Gas Turbine Outer Case Cooling via Ambient Air Convection
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Solution Overview
Problem
Gas turbine engines face increased thermal stresses and potential failures due to outer case deformation and associated stress on bearing support struts, exacerbated by high temperatures and conventional cooling methods that rely on compressor bleed air.
Innovation Solution
A thermal barrier/cooling system comprising an internal insulating layer and convective cooling channel that directs ambient air flow to reduce radiated heat, minimizing the need for compressor bleed air and reducing thermal stresses on the outer case and bearing support struts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional forced convection cooling using compressor bleed air is used, then the outer case temperature can be controlled, but the engine efficiency decreases due to loss of compressed air and the system complexity increases
Solution Approach 1:
The cooling system uses natural convection currents created by the temperature difference between the hot outer case surface and the ambient air, eliminating the need for forced air circulation from the compressor. The system serves itself by utilizing the thermal energy that needs to be dissipated to drive the cooling process, thereby maintaining engine efficiency while controlling outer case temperature.
Solution Approach 2:
The invention extracts the cooling function from the compressed air system and implements it independently using ambient air and natural convection. This separates the temperature control function from the compressed air supply system, allowing the engine to maintain full efficiency while still achieving effective cooling of the outer case.
2Power
If higher temperatures are used in the turbine section, then power output increases, but thermal expansion causes outer case deformation and increases stress on bearing support struts
Solution Approach 1:
The thermal management system is segmented into two independent components: an internal insulating layer that protects the outer case from radiant heat, and an external natural convection cooling system that dissipates heat. This segmentation allows the turbine section to operate at high temperatures for power generation while the outer case remains thermally protected, maintaining structural strength and preventing deformation.
Solution Approach 2:
The internal insulating layer acts as a protective barrier that cushions the outer case against thermal stress before it can cause deformation. By providing this thermal protection in advance, the system enables high-power operation without compromising the structural integrity of the case and bearing support struts.
3Temperature
If an internal insulating layer is added to reduce radiated heat, then the outer case temperature decreases, but the device complexity increases
Solution Approach 1:
The internal insulating layer is implemented as a thin, flexible thermal barrier that can be easily applied to the outer case surface. This thin-film approach provides effective thermal protection without adding significant structural complexity or weight to the cooling system.
4Temperature
If compressor bleed air is used for cooling, then the outer case can be cooled effectively, but the quantity of compressed air available for other functions decreases
Solution Approach 1:
The cooling system utilizes ambient air and natural convection currents to cool the outer case, making the system self-sufficient and independent of the compressor's air supply. This eliminates the trade-off between cooling effectiveness and compressed air availability, as the system draws cooling air from the environment rather than consuming valuable compressed air.
Solution Approach 2:
The cooling function is extracted from the compressed air system and implemented using independent ambient air resources. This separation allows the full quantity of compressed air to be available for its intended functions while the outer case cooling is handled by a dedicated natural convection system.
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
The system effectively controls the temperature of the outer case and reduces thermal stresses, preventing material creep deformation and strut failures, while maintaining engine efficiency by eliminating reliance on compressor bleed air for cooling.
Implementation Method 1
providing a thermal resistance to radiated energy from structure located radially inwardly from the outer case
Implementation Method 2
forms a flow path for an ambient air flow cooling the outer case surface
Data Source
AI summary
A thermal barrier/cooling system for controlling a temperature of an outer case of a gas turbine engine. The thermal barrier/cooling system includes an internal insulating layer supported on an inner case surface, the internal insulating layer extending circumferentially along the inner case surface and providing a thermal resistance to radiated energy from structure located radially inwardly from the outer case. The thermal barrier/cooling system further includes a convective cooling channel defined by a panel structure located in radially spaced relation to an outer case surface of the outer case and extending around the circumference of the outer case surface. The convective cooling channel forms a flow path for an ambient air flow cooling the outer case surface.