Supersonic external-compression diffuser and method for designing same

Abstract

A supersonic externally pressurized inlet comprising a generally scoop-shaped supersonic pressurized portion for diffusing a supersonic free jet. The supersonic pressurization portion includes a main wall having a leading edge and a throat downstream of the leading edge; and sides joined to opposed side edges of the main wall to form a generally scoop-shaped member. The sides preferably protrude far enough into the supersonic flow to encompass the initial oblique shock attached to the leading edge of the main wall. The main wall has an inner surface generally formed as an inclined sector of the surface of revolution, the inner surface of the main wall cooperating with the inner surfaces of the sides to form a three-dimensional external pressurized surface. The supersonic external pressurization inlet also includes a subsonic diffuser section arranged to receive airflow from the supersonic pressurization section and diffuse the airflow to subsonic conditions. The variable geometry inlet includes an outer ramp hinged about its forward edge and forming part of the inner surface of the spoon diffuser, the pivotal movement of the outer ramp being used to vary the throat size of the inlet. The subsonic diffuser includes an inner ramp hinged around its trailing edge to maintain a smooth transition from the outer ramp.

Description

technical field [0001] This invention relates to supersonic diffusers. The invention more particularly relates to externally pressurized supersonic diffusers, such as those used as inlets in air-breathing propulsion systems. Background technique [0002] In many types of aircraft, air-breathing propulsion systems such as turbojet or turbofan engines are used to propel the aircraft at supersonic speeds. Gas turbine engines currently on the market for aircraft propulsion are virtually invariably designed to operate in a condition in which subsonic airflow, typically on the order of Mach 0.3 to 0.6, exists in the engine at the upstream end face. Thus, there is a need for a supersonic diffuser or intake to reduce the velocity of the trapped supersonic airflow to subsonic for intake by the engine. The deceleration process is known in the art as diffusion or pressurization, as the excess kinetic energy of the airflow is converted into a static pressure in...

AI Technical Summary

Problems solved by technology

However, externally pressurized inlets are generally not conducive to flight above about Mach 2.0 because they tend to have a lot of cowling drag as a consequence of having to achieve a lot of airflow diversion ahead of the inlet duct

this large amount of airflow turning results in large fairing angles and long fairing lengths across the direction of airflow, and thus high drag

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