PIV-Informed Modeling of a Compound Helicopter Pusher Propeller

Abstract:
The objective of this study is to experimentally determine the effect a compound helicopter fuselage has on the forward flight performance of a pusher propeller through wind tunnel testing in the Glenn L. Martin Wind Tunnel (GLMWT). This systematic test campaign builds off of previous compound helicopter test campaigns at the University of Maryland (UMD) where various vehicle configurations have been tested at high advance ratios. Present wind tunnel tests were carried out with three distinct vehicle configurations: isolated propeller, isolated fuselage, and finally fuselage with propeller. The effects of fuselage placement on propeller performance are investigated through measuring propeller loads along with two-dimensional three-component phase-resolved particle image velocimetry (PIV) measurements. The PIV measurements are used to inform two different climb velocity models used in Blade Element Momentum Theory (BEMT) to predict the effects of the fuselage on the pusher propeller's performance. Flow field measurements showed a reduction in axial flow velocity closer to the propeller root with the addition of the fuselage, whereas at the outboard 20% of the propeller's radius, the flow remained close to freestream velocity. The thrust over power ratio of the propeller increased in this configuration compared with the isolated propeller, while overall propulsive efficiency remained similar when computed with the scaled climb velocity.

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