Temperature-Responsive Hydraulic Actuator for Faster Landing Gear Retraction
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Solution Overview
Problem
The retraction time of aircraft landing gear is significantly affected by the viscosity of hydraulic fluid, which increases with temperature drops, leading to reduced climb performance and maximum take-off weight.
Innovation Solution
A hydraulic actuator with a bypass line containing a flow restrictor and a temperature-responsive bypass valve, where the valve opens automatically at a predetermined temperature, allowing hydraulic fluid to flow through the bypass line and generate heat, reducing fluid viscosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the temperature of the hydraulic actuator drops, then the viscosity of the hydraulic fluid increases, but this increases the resistance to flow and the time it takes to actuate the actuator
Solution Approach 1:
The patent converts the harmful effect of cold temperatures into a beneficial automatic activation mechanism. The bypass valve utilizes the temperature drop itself as the triggering condition to open and allow heated bypass flow, transforming the problem of cold viscosity into an automatic self-activating solution that warms the fluid when needed most.
Solution Approach 2:
The bypass valve is designed to automatically open in response to temperature changes without requiring external control systems, sensors, or manual intervention. The valve material itself responds to the thermal condition, making the system self-regulating and eliminating the need for additional control infrastructure.
2Loss of time
If a bypass valve with automatic temperature response is used, then the actuation time is reduced, but the device complexity increases due to additional components
Solution Approach 1:
The bypass valve exploits changes in physical parameters (temperature-induced dimensional changes) of the valve material to control flow. By designing the valve so that thermal contraction or expansion automatically opens or closes the bypass passage, the system uses parameter changes rather than mechanical actuation, reducing the need for complex control mechanisms.
3Temperature
If the flow restrictor is opened to allow more fluid flow through the bypass line, then the heating effect is increased, but the flow restrictor must be precisely controlled to maintain optimal flow rate
Solution Approach 1:
The patent replaces complex mechanical flow control systems with a thermally-actuated valve mechanism. Instead of using precisely controlled mechanical actuators, motors, or electronic control systems to regulate the bypass flow, the invention uses the thermal environment itself to control valve opening, substituting mechanical precision requirements with thermal response characteristics.
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 reduces the time required to actuate the hydraulic actuator, thereby improving climb performance and allowing for increased maximum take-off weight by maintaining hydraulic fluid viscosity within acceptable limits.
Implementation Method 1
Flow of fluid through the flow restrictor generates heat in the fluid and its surroundings
Implementation Method 2
the material is configured to change shape, as a temperature of the material reduces to below a predetermined temperature
Data Source
Figure 1~2
Figure 3~4
Figure 5a~5b
AI summary
Disclosed is a hydraulic actuator for a hydraulic actuation system of an aircraft. The hydraulic actuator comprises: a housing configured to accommodate hydraulic fluid; an extension chamber and a retraction chamber each defined by the housing; and a bypass line in fluid communication with each of the extension chamber and the retraction chamber, wherein the bypass line comprises a flow restrictor and a bypass valve, wherein the flow restrictor is configured to restrict a rate of fluid flow through the bypass line, wherein the bypass valve has material defining a port that is openable to allow the hydraulic fluid to flow through the bypass line, and wherein the material is configured to change shape, as a temperature of the material reduces to below a predetermined temperature, to thereby open the port. Also disclosed is a hydraulic actuation system, in the form of a landing gear system, comprising the hydraulic actuator, and an aircraft comprising the hydraulic actuation system.