The Development and Experimental Testing of a Lift Augmented Propeller

125 Abstract The primary purpose of lift augmentation for fixed wing aircraft is to increase the lifting force when large lifting forces and/or slow speeds are required, such as during take-off and landing. Wing flaps and slats are currently used during landing on almost all fixed wing aircraft and on take-off by larger jets. While flaps and slats are effective in increasing lift, they do so with a penalty of increased drag, due to the added, deployed surface area. Other technologies have been tested such as circulation control to provide extra lift, and flight stability and control during these same critical portions of the crafts’ flight envelope. Taking advantage of circulation control generally includes the addition of extra weight to an aircraft or the siphoning of power from the power plant to energize the circulation control hardware. It was the goal of this research to apply some of the lessons learned in using circulation control and a passive way of pumping pressurized air to the trailing edge slot located on an unmanned aerial vehicle propeller. The design called for the rerouting of stagnation pressure from the frontal propeller area, through the inside of the propeller blades, to an ejection slot on the training edge of the propeller blade. This allowed for the forward velocity of the aircraft to drive the pressurization of the circulation control plenum passively, without additional hardware. For this study, a Clark-Y airfoil section propeller with an overall diameter of 24 inches was designed and tested in a specifically designed and constructed wind tunnel at West Virginia University. The comparison of both the augmented propeller and the unaugmented (baseline) propeller showed a 6.01 percent increase in efficiency by using the circulation control augmentation. This increase in efficiency is shown to act over the entire range of flight envelopes of the aircraft. It is shown to be particularly beneficial at advance ratios above 0.30, normal operating conditions of propeller driven UAV’s.

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