Aircraft Engine Fuel Spool Shoulder Redirection
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Solution Overview
Problem
The existing spool valves in aircraft engine fuel circuits face inaccuracies due to the 'jet force' generated by the difference in cross-sectional areas, which applies an additional axial load and disrupts the control of the spool, leading to inaccuracies in fuel flow.
Innovation Solution
A spool design with a shoulder and a recirculation groove that redirects the fuel jet onto a cylindrical section, minimizing axial loads by creating a recirculation zone that reduces the impact of fuel pressure on the spool, thereby preventing axial displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the spool has a uniform cross-section between inlet and outlet, then the fuel flow control is simple, but a jet force is generated that applies an additional axial load and disrupts spool positioning accuracy
Solution Approach 1:
The spool is segmented into distinct zones: a first cylindrical portion, a narrowed intermediate portion with a shoulder, and a second cylindrical portion. This segmentation creates a stepped structure that divides the fuel flow path into separate regions, allowing the jet to be redirected onto the cylindrical section rather than applying axial load to the spool, thereby improving positioning accuracy while maintaining manageable structural complexity
Solution Approach 2:
The invention redirects the fuel jet from an axial direction onto a cylindrical section of the spool, changing the dimension of force application from axial (problematic) to radial (beneficial). The shoulder and narrowed portion create a three-dimensional flow path that directs the jet tangentially onto the cylindrical surface, eliminating the harmful axial component while the cylindrical geometry distributes the load radially
2Measurement precision
If grooves are added to the spool to reduce jet force effects, then positioning accuracy improves slightly, but the structure becomes more complex and the reduction is insufficient for required accuracy
Solution Approach 1:
Rather than adding grooves to an existing uniform spool, the invention segments the spool itself into a stepped structure with a narrowed intermediate portion and shoulder. This fundamental segmentation creates the jet redirection capability inherently, achieving greater accuracy improvement with a more integrated structure rather than adding separate groove features to a simple cylinder
Solution Approach 2:
The invention converts the harmful jet force into a beneficial effect by redirecting it onto the cylindrical section of the spool. The shoulder and narrowed portion transform the axial jet into a radial flow pattern that applies force perpendicular to the spool axis, converting what was a harmful axial load into a beneficial radial distribution that actually helps stabilize spool positioning
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
This design significantly reduces the axial load on the spool, minimizing inaccuracies in fuel flow and maintaining precise control of the valve, ensuring accurate fuel flow rates without generating movement quantity deviations between the inlet and outlet.
Implementation Method 1
ensures the generation of a fuel jet on the cylindrical section of the narrowed intermediate portion
Implementation Method 2
a recirculation of fuel forming in a zone in front of said shoulder
Implementation Method 3
The spool is displaced along the longitudinal axis under the influence of a pressure differential between the two control chambers
Data Source
AI summary
A spool for a fuel circuit valve of an aircraft engine, extending along a longitudinal axis and including a narrowed intermediate section extending between two end cylindrical sections, a first end section being separated from the narrowed intermediate section by a shoulder having a surface arranged overall perpendicular to the longitudinal axis, the narrowed intermediate section also including, extending away from the shoulder, at least one cylindrical portion, and the shoulder is provided with a step extending away from the cylindrical surface of the first end section which, when the fuel flows along the first end section towards the narrowed intermediate section and the second end portion, generates a jet of fuel on the cylindrical portion of the narrowed intermediate section, a recirculation of fuel forming in an area in front of the shoulder.