Differential-Speed Fluid Transfer Coupling for Low-Speed Pressure Supply
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Solution Overview
Problem
Conventional fluid transfer couplings in aerospace gas turbine engines face challenges in delivering pressurized fluid at low rotational speeds, leading to potential engine shutdowns and unplanned removals, as they rely on dynamic pressure head which is insufficient at low rotation rates.
Innovation Solution
A fluid transfer coupling design featuring a first shaft assembly with an annular fin and a second shaft assembly with an annular trough, where the difference in rotational speeds between the two assemblies creates a radial pressure gradient that drives fluid from the trough to the center of the first shaft, enabling fluid delivery across the entire operational speed envelope, including start-up and low rotational speed conditions, using a seal assembly to maintain pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dynamic scoop approach is used to transfer fluid, then fluid transfer is achieved through relative rotation, but the pressure developed is insufficient at low rotational speeds
Solution Approach 1:
The invention divides the fluid transfer system into two independent shaft assemblies rotating at different speeds. The first shaft assembly rotates at a first rotational speed while the second shaft assembly rotates at a second rotational speed, allowing each to contribute differently to fluid pressure generation. This segmentation enables reliable fluid supply across the entire operational speed envelope including low rotational speeds.
Solution Approach 2:
The invention changes the rotational speed parameter by introducing two shaft assemblies rotating at different speeds. The difference between the second rotational speed and the first rotational speed creates a radial pressure gradient that drives fluid radially inwardly through internal passages. This parameter change ensures sufficient fluid pressure is generated even when the planet carrier rotates at low speeds.
2Reliability
If conventional seals are used in fluid transfer coupling, then fluid transfer is maintained, but seals are prone to failure at low speeds and start-up conditions
Solution Approach 1:
The invention extracts the seal assembly from the critical fluid transfer path. Instead of relying on seals to maintain fluid pressure across the rotating interface, the seal assembly is positioned to seal the annular trough while the fluid transfer occurs through the radial pressure gradient driven by differential rotation. This removes seals from the critical path and eliminates their failure modes.
Solution Approach 2:
The invention introduces a seal assembly as an intermediary element that seals the annular trough but does not directly control fluid transfer to the planet carrier. The seal assembly works in conjunction with the radial pressure gradient mechanism, allowing fluid to be driven through internal passages without relying on seal integrity during low-speed operation.
3Productivity
If fluid pressure is coupled to rotational speed in conventional designs, then fluid transfer works at high speeds, but fluid supply fails at low speeds and start-up
Solution Approach 1:
The invention creates a dynamic system where two shaft assemblies rotate at different speeds, and the difference between these speeds dynamically generates the radial pressure gradient. This dynamic mechanism ensures fluid transfer efficiency across the entire operational speed envelope, including start-up and low rotational speed conditions, by maintaining the pressure differential needed for fluid flow regardless of absolute rotation rate.
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 ensures reliable fluid supply to rotating systems without reliance on seals prone to failure, decouples fluid pressure from rotational speed, and maintains efficiency across a wide range of speeds, making it more reliable and versatile than conventional couplings.
Implementation Method 1
the difference between the second rotational speed and the first rotational speed causes a fluid contained within the annular trough to be driven radially inwardly through the or each internal passage to the centre portion of the first shaft
Implementation Method 2
the radial acceleration acting on the fluid within the or each internal passage is much lower than the radial acceleration acting on the fluid contained within the annular trough
Data Source
AI summary
A fluid transfer coupling comprises a first shaft assembly a second shaft assembly, and a seal assembly. The first shaft assembly comprises a first shaft and an annular fin attached to the first shaft, the annular fin having one or more internal passages extending therethrough. Each internal passage connects a centre portion of the first shaft to a radially outwardly facing side of the annular fin. The second shaft assembly comprises a second shaft and an annular trough extending radially outwardly of the second shaft.