Propeller Feathering Flow Control for Smooth Thrust Transition
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Solution Overview
Problem
Conventional propeller feathering systems in aircraft cause sudden changes in acting forces and controllability issues due to abrupt thrust transitions, leading to potential structural and flight safety hazards.
Innovation Solution
A system that gradually reduces the rate of oil drain from the propeller blades using an actively or passively controlled metering valve, allowing for a controlled transition to the feathered position, minimizing thrust and torque fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If maximum drainage flow is used to quickly feather the propeller, then the propeller transitions rapidly to the feathered position, but sudden changes in acting forces occur causing controllability issues and structural loads
Solution Approach 1:
The patent applies dynamics by making the drainage flow rate variable rather than constant. The system transitions from maximum drainage flow to a reduced drainage flow rate based on operating conditions, allowing the feathering process to adapt dynamically. This resolves the contradiction by enabling fast feathering when needed while preventing harmful sudden thrust changes when conditions permit a more gradual transition.
Solution Approach 2:
The patent changes the parameter of drainage flow rate from a fixed maximum value to a variable parameter that can be adjusted between maximum and reduced rates. The controller modifies this parameter based on detected operating conditions, thereby achieving both rapid feathering capability and smooth transition capability to avoid harmful thrust changes and structural loads.
2Reliability
If maximum drainage flow is used to prevent unsafe states, then the protective function activates quickly, but the transition creates significant loads on engine and aircraft structures
Solution Approach 1:
The system dynamically adjusts the drainage flow rate based on detected operating conditions. When an unsafe state is detected, the system can activate the protective function quickly with maximum drainage. However, once the propeller exits the unsafe state range, the system transitions to a reduced drainage flow rate, maintaining reliability while significantly reducing structural loads during the remainder of the feathering process.
Solution Approach 2:
The patent implements periodic action by switching between two distinct phases: an initial phase with maximum drainage flow for rapid protective activation, followed by a second phase with reduced drainage flow for smooth completion. This periodic switching between flow rates allows the system to achieve both quick protective response and reduced structural loading.
3Loss of time
If the propeller transitions quickly from high thrust to zero thrust, then the unsafe state is prevented rapidly, but aircraft rolling momentum changes significantly affecting controllability
Solution Approach 1:
The system uses dynamic control of drainage flow rate to optimize the trade-off between quick unsafe state prevention and maintaining controllability. Maximum drainage flow is applied only until the propeller exits the unsafe state range, minimizing the time loss. Then reduced drainage flow is used to complete feathering gradually, preventing significant rolling momentum changes and maintaining aircraft controllability during the extended transition period.
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 prevents overcorrection and reduces the time required to return to normal operation by smoothly transitioning the propeller to the feathered position, maintaining aircraft stability and reducing thrust spikes.
Implementation Method 1
gradually reduces the rate of drainage from the propeller pitch angle actuator
Data Source
Figure 1~2
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AI summary
A rotor blade control system includes a main control valve (25) having an inlet (102) for receiving liquid and an outlet (104) for issuing liquid to a rotor pitch change actuator (24). The main control valve (25) is configured to control flow of liquid from the inlet (102) to the outlet (104) to modify pitch angle of rotor blades (17). A feathering system (100) has a first conduit (106) in fluid communication with the outlet (104) of the main control valve (25), a second conduit (108) in fluid communication with the rotor pitch change actuator (24), and a drain conduit (110) in fluid communication with a liquid return system (13). The feathering system (100) has a normal operation mode for supplying liquid from the main control valve (25) to the rotor pitch change actuator (24), and a feathering mode for allowing drainage from the rotor pitch change actuator (24) to the drain conduit (110) across a range of flow rates.