Gas Turbine Casing Cooling Passage Design
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Solution Overview
Problem
Conventional aircraft gas turbine casings face structural strength reduction and efficiency decreases due to thermal stress and deformation, particularly during startup or shutdown, as the thick wall parts are not effectively cooled, leading to inappropriate clearance between rotor blades and the casing.
Innovation Solution
Incorporating a cooling passage in the thick wall part of the casing to circulate compressed air and a discharge passage to return cooled air to the combustion gas passage, eliminating the need for additional pumps and simplifying the structure, while maintaining structural integrity and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thick wall part is provided on the outer periphery side of the rotor blades to enhance containment structure, then the structural strength is improved, but the thermal stress and thermal deformation increase due to high temperature, reducing structural strength and making it difficult to maintain appropriate clearance
Solution Approach 1:
The thick wall part is segmented into an inner wall and an outer wall with a cooling passage formed between them. This segmentation allows the cooling passage to be integrated into the thick wall structure, enabling effective cooling while maintaining the containment function.
Solution Approach 2:
Compressed air from the compressor is used as a cooling medium circulated through the cooling passage. This intermediary substance transfers heat from the thick wall part to the combustion gas, reducing thermal stress and thermal deformation while maintaining structural strength.
2Temperature
If cooling air is supplied into the double-hull chamber to cool the casing, then the thermal stress is reduced, but the structure becomes complicated requiring introduction path and pump when using ventilation air
Solution Approach 1:
The cooling passage is merged with the thick wall part structure, integrating the cooling function into the containment structure. This eliminates the need for separate double-hull chambers and external cooling systems, simplifying the overall structure.
Solution Approach 2:
The compressor provides compressed air that is directly used for cooling the thick wall part through the cooling passage. This self-service approach eliminates the need for external pumps or ventilation systems, as the compressor's output is utilized for cooling purposes.
3Temperature
If bleed air from the compressor is used as cooling air, then the cooling effect is achieved, but the amount of combustion gas is reduced, decreasing efficiency
Solution Approach 1:
The compressed air used for cooling is not discarded but recovered and discharged into the combustion gas passage. This recovered air is mixed with combustion gas and utilized for driving the turbine, preventing efficiency loss that would occur if the cooled air were simply exhausted.
4Temperature
If a double hull forming a hollow annular chamber is provided to cool the casing, then the thermal stress is reduced, but the structure becomes complicated and efficiency decreases
Solution Approach 1:
The cooling passage is merged with the thick wall part structure, integrating the cooling function into the containment structure. This eliminates the need for separate double-hull chambers and external cooling systems, simplifying the overall structure.
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 effectively cools the thick wall part, reducing thermal stress and deformation, ensuring appropriate clearance between rotor blades and the casing, and preventing efficiency decreases by utilizing compressed air as a cooling medium, thus enhancing the containment structure and operational efficiency.
Implementation Method 1
a cooling passage provided in the thick wall part to circulate compressed air compressed by the compressor to cool the thick wall part
Implementation Method 2
a discharge passage for discharging compressed air having circulated in the cooling passage to a combustion gas passage
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
Disclosed is an aircraft gas turbine comprising a compressor (14), a combustor (15) and a turbine (16) housed in a cylindrical main body casing (12). The main body causing (12) is provided with a thick walled section (52) on its peripheral edge on the side of the moving blades (34), where compressed air compressed by the compressor (14) is circulated inside the thick walled section (52) which is provided with a cooling passage (53) for cooling and also an exhaust passage (55) which discharges the compressed air circulated in the cooling passage (53) through the combustion gas passage A. Accordingly, construction is simplified and loss of efficiency is prevented, while the structural strength of the thick walled sections is ensured by appropriate cooling provided by the thick walled sections in the casing, and efficient containment properties as well as sufficient clearance for the moving blades is also ensured.