Blade Clearance Control Using Hybrid CTE Ring Members
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Solution Overview
Problem
Gas turbine engines face challenges in maintaining optimal blade tip clearance due to thermal and centrifugal expansions, particularly in high-speed and pressure turbine sections, which can lead to inefficiencies and potential material abrasion during transient operating conditions.
Innovation Solution
A hybrid support ring system combining high CTE nickel-based superalloys and low CTE ceramic matrix composites, with distinct thermal expansion stages and structural configurations to manage radial expansion and maintain clearance, including a hybrid ring with both materials influencing expansion differently across operational power ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-material support ring is used, then the structure is simple and easy to manufacture, but it cannot effectively maintain optimal tip clearance across varying power conditions due to uniform thermal expansion behavior
Solution Approach 1:
The support ring is constructed as a composite structure comprising a first arcuate segment made of a first material and a second arcuate segment made of a second material with different coefficients of thermal expansion. This composite construction enables differential thermal expansion behavior across the support ring, allowing the structure to maintain optimal tip clearance across varying power conditions while managing the complexity of manufacture through modular segmentation.
Solution Approach 2:
Different portions of the support ring are made from different materials with specific thermal expansion properties tailored to their functional requirements. The first arcuate segment and second arcuate segment each contribute differently to the overall thermal response, creating localized quality variations that collectively solve the clearance control problem across the entire support ring structure.
2Temperature
If high CTE materials are used in the support ring, then thermal expansion is greater which can maintain clearance at high power, but clearance becomes excessive at low power conditions
Solution Approach 1:
The support ring utilizes materials with different coefficients of thermal expansion to create a composite structure whose overall thermal expansion parameter changes adaptively with temperature. At high power conditions, the high CTE material dominates the expansion response to maintain clearance, while at low power conditions, the low CTE material prevents excessive clearance, achieving versatile adaptation across the full power range.
Solution Approach 2:
By combining materials with different CTE values in a composite support ring structure, the system achieves a balanced thermal expansion response that adapts to varying operating conditions. The composite nature allows the support ring to exhibit appropriate clearance characteristics at both high and low power without requiring active control mechanisms.
3Stability of the object's composition
If low CTE materials are used in the support ring, then thermal expansion is reduced which maintains clearance at low power, but clearance becomes insufficient at high power conditions
Solution Approach 1:
The composite support ring structure enables the effective thermal expansion parameter to change based on operating conditions. The low CTE material provides dimensional stability at low power conditions, while the high CTE material contributes to sufficient expansion at high power conditions, achieving adaptability across the full operating range through parameter variation.
Solution Approach 2:
Different arcuate segments of the support ring are assigned different material properties to optimize local thermal responses. The low CTE material segments provide stability where needed, while high CTE material segments provide expansion where required, creating local quality variations that collectively achieve versatile clearance control.
4Measurement precision
If active control systems with actuators are used, then clearance can be precisely maintained, but the device complexity and cost increase significantly
Solution Approach 1:
The support ring structure performs clearance control autonomously through its composite material construction and differential thermal expansion properties. The structure self-adjusts to maintain optimal clearance across varying power conditions without requiring external actuators, sensors, or active control systems, thereby achieving precision clearance control while minimizing device complexity.
Solution Approach 2:
The patent replaces complex mechanical active control systems with a passive thermal expansion-based solution. Instead of using actuators and control mechanisms to adjust clearance, the invention uses the inherent thermal expansion characteristics of composite materials to automatically maintain optimal clearance, substituting a simple thermal-mechanical system for a complex active control system.
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 hybrid ring design effectively maintains optimal tip clearance across varying power conditions, preventing pinch or rub situations and enhancing engine efficiency by balancing thermal and centrifugal expansions, while avoiding structural challenges associated with single-material rings.
Implementation Method 1
a hybrid ring with both materials influencing expansion differently across operational power ranges
Data Source
Figure 1
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Figure 5
AI summary
An engine has a blade stage (10) and a circumferential array of blade outer air seal segments (66). A support ring (70) carries the blade outer air seal segments (66). The support ring (70) has a low-CTE member (72) and a high-CTE member (90) intervening between the blade outer air seal segments (66) and the low-CTE member (72).