Gas Turbine Guide Vane Box Sealing for Cooling Circuit Protection
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Solution Overview
Problem
In gas turbines, leakage of hot gases and compressed air through seals between the guide vane boxes and the fixed frame can contaminate the rotor airfoil cooling circuit, reducing efficiency due to the large flow rate of cooling air needed to prevent damage, which in turn decreases the overall performance of the turbine.
Innovation Solution
The introduction of passages within the guide vane boxes that direct leaked compressed air away from the rotor airfoil inlet, utilizing slots or pipes to redirect the air into a separate zone and employing an additional seal to prevent it from entering the rotor airfoil cooling circuit, thereby maintaining efficient cooling while minimizing efficiency loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large flow rate of cooling air is used to prevent hot gases from entering the rotor airfoil cooling circuit, then the rotor airfoil integrity is safeguarded, but the gas turbine efficiency is reduced
Solution Approach 1:
The invention divides the sealing function into two independent sealing zones: first seals (25) between the guide vane boxes and fixed frame to prevent compressed air leakage, and second seals to prevent hot gas entry into the cooling circuit. This segmentation allows each seal to be optimized for its specific function, reducing the total cooling air flow rate needed while maintaining rotor airfoil integrity.
Solution Approach 2:
The invention introduces an intermediary sealed zone between the guide vane boxes and the rotor airfoil cooling circuit. This intermediate region, sealed by the combination of first and second seals, acts as a barrier that prevents hot gases from directly contaminating the cooling circuit, thereby reducing the cooling air flow rate required for protection.
2Temperature
If compressed air is injected into the second gap to cool the rotor airfoils, then the rotor airfoil temperature is controlled, but hot gases may leak through the seals and contaminate the cooling air
Solution Approach 1:
The invention applies preliminary sealing action by installing first seals (25) between the guide vane boxes and fixed frame before the hot gases can leak into the cooling air injection zone. This preliminary sealing prevents the contamination of cooling air with hot gases, ensuring that the cooling air injected into the second gap remains clean and effective for temperature control.
Solution Approach 2:
The invention converts the potential harmful effect of seal leakage into a beneficial sealed zone. By strategically placing seals to create a sealed region, the leakage path for hot gases is transformed into a protected zone that prevents hot gas contamination of the cooling circuit, thereby benefiting the overall system performance.
Data Source
AI summary
The gas turbine (1) comprises a combustion chamber (2) followed by a stator airfoil row (4) defining a plurality of guide vanes and separated by the combustion chamber (2) by a first gap (5), and a rotor airfoil row (6) separated by the stator airfoil row (4) by a second gap (7). The stator airfoils (15) of the stator airfoil row (4) are connected to guide vane boxes (17) collecting a cooling fluid (A) and injecting it through nozzles (20) in said second gap (7) to make it to enter rotor airfoil inlets (23). The guide vane boxes (23) are provided with passages (30) connecting a zone (31) upstream of the guide vane boxes (17) to a zone (32) of the second gap (7) downstream of the guide vane boxes (32). Moreover, the mouths (3) of the passages (30) facing the rotor airfoil row (6) are closer to a hot gases path than said nozzles (20).