Aircraft Engine Fuel Valve Spool Jet Force Mitigation
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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 area, which applies an additional axial load and disrupts the control of the spool, leading to fuel flow inaccuracies.
Innovation Solution
A spool design with a shoulder and groove forming a fuel recirculation zone, where the fuel jet is redirected onto a cylindrical section, reducing axial loads and eliminating the jet force's impact on the spool's positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the spool has a difference in cross-sectional area between the first portion and the third portion, then the valve structure is simple and compact, but a jet force is generated that applies an additional axial load on the spool, perturbing the control and causing positioning inaccuracies
Solution Approach 1:
The spool is segmented into distinct portions (first cylindrical portion, third portion with narrowed cross-section, and at least one cylindrical section) with specific functional zones. The groove is introduced to segment the fuel flow path, creating a recirculation zone that separates the jet force generation from the spool's control surface, thereby eliminating the harmful axial load while preserving the compact structure.
Solution Approach 2:
A groove is introduced as an intermediary feature on the spool surface. This groove acts as a mediator that redirects the fuel jet into a recirculation zone, preventing the jet force from directly acting on the spool's control surfaces. The groove transforms the harmful direct jet impact into a controlled recirculating flow pattern.
2Measurement precision
If grooves are added to the spool to reduce jet force effects, then the positioning accuracy improves, but the device complexity increases
Solution Approach 1:
Instead of modifying the entire spool structure, the groove is introduced only in the specific location where it is most effective - on the third portion of the spool where the cross-sectional area is narrowed. This localized modification creates the recirculation zone exactly where needed to counteract the jet force, minimizing the added complexity while maximizing the positioning accuracy improvement.
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 fuel recirculation zone significantly reduces the axial load on the spool, minimizing inaccuracies and ensuring precise fuel flow control by eliminating the jet force's influence, thereby enhancing the accuracy and reliability of the fuel circuit operation.
Implementation Method 1
the difference in the cross portion area between the first portion 10 and the third portion 12 generates, in the open position, a fuel jet which applies an additional load on the spool 3
Data Source
AI summary
A slide for a fuel circuit valve of an aircraft engine extending along a longitudinal axis, and comprising a narrowed intermediate portion extending between two cylindrical end portions, a first end portion being separated from the narrowed intermediate portion by a shoulder having a surface arranged overall perpendicular to the longitudinal axis, the narrowed intermediate portion including in turn, as an extension of the shoulder, at least one cylindrical portion, the shoulder comprising at least one groove which extends radially from the cylindrical surface of the first end portion, towards the longitudinal axis, and which forms a fuel recirculation area which provides the generation of a jet of fuel on the cylindrical portion of the narrowed intermediate portion, when fuel flows along the first end portion towards the narrowed intermediate portion and the second end portion.