Turbomachine Guide Vane Cover Plate Sealing
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Solution Overview
Problem
The existing guide vane assemblies in turbomachines suffer from axial clearance issues, leading to leakage gas flow rates that penalize turbine efficiency.
Innovation Solution
The guide vane assembly incorporates a cover plate that partially or fully covers the pin and/or oblong orifice, preventing parasitic gas flow and enhancing sealing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the guide vane assembly uses a pin and oblong orifice for radial adjustment of the sealing element, then the sealing element can move radially to accommodate thermal expansion, but axial clearance allows parasitic gas flow that reduces turbine efficiency
Solution Approach 1:
The guide vane assembly is segmented into functional zones: the pin and oblong orifice handle radial adjustment, while the cover plate creates a separate sealed chamber. This segmentation allows radial movement functionality to be preserved while isolating the axial clearance region from gas flow paths, eliminating parasitic leakage without compromising thermal expansion accommodation.
Solution Approach 2:
The cover plate acts as an intermediary element that blocks the axial clearance between the first flange and second flange. It mediates between the radial adjustment mechanism (pin and orifice) and the gas flow, preventing gas from utilizing the clearance for parasitic flow while allowing the radial adjustment mechanism to continue functioning for thermal expansion compensation.
2Stress or pressure
If the sealing element is allowed to expand freely with temperature changes, then thermal stress is reduced, but axial clearance creates unwanted gas leakage paths
Solution Approach 1:
The cover plate serves as a mediator that blocks the axial clearance path for gas flow while allowing the sealing element to maintain its thermal expansion capabilities. The pin and oblong orifice configuration enables the sealing element to move radially in response to thermal changes without creating axial leakage paths, thus reducing mechanical stress while preventing energy loss.
Solution Approach 2:
The assembly segments thermal expansion functionality from gas flow paths. The pin and oblong orifice provide radial movement for thermal accommodation, while the cover plate segments off the axial clearance to prevent gas leakage. This allows thermal stress reduction and energy conservation to occur simultaneously through functional separation.
3Ease of manufacture
If the pin and oblong orifice are left uncovered, then the structure remains simple and manufacturing is easier, but parasitic gas flow through the clearance reduces efficiency
Solution Approach 1:
The cover plate is introduced as a simple intermediary component that blocks parasitic gas flow through the axial clearance. It adds minimal structural complexity while effectively preventing gas from flowing through the clearance between flanges, thus improving turbine efficiency without significantly complicating the manufacturing process.
Solution Approach 2:
The solution addresses the gas flow problem by adding a component in a different dimension (axial direction) rather than modifying the radial adjustment mechanism. The cover plate extends axially to block the clearance path, solving the efficiency problem while maintaining the simplicity of the original pin and oblong orifice radial adjustment structure.
Data Source
AI summary
A guide vane assembly for a turbomachine extending about an axis and having at least one stator vane which extends from a platform, a first flange extending radially inwards from the platform, a sealing element being mounted on the first flange by way of a sliding means that allows the sealing element to move radially with respect to the first flange, the sliding means having at least one pin mounted on the sealing element and/or on the first flange and engaged in at least one oblong orifice extending radially and formed in the first flange and/or in the sealing element, wherein the pin and/or the orifice are covered, at least partially, by a cover plate situated axially opposite of at least a part of the pin.