flows in turbomachinery are unsteady. The unsteadiness arises from the interaction of the downstream airfoils with the wakes and passage vortices generated upstream, from the motion of the rotors relative to the stators (potential effect), and from vortex shedding at blunt airfoil trailing edges. The unsteady interaction effects impact the aerodynamic, thermal, and structural performance of the airfoils and become increasingly significant as the distance between successive stator and rotor rows is decreased. The problem of rotor-stator interaction is already having an effect on existing designs, where axial gaps between adjacent airfoil rows of one-fourth to one-half of the airfoil chord are common; these effects are bound to be more severe in future designs with higher loading, lower aspect ratios, and reduced overall length. 6 Thus, a need clearly exists for analytical tools that treat the rotor and stator airfoils as a system and provide Downloaded by PURDUE UNIVERSITY on July 23, 2015 | http://arc.aiaa.org |