A DESIGN OPTIMIZATION PROCEDURE FOR EFFICIENT TURBINE AIRFOIL DESIGN

An optimization procedure has been developed for the efficient design of turbine blade airfoil sections- A shape sensitivity study of the ai rfoils has been performed considering two leading edge shapes, circula r and elliptic. Pressure and suction surfaces are approximated by poly nomials. A two-level, nonlinear constrained optimization problem is fo rmulated and is solved using the method of feasible directions. The ae rodynamic analysis is performed using a two-dimensional panel code. Si nce several evaluations of the objective functions and the constraints are required within the optimizer, and exact aerodynamic analysis at each step is computationally prohibitive, a two-point exponential appr oximation technique has been used. The procedure developed successfull y eliminates the sharp leading edge velocity spikes, characteristic of typical blade sections, without compromising blade performance. Circu lar leading edge airfoils appear to be more effective in eliminating t he spikes than elliptic leading edge airfoils. However, the elliptic l eading edge sections are more slender than the circular leading edge s ections. Optimum results are compared with a reference design.