Theory of Power Augmented Ram Lift at Zero Forward Speed
Abstract
Recent experiments by Huffman and Jackson demonstrated the possibility of an air cushion operating mode for an aircraft with low aspect ratio endplated wings wherein the propulsion system is mounted forward of the wing and exhausted into the space between the wing and the ground to generate high pressures for wing lift at zero forward speed. Gallington has derived two- dimensional potential flows relevant to this phenomenon, but applying to larger ratios of propulsive jet area to leading edge air gap area (height of wing above ground times wing span) than were employed in the experiments. In this report, simple momentum theory is applied to obtain performance estimates for a range of jet area ratios from zero to the limiting cases of the potential flow solutions. Reasonable agreement with experiment is found, suggesting that two-dimensional flow models may give useful estimates of the performance potential of such systems. It is found that, under conditions such that a large fraction of the propulsion system thrust is recovered as useful propulsive thrust, the ratio of lift to thrust is very sensitive to the jet area ratio and optimum performance is obtained for jet area ratios approaching unity. Additional experiments are needed, covering the full range of jet area ratios, to evaluate the practical potential of power augmented ram lift systems.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1976
- Accession Number
- ADA033673
Entities
People
- David W Taylor
- Harvey R. Chaplin
- Roger W. Gallington