Aircraft Strut Standpipe Restrictor for Gas Backflow Damping
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Solution Overview
Problem
Aircraft landing gear systems face reduced rebound damping due to gas backflow through the orifice plate during the transition from compression to extension, as nitrogen flows preferentially over hydraulic fluid, diminishing the strut's ability to absorb and distribute landing forces effectively.
Innovation Solution
A gas backflow restrictor system is integrated into the aircraft strut, featuring an orifice plate and a restrictor with a shelf that extends into the inner channel of the standpipe, creating a central opening to block gas flow towards the orifice plate during compression, thereby reducing gas backflow and enhancing rebound damping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gas is allowed to flow freely through the orifice plate during compression phase, then the strut can operate with simple structure, but gas backflow reduces rebound damping effectiveness
Solution Approach 1:
The standpipe is segmented into multiple functional zones: the upper portion contains the restrictor with shelf that blocks gas backflow, while the lower portion maintains open flow paths for hydraulic fluid. This segmentation allows different flow control strategies for different phases of operation without requiring complete structural redesign.
Solution Approach 2:
The restrictor shelf acts as an intermediary element between the compression chamber and the orifice plate. It selectively interferes with gas flow during compression while allowing hydraulic fluid to pass through, thereby mediating the flow dynamics to prevent gas backflow without completely blocking the standpipe.
2Force
If the orifice plate allows free flow of hydraulic fluid, then compression damping is effective, but gas preferentially flows through creating backflow issues
Solution Approach 1:
The restrictor shelf creates a localized flow restriction zone at a specific position in the standpipe. This local modification changes the flow characteristics only in the upper portion of the standpipe, allowing hydraulic fluid to maintain free flow for compression damping while preventing gas from reaching the orifice plate during compression.
Solution Approach 2:
The restrictor shelf is positioned upstream of the orifice plate to preemptively block gas flow before it can reach the orifice plate during compression. This preliminary anti-action prevents the harmful gas backflow phenomenon before it occurs, rather than attempting to correct it after the fact.
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 restrictor effectively reduces gas backflow, improving the strut's rebound damping force and overall performance by ensuring hydraulic fluid dominates the flow through the orifice plate during both phases, leading to smoother landings and takeoffs.
Implementation Method 1
The shelf is configured to reduce gaseous flow through one or more of the plurality of openings of the standpipe and toward the orifice plate
Implementation Method 2
An orifice plate is positioned within the inner volume and separates the first chamber and the second chamber
Implementation Method 3
Aircraft landing gear include shock absorbers which use a combination of gas and hydraulic fluid to reduce compression forces during landing
Data Source
AI summary
A gas backflow restrictor system as part of an aircraft strut includes the strut defining an inner volume having a first chamber and a second chamber; an orifice plate positioned within the inner volume and separating the first chamber and the second chamber; a standpipe attached to the orifice plate and extending longitudinally within the inner volume, the standpipe having openings extending through a thickness of a wall forming the standpipe, the standpipe further defining an inner channel; and a restrictor mounted within the inner channel, the restrictor having a shelf extending into the inner channel and forming a central opening; the shelf is to reduce gaseous flow through one or more of the openings of the standpipe and toward the orifice plate.