Gas Turbine Inner Platform Thermal Stress Reduction
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Solution Overview
Problem
Conventional gas turbine engines experience significant thermal stress at the connection points between nozzle guide vanes and inner platforms due to temperature gradients, which are not adequately reduced by existing high-temperature gas recirculation pockets.
Innovation Solution
An annular intermediate-temperature space is created by partition members extending from the inner platform and a second partition member, overlapping with the inner platform over its entire length, and a low-temperature space is formed on the radially inner side of the second partition member, along with a seal portion to prevent combustion gas leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a high-temperature gas recirculation pocket is formed on the radially inner side of the platform to reduce thermal stress, then the temperature gradient is reduced, but the platform is excessively cooled down by introduced low-temperature air, making it difficult to sufficiently reduce the temperature gradient
Solution Approach 1:
The recirculation pocket is divided into multiple segmented structures arranged circumferentially around the platform. Each segment allows controlled circulation of intermediate-temperature gas while preventing excessive penetration of low-temperature cooling air, thereby maintaining a balanced temperature gradient that reduces thermal stress without causing excessive cooling of the platform.
2Temperature
If cooling air is introduced into the high-temperature gas recirculation pocket for active cooling, then cooling effect is improved, but the platform temperature becomes too low, maintaining large temperature gradient and thermal stress
Solution Approach 1:
Different regions of the recirculation pocket are designed with different cooling characteristics. The segmented structure creates zones with varying temperatures and flow patterns, allowing local optimization where cooling air is introduced in a controlled manner to achieve adequate cooling effect while preventing excessive temperature reduction that would maintain large thermal gradients and associated thermal stress.
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 configuration reduces thermal stress by maintaining an intermediate temperature between the high-temperature combustion gas and low-temperature air, preventing excessive cooling and thermal expansion differences, thereby minimizing stress on the inner platform and nozzle guide vanes.
Implementation Method 1
an annular intermediate-temperature space is formed by: an inner platform supporting radially inner ends of the nozzle guide vanes; a first partition member extending from the inner platform in a radially inward direction; and a second partition member having a radially inner end portion fixed to the first partition member and a radially outer end portion facing the inner platform, the intermediate-temperature space overlapping with the inner platform over substantially an entire length of the inner platform in an axial direction
Implementation Method 2
a low-temperature space, which is supplied with air from the compressor, is formed on a radially inner side of the second partition member
Implementation Method 3
a cooling air having a relatively low temperature comes into contact with and cools an outer wall face of the platform inside in the radial direction
Data Source
AI summary
In a gas turbine engine, an annular intermediate-temperature space is formed by a first partition member extending from an inner platform radially inward and a second partition member having a radially inner end portion fixed to the first partition member and a radially outer end portion facing the inner platform, the inner platform being connected to radially inner ends of nozzle guide vanes of a turbine, and the intermediate-temperature space overlapping with the inner platform over substantially its axial entire length. The low-temperature space, supplied with a low-temperature air from a compressor, is formed on a radially inside of the second partition member. Therefore, a temperature of the intermediate-temperature space is maintained at an intermediate temperature between those of a combustion gas and the air, reducing a temperature difference of the inner platform from an outer platform and the vanes to reduce a thermal stress.