Fluid Pump with Secondary Cavity Actuator
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Solution Overview
Problem
Existing fluid pumps with disc-shaped cylindrical cavities face inefficiencies due to mismatched spatial profiles of actuator motion and pressure oscillations, leading to reduced pump efficiency, and limitations in piezoelectric material volume and high strain on the actuator, which shorten its lifespan.
Innovation Solution
A fluid pump design featuring a secondary cavity that separates the actuator mount from the side wall, using a piezoelectric or magnetostrictive ring actuator excited in a radial mode to induce axial deflection, with a secondary cavity spacing allowing the actuator to vibrate with an antinode at the cavity edge, and a compliant material filling the gap to reduce strain and increase piezoelectric material volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a composite bending-mode actuator with maximum motion amplitude at the centre is used, then the actuator is simple to construct with rigid clamping at the perimeter, but mode-matching fails at the outer radii reducing pump efficiency
Solution Approach 1:
The invention inverts the traditional actuator design by positioning the maximum motion amplitude at the perimeter rather than the centre. The cantilevered actuator configuration creates an antinode at the free end (perimeter), reversing the conventional nodal/antinodal arrangement and enabling mode-matching with the acoustic pressure field in the cavity.
Solution Approach 2:
The invention transitions from a centrally-driven actuator to a perimeter-driven cantilevered actuator, changing the spatial dimension of actuation from centre-to-edge to edge-to-centre. This dimensional reconfiguration allows the actuator motion profile to match the acoustic pressure distribution in the cavity.
2Power
If the piezoelectric disc volume is increased to deliver more power, then the power output increases, but the strain at the centre increases causing depolarisation and reducing actuator lifetime
Solution Approach 1:
The invention extracts the piezoelectric material from the high-strain centre region and relocates it to the perimeter where strain is minimal. The cantilevered actuator configuration with piezoelectric material positioned at the free end removes the depolarisation problem while maintaining power output capability.
Solution Approach 2:
The invention applies local quality by positioning piezoelectric material specifically at the perimeter region where mechanical strain is minimal, rather than uniformly distributing it. This localized placement optimizes both durability (by avoiding high-strain areas) and power output (by utilizing the full piezoelectric effect at the antinode).
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 achieves mode-matching of actuator motion and pressure oscillations across the full surface area, enhancing pump efficiency and extending the actuator's lifespan by distributing strain and increasing the volume of piezoelectric material.
Implementation Method 1
one or both actuators include an active element which is either a piezoelectric or magnetostrictive ring
Implementation Method 2
one or both actuators include an active element which is either a piezoelectric or magnetostrictive ring
Implementation Method 3
the axial oscillations of the end walls drive radial oscillations of the fluid pressure in the main cavity
Data Source
Figure 1A~1C
Figure 2A~2B
Figure 3A~4C
AI summary
A fluid pump comprising a chamber which, in use, contains a fluid to be pumped, the chamber including a main cavity having a substantially cylindrical shape bounded by first and second end walls and a side wall and a secon dary cavity extending radially outwards of the main cavity, one or more actuators which, in use, cause oscillatory motion of the first end wall in a direction substantially perpendicular to the plane of the first end wall, and whereby, in use, the axial os cillations of the end walls drive radial oscillations of the fluid pressure in the main cavity, and wherein the secondary cavity spaces the side wall from the first end wall such that the first end wall can move relative to the side wall when the actuator is activated.