Turbine Blade Tip Geometry for Walking Prevention
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Solution Overview
Problem
Turbine blades in turbine engines experience axial displacement or 'walking' due to tangential forces from shaft eccentricities, leading to inefficiencies and potential rubbing against the casing, which existing retention devices struggle to prevent effectively without adding weight or complexity.
Innovation Solution
The turbine blade design features a radially outward tip with a first portion parallel to the axis of rotation and a second portion extending aft at an inward angle, minimizing air escape and blade movement, achieved through shaping and angled shaving of the tip to enhance retention and reduce 'walking'.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional retention devices are used to prevent blade walking, then blade retention is improved, but device complexity and weight increase
Solution Approach 1:
The patent extracts the retention function from a separate retention device and integrates it into the blade tip geometry itself. The angled second portion of the tip acts as a self-retention feature that prevents walking without requiring additional retention device components.
Solution Approach 2:
The blade tip geometry is designed to be self-retaining through its angled second portion. The blade's own structure provides the retention mechanism, eliminating the need for external retention devices and reducing overall system complexity.
2Loss of energy
If blade tip is positioned parallel to casing to minimize air escape, then gas sealing is improved, but blade walking prevention deteriorates
Solution Approach 1:
The blade tip is segmented into two distinct portions: a first portion parallel to the axis for minimizing air escape, and a second portion at an inward angle for preventing blade walking. This segmentation allows each portion to optimize its specific function without compromising the other.
Solution Approach 2:
Different sections of the blade tip have different geometries optimized for different functions. The first portion has a parallel geometry for gas sealing, while the second portion has an angled geometry for walking prevention, allowing local optimization of each region's properties.
3Productivity
If blade tip extends parallel to axis for gas sealing, then energy efficiency is improved, but blade stability deteriorates
Solution Approach 1:
The blade tip is divided into two portions with different orientations. The first portion extends parallel to maintain energy efficiency, while the second portion angles inward to provide stability and prevent walking, allowing both competing requirements to be satisfied simultaneously.
Solution Approach 2:
The blade tip geometry transitions from a symmetric parallel extension to an asymmetric angled configuration. This asymmetric second portion provides the necessary stability and walking prevention while the first portion maintains the symmetric parallel geometry for optimal energy efficiency.
Data Source
AI summary
A turbine assembly has a casing, a turbine ring and a blade. The blade has a root portion having an axially extending first shape, an airfoil attaching to the root portion and having a trailing edge and a radially outward tip. The tip has a first portion disposed in parallel to the axis of rotation for minimizing escape of air between the tip and the casing and a second portion extending aft from the first portion at an inward angle. The ring has a cut-out having a second shape mating with the first shape.