Supersonic external-compression air ducts, diffuser and air ducts system

Abstract

A supersonic external-compression inlet comprises a generally scoop- shaped supersonic compression section for diffusing a supersonic free stream flow. The supersonic compression section includes a main wall having a leading edge and a throat portion downstream of the leading edge, and side portions joined to opposite side edges of the main wall so as to form a generally scoop-shaped structure. The side portions advantageously extend into the supersonic flow stream far enough to encompass the initial oblique shock wave that is attached to the leading edge of the main wall. The main wall has an inner surface formed generally as an angular sector of a surface of revolution, the inner surface of the main wall coacting with inner surfaces of the side portions to define a three-dimensional external- compression surface. The supersonic external-compression inlet also includes a subsonic diffuser section arranged to receive flow from the supersonic compression section and to diffuse the flowto a subsonic condition. A variable-geometry inlet includes an external ramp hinged about its forward edge and forming a portion of the inner surface of the scoop- shaped diffuser, pivotal movement of the external ramp serving to vary a throat size of the inlet. The subsonic diffuser includes an internal ramp hinged about its aft edge for maintaining a smooth transition from the external 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 increase. In order to m...

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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