A wind-tunnel investigation of a 7-foot- diameter ducted propeller

Power, free-stream velocity, blade angle, and duct angle of attack were varied to define the aerodynamic characteristics of a full-scale ducted propeller.Dynamic pressure ranged from 0 to 106 psf, rotational velocity from 1200 to 2590 rpm, blade angle from 14 ° to 49 ° , and power from 0 to 1250 hp.The results indicate that the ducted propeller achieved a maximum figure of merit of 81 percent and a maximum propulsive efficiency of 74 percent.Stall boundaries for both the upstream and downstream duct lips were based on pressure distributions.It was found that for a representative V/STOL configuration employing this ducted fan the upstream lip could stall at low power and at high duct angles; however, stall of the downstream lip did not appear to be likely.