Aircraft Engine Bypass Air Heating for Thrust Augmentation
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Solution Overview
Problem
Aircraft engines with high bypass ratios face a significant difference in thrust between take-off and climbing/high-altitude phases due to choked flow in the exhaust nozzle, limiting further thrust generation as the fan reaches its aerodynamic or mechanical limit.
Innovation Solution
The method involves applying a heat source to increase the temperature of bypass air flowing through the exhaust nozzle, using conductive surfaces within the engine to heat the bypass air through convection, thereby enhancing thrust without increasing fan rotational speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the fan rotational speed is increased to provide additional thrust during climbing or high-altitude flight, then thrust is improved, but the fan reaches its aerodynamic or mechanical limit and cannot rotate any faster
Solution Approach 1:
The patent changes the temperature parameter of the bypass air by applying heat sources (electric heaters, induction heaters, or combustion heaters) to increase the exhaust gas temperature. This allows the exhaust flow to accelerate beyond the speed of sound at the nozzle exit, generating additional thrust without increasing fan rotational speed. The thrust increase is achieved by modifying the thermal state of the exhaust gases rather than increasing mechanical rotation speed.
2Force
If the exhaust nozzle flow is choked (flowing at the speed of sound), then thrust is maximized for a given rotational speed, but further thrust cannot be provided by increasing rotational speed
Solution Approach 1:
The patent applies heat sources to the bypass air or exhaust gases to increase their temperature. By raising the exhaust gas temperature above the speed of sound at the nozzle exit, the system overcomes the choked flow condition and generates additional thrust. The heating process modifies the thermodynamic state of the exhaust, enabling supersonic flow and increased momentum exit velocity without increasing fan speed.
Solution Approach 2:
The patent replaces the mechanical approach of increasing fan rotational speed with a thermal approach using heat sources. Instead of mechanically accelerating the exhaust flow by spinning the fan faster, the system uses electric heaters, induction heaters, or combustion heaters to thermally accelerate the exhaust gases, substituting mechanical energy with thermal energy to overcome the choked flow limitation.
3Force
If a heat source is applied to heat the bypass air to increase thrust, then additional thrust is generated, but the device complexity increases
Solution Approach 1:
The patent explores using existing engine components for multiple functions. For example, the exhaust nozzle or combustion chamber walls, which are already present in the engine, could serve as heat transfer surfaces for induction heaters or electric heaters. This multi-functionality approach reduces the need for entirely new dedicated heating components, thereby limiting the increase in device complexity while still achieving the thrust enhancement through thermal heating of the bypass air.
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 approach allows for additional thrust to be generated by increasing the exhaust gas temperature, effectively extending the thrust limit over a wider range of ambient temperatures and enabling more efficient thrust during climbing and high-altitude phases.
Implementation Method 1
heating the bypass air through convection heat-transfer from the at least one conductive surface to the bypass air
Implementation Method 2
The heat source may be an induction heater and applying the heat source to the at least one conductive surface may comprise inductively heating the at least one conductive surface
Data Source
Figure 1
Figure 2A~2C
Figure 3A
AI summary
In a method for operating an engine (100), a request for an increase in thrust generated by the engine is received. In response to receipt of the request, a determination is made as to whether at least one operating condition for heat application-based thrust is met. If so, a heat source is applied to heat bypass air flowing through the bypass duct towards the exhaust nozzle (47) and the increase in thrust is generated from an increased temperature of mixed bypass air and core air at the exhaust nozzle.