Disc-Shaped Acoustic Sensor Radial Mode Oscillation
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Solution Overview
Problem
Existing resonant cavity speed-of-sound sensors face limitations in efficiently generating a large amplitude radial mode pressure oscillation, leading to signal attenuation, parasitic oscillations, and poor coupling between transducers, which complicates the interpretation of output and limits performance and stability.
Innovation Solution
A resonant acoustic sensor with a substantially disc-shaped cavity and circular end walls, where the transmitter and receiver are operatively associated with opposing end walls, enabling mechanical stiffness matching with the acoustic impedance of the fluid, and mode-shape matching between the displacement profiles of the transducers and fluid pressure oscillations, resulting in efficient generation of high-amplitude pressure oscillations and improved signal output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional resonant cavity sensor is used, then the device can measure fluid composition, but it fails to efficiently generate a large amplitude radial mode pressure oscillation, resulting in weak signals and poor transducer coupling
Solution Approach 1:
The patent applies mechanical vibration by using a transmitter transducer to generate radial mode pressure oscillations at the resonant frequency of the cavity. The transducer is specifically designed to couple efficiently with the radial mode, creating large amplitude oscillations that improve signal strength and measurement precision.
Solution Approach 2:
The patent changes the operational parameters by tuning the transducer frequency to match the resonant frequency of the cavity's radial mode. This parameter matching optimizes the coupling between the transducer and the cavity, maximizing the amplitude of pressure oscillations and improving signal output.
2Adaptability or versatility
If multiple competing resonant modes are present in the cavity, then the sensor can be filled with various fluids, but the interpretation of output becomes complicated due to poor mode selectivity and parasitic oscillations
Solution Approach 1:
The patent uses mechanical vibration at a specifically selected resonant frequency to excite only the desired radial mode of the cavity. By tuning the transmitter to this specific frequency, the system achieves mode selectivity that eliminates parasitic oscillations and simplifies output interpretation while maintaining versatility in fluid measurement.
Solution Approach 2:
The patent employs feedback through the receiver transducer to detect the resonant frequency and amplitude of oscillations. This feedback mechanism allows the system to identify and lock onto the desired radial mode, filtering out competing modes and providing clear, unambiguous output signals for accurate fluid composition determination.
3Reliability
If a Helmholtz oscillator design with a single aperture is used, then pressure oscillations can be generated, but fluid flow through the cavity is prevented, slowing response time and complicating fluidic integration
Solution Approach 1:
The patent segments the cavity structure by providing multiple apertures or openings in the cavity walls, allowing fluid to flow through the cavity while maintaining the integrity of the resonant oscillation. This segmentation enables both stable pressure oscillations and continuous fluid flow, improving response time and facilitating integration into fluidic systems.
Solution Approach 2:
The patent applies local quality by designing apertures with specific geometries and distributions that minimize disruption to the radial mode pressure oscillations while maximizing fluid flow capability. The local structure of the apertures is optimized to maintain oscillation stability in the bulk of the cavity while allowing efficient fluid passage through designated regions.
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 overcomes the limitations of prior sensors by achieving efficient generation of high-amplitude pressure oscillations and enhanced signal quality, allowing for accurate determination of fluid properties such as composition and temperature.
Implementation Method 1
A transducer, herein known as the transmitter, is operatively associated with one of the end walls to cause an oscillatory motion of the associated end wall
Implementation Method 2
measure the resonant frequency of an acoustic cavity... the resonant frequency of the cavity directly relates to the composition of the fluid
Implementation Method 3
The radial pressure oscillation in the cavity generates axial motion of the second end wall which is operatively associated with a second transducer, herein known as the receiver, which in turn generates an oscillatory electrical signal
Implementation Method 4
Devices which determine the composition of a gas mixture by measuring the speed of sound in that mixture
Data Source
Figure 1A~1D
Figure 2
Figure 3A~3E
AI summary
An acoustic sensor includes a side wall, closed at each end by an end wall, to form a substantially cylindrical cavity, a transmitter and a receiver operatively associated with first and second respective end walls. Properties of the relative dimensions of the cavity are configured to create a desired oscillatory motion of the end walls, and oscillations of a fluid pressure in the cavity, to generate an electrical signal via the receiver to be output from the sensor. An array of acoustic sensors can be connected to allow calibration of one of the array of sensors.