Syracuse University
Syracuse, New York, U. S. A.
Improvements of turbomachine blade aerodynamic performance require proper tailoring of the three-dimensional blade profile. At the present time, techniques employed to arrive at the initial blade shapes are at most quasi-3D. The quasi-3D blade design module typically consists of two steps: a flow-condition specification step for each blade row and a blade-geometry definition step. In the first step, an axisymmetric throughflow method with built-in loss/blockage correlations is used to select the radial work or flow-angle distributions for each blade row so as to maximize the efficiency of the multistage machine. The second step in the quasi-3D blade design module involves the use of families of standard profile shapes with correlated performance to generate the blade geometries. Because these methods model the highly complex three-dimensional flowfield in the endwall regions (secondary flows and clearance effects) and multistage effects (streamwise vorticity and unsteady wakes) through experimental correlations, they are often not reliable (e.g. designs that are outside the region of validity of the correlations).
In this talk, we summarize our progress in the development of a fully 3D and viscous inverse method to upgrade the blade generation module used in existing blade design systems. In this inverse method, the following quantities are prescribed: (1) the blade pressure loading distribution, (2) the tangential thickness distribution, and (3) a blade stacking line, and the corresponding blade camber surface is sought after. The inverse method is formulated using the JST finite-volume formulation of the unsteady Navier-Stokes equations for turbulent flows. During the time-marching process to the steady-state solution, fluid is allowed to cross the blade surfaces, and a pressure-jump condition is imposed at the blade surfaces. The blade profile is periodically updated during this time-marching process using the flow-tangency conditions along the blade surfaces. The method is demonstrated for the redesign of a high-speed transonic rotor blade (NASA Rotor 67), a Supersonic ThrougFlow (STF) fan, and an industrial compressor rotor.