Gas Turbine Shutdown Thermal Soak-back Mitigation
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Solution Overview
Problem
Thermal soak-back in gas turbine engines leads to residual heat transfer, causing physical deterioration of internal components, such as coking, seal deterioration, thermal stresses, and compressor tip rubbing, resulting in early degradation of engine performance and increased maintenance needs.
Innovation Solution
A method of operating a gas turbine engine involving a shutdown procedure that includes idle and cranked rotation operations, where a controller determines thermal parameters to assess thermally stabilised conditions, allowing for controlled heat removal and redistribution using a thermal management system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active cooling with powered fans and adapted ducts is used to mitigate thermal soak-back, then thermal damage to components is reduced, but energy consumption, mass, size and complexity of the gas turbine engine increase
Solution Approach 1:
The gas turbine engine performs its own cooling during shutdown through idle rotation, where the turbine expands hot combustion products to drive the spool and generate airflow for cooling internal components. This self-service approach eliminates the need for external powered fans and complex active cooling systems while effectively mitigating thermal soak-back.
Solution Approach 2:
The invention extracts the cooling function from complex active cooling systems and implements it through the natural expansion of hot combustion products during idle rotation. By removing the need for powered fans and specialized ducts, the solution simplifies the system while maintaining thermal management effectiveness.
2Reliability
If idle rotation operation is performed to cool the gas turbine engine during shutdown, then thermal soak-back is mitigated, but energy consumption increases
Solution Approach 1:
The invention converts the harmful residual heat in the combustion products into a beneficial cooling resource. During idle rotation, the hot combustion products expand and drive the spool, generating airflow that cools internal components. This transforms the waste heat into a useful cooling mechanism, reducing the need for additional energy-consuming cooling systems.
Solution Approach 2:
The system changes the operational parameters during shutdown by maintaining idle rotation at a controlled speed, allowing the turbine to expand combustion products efficiently. This parameter adjustment optimizes the cooling effect while minimizing energy consumption, as the rotation speed is maintained at the level where the turbine can effectively drive the spool for cooling purposes.
3Ease of operation
If thermal soak-back is not managed, then engine operation is simpler, but early degradation in engine performance occurs and maintenance frequency increases
Solution Approach 1:
The invention performs cooling action during the shutdown procedure itself, before the engine is completely stopped. By executing idle rotation and cranked rotation operations that facilitate heat removal, the system prevents thermal soak-back from causing damage. This preliminary cooling action protects components without requiring complex operational procedures during normal operation.
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 effectively mitigates thermal soak-back, reducing component degradation, maintaining engine performance, and minimizing maintenance requirements by optimizing the shutdown procedure based on real-time thermal conditions.
Implementation Method 1
a turbine of the gas turbine engine expands hot combustion products from a combustor to drive the spool to rotate
Implementation Method 2
performing a heat removal operation comprising controlling the thermal management system to cause heat to be removed from the gas turbine engine
Implementation Method 3
performing a heat redistribution operation comprising controlling the thermal management system to cause heat to be redistributed within the gas turbine engine
Implementation Method 4
thermal inertia of heated components of the gas turbine engine such as a compressor disc and/or a turbine disc may lead to residual heat being transferred to other components of the gas turbine engine and/or into surrounding air cavities within the gas turbine engine
Data Source
AI summary
A method of operating a gas turbine engine having a spool includes executing, by a controller, a shutdown procedure. The shutdown procedure includes: performing an idle rotation operation; determining a parameter associated with a thermal condition of the gas turbine engine while the idle rotation operation is performed; determining, based on the determined parameter, whether the gas turbine engine has met a pre-determined criterion corresponding to a thermally stabilised condition; and terminating the idle rotation operation in response to a determination that the gas turbine engine has met the pre-determined criterion.