Experimental and Numerical Studies on a Curved Back Transonic Airfoil

The curvature of a turbine blade airfoil downstream of the throat location significantly affects its aerodynamic performance, specifically at Mach number close to unity. In the present work, a low aspect ratio (0.64), highly curved back airfoil corresponding to stator blade 'mean' section of a high-pressure (HP) turbine stage is studied. The details of the blade parameters, experimental test setup, CFD solver and numerical setup are explained in the paper. Its aerodynamic characteristics are obtained numerically using a commercial CFD solver and are compared to those from experimental cascade test results. For numerical assessment, CFD simulations are carried out on three configurations viz. (i) Full turbine stage (stator and rotor) domain (ii) Isolated turbine stator row domain (iii) Stator mean section airfoil cascade domain. The loss predictions obtained through CFD are also compared against the loss estimates calculated using two loss models. The experimental cascade pressure loss across the blade row at design point Mach number 0.996 increases to 250% of that at lower Mach numbers. This drastic increase is not desirable. But the airfoil performs appreciably well in a 'stage' setup i.e. with downstream rotor. Therefore, the present study brings out the behaviour of the stator airfoil performance in a linear cascade, annular cascade and stage environments.