experimental comparison of controlled diffusion airfoils with double circle airfoils

In order to compare the flow characteristics of different compressor airfoils, experiments has been made on a controlled diffusion airfoil (CDA), as well as a double circle airfoil (DCA) in a high subsonic cascade wind tunnel. The two airfoils are designed for the same velocity triangle at subsonic condition, and the experiments contain the measurement of surface Mach number and the wakes profiles. The results show that the total pressure loss of the controlled diffusion airfoil is nearly half of the double circle airfoil, so is the exit flow angle 2° smaller than that of the double circle airfoil. Before the flow separates on the suction side of CDA, the variations of exit flow angles are within 1° with the incidence and inlet Mach number varying. The core region of the wakes keep fixed among the pitch. However, there is a small flow separation region near the trailing edge of the double circle airfoil, which results in the flow loss and the deficit of flow turning. With the inlet Mach number increasing, the variations of the exit flow angles amount up to 4°, and the core region of the wakes move nearly 20% pitch.