Ultrasonic mass flowmeter

Abstract

The subject matter of this specification can be embodied in a sensor that includes a first axial sensor housing portion having a first cross-sectional area, a second axial sensor housing portion disposed adjacent the first axial sensor housing portion along a sensor axis and having a second cross-sectional area that is greater than the first cross-sectional area, and a face extending from an inner surface of the first axial sensor housing portion to an inner surface of the second axial sensor housing portion, a first bumper rod within the first axial sensor housing portion and having a first axial end and a second axial end, a second bumper 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 coupled with the second axial end and the third axial end.

Description

[0001] Priority requirements This application claims priority to U.S. Provisional Application No. 63 / 162,359, filed March 17, 2021, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This manual relates to ultrasonic fluid mass flow sensors. Background Technology

[0003] Fluid measurement devices are used for the characterization and operation of fluid control systems. As the dynamic bandwidth, flow range, accuracy, and reliability of flow measurement devices improve, their potential applications expand. High dynamic bandwidth flow meters can be used as feedback sensors in control systems to improve steady-state and / or transient accuracy in fuel systems. Ultrasonic flow meters (USFM) are a proven industrial technology that can be used in the implementation of aircraft turbine systems.

[0004] Existing time-of-flight ultrasonic flow meters are used in the motorsports and automotive industries, pipeline custody transfer, industrial flow measurement, and many other applications. However, many of these applications involve steady-state flow conditions, and their respective applications allow for volumetric flow measurement. In other applications, such as aircraft gas turbine engine applications, the fluid environment conditions of fuel delivery systems present significant design challenges. Summary of the Invention

[0005] Overall, this document describes ultrasonic fluid mass flow sensors.

[0006] In a first example, a sensor includes: a sensor housing having an inner surface defining a sensor axis and an axially internal sensor housing chamber, the sensor housing including a first axial sensor housing portion having a first cross-sectional area perpendicular to the sensor axis; 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 perpendicular to the sensor axis and larger than the first cross-sectional area; and a surface extending from the inner surface of the first axial sensor housing portion to the inner surface of the second axial sensor housing portion; a first axial buffer rod disposed within the first axial sensor housing portion and including a first axial end and a second axial end; a second axial buffer rod disposed within the second axial sensor housing portion and adjacent to the surface and including a third axial end and a fourth axial end; and an acoustic transceiver element acoustically cooperating with the second axial end and the third axial end.

[0007] In the second example, according to Example 1, the acoustic transceiver element is configured to emit vibrations with a predetermined wavelength (λ), and both the first axial buffer bar and the second axial buffer bar have an axial length that is an integer multiple of approximately n / 2λ.

[0008] In a third example, according to Example 1 or 2, the sensor further includes a tubular fluid conduit having a first end and a second end opposite to the first end and defining a conduit axis, the tubular fluid conduit being arranged such that the conduit axis is substantially aligned with the sensor axis.

[0009] In the fourth example, according to Example 3, the sensor further includes: another sensor housing having another inner surface defining another sensor axis and another axial inner sensor housing chamber, the other sensor housing including another first axial sensor housing portion having another first cross-sectional area perpendicular to the other sensor axis, another second axial sensor housing portion arranged adjacent to the other first axial sensor housing portion along the other sensor axis and having another second cross-sectional area perpendicular to the other sensor axis and larger than the other first cross-sectional area, and another face extending from another inner surface of the other first axial housing portion to another inner surface of the other second housing portion; another first axial buffer rod arranged within the other first housing portion and including another first axial end and another second axial end; another second axial buffer rod arranged within the other second housing portion and adjacent to the other face and including another third axial end and another fourth axial end; and another acoustic transceiver element acoustically cooperating with the other second axial end and the other third axial end; wherein the other sensor axis is substantially aligned with the conduit axis.

[0010] In the fifth example, according to Example 3 or 4, the sensor further includes a fluid housing comprising an inner surface of the fluid housing defining an axial fluid housing chamber, a first fluid port in fluid communication with the axial fluid housing chamber, and a second fluid port in fluid communication with the axial fluid housing chamber, wherein the tubular fluid conduit is in fluid communication with the second fluid port and extends axially away from the fluid housing along the conduit axis at a first end, and the sensor housing is disposed within the first fluid housing such that the sensor axis is substantially aligned with the conduit axis.

[0011] In the sixth example, according to Example 5, the sensor further includes: another sensor housing having another inner surface defining another sensor axis and another axial internal sensor housing chamber, the other sensor housing including another first axial sensor housing portion having another first cross-sectional area perpendicular to the other sensor axis, another second axial sensor housing portion arranged adjacent to the other first axial sensor housing portion along the other sensor axis and having another second cross-sectional area perpendicular to the other sensor axis and larger than the other first cross-sectional area, and another face extending from the other inner surface of the other first axial housing portion to the other inner surface of the other second housing portion; and another first axial buffer disposed within the other first housing portion and including another first axial end and another second axial end. A rod; another second axial buffer rod disposed within and adjacent to the other face and including another third axial end and another fourth axial end; another acoustic transceiver element acoustically cooperating with the other second axial end and the other third axial end; and another fluid housing comprising another fluid housing inner surface defining another axial fluid housing chamber, another first fluid port fluidly communicating with the other axial fluid housing chamber, and another second fluid port fluidly communicating with the other axial fluid housing chamber, wherein the tubular fluid conduit fluidly communicates with the other second fluid port and extends axially away from the other fluid housing along the conduit axis at a second end, and another sensor housing is disposed within the other first fluid housing such that the other sensor axis is substantially aligned with the conduit axis.

[0012] In the seventh example, according to any of Examples 1 to 6, the acoustic transceiver element includes a piezoelectric element.

[0013] In the eighth example, according to any of Examples 1 to 7, the sensor further includes a matching layer fixed to the fourth axial end and having a thickness of approximately (2n-1)λ / 4, where n > 0.

[0014] In the ninth example, an acoustic reflector is defined at the first axial end, according to any of Examples 1 to 8.

[0015] In the tenth example, according to any of Examples 1 to 9, the first axial end is adjacent to gas or at least a partial vacuum.

[0016] In the eleventh example, a sensor system includes: a fluid housing comprising a first fluid housing portion defining a first axial fluid housing chamber and including a first fluid port in fluid communication with the first axial fluid housing chamber; a second fluid housing portion defining a second axial fluid housing chamber and including a second fluid port in fluid communication with the second axial fluid housing chamber; and a tubular fluid conduit in fluid communication with the first fluid port at a first end and with a second fluid port at a second end opposite to the first end, and defining a conduit axis; a first acoustic transceiver element disposed within the first axial fluid housing chamber and axially aligned with the conduit axis; and a second acoustic transceiver element disposed within the second axial fluid housing chamber and axially aligned with the conduit axis.

[0017] In the twelfth example, according to Example 11, the sensor system further includes circuitry configured to: activate a first acoustic transceiver element to transmit a first incident wave; activate a second acoustic transceiver element to transmit a second incident wave; detect an echo of the first incident wave by the first acoustic transceiver element; determine a fluid acoustic impedance of a fluid in a tubular fluid conduit based on the echo; detect at least a first portion of the first incident wave by the second acoustic transceiver element; determine a first time of flight of the first portion; detect at least a second portion of the second incident wave by the first acoustic transceiver element; determine a second time of flight of the second portion; and determine a mass fluid flow rate based on the determined fluid acoustic impedance, the determined first time of flight, and the determined second time of flight.

[0018] In the thirteenth example, according to Example 11 or 12, one or both of the first acoustic transceiver element or the second acoustic transceiver element include: a sensor housing having an inner surface defining a sensor axis and an axial internal sensor housing chamber, the sensor housing including a first axial sensor housing portion having a first cross-sectional area perpendicular to the sensor axis, 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 perpendicular to the sensor axis and larger than the first cross-sectional area, and a surface extending from the inner surface of the first axial sensor housing portion to the inner surface of the second axial sensor housing portion; a first axial buffer rod disposed within the first axial sensor housing portion and including a first axial end and a second axial end; a second axial buffer rod disposed within the second axial sensor housing portion and adjacent to the surface and including a third axial end and a fourth axial end; and an acoustic transceiver element acoustically cooperating with the second axial end and the third axial end.

[0019] In the fourteenth example, according to Example 13, the acoustic transceiver element is configured to emit vibrations with a predetermined wavelength (λ), and both the first axial buffer bar and the second axial buffer bar have an axial length that is an integer multiple of approximately n / 2λ.

[0020] In the fifteenth example, according to Example 13 or 14, the acoustic transceiver element includes a piezoelectric element.

[0021] In the sixteenth example, according to any one of Examples 13 to 15, the sensor further includes a matching layer fixed to the fourth end and having a thickness of approximately an odd multiple of 1 / 4λ.

[0022] In the seventeenth example, according to any of Examples 13 to 16, the first axial end is defined as an acoustic reflector.

[0023] In the eighteenth example, according to any of Examples 13 to 17, the first axial end is adjacent to gas or at least a partial vacuum.

[0024] In the nineteenth example, a sensing method includes: activating a first transmitter to emit at least a first incident wave in a first direction and a second incident wave in a second direction opposite to the first direction; transmitting the first incident wave along a first buffer rod having a first axial end adjacent to the first transmitter and a second axial end opposite to the first axial end; transmitting the second incident wave along a second buffer rod having a third axial end adjacent to the first transmitter and a fourth axial end opposite to the third axial end; reflecting a first echo of the first incident wave by a first acoustic reflector defined along a portion of the second axial end; detecting the first echo; determining a first amplitude of the first echo; reflecting a second echo of the second incident wave by the fourth 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.

[0025] In the twentieth example, according to Example 19, the method further includes determining the fluid acoustic impedance of the fluid at the second axial end based on the determined reflection coefficient and the predetermined buffer rod acoustic impedance.

[0026] In the twenty-first example, according to Example 20, the method further includes: at a second axial end, transmitting a portion of a first incident wave through the fluid to a first sensor, the first sensor being arranged at a predetermined distance from and opposite to a first transmitter, wherein the fluid is within a tubular fluid conduit having a predetermined cross-sectional area; detecting the portion of the first incident wave by the first sensor; determining a first time of flight of the detected portion of the first incident wave based on the detected portion; transmitting another first incident wave through the fluid by a second transmitter to a second sensor near the first transmitter; detecting the other first incident wave by the second sensor; and determining a second time of flight of the other first incident wave based on the detected other first incident wave.

[0027] In the twenty-second example, according to Example 21, the method further includes determining at least one of the velocity of the fluid within the tubular fluid conduit or the speed of sound within the fluid based on a first flight time, a second flight time, and a predetermined distance.

[0028] In the twenty-third example, according to Example 22, the method further includes determining the mass fluid flow rate based on a predetermined cross-sectional area and a determined sound velocity.

[0029] In the twenty-fourth example, according to Example 23, the mass fluid flow rate is given by the equation

[0030] In the twenty-fifth example, according to any of Examples 21 to 24, one or both of the first transmitter and the first sensor are piezoelectric elements.

[0031] In the twenty-sixth example, according to any one of Examples 21 to 25, the piezoelectric element includes a first transmitter and a first sensor.

[0032] In the twenty-seventh example, according to any of Examples 19 to 26, the first acoustic reflector includes a matching layer fixed to the fourth axial end and having a thickness of (2n-1)λ / 4, where n > 0.

[0033] In the twenty-eighth example, according to any of Examples 19 to 27, the first axial end is adjacent to gas or at least a partial vacuum.

[0034] In the twenty-ninth example, a method of protecting a sensor element includes: providing a sensor comprising: a sensor housing having an inner surface defining a sensor axis and an axially internal sensor housing chamber, the sensor housing including a first axial sensor housing portion having a first cross-sectional area perpendicular to the sensor axis; a second axial sensor housing portion disposed adjacent to the first axial sensor housing portion along the sensor axis and having a second cross-sectional area perpendicular to the sensor axis and larger than the first cross-sectional area; and a surface extending from the inner surface of the first axial sensor housing portion to the inner surface of the second axial sensor housing portion; a first axial buffer rod disposed within the first axial sensor housing portion and including a first axial end and a second axial end; a second axial buffer rod disposed within the second axial sensor housing portion and adjacent to the surface and including a third axial end and a fourth axial end; and an acoustic transceiver element acoustically cooperating with the second axial end and the third axial end; providing fluid at the fourth axial end; and the second axial buffer rod and the sensor housing blocking the flow of fluid from the fourth axial end to the acoustic transceiver element.

[0035] In the thirtieth example, according to Example 29, the method further includes: applying fluid pressure to the fourth axial end to generate an axial force against the second axial buffer rod; transmitting the axial force to the sensor housing by the second axial buffer rod; and preventing the transmission of the axial force to the acoustic transceiver element by the sensor housing.

[0036] In the thirty-first example, according to Example 30, the method further includes transmitting the axial force to the surface by a second axial portion, wherein the surface interferes with the axial movement of the second axial buffer rod toward the acoustic transceiver element.

[0037] In an example embodiment, a sensor includes: a sensor housing having an inner surface defining a sensor axis and an axially internal sensor housing chamber, the sensor housing including a first axial sensor housing portion having a first cross-sectional area perpendicular to the sensor axis; a second axial sensor housing portion disposed adjacent to the first axial sensor housing portion along the sensor axis and having a second cross-sectional area perpendicular to the sensor axis and larger than the first cross-sectional area; and a surface extending from the inner surface of the first axial sensor housing portion to the inner surface of the second axial sensor housing portion; a first axial buffer rod disposed within the first axial sensor housing portion and having a first axial end and a second axial end; a second axial buffer rod disposed within the second axial sensor housing portion and adjacent to the surface and having a third axial end and a fourth axial end; and an acoustic transceiver element acoustically cooperating with the second axial end and the third axial end.

[0038] Various embodiments may include some, all, or none of the following features. The acoustic transceiver element may be configured to emit vibrations having a predetermined wavelength (λ), and both the first and second axial buffer bars may have axial lengths that are integer multiples of approximately n / 2λ. The sensor may include a tubular fluid conduit having a first end and a second end opposite to the first end and defining a conduit axis, the tubular fluid conduit being arranged such that the conduit axis is substantially aligned with the sensor axis. The sensor may include: another sensor housing having another inner surface defining another sensor axis and another axial internal sensor housing chamber, the other sensor housing having: another first axial sensor housing portion having another first cross-sectional area perpendicular to the other sensor axis; another second axial sensor housing portion arranged adjacent to the other first axial sensor housing portion along the other sensor axis and having another second cross-sectional area perpendicular to the other sensor axis and larger than the other first cross-sectional area; and another face extending from another inner surface of the other first axial housing portion to another inner surface of the other second housing portion; another first axial buffer rod arranged within the other first housing portion and having another first axial end and another second axial end; another second axial buffer rod arranged within the other second housing portion and adjacent to the other face and having another third axial end and another fourth axial end; and another acoustic transceiver element acoustically cooperating with the other second axial end and the other third axial end; wherein the other sensor axis is substantially aligned with the conduit axis. The sensor of the claim may include a fluid housing having an inner surface of the fluid housing defining an axial fluid housing chamber, a first fluid port in fluid communication with the axial fluid housing chamber, and a second fluid port in fluid communication with the axial fluid housing chamber, wherein the tubular fluid conduit is in fluid communication with the second fluid port and extends axially away from the fluid housing along the conduit axis at a first end, and the sensor housing is disposed within the first fluid housing such that the sensor axis is substantially aligned with the conduit axis.The sensor may include: another sensor housing having another inner surface defining another sensor axis and another axial internal sensor housing chamber, the other sensor housing having: another first axial sensor housing portion having another first cross-sectional area perpendicular to the other sensor axis; another second axial sensor housing portion arranged adjacent to the other first axial sensor housing portion along the other sensor axis and having another second cross-sectional area perpendicular to the other sensor axis and larger than the other first cross-sectional area; and another surface extending from the other inner surface of the other first axial housing portion to the other inner surface of the other second housing portion; another first axial buffer rod disposed within the other first housing portion and having another first axial end and another second axial end; and disposed in the other... A second axial buffer rod is located within and adjacent to the other surface of a second housing portion and has a third axial end and a fourth axial end; another acoustic transceiver element is acoustically coupled to the second axial end and the third axial end; and another fluid housing has another fluid housing inner surface defining a chamber of another axial fluid housing, a first fluid port in fluid communication with the chamber of another axial fluid housing, and a second fluid port in fluid communication with the chamber of another axial fluid housing, wherein a tubular fluid conduit is in fluid communication with the second fluid port and extends axially away from the other fluid housing along the conduit axis at a second end, and another sensor housing is disposed within the other first fluid housing such that the axis of the other sensor is substantially aligned with the axis of the conduit. The acoustic transceiver element may include a piezoelectric element. The sensor may include a matching layer fixed to the fourth axial end and having a thickness of approximately (2n-1)λ / 4, where n > 0. The first axial end may define an acoustic reflector. The first axial end is adjacent to a gas or at least a partial vacuum.

[0039] In another example embodiment, a sensor system includes: a fluid housing having a first fluid housing portion defining a first axial fluid housing chamber and having a first fluid port in fluid communication with the first axial fluid housing chamber; a second fluid housing portion defining a second axial fluid housing chamber and having a second fluid port in fluid communication with the second axial fluid housing chamber; and a tubular fluid conduit having fluid communication with the first fluid port at a first end and with a second fluid port at a second end opposite to the first end, and defining a conduit axis; a first acoustic transceiver element disposed within the first axial fluid housing chamber and axially aligned with the conduit axis; and a second acoustic transceiver element disposed within the second axial fluid housing chamber and axially aligned with the conduit axis.

[0040] Various embodiments may include some, all, or none of the following features. The sensor system may include circuitry configured to: activate a first acoustic transceiver element to transmit a first incident wave; activate a second acoustic transceiver element to transmit a second incident wave; detect an echo of the first incident wave by the first acoustic transceiver element; determine a fluid acoustic impedance of a fluid in a tubular fluid conduit based on the echo; detect at least a first portion of the first incident wave by the second acoustic transceiver element; determine a first time-of-flight of the first portion; detect at least a second portion of the second incident wave by the first acoustic transceiver element; determine a second time-of-flight of the second portion; and determine a mass fluid flow rate based on the determined fluid acoustic impedance, the determined first time-of-flight, and the determined second time-of-flight. One or both of the first or second acoustic transceiver elements may include: a sensor housing having an inner surface defining a sensor axis and an axial internal sensor housing chamber, the sensor housing having: a first axial sensor housing portion having a first cross-sectional area perpendicular to the sensor axis; 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 perpendicular to the sensor axis and larger than the first cross-sectional area; and a surface extending from the inner surface of the first axial sensor housing portion to the inner surface of the second axial sensor housing portion; a first axial buffer rod disposed within the first axial sensor housing portion and having a first axial end and a second axial end; a second axial buffer rod disposed within the second axial sensor housing portion and adjacent to the surface and having a third axial end and a fourth axial end; and an acoustic transceiver element acoustically cooperating with the second axial end and the third axial end. The acoustic transceiver element may be configured to emit vibrations having a predetermined wavelength (λ), and both the first and second axial buffer rods may have axial lengths that are integer multiples of approximately n / 2λ. Acoustic transceiver element 230 may include a piezoelectric element. The sensor system may include a matching layer fixed to a fourth end and having a thickness that is an odd multiple of approximately 1 / 4λ. A first axial end may define an acoustic reflector. The first axial end may be adjacent to a gas or at least a partial vacuum.

[0041] In an example implementation, a sensing method includes: activating a first transmitter to emit at least a first incident wave in a first direction and a second incident wave in a second direction opposite to the first direction; transmitting the first incident wave along a first buffer rod having a first axial end adjacent to the first transmitter and a second axial end opposite to the first axial end; transmitting the second incident wave along a second buffer rod having a third axial end adjacent to the first transmitter and a fourth axial end opposite to the third axial end; reflecting a first echo of the first incident wave by a first acoustic reflector defined along a portion of the second axial end; detecting the first echo; determining a first amplitude of the first echo; reflecting a second echo of the second incident wave by the fourth 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.

[0042] Various implementations may include some, all, or none of the following features. The method may include determining the fluid acoustic impedance at the second axial end based on a determined reflection coefficient and a predetermined buffer rod acoustic impedance. The method may include: at the second axial end, transmitting a portion of a first incident wave through the fluid to a first sensor, the first sensor being arranged at a predetermined distance from and opposite to a first transmitter, wherein the fluid is within a tubular fluid conduit having a predetermined cross-sectional area; detecting the portion of the first incident wave by the first sensor; determining a first flight time of the detected portion of the first incident wave based on the detected portion; transmitting another first incident wave through the fluid by a second transmitter to a second sensor near the first transmitter; detecting the other first incident wave by the second sensor; and determining a second flight time of the other first incident wave based on the detected other first incident wave. The method may include determining at least one of the velocity of the fluid within the tubular fluid conduit or the speed of sound within the fluid based on the first flight time, the second flight time, and the predetermined distance. The method may include determining the mass fluid flow rate based on the predetermined cross-sectional area and the determined speed of sound. The mass fluid flow rate may be expressed by the equation... The first transmitter and the first sensor may be a piezoelectric element. The piezoelectric element may include the first transmitter and the first sensor. The first acoustic reflector may include a matching layer fixed to a fourth axial end and having a thickness of (2n-1)λ / 4, where n > 0. The first axial end may be adjacent to a gas or at least a partial vacuum.

[0043] In another example implementation, a method for protecting a sensor element includes: providing a sensor having: a sensor housing having an inner surface defining a sensor axis and an axially internal sensor housing chamber; the sensor housing having a first axial sensor housing portion having a first cross-sectional area perpendicular to the sensor axis; 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 perpendicular to the sensor axis and larger than the first cross-sectional area; and a surface extending from the inner surface of the first axial sensor housing portion to the inner surface of the second axial sensor housing portion; a first axial buffer rod disposed within the first axial sensor housing portion and having a first axial end and a second axial end; a second axial buffer rod disposed within the second axial sensor housing portion and adjacent to the surface and having a third axial end and a fourth axial end; and an acoustic transceiver element acoustically cooperating with the fourth axial end and the third axial end; providing fluid at the second axial end; and the second axial buffer rod and the sensor housing preventing fluid from flowing from the fourth axial end to the acoustic transceiver element.

[0044] Various implementations may include some, all, or none of the following features. The method may include: applying fluid pressure to a fourth axial end to generate an axial force against a first axial buffer rod; transmitting the axial force to a sensor housing via a second axial buffer rod; and preventing the transmission of the axial force to an acoustic transceiver element via the sensor housing. The method may also include transmitting the axial force to a surface via a second axial portion, wherein the surface interferes with axial movement of the second axial buffer rod toward the acoustic transceiver element.

[0045] The system and techniques described herein offer one or more of the following advantages: First, the system provides improved environmental survivability over a wide range of fluid temperatures. Second, the system provides improved environmental survivability over a wide range of fluid pressures. Third, the system provides improved environmental survivability for harsh fluids. Fourth, the system provides complete fluid density sensing. Fifth, the system is relatively unaffected by fluid flow dynamics (e.g., vortices, eddies, instabilities). Sixth, the system can be used at update rates of 100 Hz or higher while maintaining accuracy.

[0046] Details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will become apparent from the description and drawings, as well as from the claims. Attached Figure Description

[0047] Figure 1 This is a cross-sectional view of an example ultrasonic flow measurement system.

[0048] Figure 2 yes Figure 1 A cross-sectional view of an example ultrasonic sensor module for a system.

[0049] Figure 3 It shows in Figure 2 A conceptual example of incident and reflected wave propagation in the module.

[0050] Figure 4 It shows in Figure 2 A conceptual example of fluid pressure relief in the module.

[0051] Figures 5A-5C A conceptual example of incident wave traversal is shown in an ultrasonic flow measurement system.

[0052] Figure 6A and 6B It shows Figure 1 A graph showing an example of incident and echo waves in an ultrasonic flow measurement system.

[0053] Figure 7 This is a flowchart illustrating an example of a process for determining the fluid reflection coefficient.

[0054] Figure 8 This is a flowchart illustrating an example of a process for determining the flow rate of a mass fluid.

[0055] Figure 9 It shows the resistance to fluid exposure. Figure 2 A flowchart illustrating the process of how the acoustic transducer of the module affects the process.

[0056] Figure 10 This is a schematic diagram of an example of a general-purpose computer system. Detailed Implementation

[0057] This document describes an ultrasonic fluid mass flow sensor (USFM) system and the techniques used to measure the fluid flow characteristics of a fluid. In general, the USFM system described herein can be used in fluid environments that would degrade or destroy an existing USFM. Fluid environment conditions in fuel delivery systems can present significant design challenges. For current, prior art aircraft and other gas turbine engine applications, ultrasonic transducers deployed for such applications will be expected to withstand high fluid pressures (e.g., 0 psi to 4000 psi or higher) and a wide range of fluid temperatures, including high fluid temperatures (e.g., -65 degrees Fahrenheit or lower, up to 325 degrees Fahrenheit or higher).

[0058] These temperatures and pressures are far more challenging than those required for typical industrial fluid, steam, or pipeline-managed transfer applications. To remain effective in such applications, the wetted transducer must also not degrade due to prolonged immersion in corrosive fluids (such as aircraft fuel and / or additives) at high temperatures and / or high pressures. The USFM system described in this document includes features that improve the survivability of the USFM under these conditions.

[0059] In existing industrial and managed transfer applications, USFM based on time-of-flight, cross-correlation, and phase-shift measurements has accuracy limitations determined by the range of flow velocities or turn-down ratio within the flow measurement volume. For example, during low flow conditions, the difference between upstream and downstream measurements may be too insensitive to maintain target accuracy. During high flow conditions, measurement accuracy may suffer from flow instabilities, often caused by off-axis acoustic paths relative to the flow, flow separation, and / or non-axisymmetric flow conditions. Off-axis transducer configurations can also cause sensitivity and accuracy problems. Circular transducers may impose non-uniform ultrasonic fields when these waves are transmitted diagonally through the flow, thus reducing accuracy. In existing USFMs with ultrasonic beams smaller than the flow cross-section, the entire flow profile is not insonified and must therefore be estimated, typically using a single K-factor correction value or a complex coefficient matrix of the USFM using multiple acoustic paths, as in gas managed transfer applications. In existing USFM designs, maintaining flow measurement accuracy at large control ratios can be challenging when the flow regime is unstable or undergoes a significant shift from laminar to turbulent flow. For example, some existing industrial USFMs, even with ideal application piping and flow regulation, have a practical control ratio of no more than 50:1 while maintaining accuracy. In contrast, gas turbine fuel systems may require significantly higher control ratios, typically 100:1, with some applications reaching 350:1 or higher. Furthermore, gas turbine flow measurement systems must be able to maintain dynamic accuracy at update rates of 100 Hz or higher.

[0060] Mass flow rate is crucial for maintaining a safe and operable fuel-air ratio in the combustion process. An excessive fuel-air ratio can lead to compressor surge or overheating events. Conversely, an excessive air-fuel ratio can cause compressor blowout. Either of these events can be detrimental to gas turbine performance and is therefore a key design driver for gas turbine engines. Furthermore, some applications, such as gas turbine engines, are designed to operate on various fuel types under varying pressures and temperatures.

[0061] A significant variable, particularly in aircraft gas turbine applications, is the variation of fuel specific gravity with fuel type and temperature. In some applications, the expected fuel specific gravity can vary by approximately 25% across the anticipated temperature range and available fuel types. A wide range of fuel densities (if unknown) will drive a wide range of fuel mass flow rates for a given volumetric flow rate. This variability can lead to large variations in the mass-to-air fuel flow ratio, making engine designs inefficient across environmental ranges, resulting in oversized engines, conservative acceleration and / or deceleration scheduling, excessive surge margins, and / or excessive knock margins.

[0062] Figure 1 This is a cross-sectional view of an example of an ultrasonic flow measurement (USFM) system 100. The USFM system 100 includes a fluid housing 110 and two ultrasonic sensor modules 200. The fluid housing 110 includes an axial fluid housing chamber 120a defined by an inner surface 121a and an axial fluid housing chamber 120b defined by an inner surface 121b. A fluid port 122a defines a fluid path 124a connecting to the fluid chamber 120a. A fluid port 122b defines a fluid path 124b connecting to the fluid chamber 120b. The fluid housing 110 also defines a chamber 126 extending between the fluid chambers 120a and 120b.

[0063] The fluid housing 110 also includes a fluid control conduit 130 that defines a fluid path 132 along a conduit axis 134. The fluid control conduit 130 fluidly connects fluid chambers 120a and 120b, thereby enabling fluid communication between fluid chambers 120a and 120b. The fluid control conduit 130 has a predetermined flowable region 136 and a shape (e.g., square, tapered, and / or curved edges, parallel or tapered walls to influence fluid flow behavior). In some implementations, the fluid housing 110 can be used across many applications, and the fluid control conduit 130 can be an interchangeable, dedicated sub-assembly (e.g., an adapter) that allows the USFM system 100 to be adapted to a specific fluid type, application, and / or operating condition.

[0064] Now for reference Figure 2 , showed Figure 1 An enlarged cross-sectional view of an example ultrasonic sensor module 200 of the system is shown. The ultrasonic sensor module 200 includes a sensor housing 202 having an axially defined internal sensor housing chamber 204 and a sensor axis 206 defined by an inner surface 207. When the ultrasonic sensor module 200 is assembled into... Figure 1 When the fluid housing 110 is in place, the sensor axis 206 is substantially aligned with the conduit axis 134. The sensor housing 202 has an axial sensor housing portion 208a having a cross-sectional area 209a perpendicular to the sensor axis 206. The sensor housing 202 also has an axial sensor housing portion 208b having a cross-sectional area 209b perpendicular to the sensor axis 206. The cross-sectional area 209b is larger in size than the cross-sectional area 209a. A surface 210 extends from the inner surface 207 of the axial sensor housing portion 208a to the inner surface 208 of the axial sensor housing portion 208b. In the illustrated example, the surface 210 is formed as a generally square shoulder or ledge at the transition between the cross-sectional areas 209a and 209b. In some embodiments, the surface 210 may be a tapered transition between the cross-sectional areas 209a and 209b or a non-square transition in other cases.

[0065] The ultrasonic sensor module 200 also includes an acoustic transceiver element 230. The acoustic transceiver element 230 is configured to emit acoustic vibrations (e.g., ultrasonic waves) at a predetermined wavelength (λ) when excited. In some embodiments, a separate acoustic driver and acoustic receiver may be implemented as the acoustic transceiver element 230. In some embodiments, the acoustic transceiver element 230 may be configured to also detect received acoustic vibrations. In some embodiments, the acoustic transceiver element 230 may be a piezoelectric element.

[0066] Acoustic transceiver element 230 is disposed between axial buffer rod 250 and axial buffer rod 270. Face 231 of acoustic transceiver element 230 acoustically engages or otherwise abuts against the axial end 252 of buffer rod 250 via bonding layer 232. Face 233 of acoustic transceiver element 230 (opposite to face 231) acoustically engages or otherwise abuts against the axial end 272 of buffer rod 270 via bonding layer 234. In some embodiments, bonding layers 232 and 234 may be adhesive layers.

[0067] In some embodiments, the buffer bars 250 and 270 may be made of any suitable material or combination of materials that, when combined with the matching layer material, can provide an appropriate acoustic impedance ratio to improve or maximize the sensitivity of the measurement, is cost-effective, can be manufactured within reasonable manufacturing tolerances, and / or provides good mechanical and chemical compatibility in the intended application environment. Examples of buffer bar materials include titanium alloys, austenitic stainless steel, aluminum, borosilicate glass, fused (e.g., amorphous) quartz, and industrial ceramics (e.g., AlN, Al3O3, SiN, and mixtures thereof).

[0068] In some embodiments, bonding layers 232 and / or 234 may be omitted, wherein the acoustic transceiver element 230 is in direct contact with the axial ends 252 and / or 272. For example, the acoustic transceiver element 230 may be held in place by mechanically capturing it between the axial buffer bars 250 and 270, or by a fixation feature formed in the inner surface 207. In some embodiments, bonding layers 232 and / or 234 may be formed of a highly ductile material such as gold or lead, which may conform to the mating surfaces of the axial ends 252 and 272 and the acoustic transceiver element 230.

[0069] An axial buffer rod 250 extends along the sensor axis 206 from an axial end 252 to an axial end 254 opposite to the axial end 252. The axial buffer rod 250 has a predetermined axial length that is approximately an integer multiple (n / 2λ) of half the transmission wavelength of the acoustic transceiver element 230. In some embodiments where a long buffer rod is used (e.g., where n is greater than about 10), the predetermined axial length may not need to be configured as an integer multiple of half the wavelength. In some embodiments, the axial buffer rod 250 may contact the inner surface 203 directly or indirectly (e.g., through a seal, sleeve, or bonding material) to substantially seal the sensor chamber 204 and the acoustic transceiver element 230, preventing fluid ingress at the axial end 254.

[0070] An axial buffer rod 270 extends along the sensor axis 206 from an axial end 272 to an axial end 274 opposite to the axial end 272. The axial buffer rod 270 has a predetermined axial length that is approximately an integer multiple (n / 2λ) of half the transmission wavelength of the acoustic transceiver element 230. In some embodiments, the axial buffer rod 270 may directly or indirectly (e.g., through a seal, sleeve, or bonding material) contact the inner surface 207 to substantially seal the sensor chamber 204 and the acoustic transceiver element 230, preventing fluid ingress at the axial end 254 and / or enhancing the robustness of the USFM module 200.

[0071] Buffer bars 250 and 270 have a predetermined acoustic impedance (Z). buffer In the illustrated example, chamber 204 is filled with a gas, such as air or a partial vacuum. In some embodiments, within the operating temperature range of the sensor, the acoustic impedance of the contents of the chamber (e.g., a medium) may be at least 1 / 1000 of the acoustic impedance of the buffer rod. The acoustic impedance of the chamber is sufficiently different from that of the buffer rod 270 to reflect an acoustic echo when struck by a sound wave (e.g., an ultrasonic pulse (ping)). In some embodiments, chamber 204 may be evacuated to create at least a partial vacuum. Axial end 254 is formed Figure 1 A portion of the fluid conduit 130, which is filled with a fluid (e.g., fuel) in use, having an acoustic impedance sufficiently different from that of the buffer rod 250 to reflect an acoustic echo when struck by a sound wave (e.g., an ultrasonic pulse).

[0072] In some embodiments, portions of the buffer bars 250 and / or 270 may include a covering. For example, the covering may be configured to improve the efficiency and / or sensitivity of the ultrasonic sensor module 200 by guiding the propagation of the incident wave, acoustically and / or electrically isolating the buffer bars 250 and 270 from the sensor housing 202, and / or thermally insulating the buffer bars 250 and 270 from the sensor housing 202.

[0073] Still referencing Figure 2 The ultrasonic sensor module 200 includes a mating layer 280 that acoustically engages with, is fixed to, or otherwise abuts the axial end 254 of the buffer rod 250. In some embodiments, the mating layer 280 may be adhered to the axial end 254. In some embodiments, a portion of the mating layer 280 may extend into the sensor housing 202 and be fixed (e.g., welded) to the sensor housing 202. In some embodiments where the mating layer 280 is fixed to the sensor housing 202, the joint between the mating layer 280 and the sensor housing 202 may substantially seal the sensor chamber 204, preventing fluid from entering at the axial end 254. The mating layer 280 has an axial thickness that is approximately an odd multiple of the transmission wavelength of the acoustic transceiver element 230 (e.g., (2n-1)λ / 4, where n > 0), for example, 1 / 4λ.

[0074] In some embodiments, the matching layer 280 can increase reflection sensitivity, thereby improving or maximizing the rate of change of the reflection coefficient relative to the change of fluid impedance. R / dZ fluid For example, as the fuel changes temperature, Z fluidThis changes, and therefore the reflectance changes. In some embodiments, two or more are used. 1 / 4-wave discrete matching layer, multilayer 1 / 4 graded composite matching layer, or multilayer thin film 1 A 4-wave matching layer, together with an optional non-acoustic (e.g., <1 / 10 wave) abrasion plate, can provide additional reflection sensitivity beyond that achievable with a single matching layer.

[0075] Refer again Figure 1 Two ultrasonic sensor modules 200 face each other across the fluid control conduit 130. The acoustic transducer elements of the ultrasonic sensor modules 200 are separated by a predetermined distance 150.

[0076] USFM system 100 includes controller 190. Controller 190 includes circuitry configured to: activate ultrasonic sensor module 200 to emit incident sound waves, detect the reception of sound waves at ultrasonic sensor module 200; measure the timing and / or amplitude between the transmission and reception of various combinations of direct and reflected sound waves; and / or determine, in part, the various properties of USFM system 100 and / or the fluid, such as those described above, based on those measured timings. Figure 3-9 This will be discussed further in the description.

[0077] In use, fluid flows through the USFM system 100. For example, a fluid such as fuel can be supplied at fluid port 122a, where the fluid flows along fluid path 124a into fluid chamber 120a. The fluid flows around the ultrasonic sensor module 200 to the fluid control conduit 130. The fluid flows along fluid path 132 through the fluid control conduit 130 and then around the ultrasonic sensor module 200 to the fluid chamber 120b. The fluid then flows out of fluid port 122b along fluid path 124b. (As will be...) Figure 3-9 As further discussed in the description, the ultrasonic sensor module 200 is protected from direct exposure to the fluid and is used to transmit sound waves through the fluid to determine fluid properties such as acoustic impedance and mass flow rate.

[0078] Figure 3 It shows in Figure 2A conceptual example of incident wave propagation in an ultrasonic sensor module 200. In use, an acoustic transceiver element 230 is activated to transmit an incident wave (e.g., a pulse). The incident wave is emitted from both surfaces 231 and 233. The incident wave is transmitted into and along buffer bars 250 and 270. A portion of the incident wave, indicated by arrow 310, travels through the axial buffer bar 270 until it encounters the axial end 274. The junction of the axial end 274 and the chamber 204 causes a portion 310 of the incident wave to be reflected as an echo, indicated by arrow 320. The echo 320 travels back to be detected by the acoustic transceiver element 230. In some embodiments, the ultrasonic sensor module 200 may include separate acoustic transmitters and acoustic receivers for the transmission and detection of the incident wave.

[0079] Another portion of the incident wave, indicated by arrow 330, travels through the axial buffer rod 250 until it encounters the axial end 254. The junction of the fluid 301 at the axial end 254 and the mating layer 280 (e.g., or at the axial end 254 in embodiments where the mating layer 280 is not used) causes a portion 330 of the incident wave to be reflected as an echo, indicated by arrow 340. The echo 340 travels back to be detected by the acoustic transceiver element 230.

[0080] In some implementations, it can be measured (e.g., by...) Figure 1 Example controller 190) measures the time between the transmission of the incident wave and the detection of the echo 320 to determine a first time of flight. In some implementations, the time between the transmission of the incident wave and the detection of the echo 340 can be measured to determine a second time of flight. The amplitudes of the echoes 320 and 340 are measured. (As will be...) Figure 6A-7 As further discussed in the description, the measured time of flight, the measured echo amplitude, and predetermined information regarding the acoustic impedance of the buffer rods 250 and 270, and the predetermined distance between the acoustic transceiver element 230, the axial end 254, and the axial end 274, can be used to determine the properties of the fluid 301 at the axial end 254, such as the acoustic impedance (Z). fluid ) and / or the speed of sound in the fluid (C fluid ).

[0081] In some implementations, the ultrasonic sensor module 200 can be used in applications other than the USFM system 100. For example, the ultrasonic sensor module 200 can be in contact with a fluid (e.g., attached to a tank, pipe, or other fluid container or volume, or immersed therein) and can be ultrasonically processed as part of a process to determine the acoustic impedance of the fluid, the velocity of sound in the fluid, and / or the fluid density.

[0082] In some implementations, the characteristics of the buffer rods 250 and / or 270 themselves can be determined based on the measured time of flight and / or the measured echo amplitude (e.g., to calibrate for unknown buffer rod acoustic impedance and / or compensate for the effects of temperature changes on the ultrasonic sensor module 200). Similarly, in some implementations, the distance between the acoustic transceiver element 230 and one or both of the axial ends 274 and / or axial ends 254 can be determined based on the measured time of flight, the measured echo amplitude, a known distance, a known buffer rod acoustic impedance, and / or a known buffer rod temperature.

[0083] Figure 4 It shows in Figure 2 A conceptual example of fluid pressure relief in an ultrasonic sensor module 200. In use, the ultrasonic sensor module 200 is at least partially exposed to fluid 301 at an axial end 254. In some embodiments, the temperature or chemical properties of fluid 301 may damage the acoustic transceiver element 230; therefore, the ultrasonic sensor module 200 is configured to prevent direct contact between fluid 301 and the acoustic transceiver element 230. For example, direct or indirect (e.g., via shim, sleeve, cladding, seal, or sealant) contact between the axial buffer bar 250 and the axial sensor housing portion 208b and / or between the buffer bar 250 and the face 210 can substantially prevent fluid from flowing from the axial end 254 to the acoustic transceiver element 230. In some implementations, fluid seepage caused by the buffer bar 250 can be directed to the sensor chamber 204 without contacting the main face of the acoustic transceiver element 230.

[0084] In use, the ultrasonic sensor module 200 is at least partially exposed to fluid pressure at its axial end 254, indicated by arrow 410. Fluid pressure 410 is a static fluid pressure relative to the dynamic pressure caused by the acoustic signal used by the acoustic transceiver element 230. In some embodiments, direct or indirect application of fluid pressure 410 (e.g., via the buffer rod 250) can generate a compressive force on the acoustic transceiver element 230, which may cancel out or otherwise negatively affect the signal provided by the acoustic transceiver element 230 in response to the sensed acoustic signal. In some implementations, this effect can be mathematically compensated by electrically canceling the sensor signal to recover an approximation of the true signal.

[0085] The ultrasonic sensor module 200 is configured to prevent the fluid pressure 410 from affecting the acoustic transceiver element 230. For example, the acoustic transceiver element 230 acoustically engages with the axial end 252. Thus, the acoustic transceiver element 230 can "float" on the buffer rod 250 relative to the sensor housing 202 and will not become compressed by the fluid pressure 410.

[0086] The acoustic transceiver element 230 is also protected from fluid pressure 410 by a mechanical configuration of the buffer rod 250 and the sensor housing 202. Fluid pressure 410 is applied to the axial end 254, causing the buffer rod 250 to move into the sensor chamber 204. This pressure causing such movement is indicated by arrow 420. Movement of the buffer rod 250 is prevented by contact between the axial buffer rod 250 and the surface 210 of the sensor housing 202, as indicated by arrow 430. This prevents force 420 from reaching the acoustic transceiver element 230.

[0087] The smaller size of cross-sectional area 209a is adjusted to accommodate the acoustic transceiver element 230 and to decouple the thermal expansion of the sensor housing 202 from the acoustic path. The larger size of cross-sectional area 209b is adjusted to accommodate the pressure-induced force acting on the buffer rod 250. Transmitting force to the sensor housing 202 essentially eliminates the pressure-induced force from acting on the acoustic transceiver element 230, and essentially eliminates the need for pressure compensation, transducer assembly resized to respond to pressure-induced forces, and / or wetted transducer design constraints.

[0088] Several advantages have been observed by decoupling the acoustic transceiver element 230 from the fluid pressure environment. For example, fluid / fuel compatibility of the acoustic transceiver element 230 is not required. In another example, the frequency of the acoustic transceiver element 230 is not limited by thickness requirements driven by pressure-induced forces. In yet another example where the acoustic transceiver element 230 is a piezoelectric transducer, the piezoelectric thickness required to support the fluid pressure causes the operating frequency of the acoustic transceiver element 230 to be much lower than the operating requirements for time-of-flight measurements. In yet another example, the operating frequency of the acoustic transceiver element 230 can be adjusted to improve acoustic optimization and / or accuracy in low-flow-rate measurements.

[0089] Figures 5A-5C A conceptual example of incident wave ergodicity in an ultrasonic flow measurement system 500 is shown. In some implementations, the USFM system 500 may be... Figure 1An example of a USFM system 100. The USFM system 500 includes two acoustic transmitters 510a and 510b, two acoustic receivers 512a and 512b, and a fluid control conduit 520. Fluid flows along the fluid control conduit 520 in the direction indicated by arrow 501.

[0090] The following derivation assumes that acoustic receivers 512a and 512b are perpendicular to the main axis of the fluid control conduit 520 and aligned with their corresponding acoustic emitters 510a and 510b. Therefore, the angle of incidence is omitted in the following derivation. If the acoustic emitters 510a and 510b and the acoustic receivers 512a and 512b are placed off-axis, the following derivation can be re-derived using the angle of incidence. However, for simplicity, trigonometric methods used to compensate for such angles are not used here.

[0091] refer to Figure 5A First, consider the speed of sound traveling through a non-moving fluid: Distance = Speed ​​× Time or: Length (L) = Speed ​​of sound in the fluid (C) fluid ) × time(t) Therefore, L1 = C fluid ×t1 Where Cruel is the speed of sound in the fluid, L1 is the distance between the acoustic transmitter 510a and the acoustic receiver 512a, and t1 is the signal transit time between the acoustic transmitter 510a and the acoustic receiver 512a.

[0092] Assuming that the direction 501 of the control volume (fluid) movement is the same as the direction of sound travel from the acoustic transmitter 510a to the acoustic receiver 512a, as indicated by line 502a, then the speed of the sound wave traveling through the fluid will change relative to the speed of the fluid. Therefore, L2 = V2 × t2 V2 = V fluid +C fluid Therefore, L2=(V fluid +C fluid )t2

[0093] Where V fluid L1 is the average velocity of the moving fluid, L2 is the distance between the acoustic transmitter 510a and the acoustic receiver 512a, and t2 is the signal transit time between the acoustic transmitter 510a and the acoustic receiver 512a.

[0094] Now for reference Figure 5B Assume that the control volume (fluid) is opposite to the direction of sound travel from acoustic transmitter 510b to acoustic receiver 512b, as indicated by line 502b. The speed of the sound wave traveling through the fluid will change relative to the speed of the fluid. ∴L 13 =V3×t3 V3 = -V fluid +C fluid Therefore, L3 = (-V fluid +C fluid )t3

[0095] Where L3 is the distance between acoustic transmitter 510b and acoustic receiver 512b, and t3 is the signal transit time between acoustic transmitter 510b and acoustic receiver 512b.

[0096] refer to Figure 5C For a specific set of ultrasonic sensors, these devices can both transmit and receive signals. This means that for a pair of signals, the following characteristics are shared: L up =L down =L = the distance between the transmitters; D = diameter; therefore, the area of ​​the 520mm fluid control conductor. A = Cross-sectional area; C fluid =Speed ​​of sound in a fluid; V fluid = Fluid velocity; ρ fluid = Fluid density; Z fluid = Acoustic impedance of the fluid.

[0097] With the above attributes shared, the time difference between upstream and downstream signals will allow for the calculation of various fluid properties.

[0098] The upstream and downstream crossing times become: Solve for t up t down and C fluid : Since the speed of sound is common between transducers, the speeds of sound are equal to each other, allowing the fluid velocity to be determined: C fludid =C fluid L down t up -t down t up V fluid =L up t down +t up t down V fluid L down t up -L up t down =t up t down V fluid +t down t up V fluid L up =L down L(t up -t dn ) = 2V fluid t up t down Knowing the fluid velocity allows us to determine the volumetric fluid flow rate (Q). fluid ), where C d It is the predetermined discharge factor of the fluid in the fluid control conduit 520: Q fluid =C d ×A×V fluid It is also possible to determine the fluid's sound velocity properties. Since the fluid velocity is shared between a pair of transducers, the fluid velocity can be solved for. Recall: as well as: For V fluid To solve t up and t down : V fluid =(L down -t down C fluid ) / t down V fluid =(-L up +tup C fluid ) / t up Since the fluid velocity is common between the transducers, the previous two equations are equal to each other, allowing the solution for the fluid sound velocity:

[0099] Figure 6A and 6B It shows Figure 1 A graph showing an example of incident and echo waves in an ultrasonic flow measurement system. Figure 6A A graph 600 showing the acoustic amplitude over time, including sub-durations 601, is presented. Figure 6B Figure 602 is shown, where the sub-duration 601 has been enlarged for visibility.

[0100] Figure 600 illustrates the transmission of the initial incident wave 610 (e.g., when the acoustic transceiver element 230 is activated to transmit an acoustic “pulse”). The echo 620 is received a few microseconds later. In some implementations, the echo 620 can be… Figure 3 The echo 320 is a reflection of the incident wave 310 from the surface 274 at the cavity 204.

[0101] Echo 630 is received after a few microseconds. In some implementations, echo 630 can be echo 340, which is a reflection of a portion 330 of the incident wave exiting the axial end 254, which is also the interface leading to the fluid. Echo 640 represents the echo in the buffer bars 250 and 270. In operation, echo 640 can be filtered out or otherwise ignored.

[0102] Incident wave 670 represents a portion of the incident wave received by an acoustic sensor (e.g., an acoustic transceiver element 230 located downstream of or otherwise opposite to the acoustic transceiver element 230 that transmitted the incident wave). The amount of time it takes for incident wave 670 to arrive is influenced by several variables, such as fluid density, flow rate, the direction of fluid flow in the fluid control conduit 130, and distance 150. The amount of time taken for incident wave 670 can be used as t. up or t down (For example, depending on whether the wave travels upward or downward in the fluid control conduit 130).

[0103] like Figure 4As illustrated, the buffer rod 250 is designed to transfer pressure-induced forces to surface 210 of the sensor housing 202. This is achieved through the diametrical configuration of the buffer rod 250, where the smaller cross-sectional area of ​​the acoustic transceiver element 230 decouples the thermal expansion of the sensor housing 202 from the acoustic path. The larger cross-sectional area of ​​the axial buffer rod 250 is sized to accommodate the pressure-induced forces acting on the buffer rod 250. Transmitting force into the sensor housing 202 essentially eliminates pressure-induced forces from acting on the acoustic transceiver element 230, and essentially eliminates the need for pressure compensation (e.g., piezoelectric ceramic), sizing to respond to pressure-induced forces, and essentially avoids the design constraints of the wetted transducer.

[0104] Several advantages were observed by decoupling the acoustic transceiver element 230 from the fluid pressure environment. For example, fluid / fuel compatibility of the acoustic transceiver element 230 is not required, the frequency of the acoustic transceiver element 230 is not limited by the thickness requirements driven by pressure-induced forces, the thickness of the acoustic transceiver element 230 required to support fluid pressure allows the operating frequency to be much lower than the operating requirements for time-of-flight measurements, and the acoustic transducer frequency can be adjusted for acoustic optimization and low-flow-rate measurement accuracy.

[0105] For aircraft turbine fuel systems, the mass fuel flow rate can be determined to understand the combustion energy content. This is achieved through the use of buffer bars 250 and 270. The design and arrangement of buffer bars 250 and 270 achieve additional acoustic benefits that can be intentionally incorporated into the USFM system 100. For example, the configuration of buffer bars 250 and 270 enables controller 190 to determine the reflection coefficient for fuel acoustic impedance measurements. This is achieved by introducing a transducer transmission amplitude response (e.g., echo 320 or 620) through chamber 204, which acts as a substantially ideal reflector, and this amplitude can be compared with the return echo (e.g., echo 340 or 630) at the fluid interface of the buffer bars. In some embodiments, the sensitivity of the axial end 254 is further enhanced by a matching layer 280; however, this will be ignored for the sake of simplicity in the equations below.

[0106] The hydroacoustic impedance can be determined by setting the effective areas of the echo reflection to be equal to each other, for example by appropriately configuring the cross-sectional areas 209a and 209b. In some implementations, these areas may not be equal, and mathematical compensation can be integrated into the process. However, for clarity, it is assumed that these areas are equal in the equations below. This allows for direct measurement of the reflection coefficient. Wave propagation within the buffer rod 250 is articulated, such that in the air, the echo returning from surface 274 is equivalent to the echo from axial end 254.

[0107] The reflection coefficient was found using the Short Time Fourier Transform (STFT). The Fast Fourier Transform (FFT) of the two echoes was then used to determine the peak value of the returned echo: STFT → Amplitude = f (frequency) therefore: in: Echo1 is respectively Figure 3 , 6A Echo2 is one of the echoes of 320 or 620 from 6B. Figure 3 , 6A The echo of 6B is either 340 or 630, and f and f0 are the transducer drive frequencies. Then, the reflection coefficient is found according to the following formula: Furthermore, it is assumed that the buffer bar 250 is in direct contact with the fluid or fuel (e.g., in this case there is no mating layer 280): Where R is the reflection coefficient. Z2 = Z fiuid Z1 = Z buffer

[0108] In some examples, the buffer rod can have properties that change with temperature, which can be used to obtain Z as a function of temperature. buffer These changes can be compensated for by the temperature characteristics of the buffer rod and the use of temperature sensing devices located in the system, or the temperature reference can be determined based on the buffer reflection timing.

[0109] The impedance of the buffer rod 250 can be determined through characterization at the sensor level. With the buffer rod impedance known and the reflection coefficient measured, the fluid impedance can now be solved for: Z fluid =ρ fluid ×C fluid Based on the above equation, the velocity of sound in the fluid can be calculated. Since the fluid impedance and the velocity of sound are known, the fluid density can now be calculated.

[0110] Clearly: Given that the volumetric fluid flow rate and density are now known, the mass fluid flow rate can be found:

[0111] In another implementation, a different technique can be used to determine the mass fluid flow rate. The following derivation is based on the simplifying assumption that the transducer surfaces (e.g., the piezoelectric ceramic and the transducer) are all arranged perpendicular to the axis of the fluid delivery pipe. Therefore, the angle of incidence is omitted in the following derivation. In an example where the piezoelectric transducer is placed off-axis, the following derivation can be re-derived to include the angle of incidence. However, for simplicity, this angle has been ignored here.

[0112] Mass fuel flow sensing can be achieved by implementing two ultrasonic transducers per channel, where each transducer transmits and receives acoustic signals. The signals used for mass fuel flow sensing can be based on upstream and downstream time transits (e.g., for velocity) and internal transducer reflections (e.g., for impedance sensing). Q fluid =V fluid ×C d ×A z = ρ fluid ×C fluid ∴

[0113] Where C d K and K are often used interchangeably as flow correction factors in the literature: first: Distance = Speed ​​× Time or Length (L) = Speed ​​of sound (C) fluid ) × time(t) Therefore, L1 = C fluid ×t1 Where Cfuel is the speed of sound in the fluid, L1 is the distance between the acoustic transmitter 510a and the acoustic receiver 512a, and t1 is the signal transit time between the acoustic transmitter 510a and the acoustic receiver 512a.

[0114] Assuming that the direction 501 of the control volume (fluid) movement is the same as the direction of sound travel from the acoustic transmitter 510a to the acoustic receiver 512a, as indicated by line 502a, then the speed of the sound wave traveling through the fluid will change relative to the speed of the fluid. Therefore, L2 = C fluid ×t2 V2 = V fluid +C fluid Therefore, L2=(V fluid +C fluid )×t2

[0115] Where V fluid L1 is the average velocity of the moving fluid, L2 is the distance between the acoustic transmitter 510a and the acoustic receiver 512a, and t2 is the signal transit time between the acoustic transmitter 510a and the acoustic receiver 512a.

[0116] Refer again Figure 5B Assume that the control volume (fluid) is opposite to the direction of sound travel from acoustic transmitter 510b to acoustic receiver 512b, as indicated by line 502b. The speed of the sound wave traveling through the fluid will change relative to the speed of the fluid. Therefore, L3 = V3 × t3 V3 = -V fluid +C fluid Therefore, L3 = (-V fluid +C fluid )×t3

[0117] Where L3 is the distance between acoustic transmitter 510b and acoustic receiver 512b, and t3 is the signal transit time between acoustic transmitter 510b and acoustic receiver 512b.

[0118] Refer again Figure 5C For a specific set of ultrasonic sensors, and as described above, these devices can both transmit and receive signals. This means that for a pair of signals, the following characteristics are shared: L up =L down =L = the distance between the transmitters; D = diameter; therefore, the area of ​​the 520mm fluid control conductor. A = Cross-sectional area; C fluid =Speed ​​of sound in a fluid; V fluid = Fluid velocity; ρ fluid = Fluid density; Z fluid = Acoustic impedance of the fluid.

[0119] With the above attributes shared, the time difference between upstream and downstream signals will allow for the calculation of various fluid properties.

[0120] The upstream and downstream crossing times become: Solving for t with respect to L up t down : L up =t up ×C fluid -t dn ×V fluid L dn =t dn ×C fluid +t dn ×V fluid Since the length is common between the transducers, therefore L up and L dn They are equal to each other, and allow the finding of the ratio of fuel speed to sound speed. t up ×C fluid -t up ×V fluid =t dn ×C fluid +t dn ×V fluid t up ×C fluid -t dn ×C fluid =t dn ×V fluid +t dn ×V fluid

[0121] Substituting the first equation into the earlier equation for mass flow rate: Given the acoustic impedance (z), duct area (A), and the measured time transit, the mass fluid flow rate can be calculated.

[0122] As shown above: Substitute the previous mass flow rate equation into the first equation:

[0123] Figure 7 This is a flowchart illustrating an example of a process 700 for determining the fluid reflection coefficient. In some implementations, process 700 can be combined with... Figure 1-2 The example ultrasonic sensor module 200 is used together.

[0124] At 710, the first transmitter is activated to emit a first incident wave and a second incident wave. For example, the example acoustic transceiver element 230 can be activated to emit incident waves from its two surfaces.

[0125] At 720, the incident wave is transmitted along the first buffer rod, which has a first axial end adjacent to the first transmitter and a second axial end opposite to the first axial end. For example, the first incident wave can propagate through the buffer rod 250.

[0126] At position 725, the incident wave propagates along the second buffer rod, which has a third axial end adjacent to the first transmitter and a fourth axial end opposite to the third axial end. For example, the second incident wave can propagate through the buffer rod 270.

[0127] At 730, a first echo of the first incident wave is reflected by a first acoustic reflector defined along a portion of the first buffer rod. For example, a portion 330 of the incident wave may encounter surface 254 and be reflected as echo 340. In some implementations, the first echo may be reflected by a 1 / 4λ matching layer fixed to the second axial end (e.g., matching layer 280 at the axial end 254).

[0128] At 740, the first echo is detected. For example, it can be detected... Figure 6A and 6B The echo is 620.

[0129] At 750, the first amplitude of the first echo is determined. For example, an FFT can be performed on echo 620 to determine the amplitude of echo 620 (e.g., amplitude A as described above).

[0130] At 760, a second echo of the incident wave is reflected by the fourth axial end. For example, a portion 310 of the incident wave is reflected away from the axial end 274 as echo 320.

[0131] At 770, the second echo is detected. For example, it can be detected... Figure 6A and 6B The echo is 630.

[0132] At 780, the second amplitude of the second echo is determined. For example, an FFT can be performed on echo 640 to determine the amplitude of echo 640 (e.g., amplitude B as described above).

[0133] At 790, the reflection coefficient based on the first and second amplitudes can be determined. For example:

[0134] Figure 8 This is a flowchart illustrating an example of a process 800 for determining mass fluid flow rate. In some implementations, process 800 may be combined with... Figure 1 Used with the example USFM system 100.

[0135] At 805, the reflection coefficient value is received. For example, the reflection coefficient R determined at 790 can be received.

[0136] At 810, the fluid acoustic impedance at the second axial end is determined based on the determined reflection coefficient and the predetermined buffer rod acoustic impedance. For example, the reflection coefficient R can be related to the predetermined buffer rod impedance Z. buffer Together used to determine Z fluid As described above.

[0137] At 815, a portion of the incident wave is transmitted via fluid at the second axial end to a sensor arranged at a predetermined distance from and opposite to the first transmitter, wherein the fluid is within a tubular fluid conduit having a predetermined cross-sectional area. For example, Figure 6A The incident wave 670 can travel from the upstream ultrasonic sensor module 200 to the downstream ultrasonic sensor module 200 through the fluid.

[0138] At 820, the second sensor detects this portion of the incident wave. For example, the downstream ultrasonic sensor module 200 can detect the incident wave 670.

[0139] At 825, the first flight time of that portion of the incident wave is determined based on the detected portion. For example, t can be determined. down .

[0140] At 830, a second transmitter transmits another incident wave through the fluid to the first sensor. For example, the downstream ultrasonic sensor module 200 can be activated to transmit another incident wave upstream.

[0141] At 835, the first sensor detects the other incident wave, and at 840, based on the detected other incident wave, determines the second time of flight of that other incident wave. For example, t can be determined. up .

[0142] At 845, determine the velocity of the fluid within the tubular fluid conduit. For example, V fluid It can be determined as follows: Determine the speed of sound in the fluid at 850. For example, C fluid It can be determined as follows: At 855, the mass fluid flow rate is determined based at least on the predetermined cross-sectional area, the determined velocity of the fluid, the determined fluid acoustic impedance, and the determined sound velocity. For example: or:

[0143] In some implementations, one or both of the first transmitter and the first sensor may be a piezoelectric element. In some implementations, the piezoelectric element may include both the first transmitter and the first sensor. For example, the transmitter and sensor may be separate components, or the acoustic transceiver element 230 may perform the transmission and detection functions within the ultrasonic sensor module 200.

[0144] Figure 9 It shows the resistance to fluid exposure. Figure 1-4 A flowchart illustrating an example of the process 900 involving the acoustic transceiver element 230 of an example ultrasonic sensor module 200. At 910, a sensor is provided. The sensor includes: a sensor housing having an inner surface defining a sensor axis and an axially internal sensor housing chamber, the sensor housing having: a first axial sensor housing portion having a first cross-sectional area perpendicular to the sensor axis; 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 perpendicular to the sensor axis; and a surface extending from the inner surface of the first axial housing portion to the inner surface of the second housing portion; a buffer rod having a first axial end and a second axial end opposite to the first axial end, and having a first axial buffer portion disposed within the first housing portion and having the first axial end; a second axial buffer portion disposed within the second housing portion and adjacent to the surface and having the second axial end; and a third axial buffer portion extending axially between the first and second axial buffer portions and having a third cross-sectional area smaller than the first cross-sectional area perpendicular to the sensor axis; and an acoustic transceiver element acoustically cooperating with the first end. For example, an ultrasonic sensor module 200 may be provided.

[0145] At 920, fluid is provided at the second axial end. For example, a fluid 301, such as fuel, may be provided in fluid chambers 120a or 120b to contact the axial end 254.

[0146] At 930, the buffer rod and sensor housing prevent fluid from flowing from the second end to the acoustic transceiver elements. For example, as in Figure 4 As discussed in the description, the acoustic transceiver element 230 is isolated from the fluid 301 by the sensor housing 202 and the buffer rod 250, and the fluid 301 is configured by the sensor housing 202 and the buffer rod 250 to prevent the fluid 301 from flowing to the acoustic transceiver element 230.

[0147] In some implementations, the sensor housing and the second axial buffer portion can prevent fluid from flowing from the second end to the acoustic transceiver element. For example, the flow of fluid 301 to the acoustic transceiver element 230 is prevented by interference between the sensor housing 202 and the axial buffer rod 250.

[0148] At 940, fluid pressure is applied to the second axial end to generate an axial force on the buffer rod. For example, fluid force 410 can be applied to the axial end 254.

[0149] At 950, the buffer rod transmits the axial force to the sensor housing. For example, buffer rod 250 transmits force 420 to sensor housing 202.

[0150] At 960, the sensor housing prevents the transmission of axial force to the acoustic transceiver element. In some implementations, process 900 may further include transmitting the axial force to the surface by a second axial portion, wherein the surface interferes with axial movement of the buffer rod toward the acoustic transceiver element. For example, a reaction force 430 created by the contact between the axial buffer rod 250 and the surface 210 prevents any movement of the buffer rod 250 toward the sensor chamber 204.

[0151] Figure 10 This is a schematic diagram of an example of a general-purpose computer system 1000. Depending on one implementation, system 1000 can be used for the operations described in association with processes 700, 800, and / or 900. For example, system 1000 may be included in controller 190.

[0152] System 1000 includes a processor 1010, a memory 1020, a storage device 1030, and an input / output device 1040. Each of components 1010, 1020, 1030, and 1040 is interconnected via a system bus 1050. Processor 1010 is capable of processing instructions for execution within system 1000. In one implementation, processor 1010 is a single-threaded processor. In another implementation, processor 1010 is a multi-threaded processor. Processor 1010 is capable of processing instructions stored in memory 1020 or storage device 1030 to display graphical information for a user interface on input / output device 1040.

[0153] Memory 1020 stores information within system 1000. In one implementation, memory 1020 is a computer-readable medium. In one implementation, memory 1020 is a volatile memory cell. In another implementation, memory 1020 is a non-volatile memory cell.

[0154] Storage device 1030 provides large-capacity storage for system 1000. In one implementation, storage device 1030 is a computer-readable medium. In various other implementations, storage device 1030 may be a floppy disk device, hard disk device, optical disk device, or magnetic tape device.

[0155] Input / output device 1040 provides input / output operations for system 1000. In one implementation, input / output device 1040 includes a keyboard and / or pointing device. In another implementation, input / output device 1040 includes a display unit for displaying a graphical user interface.

[0156] The described features can be implemented in digital electronic circuits, or in computer hardware, firmware, software, or a combination thereof. The device can be implemented using a computer program product tangibly embodied in an information carrier, for example, in a machine-readable storage device for execution by a programmable processor; and the method steps can be executed by a programmable processor that executes a programmable instruction program to perform the functions of the described implementation by manipulating input data and generating output. The described features can advantageously be implemented in one or more computer programs executable on a programmable system comprising at least one programmable processor, at least one input device, and at least one output device, the at least one programmable processor being coupled to receive data and instructions from and to a data storage system. A computer program is a set of instructions that can be used directly or indirectly in a computer to perform an activity or cause a result. A computer program can be written in any form of programming language (including compiled or interpreted languages), and it can be deployed in any form, including as a standalone program or as a module, component, subroutine, or other unit suitable for use in a computing environment.

[0157] For example, suitable processors for executing instruction programs include both general-purpose and special-purpose microprocessors, as well as a single processor or one or more processors in any type of computer. Generally, the processor receives instructions and data from read-only memory or random access memory, or both. The basic components of a computer are a processor for executing instructions and one or more memories for storing instructions and data. Generally, a computer will also include one or more mass storage devices for storing data files, or operatively coupled to and communicating with them; such devices include disks, such as internal hard disks and removable disks; magneto-optical disks; and optical disks. Storage devices suitable for tangibly representing computer program instructions and data include all forms of non-volatile memory, for example, semiconductor memory devices such as EPROM, EEPROM, and flash memory devices; disks, such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor and memory may be supplemented or incorporated by an ASIC (Application-Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array) with or without embedded processing elements.

[0158] To provide interaction with the user, these features can be implemented on a computer that has a display device (such as a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user, as well as a keyboard and pointing device, such as a mouse or trackball, through which the user can provide input to the computer.

[0159] These features can be implemented in a computer system that includes back-end components, such as data servers, or middleware components, such as application servers or internet servers, or front-end components, such as client computers with graphical user interfaces or internet browsers, or any combination thereof. The components of the system can be connected via any form or medium of digital data communication, such as a communication network. Examples of communication networks include, for example, LANs, WANs, and the computers and networks that form the Internet.

[0160] Computer systems can include clients and servers. Clients and servers are generally geographically separated and typically interact via a network (such as the network described). The client-server relationship is established by means of computer programs running on the respective computers and having a client-server relationship with each other.

[0161] Although several implementations have been described in detail above, other modifications are possible. Furthermore, the logical flow depicted in the accompanying drawings does not require the specific order or sequence shown to achieve the desired result. Additionally, other steps can be provided from the described flow, or steps can be eliminated, and other components can be added to or removed from the described system. Therefore, other implementations are within the scope of the following claims.

Claims

1. A sensor, comprising: A sensor housing having an inner surface defining a sensor axis and an axially internal sensor housing chamber, the sensor housing comprising: The first axial sensor housing portion has a first cross-sectional area perpendicular to the sensor axis; 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 perpendicular to the sensor axis and larger than the first cross-sectional area; and A surface extending from the inner surface of the first axial sensor housing portion to the inner surface of the second axial sensor housing portion; A first axial buffer rod is disposed within a first axial sensor housing portion and includes a first axial end and a second axial end. A second axial buffer rod, disposed within and adjacent to the surface of the second axial sensor housing portion, and including a third axial end and a fourth axial end; and An acoustic transceiver element acoustically engages with a second axial end and a third axial end, wherein the acoustic transceiver element is configured to emit vibrations having a predetermined wavelength λ, and both the first axial buffer rod and the second axial buffer rod have an axial length of nλ / 2, where nλ / 2 is an integer multiple of half the predetermined wavelength λ of the acoustic transceiver element.

2. The sensor of claim 1, further comprising a tubular fluid conduit having a first end and a second end opposite to the first end and defining a conduit axis, the tubular fluid conduit being arranged such that the conduit axis is substantially aligned with the sensor axis.

3. The sensor according to claim 2, further comprising: Another sensor housing, having another inner surface defining another sensor axis and another axial internal sensor housing chamber, the other sensor housing comprising: Another first axial sensor housing portion has another first cross-sectional area perpendicular to the other sensor axis; Another second axial sensor housing portion, arranged adjacent to the other first axial sensor housing portion along the other sensor axis, and having a second cross-sectional area perpendicular to the other sensor axis and larger than the other first cross-sectional area; and From another inner surface of the other first axial sensor housing portion to another side of another inner surface of the other second axial sensor housing portion; Another first axial buffer rod is disposed within the other first axial sensor housing portion and includes another first axial end and another second axial end; Another second axial buffer rod, which is disposed within the other second axial sensor housing portion and adjacent to the other face, and includes another third axial end and another fourth axial end; and Another acoustic transceiver element, which acoustically engages with the other second axial end and the other third axial end; The axis of the other sensor is substantially aligned with the axis of the conduit.

4. The sensor according to claim 2 or 3, further comprising: Fluid housing, comprising: The fluid housing inner surface of the axial fluid housing chamber is defined; A first fluid port in fluid communication with the axial fluid housing chamber; and A second fluid port that is in fluid communication with the axial fluid housing chamber; The tubular fluid conduit is in fluid communication with the second fluid port and extends axially away from the fluid housing along the conduit axis at the first end, and the sensor housing is disposed within the first fluid housing such that the sensor axis is substantially aligned with the conduit axis.

5. The sensor according to claim 4, further comprising: Another sensor housing, having another inner surface defining another sensor axis and another axial internal sensor housing chamber, the other sensor housing comprising: Another first axial sensor housing portion has another first cross-sectional area perpendicular to the other sensor axis; Another second axial sensor housing portion, arranged adjacent to the other first axial sensor housing portion along the other sensor axis, and having a second cross-sectional area perpendicular to the other sensor axis and larger than the other first cross-sectional area; and From another inner surface of the other first axial sensor housing portion to another side of another inner surface of the other second axial sensor housing portion; Another first axial buffer rod is disposed within the other first axial sensor housing portion and includes another first axial end and another second axial end; Another second axial buffer rod is arranged within the other second axial sensor housing portion and adjacent to the other face, and includes another third axial end and another fourth axial end; Another acoustic transceiver element, which acoustically engages with the other second axial end and the other third axial end; and Another fluid housing, comprising: Defines another fluid housing inner surface of another axial fluid housing chamber; Another first fluid port in fluid communication with the other axial fluid housing chamber; and Another second fluid port is in fluid communication with the other axial fluid housing chamber; The tubular fluid conduit is in fluid communication with the other second fluid port and extends axially at a second end along the conduit axis away from the other fluid housing, and the other sensor housing is disposed within another first fluid housing such that the axis of the other sensor is substantially aligned with the axis of the conduit.

6. The sensor according to any one of claims 1 to 3, wherein the acoustic transceiver element comprises a piezoelectric element.

7. The sensor according to any one of claims 1 to 3, further comprising a matching layer fixed to a fourth axial end and having a thickness of (2n-1)λ / 4, wherein n > 0, and (2n-1)λ / 4 is an odd multiple of a quarter of the predetermined wavelength λ of the acoustic transceiver element.

8. The sensor according to any one of claims 1 to 3, wherein an acoustic reflector is defined at the first axial end.

9. The sensor according to any one of claims 1 to 3, wherein the first axial end is adjacent to gas or at least a partial vacuum.

10. A method for protecting a sensor element, comprising: Provide a sensor, the sensor comprising: A sensor housing having an inner surface defining a sensor axis and an axially internal sensor housing chamber, the sensor housing comprising: The first axial sensor housing portion has a first cross-sectional area perpendicular to the sensor axis; 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 perpendicular to the sensor axis and larger than the first cross-sectional area; and A surface extending from the inner surface of the first axial sensor housing portion to the inner surface of the second axial sensor housing portion; A first axial buffer rod is disposed within a first axial sensor housing portion and includes a first axial end and a second axial end. A second axial buffer rod, disposed within and adjacent to the surface of the second axial sensor housing portion, and including a third axial end and a fourth axial end; and An acoustic transceiver element that acoustically engages with the second and third axial ends. The acoustic transceiver element is configured to emit vibrations with a predetermined wavelength λ, and both the first axial buffer rod and the second axial buffer rod have an axial length of nλ / 2, where nλ / 2 is an integer multiple of half the predetermined wavelength λ of the acoustic transceiver element. Fluid is provided at the fourth axial end, and The second axial buffer rod and the sensor housing prevent fluid from flowing from the fourth axial end to the acoustic transceiver element.

11. The method of claim 10, further comprising: Fluid pressure is applied to the fourth axial end to generate an axial force against the second axial buffer rod; The axial force is transmitted to the sensor housing by the second axial buffer rod; as well as The sensor housing prevents the transmission of the axial force to the acoustic transceiver element.

12. The method of claim 11, further comprising transmitting the axial force to the surface by a second axial portion, wherein the surface interferes with the axial movement of the second axial buffer rod toward the acoustic transceiver element.

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