Ultrasonic Buffer Rod Sensing for Harsh Fluid Flow Measurement
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Solution Overview
Problem
Existing ultrasonic flow meters face challenges in maintaining accuracy and survivability under extreme fluid environmental conditions, such as high pressures and temperatures, and fluid variability, particularly in applications like aircraft gas turbine engines, where they are required to operate over a wide turndown ratio and maintain dynamic accuracy with high update rates.
Innovation Solution
The ultrasonic fluid mass flow sensor system employs a buffer rod and acoustic transceiver element configuration that decouples the transducer from direct fluid contact, using a buffer rod with specific acoustic impedance and a matching layer to protect the transducer from fluid pressure and temperature, allowing for accurate mass flow rate determination through time-of-flight measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the acoustic transceiver element is directly exposed to the fluid in harsh environments, then the measurement capability is maintained, but the reliability and durability deteriorate due to high pressure and temperature damage
Solution Approach 1:
The sensor is divided into separate functional sections: the acoustic transceiver element is housed in a protected chamber isolated from the harsh fluid environment, while the buffer rod extends into the fluid. This segmentation allows the sensitive transceiver to remain protected while still enabling measurement through the buffer rod interface.
Solution Approach 2:
The buffer rod acts as an intermediary element between the protected acoustic transceiver and the harsh fluid environment. It transmits acoustic signals and mechanical forces while isolating the transceiver from direct exposure to high pressure and temperature, thereby maintaining both reliability and measurement capability.
2Strength
If the sensor housing is designed with large cross-sectional area to accommodate high pressure forces, then the strength improves, but the measurement precision deteriorates due to increased acoustic path length and signal attenuation
Solution Approach 1:
The buffer rod features a stepped cross-sectional design where the first section has a larger cross-sectional area for strength and pressure resistance, while the second section has a smaller cross-sectional area optimized for acoustic transmission. This dimensional variation along the axial direction allows simultaneous optimization of both strength and measurement precision.
Solution Approach 2:
Different sections of the buffer rod are designed with different cross-sectional areas suited to their specific functions: the first section near the transceiver has larger area for withstanding pressure forces, while the second section has smaller area to minimize acoustic path length and signal attenuation. Each local region is optimized for its primary requirement.
3Strength
If the buffer rod has large cross-sectional area throughout to withstand pressure forces, then the strength improves, but the accuracy deteriorates due to increased acoustic impedance and signal loss
Solution Approach 1:
The buffer rod employs a dynamic cross-sectional area design that varies along its length rather than remaining uniform. The first section has larger area for strength, while the second section transitions to smaller area for optimized acoustic properties. This dynamic variation allows the structure to adapt to different functional requirements at different locations.
Solution Approach 2:
The cross-sectional area parameter of the buffer rod is changed along its axial length to optimize performance. The first section maintains larger area for mechanical strength, while the second section reduces area to minimize acoustic impedance and improve signal transmission quality, thereby maintaining measurement accuracy under pressure.
4Device complexity
If the sensor housing is made compact to reduce size, then the device complexity reduces, but the reliability deteriorates due to insufficient isolation of the transceiver from harsh environments
Solution Approach 1:
The acoustic transceiver is nested within a protected housing chamber that is itself nested within the overall sensor assembly. The buffer rod passes through the housing structure, creating a nested configuration that provides robust isolation of the transceiver from the external harsh environment while maintaining a compact overall form factor.
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 system provides improved environmental survivability, maintains accuracy across wide temperature and pressure ranges, and is unaffected by fluid dynamics, enabling high turndown ratios and update rates of 100 Hz or greater, ensuring reliable fluid property measurements.
Implementation Method 1
an acoustic transceiver element acoustically mated to the first end... configured to emit a vibration having a predetermined wavelength
Implementation Method 2
transmitting the incident wave along a buffer rod having a first axial end abutted to the first emitter and a second axial end opposite the first axial end
Implementation Method 3
reflecting a first echo of the incident wave by a gap defined along a portion of the buffer rod, detecting the first echo
Implementation Method 4
determine a fluid acoustic impedance of a fluid in the tubular fluid conduit based on the echo
Implementation Method 5
determine a first time of flight of the portion of the first incident wave... determine a second time of flight of the second incident wave
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
The subject matter of this specification can be embodied in, among other things, a method of sensing that includes activating a first emitter to emit at least one incident wave, transmitting the incident wave along a buffer rod having a first axial end abutted to the first emitter and a second axial end opposite the first axial end, reflecting a first echo of the incident wave by a gap defined along a portion of the buffer rod, detecting the first echo, determining a first amplitude of the first echo, reflecting a second echo of the incident wave by the second axial end, detecting the second echo, determining a second amplitude of the second echo, and determining a reflection coefficient based on the first amplitude and the second amplitude.