Turbine Ring Sealing for Thermal Expansion Mismatch
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Solution Overview
Problem
CMC materials used in turbomachine turbines exhibit a lower coefficient of thermal expansion than metallic materials, leading to relative displacement and wear between ring sectors and flanges/walls, causing radial gas leakage and performance loss.
Innovation Solution
Incorporation of sealing means with intermediate thermal expansion coefficients between the ring and flange/wall materials to reduce thermal displacement-induced wear, using ceramic matrix oxide/oxide composites or metallic materials like titanium alloys.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If CMC materials are used for the ring to maintain mechanical integrity at high temperatures and reduce density, then the ring can withstand high temperatures and be lighter, but the lower coefficient of thermal expansion causes relative displacement and wear between ring sectors and flanges/walls, leading to gas leakage and performance loss
Solution Approach 1:
The patent introduces sealing means (sealing rings or sealing elements) as intermediary components between the CMC ring sectors and the metallic flanges/walls. These sealing means have a coefficient of thermal expansion intermediate between that of CMC and metallic materials, acting as a mediator that accommodates the thermal expansion difference and prevents relative displacement and wear, thereby maintaining sealing reliability at high temperatures
Solution Approach 2:
The patent employs composite material strategy by selecting sealing means made from materials whose thermal expansion properties are intermediate between CMC and metallic materials. This composite approach allows the sealing system to bridge the thermal expansion gap, preventing wear and gas leakage while maintaining the high temperature resistance of the CMC ring structure
2Weight of moving object
If CMC materials are used for the ring to reduce density, then the ring becomes lighter, but the lower coefficient of thermal expansion causes wear and radial passages, resulting in gas leakage and turbomachine performance loss
Solution Approach 1:
The sealing means serve as intermediary components that prevent gas leakage through the radial passages caused by thermal expansion mismatch. By accommodating the displacement between lightweight CMC ring sectors and metallic flanges/walls, the sealing means maintain the integrity of the gas flow path, preserving turbomachine performance while allowing the use of lightweight CMC materials
Solution Approach 2:
The patent converts the potentially harmful effect of thermal expansion mismatch into a beneficial design feature by intentionally selecting sealing means with intermediate thermal expansion coefficients. This approach transforms the material incompatibility issue into an opportunity to implement effective sealing solutions that protect the lightweight CMC structure from wear and gas leakage, thereby maintaining high turbomachine performance
3Strength
If CMC materials are used for the ring, then mechanical integrity at high temperatures is maintained, but relative displacement causes wear on flanges and walls, creating radial passages and risk of damage to external casing
Solution Approach 1:
The sealing means act as protective intermediary elements between the CMC ring sectors and the metallic flanges/walls. By having intermediate thermal expansion properties, they absorb the differential thermal movement, preventing direct contact and wear between the CMC ring and metallic components, thereby eliminating the risk of damage to the external casing while maintaining the mechanical integrity benefits of CMC materials
Solution Approach 2:
The patent implements beforehand cushioning by pre-installing sealing means that are specifically designed to accommodate thermal expansion differences. These sealing elements are positioned in advance to cushion and absorb the relative displacement that occurs during thermal cycling, preventing wear and potential damage before they can occur to the flanges, walls, or external casing
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
Reduces wear and gas leakage, enhancing turbomachine performance and efficiency by minimizing thermal expansion discrepancies, thereby reducing fuel consumption and pollutant emissions.
Implementation Method 1
CMC materials have a lower coefficient of thermal expansion than metallic materials. Consequently, during turbomachine operation, a relative displacement was observed in the circumferential and radial directions between the sectors of the ring 30 and, on the one hand, the flange 23 upstream and the radial annular wall 22 downstream.
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
Turbine comprising: - an outer annular casing (100) including a radial annular wall (102), - a radial flange (110) fixed to the outer annular casing (100), - a ring (120) including an upstream annular flange (123) and a downstream annular flange (124), - upstream sealing means (140) interposed longitudinally between the upstream annular flange (123) of the ring (120) and the flange (110), and having a coefficient of thermal expansion between that of the flange (110) and that of the upstream annular flange (123), and/or - downstream sealing means (150) interposed longitudinally between the downstream annular flange (124) of the ring (120) and the radial annular wall (102) of the outer casing, the downstream sealing means (150) having a coefficient of expansion thermal between that of the radial annular wall (102) of the external annular housing (100) and that of the downstream annular flange (124).