Nested Cooling Air Duct with Buffer Layer for Gas Turbine
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Solution Overview
Problem
Existing thermal management systems in gas turbine engines face inefficiencies due to thermal pollution of cooling air as it passes through combustion chambers, reducing its effectiveness by increasing thermal energy, which necessitates improvements in air duct designs.
Innovation Solution
A nested tube configuration forming a double wall with a buffer air layer around the cooled cooling air delivery duct reduces thermal pollution by creating a boundary layer, allowing the buffer air to be delivered for thermal management to other engine components, thereby enhancing cooling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If air ducts pass through combustion chamber to deliver cooling air, then cooling air can be delivered to turbine section, but thermal pollution increases thermal energy of cooling air reducing cooling effectiveness
Solution Approach 1:
The patent introduces a buffer air layer as an intermediary substance between the hot combustion chamber environment and the cooling air duct. This buffer air absorbs thermal energy from the combustion chamber, preventing direct heat transfer to the cooling air, thereby maintaining lower cooling air temperature and preserving cooling effectiveness
Solution Approach 2:
The patent converts the harmful thermal energy in the combustion chamber into a beneficial buffer air layer that protects the cooling air duct. The thermal energy that would otherwise directly heat the cooling air is instead used to create and maintain the buffer air layer, transforming the harmful thermal pollution into a protective thermal barrier
2Loss of energy
If cooling air flow rate is increased to compensate for thermal pollution, then cooling effectiveness improves, but system complexity and air source size increase
Solution Approach 1:
The buffer air layer acts as a thermal intermediary that reduces the temperature rise of cooling air passing through the combustion chamber. By introducing this intermediate layer, the system maintains cooling effectiveness without requiring excessive cooling air flow rates, thereby avoiding the need for oversized air sources and complex flow control systems
3Temperature
If buffer air layer is introduced to reduce thermal pollution, then cooling air temperature is maintained, but device complexity increases due to nested duct configuration
Solution Approach 1:
The patent employs a nested duct configuration where the cooling air duct is positioned within the buffer air layer, which itself is contained within the combustion chamber. This nesting arrangement allows multiple functional layers (buffer air layer, cooling air duct, combustion chamber) to be integrated in a compact manner, reducing overall system complexity compared to separate distributed systems
Solution Approach 2:
The buffer air layer serves multiple functions simultaneously: it acts as a thermal barrier protecting the cooling air duct, provides structural support for the nested configuration, and can be utilized as a cooling source for other engine components. This multi-functionality reduces the need for separate dedicated systems, thereby offsetting the complexity introduced by the nested duct arrangement
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 reduces the thermal pollution of cooled air, potentially decreasing the flow rate needed for cooling, enabling a smaller cooling air source and improving rotor temperatures and combustion efficiency by utilizing buffer air for high-pressure compressor and turbine components.
Implementation Method 1
A nested tube configuration forming a double wall with a buffer air layer around the cooled cooling air delivery duct reduces thermal pollution by creating a boundary layer
Implementation Method 2
The outer duct defines a gap with the cooling duct and is configured to transport a flow of buffer air through the gap
Data Source
AI summary
A gas turbine engine includes a combustion section, a turbine section, and a compressor section. The combustion section includes a combustor casing, a combustor, a cooling duct, and an outer duct. The combustor casing defines at least in part a diffuser cavity and a fluid inlet. The combustor disposed is in the diffuser cavity. The cooling duct is in fluid communication with the fluid inlet in the combustor casing and is configured to transport a flow of cooled air. The outer duct surrounds at least a portion of the cooling duct and extends along a portion of an entire length of the cooling duct. The outer duct defines a gap with the cooling duct and is configured to transport a flow of buffer air. The turbine section is disposed downstream from the combustion section. The cooling duct is in fluid communication with the turbine section.