Numerical optimization program for designing controlled diffusion compressor blading

A numerical optimization design procedure has been worked out for generation of the Controlled Diffusion Airfoil (CDA) of axial-flow compressors. The cascade total pressure loss coefficient is chosen as an objective function. The numerical optimization design procedure is composed of four programs, i.e., the program for optimization of the prescribed velocity distribution, the initial blade profile generation program, the program for compressible, inviscid flow computation and the program for inverse boundary layer computation. At first the initial blade shape is generated; then the design procedure can be used to optimize the initial blade profile at design and off-design conditions until the final shape of the blade is satisfactory. In order to demonstrate the feasibility of the procedure, the numerical optimization design program was carried out for a compressor stator blade at hub section with high loading and large flow turning angle. The designed cascade has been tested. The test data show that the flow at design conditions is shock-free. Compared with the conventional cascade, the Controlled Diffusion Airfoil (CDA) cascade designed can enlarge the incidence angle range, increase critical Mach number and strengthen the tail edge of the blade. Besides, the CDA cascade has much smaller losses and deviation angle than the conventional cascade.