Aircraft Engine Fuel Pump Axial Force Balancing
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Solution Overview
Problem
In aircraft fuel pumps with closed-type centrifugal impellers, balancing axial forces is challenging due to the complexity of pressure fields and significant pressure losses caused by the rotation of the impeller, leading to performance issues.
Innovation Solution
The design incorporates a closed-type centrifugal impeller with axial balancing holes and plenum chambers that allow fluid recirculation, reducing axial forces and pressure losses by standardizing the speed field and limiting turbulence, while maintaining structural stability through a discontinuous contact surface and symmetrical plenum chamber arrangement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a closed-type centrifugal impeller with upstream flange is used, then structural stability is improved, but axial force balancing becomes difficult and pressure losses increase
Solution Approach 1:
The upstream flange is segmented into multiple discrete contact portions rather than being continuous, creating gaps that form plenum chambers. This segmentation allows fluid communication between high and low pressure zones while maintaining structural integrity, thereby reducing pressure losses without compromising structural stability.
Solution Approach 2:
Plenum chambers are introduced as intermediary spaces between the inductor and impeller, filled with fluid that acts as a mediator to balance axial forces. These chambers communicate pressure between different zones, enabling force balancing while preserving the closed-type impeller structure.
2Force
If balancing holes are added to reduce axial forces, then axial force balancing is improved, but pressure field control becomes difficult and turbulence increases
Solution Approach 1:
Plenum chambers serve as intermediary spaces that organize and control the pressure field between balancing holes. Rather than allowing uncontrolled pressure equalization through scattered holes, the plenum chambers provide structured fluid communication paths, making pressure field control more manageable while maintaining axial force balance.
Solution Approach 2:
The solution moves from two-dimensional hole distribution to three-dimensional plenum chamber structures. By adding the volumetric dimension with plenum chambers, the system gains better control over pressure distribution and fluid flow patterns, reducing turbulence while maintaining force balancing.
3Productivity
If impeller rotation speed is increased to improve pump performance, then productivity is improved, but pressure losses and turbulence increase
Solution Approach 1:
The plenum chambers convert the harmful effect of impeller rotation (which creates pressure fluctuations and turbulence) into a beneficial force-balancing mechanism. The rotating impeller generates pressure differences that are harnessed by the plenum chambers to maintain axial force balance, allowing higher rotation speeds without proportional increases in pressure losses.
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 configuration effectively balances axial forces, reduces pressure losses, and enhances the performance of the fuel pump by standardizing the pressure field and minimizing the impact of transverse flow on the main flow.
Implementation Method 1
two contact portions between the inductor and the impeller arranged radially outside the annular space, a first plenum chamber and a second plenum chamber, in which the inductor and the impeller are axially spaced from each other, each being arranged circumferentially between the two contact portions
Implementation Method 2
the impeller comprising a plurality of axial balancing holes distributed circumferentially around the axis of rotation and opening into the annular space at one end, and into a downstream space of the impeller at the other end
Implementation Method 3
The LP stage typically consists of an inducer and a centrifugal impeller, along with a volute
Implementation Method 4
Its flow and pressure also serve to generate the hydraulic power to operate the engine's variable geometry
Implementation Method 5
The inductor being fixed to the centrifugal impeller upstream thereof so as to define an annular interface between the inductor and the impeller
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
Fuel pump (1) for an aircraft engine, comprising an inductor (10) and an impeller (20) which are attached to each other and have an axis of rotation (X), an annular space (E) axially spacing the inductor (10) and the impeller (20), and two contact portions between the inductor (10) and the impeller (20) which are arranged radially on the outside of the annular space (E), a first plenum chamber (C1) and a second plenum chamber (C2), in which the inductor (10) and the impeller (20) are axially spaced relative to each other, each being arranged between the two contact portions, the plenum chambers (C1, C2) being symmetrical relative to each other and relative to the axis of rotation (X) and in fluidic communication with the annular space (E), the impeller (20) comprising a plurality of axial balancing holes (26) distributed around the axis of rotation (X) and opening into the annular space (E) at one end and into a space (70) downstream of the impeller (20) at the other end.