Nozzle Guide Vane Ring Seal Venting for Thermal Clearance Stability
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Solution Overview
Problem
Existing turbine nozzle guide vanes are sensitive to temperature variations, leading to increased leakage flow and accelerated wear due to varying clearances between the ring seal and knife-edges, which deteriorates engine performance and reduces seal lifetime.
Innovation Solution
Incorporation of a deflector to guide airflow into a ventilation cavity, combined with through-openings in the ring seal, to mix cooling fluid with hot gases and reduce temperature gradients, thereby stabilizing the ring seal's temperature and reducing thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ring seal with abradable element and knife-edges is used to reduce gas circulation outside the primary annular duct, then sealing performance is improved, but the seal becomes sensitive to temperature variations causing clearance changes that increase leakage flow and accelerate wear
Solution Approach 1:
The invention introduces a ventilation cavity that changes the thermal parameters of the ring seal by allowing hot gas to circulate within the seal structure. This parameter change stabilizes the temperature distribution, reducing thermal expansion variations and maintaining consistent clearance between the abradable element and knife-edges, thereby reducing leakage flow and wear while preserving sealing performance
Solution Approach 2:
The ventilation cavity acts as an intermediary thermal management system between the hot gas path and the ring seal structure. It mediates the thermal effects by allowing controlled hot gas circulation, which stabilizes the seal temperature and reduces the harmful temperature sensitivity without compromising the sealing function
2Temperature
If cooling flow is injected between the abradable element and knife-edges, then localized cooling is achieved, but the cooling flow does not mix with hot air from leakage, causing differential thermal expansion that blocks radial movement of the ring seal
Solution Approach 1:
The invention merges the cooling flow path with the hot gas leakage path by designing the ventilation cavity to allow mixing of cooling air with hot gas. This combination creates a unified thermal environment that prevents differential thermal expansion between different parts of the seal structure, maintaining radial movement capability while providing necessary cooling
Solution Approach 2:
The invention uses pneumatic principles by introducing a ventilation cavity that utilizes gas flow dynamics. The cavity allows cooling air to mix with hot gas through controlled flow paths, using pressure gradients and flow mixing to achieve uniform temperature distribution without blocking the radial movement of the ring seal
3Adaptability or versatility
If the ring seal is mounted with radial clearance to allow thermal expansion, then radial movement is enabled, but temperature variations cause opening of clearances between abradable element and knife-edges, increasing leakage and reducing seal performance
Solution Approach 1:
The invention changes the thermal parameters within the ring seal by introducing hot gas circulation through the ventilation cavity. This parameter change creates a more uniform temperature distribution that reduces differential thermal expansion, allowing the seal to maintain radial movement capability while keeping clearance variations between abradable element and knife-edges minimal, thus preserving seal tightness
Data Source
AI summary
The present invention relates to a nozzle guide vane for a turbine, having an axis of revolution and comprising:a flange extending radially relative to the axis; —a ring seal mounted on the flange and comprising an inner face that is configured to bear an abradable element; —a ventilation cavity delimited radially on the inside by an outer face of the ring seal and downstream by an upstream face of the flange; —a baffle configured to guide an airflow toward the ventilation cavity; and—at least one through-opening formed in the ring seal and configured to put the ventilation cavity in fluidic communication with the inner face of the ring seal.