Turbine Overspeed Limiting Pin Mechanism
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Solution Overview
Problem
Existing overspeed limiting devices in turbomachines are complex, expensive, slow, and unreliable, particularly in small engines, due to their dependence on mechanical contact and friction, which can be ineffective if the rotor bounces back or orbits, and they increase the turbine's mass and alter its aerodynamic profile.
Innovation Solution
A device that uses a pin propelled by an explosive capsule or pressurized gas to shear turbine blades, destroying them and preventing overspeed, with a rupture disk and sodium azide pellets for rapid response, independent of rotor shifting, and minimal impact on engine performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical slowing devices are used that depend on rotor downstream displacement and positive contact between components, then the device can slow the turbine rotor, but the response time becomes slow and the device may become inoperative if the rotor bounces back or orbits
Solution Approach 1:
The pin is pre-positioned in a capsule within the stator assembly, ready for immediate deployment. Upon detection of overspeed or shaft breakage, the pin is propelled into the rotor blades without waiting for rotor downstream displacement, eliminating the time delay inherent in mechanical contact devices and ensuring reliable operation regardless of rotor movement patterns
Solution Approach 2:
The invention replaces the mechanical contact-based slowing mechanism with a propelling mechanism that uses explosive or pneumatic force to launch a pin into the rotor blades. This substitution eliminates dependence on rotor downstream displacement and positive contact between components, providing faster and more reliable overspeed limitation
2Reliability
If friction-based slowing devices are used between components, then the turbine rotor can be slowed, but the effectiveness becomes difficult to predict due to uncertain parameters such as temperature and force
Solution Approach 1:
The invention replaces friction-based mechanical slowing with a direct impact mechanism using a propelled pin. This eliminates the uncertain parameters of friction (temperature, force variability) and provides predictable, controllable deceleration through the known mass, velocity, and impact point of the pin
Solution Approach 2:
The invention changes the fundamental parameter from friction force (which varies with temperature and contact pressure) to impact force from a propelled pin (which can be precisely controlled through the propelling mechanism). This parameter change makes the slowing effectiveness predictable and controllable
3Reliability
If known overspeed limiting devices are used, then the turbine overspeed can be limited, but the overall mass of the turbine increases and the aerodynamic profile of components is altered
Solution Approach 1:
The pin and its propelling mechanism are integrated within the existing stator assembly structure. The capsule containing the pin is housed within the stator, and the pin is launched through an opening in the stator assembly. This nesting approach adds minimal mass to the turbine while maintaining the aerodynamic profile of the stator and rotor components
Solution Approach 2:
The invention extracts the overspeed limitation function from bulky mechanical contact devices and implements it through a compact pin-propulsion system. This extraction reduces the mass addition to the turbine while preserving the aerodynamic characteristics of the main components
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 provides a fast and reliable means to prevent turbine overspeed, with a response time of approximately 40 milliseconds, unaffected by rotor movement or bouncing, and without compromising engine performance or increasing mass.
Implementation Method 1
the propelling means comprise a capsule of explosive substance housed in a cylinder suitable for guiding the pin as the capsule explodes
Implementation Method 2
pellets of a substance capable of generating a gas under the effect of detonation, such as sodium azide for example
Implementation Method 3
pellets of a substance capable of generating a gas under the effect of detonation
Implementation Method 4
The blades intercepted by the pin are destroyed under the effect of the collision with this pin
Data Source
AI summary
A device (40) for limiting overspeed in a turbomachine in the event of breakage of the turbine shaft (24), comprising means (38, 44) of propelling a pin (42) into the path of the blades (22), these propelling means being controlled by means (36) that detect overspeed or that the turbine shaft has broken.