Turbine Blade Shroud Seal Guide for Lower Mixing Loss
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Solution Overview
Problem
In aircraft gas turbines, the flow of combustion gas through the gap in the seal structure collides with the main flow, causing mixing loss due to a mismatch in flow direction, which reduces efficiency.
Innovation Solution
The design includes a rotor blade shroud with a fin and a guide member in the cavity formed by the rotor blade shroud, stationary blade shroud, and casing, where the guide member directs the combustion gas radially inward to align its flow with the main flow, reducing mixing loss by contracting the gas flow and increasing the path area, thus minimizing interference with the main flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a fin or honeycomb seal structure is provided to reduce combustion gas leakage through the gap, then the flow rate of combustion gas passing through the gap is reduced, but the combustion gas collides with the main flow causing mixing loss
Solution Approach 1:
A guide member is introduced as an intermediary component between the cavity and the main flow path. This guide member includes a guide surface that redirects the combustion gas flow from the cavity, causing it to merge with the main flow in a direction that reduces collision and mixing loss. The guide member acts as a mediator that transforms the flow direction without requiring direct contact between the cavity flow and main flow.
Solution Approach 2:
The flow direction parameter of the combustion gas is changed by the guide member. The guide surface is designed to alter the flow angle and direction of the combustion gas exiting the cavity, transforming it from a radial inward flow to a flow that aligns better with the main flow direction, thereby reducing mixing loss.
2Productivity
If the gap between rotor blade and housing is reduced to improve output, then combustion gas leakage is reduced, but the seal structure complexity increases
Solution Approach 1:
The seal structure is segmented into multiple functional components: the fin extending from the rotor blade shroud, the cavity formed between the fin and casing, and the guide member with its guide surface. This segmentation allows each component to perform a specific function - the fin and cavity control the leakage flow, while the guide member directs the flow to merge with the main flow, achieving effective sealing without excessive complexity.
Solution Approach 2:
The guide member serves as an intermediary that simplifies the overall seal system by providing a controlled path for the combustion gas. Instead of requiring direct contact seals or complex active clearance control systems, the guide member mediates the flow transition, allowing the seal structure to remain relatively simple while effectively reducing leakage and mixing loss.
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
This configuration reduces mixing loss and enhances the output of the gas turbine by aligning the combustion gas flow with the main flow, preventing hindrance and further reducing flow speed before merging, thereby improving overall efficiency.
Implementation Method 1
the combustion gas G passes between the inner-side end part of the guide member and the outer peripheral surface of the rotor blade shroud, which are spaced apart in the radial direction about the axis. Accordingly, the combustion gas G is blown out in an axial direction from the cavity. In other words, it is possible to align the direction of flow of the combustion gas blown out of the cavity with the direction of flow of a main flow
Data Source
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AI summary
This aircraft gas turbine is provided with a rotor, a moving blade (24), a casing, a stationary blade (26), and a guide member (53). The moving blade (24) has fins (43) projecting from the outer peripheral surface (42a) of a moving blade shroud (42). A stationary blade shroud (51) of the stationary blade (26) forms a cavity (Ct) with at least the moving blade shroud (42) and the fins (43). The guide member (53) is provided inside the cavity (Ct) and extends inward from the radial outer side, and an inner-side end part (53a) on the radial inner side faces the outer peripheral surface (42a) of the moving blade shroud (42) with a gap therebetween.