EFFECT OF CRITICAL MACH NUMBER AND FLUTTER ON MAXIMUM POWER LOADING OF DUCTED FANS

摘要

Flutter tests were made of two wind-tunnel-fan models, one of which had conventional Clark Y airfoil sections end the other of which had high-camber blade sections. The results of the tests confirm the stall-flutter theory which predicts much higher flutter speeds at the high lift coefficients for the high-camber blades. The high-camber blades could, therefore, be operated at much higher power loading than could the low-camber blades. Aerodynamic data of these tests indicated little difference in efficiency for the two fans but somewhat higher maximum lift coefficient for the high-camber fan. The efficiency of the fans decreased after the velocity, as calculated by two-dimensional theory, exceeded the 3peed of sound on the Upper blade surface.