Gas Turbine Compressor Case Clearance Control
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Solution Overview
Problem
Gas turbine engines face challenges in controlling and reducing tip clearances between rotating blades and the static case, as these clearances vary during different operating conditions due to thermal expansion and contraction, affecting aerodynamic efficiency and leading to gas leaks and reduced engine performance.
Innovation Solution
A compressor case with a clearance control system that includes cooling passages and manifolds, allowing airflow to cool and contract the case, thereby reducing tip clearances, and can also expand to accommodate thermal growth during transient conditions, using valves and a control system to manage airflow and maintain optimal clearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If tip clearance is reduced to improve aerodynamic efficiency, then engine efficiency is improved, but the clearance varies during different operating conditions causing blade contact or excessive leakage
Solution Approach 1:
The patent implements an active clearance control system that dynamically adjusts tip clearance based on operating conditions. The system uses actuators to move the compressor case or blade tips in real-time, maintaining optimal clearance across different engine operating states rather than using a fixed clearance design.
Solution Approach 2:
The system changes the physical parameter of tip clearance dynamically by controlling thermal expansion through cooling passages or using actuators to adjust the position of blade tips or case surfaces. This allows the clearance parameter to be optimized for different operating conditions.
2Length of moving object
If cooling passages are added to control thermal contraction, then tip clearance is reduced, but device complexity increases
Solution Approach 1:
The compressor case structure serves multiple functions: it provides structural support, contains cooling passages for thermal management, and acts as part of the clearance control mechanism. This multi-functionality reduces the need for separate dedicated components for each function.
Solution Approach 2:
The cooling passages are nested within the compressor case structure, utilizing the existing case geometry to house the thermal management system. This nesting approach integrates the cooling function into the structural component without requiring additional external systems.
3Reliability
If thermal expansion is allowed to accommodate transient conditions, then blade contact is prevented, but tip clearance increases reducing efficiency
Solution Approach 1:
The system takes preliminary action by cooling the compressor case or adjusting blade positions before thermal expansion occurs during transient conditions. This proactive approach prevents excessive clearance development while avoiding blade contact, maintaining efficiency during transitions.
Solution Approach 2:
The clearance control system uses feedback from sensors monitoring clearance, temperature, and operating conditions to actively adjust the position of blade tips or case surfaces. This closed-loop control prevents blade contact while minimizing clearance increases that would reduce efficiency.
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 tip clearances, improving aerodynamic efficiency, reducing gas leaks, and optimizing engine performance by actively managing thermal expansion and contraction, thus enhancing fuel efficiency and preventing blade contact with the case.
Implementation Method 1
Cooling passages are formed in the case and extend between the first manifold and the second manifold. The airflow in the cooling passages cools the compressor case and causes the compressor to contract in diameter.
Implementation Method 2
A bleed inlet extends through the case and allows airflow to enter the first manifold, the cooling passages, and the second manifold. The airflow in the cooling passages cools the compressor case.
Data Source
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AI summary
A compressor case (62) for a gas turbine engine (20) includes an annular body that extends circumferentially around a center axis (A) and extends axially along the center axis (A). A first bleed manifold (70) is formed on an outer surface of the annular body and encloses a first plenum (71). A second bleed manifold (72) is formed on the outer surface of the annular body and is axially aft of the first bleed manifold (70). The second bleed manifold (72) encloses a second plenum (73). A bleed inlet (74) extends through the annular body and into the first bleed manifold (70). Cooling passages (76) are formed in the annular body, and each of the cooling passages (76) extends from the first plenum (71) to the second plenum (73) and fluidically connects the first plenum (71) to the second plenum (73).