RAT Actuator Damping via Progressive Orifice
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Solution Overview
Problem
Ram air turbine (RAT) actuators face stress and potential abrupt motion during deployment due to the lack of effective damping mechanisms, particularly at the end of their travel, which can lead to violent cessation of motion and increased wear on seals.
Innovation Solution
Incorporating a fluid flow regulating feature with progressively smaller orifices between the piston rod and cylinder, which blocks fluid flow to increase pressure and slow the actuator's extension, ensuring controlled deployment and timed damping to coincide with high stopping forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydraulic fluid fills the piston rod and cylinder to prevent vacuum creation, then the actuator can operate without vacuum damage, but the actuator experiences great stress during deployment especially at the end of travel
Solution Approach 1:
A damping orifice is introduced as an intermediary element in the hydraulic circuit between the piston rod and cylinder. This orifice acts as a flow restrictor that mediates the fluid flow during actuator deployment, reducing the rate of volume change and thereby reducing the stress and pressure spikes that occur at the end of travel, while still allowing sufficient fluid flow to prevent vacuum formation.
2Speed
If the actuator deploys quickly to ensure timely deployment, then the deployment speed is improved, but abrupt motion and violent cessation occur at the end of travel
Solution Approach 1:
The damping orifice changes the flow parameters of the hydraulic fluid by restricting its flow path. This parameter change reduces the rate at which fluid can enter or leave the actuator chambers during deployment, thereby controlling the speed of actuator movement and preventing abrupt motion and violent cessation at the end of travel while maintaining timely deployment.
3Device complexity
If no damping mechanism is used, then the device complexity is reduced, but wear on seals increases due to abrupt motion
Solution Approach 1:
The damping orifice serves as a simple intermediary component that introduces controlled resistance to fluid flow. This simple design increases device complexity minimally while effectively reducing the rate of volume change during actuator deployment, thereby reducing seal wear caused by abrupt motion and violent cessation.
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 solution provides controlled and gradual extension of the RAT actuator, reducing wear and ensuring timely deployment by managing fluid flow and pressure, thus mitigating stress and abrupt motion.
Implementation Method 1
Fluid flow is forced from the annular space through a flow regulating feature to a cavity. The size of the flow regulating feature reduces to slow the actuator's extension during the deploy sequence.
Implementation Method 2
Fluid flow is forced from the annular space through a flow regulating feature to a cavity. The size of the flow regulating feature reduces to slow the actuator's extension during the deploy sequence.
Data Source
AI summary
A ram air turbine actuator includes a piston rod arranged in a cylinder. The cylinder and piston rod are configured to move longitudinally relative to one another between retracted and deployed positions. An annular space provided between the cylinder and piston rod, and a fluid flow regulating feature is provided in the piston rod. The fluid flow regulating feature is progressively blocked from the retracted position to the deployed position. The RAT actuator is deployed by initiating a deploy sequence and reducing a volume of an annular space. Fluid flow is forced from the annular space through a flow regulating feature to a cavity. The size of the flow regulating feature reduces to damp the actuator during the deploy sequence.