Propeller Pitch Control via Mode-Specific Fluid Passages
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Solution Overview
Problem
Existing pitch control systems for gas turbine engine propellers lack the ability to accurately and selectively limit propeller pitch angles, which can lead to catastrophic failures under different ambient conditions or operation states.
Innovation Solution
A propeller pitch control system that includes a linear actuator with a cylinder, piston, and oil transfer bearing, featuring discrete fluid passages that change communication modes between ground-based and flight-based operations to control hydraulic fluid flow, thereby limiting pitch angle adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If pitch control systems allow full pitch adjustment range, then propeller performance can be optimized for various conditions, but the risk of catastrophic failure increases under unsuitable ambient conditions or operation states
Solution Approach 1:
The system dynamically adjusts the pitch control range based on operational mode (ground-based vs. flight-based). The pitch control valve selectively restricts hydraulic fluid flow to limit pitch angle adjustments within specific ranges appropriate for each operational mode, transforming a static pitch control system into a dynamic one that adapts to current operating conditions
Solution Approach 2:
The system changes the pitch angle parameter range based on operational mode. By controlling the pitch control valve, the system limits the pitch angle to specific ranges for ground-based operation versus flight-based operation, optimizing performance and safety for each mode while maintaining adaptability across different conditions
2Device complexity
If pitch control systems use a single fluid passage configuration, then the system structure is simple, but the system cannot selectively limit pitch angles for different operational modes
Solution Approach 1:
The fluid passage system is segmented into multiple discrete passages (first fluid passage and second fluid passage) that are selectively activated based on operational mode. The pitch control valve divides the hydraulic fluid flow paths, allowing independent control for ground-based and flight-based operations, thereby enabling mode-specific pitch angle limitations without requiring completely separate systems
Solution Approach 2:
The pitch control valve serves multiple functions by controlling different fluid passages for different operational modes. A single valve mechanism provides both ground-based mode pitch limitation and flight-based mode pitch limitation, making the system multi-functional while avoiding the need for separate control mechanisms for each operational condition
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 system effectively limits propeller pitch angles during specific modes of operation, enhancing safety and performance by ensuring accurate pitch adjustments based on operational conditions.
Implementation Method 1
The actuator includes a cylinder having a fluidly-sealed cylinder wall, as well as a piston translatably attached to the propeller blade crankshaft... an oil transfer bearing (OTB) positioned along a central axis and joined to the cylinder wall in fluid communication with the forward chamber... a fine stop collar annularly positioned about the OTB and defining discrete first and second fluid passages
Data Source
AI summary
Systems and methods are disclosed for controlling the pitch angle of a propeller and rotor assembly that selectively limit the pitch angle according to a selected mode of operation. The system includes an actuator having forward and aft chambers, an oil transfer bearing (OTB), and a fine stop collar. The fine stop collar including a first passage in fluid communication with the OTB and forward chamber during a ground-based mode of operation, and a second fluid passage being in fluid communication with the OTB and forward chamber during a flight-based mode of operation.