Turbine Back-Pressure Injection for Shaft Break Overspeed Control
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Solution Overview
Problem
Gas turbine engines face the risk of turbine disintegration due to rapid acceleration during a shaft break event, which can cause extensive damage, and existing overspeed protection methods are not rapid enough to prevent this.
Innovation Solution
A pressure equalization apparatus that directly introduces pressurized fluid into the core airflow downstream of the turbine using a regulating element with a retaining barrier and piercing element, activated by the shaft break event, to reduce pressure differential and stabilize turbine speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing overspeed protection methods are used (detecting shaft break and activating mitigation system), then turbine speed can be reduced, but the response time is too slow to prevent turbine disintegration
Solution Approach 1:
The patent introduces a pressurized fluid supply system that is pre-positioned upstream of the turbine, with a regulating element (such as a rupture disk or shear pin) that automatically activates upon shaft break detection. This preliminary arrangement allows the pressurized fluid to immediately equalize the pressure differential across the turbine when the regulating element fails, eliminating detection and actuation delays. The system is prepared in advance with all components in place, requiring only the failure of the regulating element to initiate protection.
Solution Approach 2:
The patent replaces electronic detection and control systems with a purely mechanical failure-mode activation system. Instead of using sensors to detect shaft break and electronically controlling fluid introduction, the system uses a mechanically-linked regulating element (such as a shear pin or rupture disk) that fails automatically when subjected to the sudden load change from shaft break. This mechanical substitution eliminates electronic response delays and provides instantaneous activation of the pressurized fluid supply.
2Reliability
If a fluid is introduced into the gas flow downstream of the turbine to increase back pressure, then turbine speed is reduced, but the device complexity increases
Solution Approach 1:
The patent employs a self-activating system where the shaft break event itself triggers the protection mechanism. The sudden load change from shaft break causes the regulating element (shear pin or rupture disk) to fail automatically, which in turn opens the pressurized fluid supply without requiring external control. The system serves itself by using the failure condition as the activation signal, eliminating the need for separate detection and control systems.
Solution Approach 2:
The patent combines the pressurized fluid supply system with the existing turbine structure by integrating the fluid introduction point directly into the gas flow path upstream of the turbine. The regulating element is mechanically linked to both the shaft and the fluid supply, merging the detection and actuation functions into a single integrated system. This reduces overall device complexity by eliminating separate components and interconnections.
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 apparatus effectively reduces the time delay in mitigating turbine overspeed, minimizing damage and enhancing safety by stabilizing turbine rotation during a shaft break event.
Implementation Method 1
The apparatus comprises a pressurised fluid supply in communication with the core airflow at the downstream region... configured to reduce a pressure differential across the turbine
Data Source
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AI summary
An apparatus and method for reducing a pressure differential across a turbine 19 of a gas turbine engine 10 during a shaft break event, comprises a pressure equalization apparatus 300, 400, 500, 600, 700 configured to introduce a pressurised fluid into a core airflow A at a region downstream of the turbine 19, wherein a rearward movement of the turbine 19 or a shaft 26 in a shaft break event directly actuates the pressure equalisation apparatus 300, 400, 500, 600, 700 to directly increase a local pressure at the downstream region 29 of the turbine 19 and thereby reduce the pressure differential across the turbine 19. The reduction in the pressure differential may result in a reduction in the acceleration of the turbine 19.