Gas Turbine Exhaust Diffuser Cooling via Segmented Airflow
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Solution Overview
Problem
Conventional exhaust diffuser cooling systems in gas turbines face inefficiencies due to insufficient cooling performance and structural challenges when trying to manage higher exhaust gas temperatures, leading to reduced turbine efficiency and increased cooling air discharge.
Innovation Solution
An exhaust system with an annular partition member supported by the casing, which guides cooling air through a smaller flow passage area to enhance cooling efficiency and maintainability, while reducing thermal stress on the outer diffuser and strut covers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the amount of cooling air drawn from the outside into the gap between the strut and the strut shield is increased to cool the exhaust diffuser, then the cooling performance of the exhaust diffuser is improved, but the turbine efficiency decreases due to lower exhaust gas temperature
Solution Approach 1:
The invention divides the cooling air flow into two separate paths: one path draws cooling air into the gap between the strut and strut shield to cool the exhaust diffuser, while another path supplies cooling air to the outer diffuser through a dedicated cooling air introduction portion. This segmentation allows independent control of cooling air flow rates for different components, enabling efficient cooling of the exhaust diffuser without excessive cooling air discharge that would reduce turbine efficiency.
Solution Approach 2:
The invention introduces a partition member as an intermediary structure that separates the cooling air introduction portion from the exhaust gas flow passage. The partition member has a cooling air flow passage that guides cooling air to the strut cover flow passage inside the strut cover, preventing direct mixing of cooling air with exhaust gas while still achieving effective cooling of the outer diffuser.
2Temperature
If a perforated plate is used to divide the cooling fluid passage into non-heated and heated parts, then the cooling fluid can be protected from overheating by radiation, but the cooling efficiency and performance are reduced
Solution Approach 1:
The partition member acts as an intermediary structure that separates the cooling air introduction portion from the exhaust gas flow passage without using a perforated plate. The partition member has a dedicated cooling air flow passage that guides cooling air to the strut cover flow passage, maintaining cooling effectiveness while preventing direct exposure to radiant heat from the exhaust diffuser.
Solution Approach 2:
The invention segments the cooling air flow paths and introduces a dedicated cooling air introduction portion for the outer diffuser, separate from the conventional cooling path through the strut gap. This segmentation allows optimized cooling air flow rates for each component without the need for perforated plates that would reduce cooling performance.
3Temperature
If an air chamber is mounted on the outer diffuser to cool it, then the cooling effectiveness is improved, but the structural load on the outer diffuser increases
Solution Approach 1:
The partition member serves as an intermediary structure that is supported by the exhaust casing rather than the outer diffuser. The cooling air flow passage is formed between the partition member and the outer diffuser, allowing the outer diffuser to be cooled effectively while the partition member bears the structural load, preventing additional stress on the outer diffuser.
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 system efficiently cools the outer diffuser with a lower flow of cooling air, preventing a decrease in exhaust gas temperature and maintaining turbine efficiency, while simplifying the structure and improving maintainability.
Implementation Method 1
a cooling air flow passage provided between the outer diffuser and the partition member and formed so as to guide cooling air, introduced from the cooling air introduction portion, to a strut cover flow passage inside the strut cover
Data Source
AI summary
An exhaust system and a gas turbine, in which the exhaust system includes an exhaust casing; an outer diffuser supported inside the exhaust casing; an inner diffuser disposed inside the outer diffuser to form an exhaust gas flow passage between the inner diffuser and the outer diffuser; a strut cover coupled at a first end to the outer diffuser and coupled at a second end to the inner diffuser; and a second cooling air introduction port provided in the exhaust casing, further on the downstream side of the exhaust gas flow passage than the strut cover. Furthermore, a non-perforated partition member having an annular shape is arranged so as to cover the outer side of the outer diffuser and is supported by the exhaust casing to form a cooling air flow passage.