Turbine Stator Blade Slit Design for Thermal Stress
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Solution Overview
Problem
Turbine stator blades in CO2 turbines face high thermal stress due to large metal temperature differences, leading to potential damage and performance degradation under high-temperature and high-pressure conditions, which existing cooling structures struggle to manage effectively.
Innovation Solution
The turbine stator blade design incorporates slits in the outer circumferential sidewall, reducing the stiffness of the sidewall and alleviating thermal stress by allowing controlled deformation, while maintaining sealing performance through the use of seal members to prevent cooling medium leakage into the working fluid path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the outer circumferential sidewall and hook are made with thicker wall thicknesses to withstand high pressure, then the strength and pressure resistance are improved, but the thermal stress increases due to large metal temperature difference between the working fluid-exposed portion and cooling medium-exposed portion
Solution Approach 1:
The outer circumferential sidewall is segmented by forming slits that divide the continuous structure into sections. These slits allow the sidewall to deform more freely in response to thermal expansion, reducing thermal stress concentration while maintaining overall structural integrity and pressure resistance through the segmented architecture.
Solution Approach 2:
The slits transform the rigid outer circumferential sidewall into a more flexible structure that can accommodate thermal deformation. The sidewall with slits acts as a flexible shell that can expand and contract with temperature changes, reducing the buildup of thermal stress while still maintaining sufficient strength to withstand high operating pressures.
2Stress or pressure
If slits are formed in the outer circumferential sidewall to reduce thermal stress, then the thermal stress is alleviated, but the sealing performance may deteriorate due to potential leakage paths
Solution Approach 1:
A seal member is introduced as an intermediary element that fills or bridges the slits in the outer circumferential sidewall. This seal member prevents cooling medium from leaking through the slits into the working fluid path, thereby maintaining sealing performance while allowing the slits to continue functioning in reducing thermal stress.
Solution Approach 2:
The seal member is selectively placed only at the slit locations where sealing is needed, rather than making the entire sidewall structure more complex. This localized sealing approach maintains the overall flexibility and stress-relief benefits of the slits while addressing the sealing requirement only where necessary.
3Stress or pressure
If the stiffness of the outer circumferential sidewall is reduced by forming slits, then the thermal stress is reduced through controlled deformation, but the structural rigidity decreases
Solution Approach 1:
The slits segment the sidewall structure, creating a balance between flexibility and rigidity. The segmented structure allows localized deformation to relieve thermal stress while the overall segmented architecture maintains sufficient structural stability to support the blade assembly under operating conditions.
Solution Approach 2:
The formation of slits changes the physical parameters of the sidewall, specifically its stiffness and rigidity characteristics. By controlling the number, size, and distribution of slits, the sidewall achieves an optimal parameter balance that allows thermal deformation while maintaining adequate structural rigidity for support functions.
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 design effectively reduces thermal stress at the blade root, ensuring the soundness of the turbine stator blade and maintaining turbine performance by mitigating thermal expansion-induced deformation and maintaining efficient sealing.
Implementation Method 1
large metal temperature difference is produced between a portion that is exposed to the high-temperature working fluid during operation and a portion such as hook portion that is exposed to the low-temperature cooling medium. Therefore, there has been a problem that when thermally deformed, thermal stress at a root of the blade effective part
Data Source
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AI summary
According to an embodiment, a turbine stator blade (100) disposed in a working fluid flow path (15) in a casing (20) of a gas turbine (10), includes: a blade effective part (110) disposed in the working fluid flow path (15); an outer circumferential sidewall (120) having a plate-shaped part (123) that is connected to a radially outer end portion of the blade effective part (110), and hooks (121, 122) each extending radially outward and circumferentially from the plate-shaped part (123) and having a tip engaged with the casing (20); and an inner circumferential sidewall (130) connected to a radially inner end portion of the blade effective part (110). At least one slit (121s, 122s) is formed at the rear hook (121) or front hook (122) to divide the hook (121, 122) in a circumferential direction, and the hook (121, 122) has a seal member to seal the slit (121s, 122s).