DRAG AND PROPULSIVE EFFICIENCY OF SHROUDED AIR PROPELLERS IN AXIAL FLOW. AN ANALYTICAL REVIEW OF EXPERIMENTAL INVESTIGATIONS,
Abstract
Experimental investigations of shrouded air propellers in which propulsive efficiency in axial flow was measured have been reviewed. A simple, semi-empirical formula, using either measured or estimated shroud drag, gives good predictions of the propulsive efficiency at Mach numbers below the drag rise Mach number, provided the shroud does not have appreciable drag due to separation or interference between its various parts. For each shrouded propeller, there is a range of thrust coefficients in which near-maximum efficiency occurs that helps determine that shrouded propeller's applicability to a given aircraft propulsion requirement. Because of this characteristic, shrouded propellers for VTOL aircraft with good efficiency in both hover and cruise will probably have to have either variable intake lip geometry or variable disc area. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1968
- Accession Number
- AD0840750
Entities
People
- Arthur E. Johnson
- David W Taylor