Variable compression air intakes for aircraft propulsion systems and methods for varying compression of an air intake

An aircraft comprising:

• an airframe;
• and
• a propulsion system comprising:
• an engine coupled to the airframe;
• and
• an air intake in fluid communication with the engine and comprising:
• an inlet cowl comprising a cowl lip;
• a compression ramp spaced away from the cowl lip and comprising a first bump and a second bump that is spaced away from the first bump;
• a diffuser ramp positioned between the second bump of the compression ramp and the engine;
• a throat formed by the cowl and the compression ramp and comprising an inlet formed between the cowl lip and the compression ramp;
• and
• a diffuser formed by the cowl and the diffuser ramp,
• wherein:
• the first bump of the compression ramp protrudes into space upstream of the inlet of the throat;
• the second bump of the compression ramp protrudes into space downstream of the inlet of the throat;
• the compression ramp and the diffuser ramp are movable between a low-speed configuration of the propulsion system and a high-speed configuration of the propulsion system;
• upon transition from the high-speed configuration to the low-speed configuration of the propulsion system:
• the compression ramp is positioned relative to the cowl lip to expand a cross-sectional geometry of the throat at the inlet, as viewed along a central axis of the engine, and reduce compression of an inlet airflow through the inlet;
• and
• the diffuser ramp is positioned relative to the cowl to form a substantially constant cross-sectional geometry of the diffuser, as viewed along the central axis of the engine, in a downstream direction;
• and
• upon transition from the low-speed configuration to the high-speed configuration of the propulsion system:
• the compression ramp is positioned relative to the cowl lip to reduce the cross-sectional geometry of the inlet, as viewed along the central axis of the engine, and increase the compression of the inlet airflow through the inlet;
• and
• the diffuser ramp is positioned relative to the cowl to expand the cross-sectional geometry of the diffuser, as viewed along the central axis of the engine, in the downstream direction from the compression ramp to the engine.

A variable compression air intake for a turbofan engine comprising:

• a cowl comprising a cowl lip and a longitudinal axis;
• a first compression surface protruding into space, wherein the first compression surface is spaced upstream from and is fixed relative to the cowl lip;
• a second compression surface protruding into space, wherein the second compression surface is positioned downstream of the first compression surface and the cowl lip and is movable relative to the cowl lip;
• a diffuser surface positioned downstream of the second compression surface and moveable relative to the cowl;
• a throat formed by the second compression surface and the cowl lip;
• and
• a diffuser formed by the diffuser surface and the cowl,
• wherein:
• the second compression surface and the diffuser surface are movable between a low-speed configuration of the variable compression air intake and a high-speed configuration of the variable compression air intake;
• upon transition from the high-speed configuration to the low-speed configuration of the variable compression air intake:
• the second compression surface is positioned relative to the cowl lip to increase a cross-sectional geometry of the throat, as viewed along the longitudinal axis, and reduce a compression of an inlet airflow through the throat;
• and
• the diffuser surface is positioned relative to the cowl to form a cross-sectional geometry of the diffuser that is substantially constant, as viewed along the longitudinal axis, in a downstream direction;
• and
• upon transition from the low-speed configuration to the high-speed configuration of the variable compression air intake;
• the second compression surface is positioned relative to the cowl lip to decrease the cross-sectional geometry of the throat, as viewed along the longitudinal axis, and increase the compression of the inlet airflow through the throat;
• and
• the diffuser surface is positioned relative to the cowl to increase the cross-sectional geometry of the diffuser, as viewed along the longitudinal axis, in the downstream direction.

A method for varying compression at an air intake of a turbofan engine, the method comprising:

• moving a compression ramp relative to a cowl lip of a cowl between a low-speed configuration of the air intake and a high-speed configuration of the air intake, wherein the compression ramp comprises a first bump that protrudes into space upstream of an inlet of the air intake and a second bump that protrudes into space downstream of the inlet of the air intake;
• moving a diffuser ramp positioned between the compression ramp and the engine between the low-speed configuration of the air intake and the high-speed configuration of the air intake;
• varying compression of an inlet airflow through the inlet of the air intake such that:
• upon transition from the high-speed configuration to the low-speed configuration of the air intake, the compression ramp expands a cross-sectional geometry of the inlet, as viewed along a central axis of the turbofan engine, and reduces the compression of the inlet airflow through the inlet;
• and
• upon transition from the low-speed configuration to the high-speed configuration of the air intake, the compression ramp reduces the cross-sectional geometry of the inlet, as viewed along the central axis of the turbofan engine, and increases the compression of the inlet airflow through the inlet;
• and
• varying a cross-sectional geometry of a diffuser formed by the diffuser ramp and the cowl such that:
• upon transition from the high-speed configuration to the low-speed configuration of the air intake, the cross-sectional geometry of the diffuser, as viewed along the central axis of the turbofan engine, is substantially constant in a downstream direction;
• and
• upon transition from the low-speed configuration to the high-speed configuration of the air intake, the cross-sectional geometry of the diffuser, as viewed along the central axis of the turbofan engine, expands in the downstream direction.