Turbine Fan Blade Pitch Control via Locking Peg
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Solution Overview
Problem
Existing systems for controlling the pitch of fan blades in turbine engines, particularly in open rotor turbojets, face challenges with weight and space constraints due to the use of counterweights for feathering mechanisms, which increase the engine's weight and reduce available space.
Innovation Solution
A system comprising an actuator with a movable portion and a locking peg that mechanically locks the fan blades in a feathered position in case of actuator malfunction, eliminating the need for counterweights and reducing overall size by allowing the locking peg to be housed within the load transfer bearing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If counterweights are used for feathering fan blades, then the blades can be held in the feathered position in case of control system failure, but the engine weight increases significantly
Solution Approach 1:
The invention extracts the feathering function from the traditional counterweight mechanism and relocates it to a locking peg system integrated into the actuator assembly. The locking peg can engage with a locking surface on the pitch control bearing to hold the blades in the feathered position, eliminating the need for separate counterweights and their associated mounting structures.
Solution Approach 2:
The locking peg is integrated into the actuator assembly, merging the feathering/locking function with the existing pitch control mechanism. This consolidation eliminates the need for separate counterweight components and reduces the overall system weight while maintaining the safety function.
2Reliability
If counterweights are installed at the pivots of fan blades, then the feathering function is achieved, but the engine length increases and center of gravity shifts
Solution Approach 1:
The invention extracts the counterweight function from the blade pivot location and relocates it to the actuator assembly. The locking peg, when engaged, provides the feathering function without requiring the extensive radial space that would be needed for equivalent counterweights at the blade pivots, thus maintaining a more compact engine configuration.
3Adaptability or versatility
If the actuator movable portion is allowed to move freely, then the pitch angle can be adjusted for thrust control, but the blades may become blocked in the flat position in case of malfunction
Solution Approach 1:
The locking peg is designed to be dynamically positionable - it can be retracted to allow free movement of the actuator movable portion for normal pitch angle adjustment, or extended to engage with the locking surface to prevent movement and hold the blades in the feathered position. This dynamic capability allows the system to switch between operational flexibility and safety lockdown as needed.
Solution Approach 2:
The locking peg is positioned and configured in advance within the actuator assembly, ready to engage with the locking surface on the pitch control bearing. In the event of a malfunction, the peg can quickly engage to prevent the blades from becoming blocked in the dangerous flat position, providing preliminary protection before the malfunction fully develops.
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 reduces weight and size, ensuring safe operation by preventing blade overspeeding and loss, while maintaining efficient thrust control without the need for counterweights, thus enhancing the engine's performance and safety.
Implementation Method 1
at least one locking peg secured to the casing of the turbine engine and suitable, in the event of the actuator malfunctioning, for mechanically locking the LTB in a position in which the fan blades are feathered
Implementation Method 2
the movable portion of the actuator being mechanically coupled to a load transfer bearing (LTB) having an outer ring that is coupled to fan blade pivots so that a movement in translation of the movable portion of the actuator leads to a change in the pitch angle of said fan blades
Data Source
AI summary
A system for controlling the pitch of fan blades of a turbine engine propeller, the system including an actuator secured to a casing of the turbine engine, having a movable portion that is movable in translation relative to the casing, the movable portion being mechanically coupled to a load transfer bearing having an outer ring that is coupled to fan blade pivots so that a movement in translation of the movable portion of the actuator leads to a change in the pitch angle of the fan blades, and at least one locking peg secured to the casing of the turbine engine and suitable, in the event of the actuator malfunctioning, for mechanically locking the load transfer bearing in a position wherein the fan blades are feathered.