Cooling Aft Aerodynamic Fairing Floor via Secondary Air Injection
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Solution Overview
Problem
The increasing temperatures of the primary airstream from turbojet exhaust nozzles pose challenges for thermal resistance and expansion in the thermal protection floor of aircraft engine mounting structures, leading to potential overheating and reduced durability, as well as noise issues due to temperature gradients and inadequate cooling.
Innovation Solution
A propulsion system that extracts a cooling airstream from the secondary airstream of the turbojet and injects it into the thin space between the thermal protection floor and the exhaust nozzle using an air circulator, with strategically placed air inlets and outlets to homogenize temperatures and enhance cooling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the thermal protection floor is positioned close to the exhaust nozzle to reduce space, then the structural compactness is improved, but the temperature of the thermal protection floor increases due to radiant heat from the hot region of the nozzle
Solution Approach 1:
A cooling airstream is introduced as an intermediary substance between the hot exhaust nozzle and the thermal protection floor. This cooling air acts as a thermal mediator, absorbing radiant heat from the nozzle and convecting it away, thereby protecting the floor from excessive temperatures while maintaining the compact spatial arrangement.
Solution Approach 2:
The invention utilizes pneumatic flow of cooling air to manage thermal conditions. By directing a controlled airstream through the gap between the nozzle and thermal protection floor, the system uses fluid dynamics to transfer heat away from critical components, resolving the contradiction between spatial compactness and thermal protection.
2Power
If the primary airstream temperature increases to improve turbojet performance, then the propulsion efficiency is improved, but the thermal resistance and thermal expansion of the thermal protection floor materials worsen
Solution Approach 1:
The cooling airstream serves as a thermal barrier and heat transfer medium, intercepting radiant heat from the high-temperature primary airstream before it reaches the thermal protection floor. This intermediary cooling flow allows the turbojet to operate at higher powers while protecting the structural materials from excessive thermal stress.
Solution Approach 2:
The invention changes the thermal parameters of the environment surrounding the thermal protection floor by introducing a controlled cooling airstream. This modifies the local temperature field, reducing the thermal load on the floor materials and allowing the turbojet to operate with higher primary airstream temperatures without compromising material reliability.
3Temperature
If cooling air is extracted from the secondary airstream, then the cooling effect on the thermal protection floor is improved, but the secondary airstream flow is disturbed
Solution Approach 1:
A portion of the cooling air is extracted from the secondary airstream to be redirected into the gap between the exhaust nozzle and thermal protection floor. This extraction provides the necessary cooling effect while attempting to minimize disruption to the overall secondary flow by taking only a controlled portion of the available air.
Solution Approach 2:
The cooling air extraction and injection is localized to specific regions where thermal protection is most needed. By applying cooling only in the critical gap area rather than disrupting the entire secondary airstream, the system achieves effective local cooling while minimizing global flow disturbances.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution significantly increases the lifespan of the thermal protection floor and exhaust nozzle by maintaining a cooler temperature, reducing noise, and preventing overheating, while minimizing disturbances to the secondary airstream.
Implementation Method 1
a cooling airstream being extracted from a secondary airstream of the turbojet and being injected into a space delimited by the thermal protection floor and the exhaust nozzle
Data Source
AI summary
A propulsion system for an aircraft, including a dual-flow turbojet and a mounting structure for mounting this turbojet on the wing surface or on the fuselage of an aircraft. The mounting structure includes an aft aerodynamic fairing including a thermal protection floor to protect the mounting structure from the heat of a primary airstream channelled by an exhaust nozzle of the turbojet, as well as an air inlet provided in a longitudinal aerodynamic wall washed by a secondary airstream of the turbojet and delimiting together with an other similar wall a cavity isolated from the secondary airstream for extracting a cooling airstream from the secondary airstream, and air circulation means fed by the air inlet and having at least one outlet aperture emerging in a space between the thermal protection floor and the exhaust nozzle.