THEORETICAL STABILITY DERIVATIVES FOR A DUCTED PROPELLER.
Abstract
Static force and moment coefficients at angle of attack and their dynamic pitching derivatives are given for an isolated ducted propeller. These result from a potential flow analysis which is based upon Fourier expansion of the vorticity distribution. The analysis offers a valid technique for combining existing theory for ring wings at angle of attack and ducted propellers in axial flow. The propeller is represented as a uniformly loaded actuator disk and the effects of duct chord-to-diameter ratio, circular arc camber, taper, and thickness are shown for the duct coefficients and their pitching derivatives. The predicted thrust ratio of duct to disk for hovering flight is only slightly less than the asymptotic value of unity for thin cylindrical ducts with chord-to-diameter ratio greater than one half. For either hovering or axial flight, the duct thrust, the thrust ratio, and the propulsive efficiency all increase with duct chordto-diameter ratio, with outward taper downstream, with inward circular arc camber, and also with duct profile thickness if the actuator disk is located in the most favorable position in the duct where the internal cross-sectional area is minimum. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 18, 1963
- Accession Number
- AD0428819
Entities
People
- A. R. Kriebel