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Date of Award

7-1994

Document Type

Thesis - Open Access

Degree Name

Master of Science in Aerospace Engineering

Department

Graduate Studies

Committee Chair

Dr. Jose Rodriguez

Committee Member

Dr. George Emanuel

Committee Member

Dr. Lakshmanan Narayanaswaml

Abstract

The goal of a diffuser is to transform kinetic energy into potential energy with minimum losses in total pressure. Existing supersonic diffusers are based on compression through shock waves. This process is inherently inefficient because of the large losses caused by the shocks. We investigate by means of Computational Fluid Dynamics (CFD) the viscous flow in a supersonic diffuser designed by means of inviscid theory to produce a shock-free isentropic compression. The design is based on the combination of elementary flows. Two simple wave regions connected by a sink flow are used to take a uniform supersonic flow at one Mach number to a uniform supersonic flow at a lower Mach number. The theory gives an exact solution for two-dimensional flow. The shape of the diffuser depends on the entrance and exit Mach numbers. For a given inlet Mach number, there is a minimum outlet Mach number determined by a limit line that forms at the throat. Multiple stage diffusers may be used to reduce the Mach number and minimize the shock losses. The results indicate the existence of oblique shock waves and flow separation. Nevertheless, the diffuser efficiency is very high when compared to existing diffuser data. The diffusers may be used for engine inlets or supersonic wind tunnels. Only laminar flows are considered.

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