Gas Turbine Inner Casing Axial Positioning
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Solution Overview
Problem
Existing gas turbine engines face inefficiencies due to varying radial clearances between rotating and non-rotating components, leading to leakage or potential contact damage, and current active control systems are costly and complex.
Innovation Solution
A passive system that adjusts the axial position of an inner casing based on flowpath pressures using a connection assembly, biasing means, and pressure differential to maintain optimal clearance, allowing for axial movement between predefined positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If active control systems are used to maintain blade tip clearance, then clearance control precision is improved, but device complexity and cost increase
Solution Approach 1:
The system uses the engine's own operating parameters (rotational speed, temperature, pressure) to automatically adjust blade tip clearance through the casing displacement mechanism, eliminating the need for external sensors and control systems. The casing self-adjusts based on thermal expansion and rotational effects during operation.
Solution Approach 2:
The patent replaces complex electronic control systems with a passive mechanical mechanism where the casing position is automatically adjusted through thermal expansion, rotational centrifugal forces, and spring-loaded displacement mechanisms that respond directly to operating conditions.
2Device complexity
If passive control systems are used for blade tip clearance, then device complexity is reduced, but clearance control precision deteriorates
Solution Approach 1:
The system exploits changes in physical parameters (temperature, rotational speed, pressure) during engine operation to automatically adjust casing position. Thermal expansion coefficients, centrifugal forces, and pressure differentials are harnessed to achieve precise clearance control without complex mechanisms.
Solution Approach 2:
The casing structure incorporates thermal expansion characteristics to automatically adjust its position relative to the rotor. Different thermal expansion rates between stationary and rotating components are utilized to maintain optimal clearance across the operating range.
3Reliability
If radial clearance between rotor blade tips and casing shroud is increased, then risk of contact damage is reduced, but working fluid leakage increases
Solution Approach 1:
The system dynamically adjusts the radial clearance between rotor blade tips and casing shroud based on operating conditions. The casing position changes with temperature, rotational speed, and pressure to maintain optimal clearance that prevents contact during high-stress conditions while minimizing leakage during steady-state operation.
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 solution reduces fuel consumption and improves engine performance by maintaining a narrow tip-shroud clearance through operational range without the need for complex feedback systems, enhancing robustness and reducing costs.
Implementation Method 1
biasing means for axially preloading the inner casing toward the first position
Implementation Method 2
an inner casing receiving surface configured to receive a pressure in the annulus for axially loading the inner casing in opposition to the axial preload of the biasing means
Data Source
AI summary
A system for passively varying an axial position of an inner casing of a gas turbine pursuant to changing pressure in a flowpath during transient engine operation. The system may include: a connection assembly slidably connecting the inner casing to the outer casing for axial movement of the inner casing between a first position and a second position; means for pressurizing the annulus relative to a flowpath pressure; biasing means for axially preloading the inner casing toward the first position; and an inner casing receiving surface configured to receive a pressure in the annulus for axially loading the inner casing in opposition to the axial preload of the biasing means.