Gas Turbine Clearance Control Ring Cactus Design
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Solution Overview
Problem
The varying thermal environment in gas turbine engines causes radial tip clearance changes due to thermal expansion and centrifugal loading, leading to increased core air leakage and reduced engine performance, efficiency, and component life when power is reduced.
Innovation Solution
A blade tip clearance control system using a clearance control ring with a contoured radial outer portion and radial inner portion, featuring fins and slots that define a 'cactus' shape, which includes axially and radially displaced feet and lands to form a 'dead' cavity, allowing for controlled radial movement of the blade outer air seal assembly to maintain optimal tip clearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the radial tip clearance is designed to prevent blade rub under high power operations, then blade safety is improved, but core air leakage increases when engine power is reduced
Solution Approach 1:
The BOAS assembly is designed with dynamic radial movement capability through a control system that adjusts the position of the BOAS relative to the blade tips based on operating conditions. The system transitions from a static clearance design to a dynamic one where the clearance can be actively controlled to optimize performance across different power levels.
Solution Approach 2:
The system changes the radial position parameter of the BOAS assembly to maintain optimal tip clearance. By actively adjusting the BOAS position rather than relying on fixed thermal expansion characteristics, the system adapts the clearance parameter to different operating conditions, reducing energy leakage while preventing blade rub.
2Productivity
If active control systems with actuators are used to maintain desired tip clearance, then engine performance is improved, but device complexity increases
Solution Approach 1:
The control system utilizes the existing thermal environment and temperature differentials within the engine to drive the radial movement of the BOAS assembly. Rather than requiring external actuators, the system self-regulates by exploiting the natural thermal expansion and contraction of components, thereby maintaining performance while reducing mechanical complexity.
Solution Approach 2:
The invention replaces traditional mechanical actuator systems with a thermally-driven control mechanism. Instead of using motors or pneumatic actuators to adjust BOAS position, the system uses thermal fields and temperature gradients to automatically position the BOAS, substituting a complex mechanical control system with a simpler thermal-based solution.
3Manufacturing precision
If thermal systems with selective cooling are used to control clearance, then clearance control precision is improved, but device complexity and energy consumption increase
Solution Approach 1:
The system uses the existing cooling air infrastructure of the gas turbine engine for dual purposes: both for engine component cooling and for controlling the radial position of the BOAS assembly. By making the cooling air system multi-functional, the invention achieves precise clearance control without adding separate thermal control hardware, thereby reducing overall system complexity.
Solution Approach 2:
The cooling air acts as an intermediary medium that transfers thermal energy to control the BOAS position. Rather than directly mechanically positioning the BOAS or using complex thermal actuators, the system uses cooling air as a mediator to indirectly control clearance through thermal expansion and contraction of the BOAS support structure.
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 maintains optimal radial tip clearance by counteracting thermal expansion and centrifugal loading, reducing core air leakage and enhancing engine performance, efficiency, and component life across varying operating conditions.
Implementation Method 1
When in operation, the thermal environment in the engine varies and may cause thermal expansion and contraction such that the radial tip clearance varies
Implementation Method 2
The radial tip clearance may be influenced by mechanical loading, e.g., radial expansion of the blades and/or their supporting disks due to speed-dependent centrifugal loading
Data Source
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AI summary
A clearance control ring for a clearance control system of a gas turbine engine includes a contoured radial outer portion that defines a multiple of fins and a multiple of slots. A clearance control system of a gas turbine engine includes a clearance control ring with a radial inner portion from which a contoured radial outer portion extends. The contoured radial outer portion defines a multiple of fins and a multiple of slots. A blade outer air seal assembly with a clearance control ring land which receives the radial inner portion. A method of controlling a radial tip clearance within a gas turbine engine includes tailoring a multiple of fins and a multiple of slots of a clearance control ring for both steady state and transient clearance operations.