Abstract
A controlled diffusion airfoil (CDA) for application to a variable-pitch axial-flow fan has been developed. The points of maximum camber height and maximum thickness in the CDA are located at 45% and 35% of the chord length, respectively. The performance of the CDA was investigated by two-dimensional cascade tests. The CDA was then applied to a rotor blade of a low-speed axial-flow fan. The results of the cascade tests show that the loss of the CDA cascade is 5% lower than that of the NACA 65 cascade. Moreover, the tests using the low-speed axial-flow fan show that the CDA rotor blade has better performance than that of the NACA 65 roter blade; namely, the surge margin and the efficiency of the CDA rotor are 13% larger and 3% higher than those of the NACA 65 rotor, respectively. It is thus concluded that the CDA can be applied to a variable-pitch axial-flow fan and provide wide operating range and high efficiency.
