Ultrasonic Fuel Flow Meter Buffer Rod Layout for Harsh Conditions
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Solution Overview
Problem
Existing ultrasonic flow meters face challenges in maintaining accuracy and survivability under high pressure and temperature conditions, particularly in aircraft gas turbine engine applications, where fluid environmental conditions impose significant design constraints, including wide temperature and pressure ranges, caustic fluids, and flow instabilities, leading to inaccuracies and potential engine performance issues.
Innovation Solution
The ultrasonic fluid mass flow sensor system employs a design with acoustic transceiver elements acoustically mated to buffer rods of specific lengths and matching layers, aligned with a fluid conduit, to measure fluid properties while protecting the transceiver from direct fluid contact, using buffer rods to seal and isolate the transceiver from fluid pressure and temperature, and employing matching layers for improved reflection sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the acoustic transceiver element is directly exposed to the fluid medium for measurement, then measurement accuracy is improved, but the transceiver element suffers degradation under high pressure and temperature conditions
Solution Approach 1:
The patent introduces buffer rods as intermediary elements between the acoustic transceiver and the fluid medium. These buffer rods transmit acoustic signals while isolating the transceiver from direct fluid contact, thereby protecting it from harsh environmental conditions (high pressure and temperature) while maintaining measurement capability through acoustic coupling.
Solution Approach 2:
The system separates the measurement function (acoustic signal transmission through fluid) from the transceiver protection function (isolation from fluid environment). The buffer rods act as separate components that bridge the acoustic path while providing environmental isolation, allowing the transceiver to remain in a protected state.
2Reliability
If buffer rods are used to isolate the transceiver from fluid pressure, then environmental survivability is improved, but acoustic signal transmission may be affected
Solution Approach 1:
The buffer rods are designed with specific acoustic properties (impedance matching, length, material composition) that optimize acoustic signal transmission while maintaining environmental isolation. By carefully selecting and tuning these parameters, the system achieves both protection and effective signal transmission.
3Duration of action of stationary object
If the transceiver is protected from direct fluid contact, then durability under harsh conditions is improved, but direct acoustic coupling with the fluid is reduced
Solution Approach 1:
The buffer rods serve as acoustic mediators that couple the transceiver to the fluid environment without requiring direct contact. They transmit acoustic energy efficiently while maintaining the physical barrier that protects the transceiver from harsh fluid conditions.
Solution Approach 2:
The system replaces direct mechanical/acoustic contact between the transceiver and fluid with an indirect acoustic coupling mechanism through the buffer rods. This substitution allows the transceiver to operate in a protected environment while still achieving effective acoustic measurement.
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 against wide temperature and pressure ranges, maintains accuracy despite harsh fluids, and is unaffected by fluid flow dynamics, enabling update rates of 100Hz or greater with integral fluid density sensing.
Implementation Method 1
an acoustic transceiver element acoustically mated to the second axial end and the third axial end. The acoustic transceiver element is configured to emit a vibration having a predetermined wavelength λ
Implementation Method 2
The first axial buffer rod and the second axial buffer rod both have axial lengths of n/2 λ that is a round multiple of one-half of the transmission wavelength λ of the acoustic transceiver element
Implementation Method 3
detect a speed of sound in the fluid based on the detected portion of the incident wave
Implementation Method 4
employing matching layers for improved reflection sensitivity
Data Source
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AI summary
The subject matter of this specification can be embodied in, among other things, a sensor that includes a first axial sensor housing portion having a first cross-sectional area, a second axial sensor housing portion arranged adjacent to the first axial sensor housing portion along the sensor axis and having a second cross-sectional area larger than the first cross-sectional area, and a face extending from the interior surface of the first axial sensor housing portion to the interior surface of the second axial sensor housing portion, a first buffer rod within the first axial sensor housing portion and having a first axial end and a second axial end, a second buffer rod within the second axial sensor housing portion and abutting the face, and having a third axial end and a fourth axial end, and an acoustic transceiver element acoustically mated to the second axial end and the third axial end.