Theoretical Analysis of the Flow in External Aerodynamic Diffusers.
Abstract
The thrust to power ratio for shrouded propellers or ejector type thrust augmentors can be increased by lowering the exhaust velocity. This can be achieved by applying a heavy variable area exit diffuser or by employing light weight external aerodynamic diffusion. Either boundary layer control or a jet flap is required to obtain larger divergence angles of the existing flow. The resulting external aerodynamic diffusion lowers the back pressure at the propeller or ejector and increases the mass flow rate but lowers the final downstream velocity. A numerical method was employed to solve the axisymmetric case. Since the boundary conditions cannot be determined in the physical plane, the governing equations were therefore transformed into those in the von Mises plane. The boundary conditions in the von Mises plane are well defined. A finite difference method was applied, with an over-relaxation method to speed up convergence. The Newton-Raphson method was used to obtain the solution of each of the difference equations in the iteration loop. The Gauss-Seidel process was used for the iteration process in the computer program. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1974
- Accession Number
- ADA020645
Entities
People
- John L. Loth
- Ying-chieh Albert Lee
Organizations
- West Virginia University