Gas Turbine Fan Assembly With Remote Counterweight Levers
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Solution Overview
Problem
The aerodynamic and mechanical twisting of fan blades in a gas turbine engine imparts a torque moment to the trunnion mounting, which results in axial forces that conventional counterweight systems struggle to effectively counteract, leading to inefficiencies and potential stress on the actuator.
Innovation Solution
A remotely located counterweight system with a cantilever structure and counterweight levers is used to provide a counter-acting axial force to the actuator, reducing the need for excessive counterweight mass by leveraging centrifugal forces and optimizing lever design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional counterweight systems are used to counteract axial forces from fan blade twisting, then the counterweight mass must be excessive, but this increases the overall weight and complexity of the system
Solution Approach 1:
The patent applies counterweight levers with counterweights positioned to generate counterbalancing moments that directly oppose the axial forces from fan blade twisting. The counterweight levers are rotationally connected to the fan blade hub and positioned radially outward, creating an efficient counterbalancing mechanism that reduces the required counterweight mass compared to conventional systems.
Solution Approach 2:
The patent transitions from conventional counterweight positioning to a spatial arrangement where counterweight levers extend radially outward from the fan blade hub in a plane perpendicular to the rotation axis. This dimensional repositioning allows the counterweights to leverage centrifugal forces more effectively, reducing the mass required while maintaining counterbalancing effectiveness.
2Device complexity
If conventional counterweight systems are used to counteract axial forces, then the system becomes complex and heavy, but simplifying the system reduces its ability to effectively balance forces
Solution Approach 1:
The patent divides the counterweight system into multiple independent counterweight levers, each rotationally connected to the fan blade hub. Each lever can be independently positioned and adjusted, allowing the system to effectively balance forces while maintaining modular simplicity. This segmentation enables precise force balancing without requiring a complex integrated structure.
Solution Approach 2:
The counterweight levers serve multiple functions: they provide counterbalancing moments to offset axial forces from fan blade twisting, maintain rotational stability, and can be adjusted to adapt to different operating conditions. This multi-functionality reduces the need for separate components, simplifying the overall system while maintaining effectiveness.
3Weight of moving object
If counterweight mass is reduced to minimize system weight, then the system becomes lighter, but the ability to counteract axial forces is compromised
Solution Approach 1:
The patent positions counterweights radially outward from the rotation axis, leveraging the rotational motion to generate centrifugal forces that amplify the counterbalancing effect. This dimensional positioning allows smaller mass to produce sufficient counteracting force by utilizing the rotational dynamics of the system.
Solution Approach 2:
The counterweight levers are specifically designed with optimized lever arm lengths and counterweight positions to maximize the counterbalancing moment for a given mass. This optimized configuration ensures that the counteracting force is sufficient while minimizing the required counterweight mass.
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 counterweight system effectively balances the axial forces imparted by the fan blades, reducing stress on the actuator and hydraulic components, while minimizing the overall weight and complexity of the counterweight system.
Implementation Method 1
providing a counter-acting axial force to the actuator, reducing the need for excessive counterweight mass by leveraging centrifugal forces
Data Source
AI summary
A fan assembly for a gas turbine engine includes a fan actuation system, a fan blade hub, a plurality of fan blades, and a counterweight system arranged disconnected from the plurality of fan blades. The counterweight system includes a counterweight hub, and a plurality of counterweight levers each having a counterweight trunnion rotationally connected to the counterweight hub, a cantilever arm with a counterweight connected thereto. The fan blades are rotationally connected to the fan blade hub and to the fan actuation system, and the counterweight levers are rotationally connected to the counterweight hub and to the fan actuation system. The fan actuation system is arranged to correspondingly rotate each of the plurality of fan blades about a respective fan blade pitch change axis, and each of the plurality of counterweight levers about a counterweight lever rotational axis in unison.