Blade Tip Clearance Control via Differential Thermal Expansion
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Solution Overview
Problem
Conventional sealing systems in turbomachinery, such as gas turbine engines, face inefficiencies due to large tip clearances resulting from thermal mismatch between rotating and static structures, leading to leakage and reduced performance.
Innovation Solution
A rotating blade tip clearance system featuring a control ring carrier with a cover and connector segments, manufactured using direct metal laser sintering, which includes thermally isolated components with different thermal expansion coefficients to minimize tip clearance through controlled thermal response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large tip clearances are used to accommodate thermal mismatch between rotating and static structures, then reliability is improved, but efficiency deteriorates due to increased leakage
Solution Approach 1:
The control ring is designed with different thermal expansion characteristics than the control ring carrier, allowing the radial position of the outer air seal to change in response to temperature variations. This parameter change enables the system to adapt tip clearance dynamically based on thermal conditions, reducing leakage while accommodating thermal mismatch.
Solution Approach 2:
The control ring and control ring carrier are made of materials with different coefficients of thermal expansion. As temperature changes during engine operation, the control ring expands or contracts at a different rate than the carrier, causing the outer air seal to move radially and adjust tip clearance accordingly, thereby reducing energy loss from leakage.
2Manufacturing precision
If a cover is added to thermally isolate the control ring from the control ring carrier, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
A cover is introduced as an intermediary component between the control ring and control ring carrier. This cover provides thermal isolation, preventing unwanted heat transfer that would compromise the differential thermal expansion mechanism. The cover ensures precise tip clearance control by maintaining the intended thermal behavior of the control ring assembly.
Solution Approach 2:
The control ring assembly utilizes multiple materials with different thermal properties - the control ring, control ring carrier, and cover are made of materials selected for their specific thermal expansion characteristics. This composite approach enables precise control of tip clearance through controlled thermal responses while managing heat transfer between components.
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 reduces blade tip clearance, enhancing efficiency and performance by maintaining optimal clearance across various operating conditions, thereby improving fuel burn and component life.
Implementation Method 1
conventionally requires large tip clearances due to the mismatch in thermal responses between the rotating structure and the static structure
Implementation Method 2
The control ring, the control ring carrier and the connector segments can be manufactured as a single unit by casting, direct metal laser sintering (DMLS), or by any other suitable process
Data Source
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AI summary
A rotating blade tip clearance system (100) includes a control ring carrier (105) defining a centerline axis. The control ring carrier has a connecting portion (107), a retaining portion (109) radially inward of the connecting portion, and a flange (111) connecting radially between the connecting portion and the retaining portion. The flange isolates the retaining portion of the control ring carrier from the thermal deflection of a case and assists in keeping the control ring carrier aligned about centerline axis A during thermal deflection. The retaining portion includes radially inner (113) and outer (115) diameter sides defining a retaining cavity therebetween. The system includes a control ring (119) within the retaining cavity. The control ring has a different thermal response rate from the control ring carrier so that the control ring thermally deflects slower than the control ring carrier, thereby controlling the rate and/or extent of thermal deflection of the control ring carrier.