Turbomachine Turbine Shroud Variable Air Gap Cooling
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Solution Overview
Problem
Turbine ring sectors in turbomachines experience non-homogeneous temperature distribution due to constant air gaps in multi-perforated sheets, leading to deformations and mechanical wear, which reduces the performance and lifespan of the turbomachine.
Innovation Solution
A multi-perforated sheet with a variable air gap design, scalable linearly, curvilinearly, or in stages, to enhance heat exchange and reduce thermal gradients, allowing for more effective cooling of turbine ring sectors by varying the distance between the sheet and the ring sector wall.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a constant air gap is used in multi-perforated sheets, then the structure is simple and easy to manufacture, but the temperature distribution becomes non-homogeneous causing deformations and mechanical wear
Solution Approach 1:
The air gap between the multi-perforated sheet and the ring sector wall is varied locally along the axial direction, with different gap values in different zones. This local variation in air gap creates non-uniform cooling that compensates for the non-homogeneous temperature distribution, reducing thermal deformations and improving reliability while maintaining manufacturing feasibility
Solution Approach 2:
The air gap parameter is changed along the axial direction of the ring sector, transitioning from a constant value to a variable value. This parameter change allows optimization of heat exchange in different zones, creating a more homogeneous temperature distribution and reducing thermal gradients that cause deformations and mechanical wear
2Device complexity
If a constant air gap is used in multi-perforated sheets, then the device complexity is low, but thermal gradients cause sector deformations and mechanical wear
Solution Approach 1:
Different air gap values are applied in different axial zones of the ring sector, creating local variations in cooling intensity. This local quality approach addresses the thermal gradient problem by providing enhanced cooling where needed most, reducing harmful thermal effects without requiring complete redesign of the entire cooling system
Solution Approach 2:
The air gap variation is introduced along the axial dimension, adding a new degree of freedom to the cooling system design. This dimensional approach allows control of thermal gradients by varying the gap distance in the axial direction, effectively managing heat exchange without increasing radial or circumferential complexity
3Temperature
If the air gap is varied to reduce thermal gradients, then temperature homogeneity improves, but the manufacturing complexity increases
Solution Approach 1:
The air gap is varied locally in specific axial zones rather than uniformly throughout, allowing temperature homogeneity to be improved in critical areas while limiting the overall complexity increase. This targeted approach focuses cooling optimization where thermal gradients are most problematic
4Duration of action of stationary object
If a variable air gap design is implemented, then thermal gradients are reduced and lifespan increased, but the manufacturing precision requirements increase
Solution Approach 1:
The air gap parameter is systematically varied along the axial direction with defined zones and transitions. This parameter change approach improves lifespan by reducing thermal gradients and deformations, while the structured variation pattern helps manage manufacturing precision requirements through standardized design zones
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
The solution reduces thermal gradients by up to 40 Kelvin, increasing the lifespan of turbine ring sectors and improving turbomachine performance, and can be retrofitted to existing turbines without modifying surrounding parts.
Implementation Method 1
Cooling air passes through the multi-perforated sheet through the holes and impacts the wall of the ring to cool it
Implementation Method 2
The invention advantageously makes it possible to reduce the thermal gradient on the ring sectors
Data Source
Figure 1~2
Figure 3~5
Figure 6
AI summary
The sector has a wall bounding an aerodynamic flowpath in which gases flow from an upstream region toward a downstream region, and a multiperforated plate (2) is situated on an opposite side of the aerodynamic flowpath with respect to the wall. The multiperforated plate comprises a bottom and side walls, where the distance between the wall and the bottom of the plate defining a gap is progressive in an axial direction. A value of the gap situated at the upstream region is below the value situated at the downstream region.