Gas Turbine Case Cooling via Bypass Air Pre-cooler
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Solution Overview
Problem
During operational points where the environmental control system of an aircraft is not actively used, high pressure turbine and low pressure turbine case clearances and case temperatures require additional control to prevent overheating and maintain optimal conditions.
Innovation Solution
A gas turbine engine system comprising a pre-cooler, fan air valve, and pressure regulating/shut-off valve, controlled by a controller that assesses the core compartment temperature and adjusts the flow of bypass air to maintain target temperatures, even when the environmental control system is off, using bleed air from the compressor sections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the environmental control system is not actively used, then energy consumption is reduced, but turbine case temperatures increase and clearances become uncontrolled
Solution Approach 1:
The system performs preliminary cooling action by directing bypass air to the core compartment before the turbine case temperature becomes excessive. The controller monitors temperature conditions and activates cooling flow in advance to prevent temperature rise, rather than reacting after overheating occurs.
Solution Approach 2:
The system uses the engine's own bypass air flow to cool the turbine case, utilizing resources already present in the engine system. The bypass air, which would otherwise be wasted, is redirected to serve the cooling function, making the system self-sufficient without requiring external cooling sources.
2Temperature
If bypass air is continuously directed to cool the core compartment, then turbine case temperature is maintained, but energy efficiency decreases
Solution Approach 1:
The system dynamically adjusts the bypass air flow to the core compartment based on real-time temperature conditions and engine operational state. The controller modulates the cooling flow rate to match the actual cooling demand, increasing flow when temperature rises and reducing or stopping flow when temperature is adequate, thereby optimizing energy efficiency.
Solution Approach 2:
The system implements feedback control by continuously monitoring turbine case temperature and using this information to adjust bypass air flow. The controller receives temperature data and modifies the cooling flow accordingly, creating a closed-loop control system that maintains temperature within target ranges while minimizing unnecessary energy loss.
3Adaptability or versatility
If the pressure regulating/shut-off valve is kept open to provide bleed air, then pre-cooler functionality is maintained, but system complexity increases
Solution Approach 1:
The pressure regulating/shut-off valve serves multiple functions: it controls bleed air flow to the pre-cooler for cooling operations, regulates pressure in the bleed air system, and can be modulated to provide different flow rates based on operational requirements. This multi-functionality reduces the need for separate dedicated components.
Solution Approach 2:
The system combines the pressure regulation and shut-off functions into a single valve mechanism that is already present in the bleed air system. By utilizing this existing valve for dual purposes (pressure control and flow control for cooling), the system avoids adding separate control components, thereby minimizing added complexity.
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
Effectively cools the gas turbine engine cases, maintaining optimal clearances and temperatures by providing bypass air to the core compartment when needed, thus preventing overheating and ensuring efficient engine operation.
Implementation Method 1
The pre-cooler has a bypass inlet, a bleed air inlet, a bleed air outlet that is operatively connected to an environmental control system
Implementation Method 2
This spent bypass air can have a significant cooling effect on the core engine cases
Data Source
Figure 1
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Figure 4~5
AI summary
A method of cooling a gas turbine engine case assembly includes moving a fan air valve (62) that is operatively connected to a pre-cooler (64) having a bypass inlet (70) that is configured to receive bypass air that bypasses a gas turbine engine core to facilitate a provision of bypass air through a fan air valve inlet (60) to the bypass inlet to a first open position, in response to a core compartment (34) temperature being greater than a target core compartment temperature. The method further includes bleeding the bypass air through a bypass outlet (72) of the pre-cooler into a core compartment.