Blade Pitch Control via Dual Electrical Systems
Solution Overview
Problem
Conventional rotor blade control systems in gas turbine engines, particularly those with contra-rotating propeller stages, face challenges in maintaining optimal pitch angles to prevent overspeeding and excessive drag, leading to potential engine failure and loss of aircraft control due to mechanical or hydraulic complexity and reliability issues.
Innovation Solution
A dual electrical control system is implemented, comprising a primary and secondary system that compares demanded and measured blade pitch angles, applying torque to correct deviations, with redundancy and failsafe mechanisms to ensure rapid control and minimize failure risks, including a failsafe blade feather apparatus for emergency situations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical or hydraulic control systems are used for rotor blade pitch control, then the system can provide robust control authority, but the device complexity and maintenance costs increase significantly
Solution Approach 1:
The patent replaces mechanical and hydraulic control systems with an electrical control system comprising electric motors coupled to blade spindles. This substitution maintains control authority while reducing mechanical complexity, maintenance requirements, and failure points associated with traditional hydraulic systems
Solution Approach 2:
The electrical control system incorporates self-diagnostic capabilities where the control system monitors its own operational status, detects faults, and can command failsafe positions autonomously. This self-monitoring reduces the need for complex external monitoring systems and manual maintenance interventions
2Device complexity
If a single electrical control system is used for blade pitch control, then the device complexity is reduced, but the reliability decreases due to lack of backup
Solution Approach 1:
The control system is segmented into two independent electrical control systems, each capable of independently controlling the blade pitch. This segmentation provides redundancy so that if one system fails, the other can maintain control, thereby improving reliability without requiring a completely complex backup mechanism
Solution Approach 2:
The patent implements a failsafe mechanism that automatically commands the blades to a safe position (typically feathered position) upon detection of system faults or loss of electrical power. This beforehand cushioning ensures that even in failure scenarios, the system maintains safety margins and prevents catastrophic outcomes
3Productivity
If blade pitch is commanded to fine angle to reduce drag, then the engine efficiency improves, but the risk of overspeeding and catastrophic failure increases
Solution Approach 1:
The control system continuously monitors blade pitch position using sensors and compares actual position with commanded position. This feedback mechanism allows the system to detect deviations and correct them rapidly, preventing the blades from reaching dangerous fine pitch angles that could cause overspeeding while still allowing efficient operation within safe parameters
Solution Approach 2:
The control system is programmed with predetermined limits and constraints on blade pitch angles that prevent the blades from being commanded to dangerously fine positions in the first place. This preliminary anti-action blocks harmful commands before they can execute, while still allowing the system to operate efficiently within the safe envelope
Data Source
AI summary
A method of controlling blade pitch angle, including comparing demanded and measured blade pitch angle and calculating any difference therebetween, in a primary electrical control system, where there is a difference, applying torque to a blade pitch regulator to reduce the magnitude of the difference to zero, and in a secondary electrical control system, where the difference is greater than a pre-determined threshold, applying torque to a blade pitch regulator to reduce the magnitude of the difference to the threshold. Also an electrical system of blade pitch angle control for a set of blades including primary and secondary electrical control systems, means for comparing demanded and measured blade pitch angle and calculating any difference therebetween, a look-up function having the difference as its input and outputting a required torque, and a torque regulator to apply the required torque to the set of blades.