Blade Positioning via Inflated Bag for Gas Turbine Grinding
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Solution Overview
Problem
In gas turbine engines, the inefficiency due to over-tip leakage arises from variations in the radial position of blade tips during the grinding process, caused by the play between blade roots and disc slots, leading to inconsistent blade geometry and increased abrasion of the abradable liner.
Innovation Solution
A method and apparatus involving a fluid-tight bag are used to ensure consistent radial positioning of blade tips by inflating the bag to push the blades radially outward, aligning them with a grinding surface, thereby maintaining uniform tip positions during grinding and operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If blades are secured into slots in the rotor disc with necessary play for assembly, then ease of manufacture is improved, but manufacturing precision deteriorates due to varying blade root engagement positions during grinding
Solution Approach 1:
A fluid-tight bag is introduced as an intermediary element between the blade root and the slot in the rotor disc. When inflated, this bag applies radial force to push the blade root against the slot, eliminating play and ensuring consistent engagement position. This mediator allows the blade to be securely positioned during grinding without requiring complex fixing mechanisms, thus resolving the contradiction between ease of assembly and manufacturing precision.
Solution Approach 2:
The invention changes the physical state of the fluid-tight bag from deflated (during assembly) to inflated (during grinding). This parameter change enables the bag to transition from a non-intrusive assembly aid to an active positioning device that applies radial force, ensuring consistent blade root engagement and thereby improving manufacturing precision while maintaining ease of manufacture.
2Adaptability or versatility
If blade roots are allowed to move within slots during rotation, then adaptability during assembly is improved, but reliability deteriorates due to inconsistent blade geometry affecting abradable liner abrasion
Solution Approach 1:
The fluid-tight bag is inflated before the grinding operation begins, preliminarily establishing the correct radial position of the blade root in the slot. This preliminary action ensures that the blade is properly positioned and constrained before any grinding occurs, preventing any movement or play during the grinding process. As a result, all blades achieve consistent geometry and radial tip positions, improving reliability while maintaining the adaptability needed during assembly.
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 approach results in more accurately positioned blade tips, reducing over-tip leakage and enhancing engine efficiency by ensuring consistent blade geometry during both manufacturing and operation.
Implementation Method 1
A method and apparatus involving a fluid-tight bag are used to ensure consistent radial positioning of blade tips by inflating the bag to push the blades radially outward
Data Source
AI summary
A method of, and apparatus for, urging blades of a gas turbine engine radially outwardly is disclosed. The method may be used to grind blade tips of blades of a rotor stage of a gas turbine engine. The method comprises locating a fluid-tight bag which is in a radial gap formed between a radially inner surface of a respective blade root and a slot in a disc which the blade root cooperates. The method comprises inflating the fluid-tight bag and rotating the rotor stage relative to a grinding surface so as to grind any blade tips that contact the grinding surface during rotation. This results in more accurate positioning of the blades during the grinding process and/or during operation.