Acoustic Array Sensor Wave Mode Conversion for Aerated Fluid Level

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional liquid level sensors are ineffective in measuring fluid levels in highly aerated fluids due to transmission losses and issues with sealing and non-immersed fluid residue, particularly in viscous fluids at low temperatures.

Innovation Solution

A liquid level sensor using a substrate with reflective side surfaces and echelons angled at approximately 39.1 degrees to convert zeroth order shear waves into anti-symmetric, first order Lamb flexural waves, reducing absorption by fluid immersion and minimizing effects of fluid residue on non-immersed sections.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If Rayleigh surface acoustic waves are used for fluid level sensing, then the sensor can detect fluid levels, but the sensor suffers large propagation losses in the presence of aerated fluids

Engineering Contradiction:

Improvefluid level detection capabilityVSAvoidpropagation losses

Core Design Contradiction:

Measurement precisionVSLoss of energy

Solution Approach 1:

The patent changes the wave mode parameter from Rayleigh surface waves to shear horizontal (SH) waves, which have different propagation characteristics that are less sensitive to aerated fluid conditions, thereby reducing propagation losses while maintaining detection capability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the mechanical Rayleigh wave system with an SH wave system that uses different mechanical displacement patterns (horizontal shear motion parallel to the surface) to achieve fluid level sensing with reduced sensitivity to aeration

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If compliant elastomeric polymers (0-rings) are used to seal the probes, then sealing is achieved over a wide temperature range, but out of plane modes are greatly absorbed by these polymer 0-rings

Engineering Contradiction:

Improvesealing effectivenessVSAvoidwave absorption

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent replaces out-of-plane longitudinal wave modes with in-plane shear horizontal wave modes, which are not absorbed by the elastomeric sealing polymers, thereby eliminating the trade-off between sealing effectiveness and wave absorption losses

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent uses asymmetric wave propagation where the SH waves travel parallel to the substrate surface without requiring out-of-plane motion, allowing the sealing polymer to remain in place without absorbing the wave energy

Inventive Principle:

Principle #4Asymmetry

3Measurement precision

If the sensor uses out of plane, or longitudinal modes, then fluid level can be detected, but fluid remaining on non-immersed surfaces causes additional propagation losses

Engineering Contradiction:

Improvefluid level detectionVSAvoidpropagation losses from fluid residue

Core Design Contradiction:

Measurement precisionVSLoss of energy

Solution Approach 1:

The patent substitutes out-of-plane longitudinal wave modes with in-plane shear horizontal wave modes that propagate parallel to the substrate surface, making the wave propagation insensitive to fluid residue on non-immersed surfaces and eliminating the associated energy losses

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 sensor effectively measures fluid levels in aerated liquids with reduced sealing losses and residue issues, providing accurate and reliable readings by utilizing wave mode conversion to minimize absorption and spurious reflections.

Implementation Method 1

at least one wave generator on one end of the substrate configured to transmit a wave along the surface of the substrate

Methodology Applied

Scientific EffectShear wave propagation: Surface Acoustic Wave

Implementation Method 2

a plurality of reflective echelons mounted on the substrate such that each echelon is at an angle relative to a reflective side surface, where the reflective echelons are configured to convert a wave of a first mode to a wave of a second mode

Methodology Applied

Scientific EffectWave mode conversion: Surface Acoustic Wave

Implementation Method 3

The Lamb flexural wave has substantial out of plane displacements and is absorbed by fluid immersion

Methodology Applied

Scientific EffectAcoustic absorption: Acoustic Absorption

Data Source

PatentEP2780673B1Acoustic array sensor

Publication Date: 2021.03.31 STREET SMART SENSORS

Figure 1A
Figure 1B~1D
Figure 2~2A

AI summary

A level sensor includes a substrate having at least one reflective side surface, at least one wave generator on one end of the substrate configured to transmit a wave down the surface of the substrate and a plurality of reflective echelons mounted on the substrate such that each echelon is at an angle relative to reflective side surface. The reflective echelons are configured to convert a wave of a first mode in to a wave of a second mode.