Turbomachine Casing Cooling via Hook Suspension Air
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Solution Overview
Problem
The existing cooling systems for turbomachine turbine casings, particularly in turbojets and turboprops, fail to effectively cool the suspension hooks, leading to potential thermal damage and crack formation due to hot gas leaks, and adding a fresh air intake duct is impractical due to complexity, size, and cost constraints.
Innovation Solution
A device that supplies cooling air from the internal cavities of the distributor blades to the annular space housing the suspension hooks through inserts and holes in the outer annular rim, maintaining a higher pressure than combustion gases and reducing thermal stress without the need for additional air intake ducts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If an additional cooling circuit is added to supply fresh air to the suspension hooks, then the thermal protection of hooks is improved, but the device complexity and cost increase
Solution Approach 1:
The system uses the cooling air already circulating through the distributor blade cavities to cool the suspension hooks. The cooling air performs dual function: cooling the blades and cooling the hooks, eliminating the need for a separate cooling circuit. This self-service approach resolves the contradiction by improving hook temperature protection without adding circuit complexity.
Solution Approach 2:
The cooling air circuit is designed to serve multiple functions simultaneously: it cools the distributor blades through internal cavities and also cools the suspension hooks by introducing air into the annular space where hooks are located. This multi-functionality allows one cooling system to address both thermal protection needs without increasing overall system complexity.
2Temperature
If an additional cooling circuit with fresh air intake ducts is added, then the thermal protection of hooks is improved, but the size and cost of the turbine increase
Solution Approach 1:
The system repurposes the existing cooling air infrastructure to also cool the suspension hooks. By using air already drawn from upstream of the combustion chamber and circulated through the blade cavities, the design avoids the need for additional air intake ducts and associated manufacturing costs, while still achieving effective hook cooling.
Solution Approach 2:
The design recovers and reuses the cooling air that flows through the distributor blade cavities by directing a portion of it to the annular space around the suspension hooks. This recovery approach eliminates the need for separate fresh air intake ducts, reducing both size and manufacturing cost while maintaining effective thermal protection.
3Temperature
If the sealing plate is used to limit hot gas passage, then the thermal protection of hooks is partially improved, but hot gas leaks still occur and raise hook temperature
Solution Approach 1:
Cooling air is introduced as an intermediary substance into the annular space where suspension hooks are located. This cooling air acts as a thermal barrier and pressure medium that prevents hot gas from reaching the hooks, supplementing the sealing plate function and ensuring reliable thermal protection even when the sealing plate is not perfectly effective.
Solution Approach 2:
Cooling air is supplied to the annular space around the suspension hooks in advance to create a protective atmosphere before hot gas can leak through imperfect sealing. This preliminary action establishes a pressure and temperature environment that prevents hot gas intrusion, enhancing the reliability of thermal protection beyond what the sealing plate alone can provide.
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 solution effectively reduces the risk of thermal damage to the hooks by maintaining a lower temperature and higher pressure in the annular space, preventing crack formation without increasing the complexity or cost of the cooling system, and has a minimal impact on the turbomachine's performance.
Implementation Method 1
The air taken from the cavities of the vanes of the distributor of the stage upstream of the casing is brought into the annular space housing the hooks upstream of the casing and makes it possible to reduce their temperature
Implementation Method 2
This air also makes it possible to maintain the annular space for housing the hooks at a pressure greater than that of the combustion gases passing through the turbine, which opposes the introduction of these gases into the annular space for housing the hooks
Data Source
Figure 1
Figure 2~2a
Figure 3
AI summary
The device has several stages including a nozzle assembly (18) formed of annular row of fixed vanes (20) borne by casing of turbine and an impeller mounted to rotate inside the casing. The air-spreading unit comprises drillings formed in plates and external annular rim of nozzle assembly which extends between external walls of vane cooling cavities (46) and upstream hooks (72) for suspending the ring sectors (34).