Ultrasonic mass flowmeter

Abstract

The subject matter of the present specification can be embodied in a sensing method that includes activating a first emitter to emit at least one incident wave, transmitting the incident wave along a buffer rod having a first axial end proximate the first emitter and a second axial end opposite the first axial end, reflecting a first echo of the incident wave through a gap defined along a portion of the buffer rod, detecting the first echo, determining a first amplitude of the first echo, reflecting a second echo of the incident wave through the second axial end, detecting the second echo, determining a second amplitude of the second echo, and determining a reflection coefficient based on the first amplitude and the second amplitude.

Description

[0001] Claiming priority This application claims priority to U.S. Patent Application No. 16 / 702,152, filed December 3, 2019, 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. With improvements in the dynamic bandwidth, flow range, accuracy, and reliability of flow measurement devices, their potential applications are expanding. 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 mature industrial technology that can be implemented in aircraft turbine systems.

[0004] Existing time-of-flight ultrasonic flow meters are used in the racing and automotive industries, closed-loop pipeline transport, 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] In summary, this document describes an ultrasonic fluid mass flow sensor.

[0006] In a first aspect, the sensor includes: a sensor housing having an inner surface defining a sensor axis and an axially internal sensor housing cavity, the axially internal sensor housing cavity 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 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 axial housing portion; a buffer rod having a first axial end and a second axial end opposite to the first axial end, and including a first axial buffer portion disposed within the first housing portion and including the first axial end, a second axial buffer portion disposed within the second housing portion and adjacent to the surface and including the second axial end, and a third axial buffer portion extending axially between the first axial buffer portion and the second axial buffer portion and having a third cross-sectional area perpendicular to the sensor axis, the third cross-sectional area being smaller than the first cross-sectional area; a cavity defined between the inner surface and the third axial buffer portion; and an acoustic transceiver element acoustically fitted to the first end.

[0007] In a second aspect, according to aspect 1, the transceiver element is configured to emit vibrations having a predetermined wavelength, and the buffer rod has an axial length that is an integer multiple of approximately n / 2.

[0008] In the third aspect, according to aspect 1 or 2, the third cross-sectional region is approximately half the size of the first cross-sectional region.

[0009] In a fourth aspect, according to any one of aspects 1 to 3, 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.

[0010] In a fifth aspect, according to aspect 4, the sensor further includes: another sensor housing having another inner surface defining another sensor axis and another axial internal sensor housing cavity, the other axial internal sensor housing cavity comprising: another first axial sensor housing portion having another first cross-sectional region 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 region larger than the other first cross-sectional region perpendicular to the other sensor axis; and another side 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 buffer rod having another first axis The device includes an end portion and a second axial end portion opposite to the other first axial end portion, and includes another first axial buffer portion disposed within another first housing portion and including the other first axial end portion, another second axial buffer portion disposed within another second housing portion and adjacent to another surface and including the other second axial end portion, and another third axial buffer portion extending axially between the other first axial buffer portion and the other second axial buffer portion, and having another third cross-sectional area perpendicular to the other sensor axis and smaller than the other first cross-sectional area; another cavity defined between another inner surface and the other third axial buffer portion; and another acoustic transceiver element acoustically mated to the other first end portion, wherein the other sensor axis is substantially aligned with the conduit axis.

[0011] In a sixth aspect, according to aspect 4 or 5, the sensor further includes a fluid housing comprising an inner surface of the fluid housing defining an axial fluid housing cavity, a first fluid port in fluid communication with the axial fluid housing cavity, and a second fluid port in fluid communication with the axial fluid housing cavity, wherein a tubular fluid conduit is in fluid communication with the second fluid port and extends at a first end along the conduit axis away from the fluid housing axial direction, and the sensor housing is disposed within the first fluid housing such that the sensor axis is substantially aligned with the conduit axis.

[0012] In a seventh aspect, according to aspect 6, the sensor further includes: another sensor housing having another inner surface defining a second sensor axis and a second axial internal sensor housing cavity, the second axial internal sensor housing cavity comprising: another first axial sensor housing portion having a second first cross-sectional area perpendicular to the second sensor axis; another second axial sensor housing portion disposed adjacent to the second first axial sensor housing portion along the second sensor axis and having a second second cross-sectional area larger than the second first cross-sectional area perpendicular to the second sensor axis; and another face extending from the second inner surface of the second first axial housing portion to the second inner surface of the third second housing portion; another buffer rod having a second first axial end and a second axial end opposite to the second first axial end, and comprising: another first axial buffer portion disposed within the second first housing portion and including the second first axial end; and a second face disposed within the second second housing portion and adjacent to the second face and encompassing the second axial housing portion. The first axial buffer portion includes another second axial end; and another third axial buffer portion extending axially between another first axial buffer portion and another second axial buffer portion, and having another third cross-sectional area smaller than the other first cross-sectional area perpendicular to the other sensor axis; another cavity defined between another inner surface and another third axial buffer portion; another transceiver element acoustically mated to the other first end; and another fluid housing including another fluid housing inner surface defining the other axial fluid housing cavity, another first fluid port in fluid communication with the other axial fluid housing cavity, and another second fluid port in fluid communication with the other axial fluid housing cavity, wherein the tubular fluid conduit is in fluid communication with the other second fluid port and extends axially away from the other fluid housing along the conduit axis at the second end, and the other sensor housing is disposed within the other first fluid housing such that the other sensor axis is substantially aligned with the conduit axis.

[0013] In the eighth aspect, according to any one of aspects 1 to 7, the acoustic transceiver element includes a piezoelectric element.

[0014] In the ninth aspect, according to any one of aspects 1 to 8, the sensor further includes a matching layer fixed to the second end and having a thickness of approximately 1 / 4 odd multiple.

[0015] In the tenth aspect, according to any one of the first to ninth aspects, the sensor further includes a backing that is adjacent to the acoustic transceiver element and axially opposite to the first end.

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

[0017] In a twelfth aspect, according to aspect 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 via the first acoustic transceiver element, determine a fluid acoustic impedance of the fluid in the tubular fluid conduit based on the echo, detect at least a first portion of the first incident wave via 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 via 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 a thirteenth aspect, according to aspect 11 or 12, one or both of the first sensor or the second sensor each include: a sensor housing having an inner surface defining a sensor axis and an axially internal sensor housing cavity, the axially internal sensor housing cavity including: a first axial sensor housing portion having a first cross-sectional region 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 region larger than the first cross-sectional region 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 including: a first axial buffer portion disposed within the first housing portion and including the first axial end, a second axial buffer portion disposed within the second housing portion and adjacent to the surface and including the second axial end, and a third axial buffer portion extending axially between the first axial buffer portion and the second axial buffer portion and having a third cross-sectional region perpendicular to the sensor axis and smaller than the first cross-sectional region; a cavity defined between the inner surface and the third axial buffer portion; and an acoustic transceiver element acoustically fitted to the first end.

[0019] In the fourteenth aspect, according to aspect 13, the acoustic transceiver element is configured to emit vibrations having a predetermined wavelength, and the buffer rod has an axial length that is an integer multiple of approximately n / 2.

[0020] In the fifteenth aspect, according to aspect 13 or 14, the third cross-sectional region is approximately half the size of the first cross-sectional region.

[0021] In the sixteenth aspect, according to any one of aspects 13 to 15, the acoustic transceiver element includes a piezoelectric element.

[0022] In the seventeenth aspect, according to any one of aspects 13 to 16, the sensor system further includes a matching layer fixed to the second end and having a thickness of approximately 1 / 4 odd multiple.

[0023] In the eighteenth aspect, according to any one of aspects 13 to 17, the sensor system further includes a backing that is axially adjacent to the acoustic transceiver element at the first end.

[0024] In a nineteenth aspect, a sensing method includes: activating a first transmitter to emit at least one incident wave; transmitting the incident wave along a buffer rod having a first axial end adjacent to the first transmitter and a second axial end opposite to the first axial end; reflecting a first echo of the incident wave through a gap defined along a portion of the buffer rod; detecting the first echo; determining a first amplitude of the first echo; reflecting a second echo of the incident wave by the second axial end; detecting the second echo; determining a second amplitude of the second echo; and determining a reflection coefficient based on the first amplitude and the second amplitude.

[0025] In a twentieth aspect, according to aspect 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 a twenty-first aspect, according to aspect 20, the method further includes: at a second axial end, transmitting a portion of the incident wave to a sensor via fluid, the sensor being arranged at and opposite to the first transmitter at a predetermined distance away from it, wherein the fluid is within a tubular fluid conduit having a predetermined cross-sectional area; detecting the portion of the incident wave via the second sensor; determining a first time of flight of the detected portion of the incident wave based on the detected portion of the incident wave; transmitting another incident wave via fluid from the second transmitter to another sensor; detecting the other incident wave by the first sensor; and determining a second time of flight of the other incident wave based on the detected other incident wave.

[0027] In a twenty-second aspect, according to aspect 21, the method further includes determining at least one of the fluid velocity 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 a twenty-third aspect, according to aspect 21 or 22, the method further includes determining the mass fluid flow rate based on a predetermined cross-sectional region and a determined sound velocity.

[0029] In the twenty-fourth aspect, according to any one of aspects 19 to 23, the second echo reflecting the incident wave through the second axial end also includes the reflection of the second echo through a 1 / 4 matching layer fixed to the second axial end.

[0030] In the twenty-fifth aspect, according to any of aspects 19 to 24, one or both of the first transmitter and the first sensor are piezoelectric elements.

[0031] In the twenty-sixth aspect, according to any one of aspects 19 to 25, the piezoelectric element includes a first transmitter and a first sensor.

[0032] In a twenty-seventh aspect, 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 cavity, the axially internal sensor housing cavity comprising: a first axial sensor housing portion having a first cross-sectional region 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 region larger than the first cross-sectional region 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; and a buffer rod having a first axial end. The sensor housing includes a first axial buffer portion disposed within the first housing portion and including the first axial end; a second axial buffer portion disposed within the second housing portion and adjacent to the first axial end and including 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 perpendicular to the sensor axis, the third cross-sectional area being smaller than the first cross-sectional area; and an acoustic transceiver element acoustically fitted to the first end; fluid is provided at the second axial end; and fluid flow from the second end to the acoustic transceiver element is blocked by a buffer rod and the sensor housing.

[0033] In the twenty-eighth aspect, according to aspect 27, fluid flow from the second end to the transceiver element is blocked by the sensor housing and the second axial buffer portion.

[0034] In a twenty-ninth aspect, according to aspect 27 or 28, the method further includes: applying fluid pressure to the second axial end to generate an axial force on the buffer rod; transmitting the axial force to the sensor housing via the buffer rod; and preventing the axial force from being transmitted to the transceiver element via the sensor housing.

[0035] In a thirtieth aspect, according to aspect 29, the method further includes transmitting an axial force to the surface via a second axial portion, wherein the surface interference buffer rod moves axially toward the acoustic transceiver element.

[0036] In general, the sensor includes: a sensor housing having an inner surface defining a sensor axis and an axially internal sensor housing cavity, the axially internal sensor housing cavity 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 axial 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 perpendicular to the sensor axis, the third cross-sectional area being smaller than the first cross-sectional area; a cavity defined between the inner surface and the third axial buffer portion; and an acoustic transceiver element acoustically fitted to the first end.

[0037] 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 the buffer rod has an axial length that is an integer multiple of approximately n / 2λ. The third cross-sectional region may be approximately half of the first cross-sectional region. The sensor may also include a tubular fluid conduit having a first end and a second end opposite to the first end, and defining a conduit axis arranged such that the conduit axis is substantially aligned with the sensor axis. The sensor may also include another sensor housing having another inner surface defining another sensor axis and another axial internal sensor housing cavity, the cavity including: another first axial sensor housing portion having another first cross-sectional region 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 region larger than the other first cross-sectional region perpendicular to the other sensor axis; and another side 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 buffer rod having another first axial end and an axial end opposite to the other first axial end. The sensor includes a second axial end portion, comprising: another first axial buffer portion disposed within another first housing portion and having another first axial end portion; another second axial buffer portion disposed within another second housing portion and adjacent to another surface, and having another second axial end portion; and another third axial buffer portion extending axially between the other first axial buffer portion and the other second axial buffer portion, and having another third cross-sectional area perpendicular to the other sensor axis and smaller than the other first cross-sectional area; another cavity defined between another inner surface and the other third axial buffer portion, and another acoustic transceiver element acoustically fitted to the other first end portion, wherein the other sensor axis is substantially aligned with the conduit axis. The sensor may also include a fluid housing comprising an inner surface defining an axial fluid housing cavity, a first fluid port in fluid communication with the axial fluid housing cavity, and a second fluid port in fluid communication with the axial fluid housing cavity, wherein a 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 portion, 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 further include another sensor housing having another inner surface defining another sensor axis and another axial internal sensor housing cavity, the cavity 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 larger than the other first cross-sectional area perpendicular to the other sensor axis, and another surface extending from another inner surface of the other first axial housing portion to another inner surface of the other second housing portion; another buffer rod having another first axial end and another second axial end opposite to the other first axial end, and including: another first axial buffer portion disposed within the other first housing portion and having another first axial end; another second axial buffer portion disposed within the other second housing portion and adjacent to the other surface. The sensor comprises: a second axial end; a third axial buffer portion extending axially between the first and second axial buffer portions and having a third cross-sectional area perpendicular to the axis of the first sensor and smaller than the first cross-sectional area; a cavity defined between the second inner surface and the third axial buffer portion; another acoustic transceiver element acoustically fitted to the first end; and a fluid housing having an inner surface defining the cavity of the second axial fluid housing, a first fluid port in fluid communication with the cavity, and a second fluid port in fluid communication with the cavity, wherein a tubular fluid conduit is in fluid communication with the second fluid port and extends axially away from the second fluid housing along the conduit axis at the second end, and a second sensor housing is disposed within the first fluid housing such that the axis of the second sensor is substantially aligned with the conduit axis. The acoustic transceiver element may include a piezoelectric element. The sensor may also include a matching layer fixed to the second end and having a thickness approximately an odd multiple of 1 / 4λ. The sensor may also include a backing adjacent to the acoustic transceiver element and axially opposite to the first end.

[0038] In another general aspect, the sensor system includes a fluid housing having: a first fluid housing portion defining a first axial fluid housing cavity and having a first fluid port in fluid communication with the first axial fluid housing cavity; a second fluid housing portion defining a second axial fluid housing cavity and having a second fluid port in fluid communication with the second axial fluid housing cavity; and a tubular fluid conduit in fluid communication with the first fluid port at a first end and with the 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 cavity and axially aligned with the conduit axis; and a second acoustic transceiver element disposed within the second axial fluid housing cavity and axially aligned with the conduit axis.

[0039] Various embodiments may include some, all, or none of the following features. The sensor system may also 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 the fluid acoustic impedance of the fluid in the 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 sensor may include: a sensor housing having an inner surface defining a sensor axis and an axially internal sensor housing cavity, comprising: 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 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; a cavity defined between the inner surface and the third axial buffer portion; and an acoustic transceiver element acoustically fitted to the first end. The acoustic transceiver element can be configured to emit vibrations having a predetermined wavelength (λ), and the buffer rod can have an axial length that is an integer multiple of approximately n / 2λ. The third cross-sectional region can be approximately half of the first cross-sectional region. The acoustic transceiver element can include a piezoelectric element. The sensor system can also include a matching layer fixed to the second end and having a thickness that is an odd multiple of approximately 1 / 4λ. The sensor system can also include a backing adjacent to the acoustic transceiver element and axially opposite to the first end.

[0040] In another general aspect, a sensing method includes: activating a first transmitter to emit at least one incident wave; emitting the incident wave along a buffer rod having a first axial end adjacent to the first transmitter and a second axial end opposite to the first axial end; reflecting a first echo of the incident wave through a gap defined along a portion of the buffer rod; detecting the first echo; determining a first amplitude of the first echo; reflecting a second echo of the incident wave by the second axial end; detecting the second echo; determining a second amplitude of the second echo; and determining a reflection coefficient based on the first amplitude and the second amplitude.

[0041] Various implementations may include some, all, or none of the following features. The method may also include determining the fluid acoustic impedance of the fluid at the second axial end based on a determined reflection coefficient and a predetermined buffer rod acoustic impedance. The method may further include: at the second axial end, transmitting a portion of an incident wave through the fluid to a sensor arranged at a predetermined distance away 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 incident wave by a second sensor; determining a first time of flight of the detected portion of the incident wave based on the detected portion; transmitting another incident wave through the fluid to the first sensor by the second transmitter; detecting the other incident wave by the first sensor; and determining a second time of flight of the other incident wave based on the detected other incident wave. The method may further include determining at least one of the fluid velocity or the speed of sound within the tubular fluid conduit based on the first time of flight, the second time of flight, and the predetermined distance. The method may further include determining the mass fluid flow rate based on the predetermined cross-sectional area and the determined speed of sound. The second echo, which reflects the incident wave through the second axial end, may also include a second echo reflected through a 1 / 4λ matching layer fixed to the second axial end. One or both of the first transmitter and the first sensor may include a piezoelectric element. The piezoelectric element may include both the first transmitter and the first sensor.

[0042] In another general aspect, a method of 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 cavity 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; and a buffer rod. It has a first axial end and a second axial end opposite to the first axial end, and includes a first axial buffer portion disposed within a first housing portion and having the first axial end, a second axial buffer portion disposed within a 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 perpendicular to the sensor axis and smaller than the first cross-sectional area; and an acoustic transceiver element acoustically fitted to the first end; fluid is provided at the second axial end; and fluid flow from the second end to the acoustic transceiver element is blocked by a buffer rod and the sensor housing.

[0043] Various implementations may include some or all of the following features ， Alternatively, the following features may not be included. Fluid flow from the second end to the transceiver element may be blocked by the sensor housing and the second axial buffer portion. The method may further include: applying fluid pressure to the second axial end to generate an axial force on the buffer rod; transmitting the axial force to the sensor housing through the buffer rod; and preventing the transmission of the axial force to the transceiver element through the sensor housing. The method may further include transmitting the axial force to a surface through the second axial portion, wherein the surface interferes with the axial movement of the buffer rod toward the transceiver element.

[0044] The system and technology 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 enhances survivability in harsh fluid environments. Fourth, the system provides overall 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.

[0045] Details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features and advantages will become apparent from the specification, the drawings, and the claims. Attached Figure Description

[0046] Figure 1 This is a cross-sectional view of an example ultrasonic flow measurement system.

[0047] Figure 2A yes Figure 1 A cross-sectional view of an example ultrasonic sensor module for a system.

[0048] Figure 2B It shows Figure 2A A conceptual example of a reflective surface region in an example ultrasonic sensor module.

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

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

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

[0052] Figure 6A and 6B It is shown Figure 1 Example incident wave and echo curves 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 This shows the resistance to fluid exposure. Figure 2A 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 fluids. Generally, the USFM system described herein can be used in fluid environments that would degrade or destroy existing USFMs. Fluid environment conditions in fuel delivery systems present significant design challenges. For current-level 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 to 325 degrees Fahrenheit or higher).

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

[0059] Existing USFMs for industrial and closed-loop transportation based on time-of-flight, cross-correlation, and phase shift measurements have accuracy limitations determined by the velocity range or control 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 is affected by flow instability, which is typically caused by the acoustic path being off-axis relative to the flow, flow separation, and / or non-axisymmetric flow conditions. Off-axis transducer configurations also lead to sensitivity and accuracy issues. Circular transducers generate non-uniform ultrasonic fields when ultrasound passes 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 penetrated by sound and must therefore be estimated, typically using a single K-factor correction value or a complex coefficient matrix of the USFM with multiple acoustic paths, as in closed-loop gas transportation applications. In existing USFM designs, maintaining flow measurement accuracy is difficult at large control ratios when the flow regime is unstable or changes significantly from laminar to turbulent. For example, some existing industrial USFMs have an actual control ratio of no more than 50:1 while maintaining accuracy, even when application piping and flow regulation are ideally performed. In contrast, gas turbine fuel systems may require much higher regulation ratios, typically 100:1, and in some applications as high as 350:1 or higher. Furthermore, gas turbine flow measurement systems must be able to maintain dynamic accuracy with 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, excessive air / fuel can cause compressor failure. Any of these events is 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% over the expected temperature range and the available fuel types. Without knowing the wide range of fuel densities, a given volumetric flow rate will drive a wide range of fuel mass flow rates. This variability leads to large variations in the mass air / fuel flow ratio, resulting in inefficient engine design across the entire environmental range, oversized engines, conservative acceleration and / or deceleration schemes, excessive surge margins, and / or excessive shutdown 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 cavity 120a defined by an inner surface 121a and an axial fluid housing cavity 120b defined by an inner surface 121b. A fluid port 122a defines a fluid path 124a connected to the fluid cavity 120a. A fluid port 122b defines a fluid path 124b connected to the fluid cavity 120b. The fluid housing 110 also defines a cavity 126 extending between the fluid cavities 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 embodiments, the fluid housing 110 can be used for a variety of applications, and the fluid control conduit 130 can be an interchangeable dedicated sub-component (e.g., an adapter) that allows the USFM system 100 to be adapted to specific fluid types, applications, and / or operating conditions.

[0064] Now for reference Figure 2A , showed Figure 1An 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 cavity 204 and a sensor axis 206 defined by an inner surface 207. When the ultrasonic sensor module 200 is assembled to... 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 region 209a perpendicular to the sensor axis 206. The sensor housing 202 also has an axial sensor housing portion 208b having a cross-sectional region 209b perpendicular to the sensor axis 206. The cross-sectional region 209b is larger in size than the cross-sectional region 209a. A surface 210 extends from the inner surface 207 of the axial sensor housing portion 208a to the inner surface 108 of the axial sensor housing portion 208b. In the example shown, the surface 210 is formed as a substantially square shoulder or crossbar at the transition between the cross-sectional regions 209a and 209b. In some embodiments, the surface 210 may be a tapered or non-square transition between the cross-sectional regions 209a and 209b.

[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] The transceiver element 230 is acoustically mated or otherwise abutted to the axial end 252 of the buffer rod 250 via a bonding layer 232. In some embodiments, the bonding layer 232 may be an adhesive layer. In some embodiments, the buffer rod may be made of any suitable material or combination of materials that, when combined with the mating layer material, provides 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 rod 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).

[0067] In some embodiments, the bonding layer 232 may be omitted, and the transceiver element 230 is in direct contact with the axial end portion 252. For example, the transceiver element 230 may be held in place by a mechanical clamp or other suitable securing assembly, or the transceiver element 230 may be held in place by a securing feature formed in the inner surface 207. In some embodiments, the bonding layer 232 may be formed of a highly ductile material, such as gold or lead, which may conform to the mating surfaces of the transceiver element 230 and the axial end portion 252.

[0068] The transceiver element 230 is supported by a backing 234. The backing 234 has a predetermined shape and is made of a material that improves the sensitivity and / or efficiency of the transceiver element 230.

[0069] A 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 buffer rod 250 has a predetermined axial length that is approximately an integer multiple (n / 2λ) of half the transmission wavelength of the transceiver element 230. The buffer rod 250 includes an axial buffer portion 256a disposed within the axial sensor housing portion 208a and includes an axial end 252. The buffer rod 250 includes an axial buffer portion 256b disposed within the axial sensor housing portion 208b and includes an axial end 254. In some embodiments, the axial buffer portion 256b may contact the inner surface directly or indirectly (e.g., through a seal, sleeve, or bonding material) to substantially seal the sensor cavity 204, preventing fluid intrusion at the axial end 254.

[0070] The buffer rod 250 also includes an axial buffer portion 256c extending axially between axial buffer portions 256a and axial buffer portions 256b. The cross-sectional area 209c of the axial buffer portion 256c is smaller than the cross-sectional area 209a perpendicular to the sensor axis 206. A cavity 260 is defined between the inner surface 207 and the axial buffer portion 256c. The cavity 260 is partially defined by a surface 262 defined between the axial buffer portions 256a and axial buffer portions 256c. The surface 262 is at a predetermined distance from the axial end 252. (Reference) Figure 2B Cross-sectional region 209a is approximately twice the size of cross-sectional region 209c. In other words, the area within the axial buffer portion 256c is approximately the same as the area of ​​surface 262.

[0071] The buffer rod 250 has a predetermined acoustic impedance (Z). 缓冲In the illustrated example, cavity 260 is filled with air (e.g., an air gap), fluid (e.g., oil), or a solid whose acoustic impedance is sufficiently different from that of the buffer rod 250 to reflect an acoustic echo when struck by a sound wave (e.g., an ultrasonic ping). In some embodiments, cavity 260 is evacuated to create at least a partial vacuum.

[0072] In the illustrated example, the axial buffer portion 256a is partially tapered and covered by a cladding 270. This tapered portion has a predetermined shape configured to improve the efficiency and / or sensitivity of the ultrasonic sensor module 200 by guiding the propagation of the incident wave. The cladding 270 is configured to improve the efficiency and / or sensitivity of the ultrasonic sensor module 200 by guiding the propagation of the incident wave, acoustically isolating the buffer rod 250 from the sensor housing 202, and / or thermally isolating the buffer rod 250 from the sensor housing 202. In some embodiments, the tapered portion, the cladding, or both may be omitted. In some embodiments, other portions of the buffer rod 250 may include a cladding.

[0073] Refer again Figure 2A The ultrasonic sensor module 200 includes a mating layer 280 that acoustically engages, is fixed to, or otherwise abuts the axial end 252 of the buffer rod 250. In some embodiments, the mating layer 280 may be adhered to the axial end 252. In some embodiments, a portion of the mating layer 280 may extend into the sensor housing 202 and be fixed (e.g., welded) to it. 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 cavity 204, preventing fluid intrusion at the axial end 254. The axial thickness of the mating layer 280 is approximately an integer multiple (n / 4λ) of the transmission wavelength of the acoustic transceiver element 230, for example, 1 / 4λ.

[0074] Refer again Figure 1 Two ultrasonic sensor modules 200 span the fluid control conduit 130, facing each other. The acoustic transducer elements of the ultrasonic sensor modules 200 are separated by a predetermined distance 150.

[0075] USFM system 100 includes controller 190. Controller 190 includes circuitry configured to activate ultrasonic sensor module 200 such that an incident acoustic wave is emitted, detect the reception of ultrasonic waves at ultrasonic sensor module 200, measure the timing between the emission and reception of various combinations of direct and reflected acoustic waves, and / or determine, in part, the various properties of USFM system 100 and / or the fluid based on those measured timings. Figure 3-9 Further discussion will follow in the description.

[0076] In use, fluid flows through the USFM system 100. For example, a fluid such as fuel can be supplied at fluid port 122a, where it will flow 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 the properties of the fluid, such as acoustic impedance and mass flow rate.

[0077] Figure 3 It shows Figure 2A A conceptual example of incident wave propagation in an ultrasonic sensor module 200. In use, an acoustic transceiver element 230 is activated to emit an incident wave (e.g., an acoustic pulse). The incident wave is transmitted into and along a buffer rod 250. A portion of the incident wave, indicated by arrow 310, travels until it encounters a surface 262. The engagement of surface 262 and cavity 260 causes a portion of the incident wave 310 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 receivers for emitting and detecting the incident wave.

[0078] Another portion of the incident wave, indicated by arrow 330, travels until it encounters the axial end 254. The engagement of the axial end and the fluid 301 at the axial end 254 causes a portion of the incident wave 330 to be reflected as an echo, indicated by arrow 340. The echo 340 travels back to be detected by the acoustic transceiver element 230. Another portion of the incident wave, indicated by arrow 350, propagates into the fluid 301 at the axial end 254.

[0079] Measure the time between the propagation of the incident wave and the detection of the echo 320 (e.g., via...). Figure 1 Example controller 190) is used to determine the first flight time. The time between the transmission of the incident wave and the detection of the echo 340 is measured to determine the second flight time. The amplitudes of the echoes 320 and 340 are also measured. As will be... Figure 6A-7 As further discussed in the description, the measured time of flight, the measured echo amplitude, and the predetermined information regarding the acoustic impedance of the buffer rod 250 and the predetermined distance between the transceiver element 230, the surface 262, and the axial end 254 can be used to determine the properties of the fluid 301 at the axial end 254, such as the acoustic impedance (Z). 流体 ) and / or the speed of sound in the fluid (C 流体 ).

[0080] 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 or immersed in a tank, pipe, or other fluid container or volume) and can be acoustically 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.

[0081] In some embodiments, the characteristics of the buffer rod 250 itself can be determined based on measured flight time and / or measured echo amplitude (e.g., to calibrate unknown buffer rod acoustic impedance and / or compensate for the effects of temperature variations on the ultrasonic sensor module 200). Similarly, in some embodiments, the distance between the transceiver element 230 and one or both of the face 262 and / or axial end 254 can be determined based on measured flight time, measured echo amplitude, known distance, known buffer rod acoustic impedance, and / or known buffer rod temperature.

[0082] Figure 4 It shows Figure 2A 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 its axial end 254. In some embodiments, the temperature or chemical properties of the fluid 301 may damage the transceiver element 230, therefore the ultrasonic sensor module 200 is configured to prevent direct contact between the fluid 301 and the transceiver element 230. For example, direct or indirect (e.g., via gaskets, sleeves, cladding, seals, or sealants) contact between the axial buffer portion 256b and the axial sensor housing portion 208b and / or between the buffer rod 250 and the face 210 can substantially block fluid flow from the axial end 254 to the transceiver element 230. In some embodiments, fluid leakage through the buffer rod 250 can be directed to the sensor cavity 204 without contacting the main face of the transceiver element 230.

[0083] 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 create a compressive force on the acoustic transceiver element 230, which can cancel out or otherwise negatively affect the signal provided by the acoustic transceiver element 230 in response to the sensed acoustic signal. In some embodiments, this effect can be mathematically compensated for by an electrically offset sensor signal to recover an approximation of the true signal.

[0084] 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 is acoustically fitted to the axial end 252. In this way, the acoustic transceiver element 230 can "float" on the buffer rod 250 relative to the sensor housing 202 and will not be compressed by the fluid pressure 410.

[0085] The transceiver element 230 is also protected from the fluid pressure 410 by the mechanical configuration of the buffer rod 250 and the sensor housing 202. The fluid pressure 410 is applied to the axial end 254, which causes the buffer rod 250 to move into the sensor cavity 204. The pressure causing this movement is indicated by arrow 420. The movement of the buffer rod 250 is stopped by the contact between the axial buffer portion 256b and the surface 210 of the sensor housing 202, as indicated by arrow 430. Thus, the force 420 is prevented from reaching the transceiver element 230.

[0086] The smaller cross-sectional region 209a is sized to accommodate the acoustic transceiver element 230 and decouples the thermal expansion of the sensor housing 202 from the acoustic path. The larger cross-sectional region 209b is sized to accommodate the pressure-sensitive force acting on the buffer rod 250. Transmitting the force to the sensor housing 202 essentially eliminates the pressure-sensitive force acting on the acoustic transceiver element 230, and essentially eliminates the need for pressure compensation, transducer components sized to react to the pressure-sensitive force, and / or wet transducer design constraints.

[0087] Several advantages can be 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 the thickness requirements driven by the pressure-sensing force. In another example where the acoustic transceiver element 230 is a piezoelectric transducer, the piezoelectric thickness required to support the fluid pressure makes the operating frequency of the acoustic transceiver element 230 much lower than the operating requirements for time-of-flight measurements. In yet another example, the magnitude of the operating frequency of the acoustic transceiver element 230 can be set to improve acoustic optimization and / or accuracy in low-flow-rate measurements.

[0088] Figures 5A-5C A conceptual example of incident wave traversal in an ultrasonic flow measurement system 500 is shown. In some embodiments, the USFM system 500 may be... Figure 1 An 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.

[0089] The following derivation assumes that acoustic receivers 512a and 512b are aligned with their corresponding acoustic emitters 510a and 510b, perpendicular to the main axis of the fluid control conduit 520. 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, trigonometry used to compensate for this angle is not employed here.

[0090] refer to Figure 5A First, consider the speed at which sound travels through a non-moving fluid: Distance = Speed ​​× Time or: Among them, 𝐶 流体 It is the speed of sound in a fluid. L 1 It is the distance between the sound transmitter 510a and the sound receiver 512a, and t 1 It is the signal transmission time between the acoustic transmitter 510a and the acoustic receiver 512a.

[0091] Assuming that the direction 501 of the control volume (fluid) movement is the same as the direction of sound travel, represented by line 502a from sound emitter 510a to sound receiver 512a, the speed of the sound wave traveling through the fluid will change relative to the speed of the fluid.

[0092] in V 流体 It is the average velocity of the moving fluid. L 2 It is the distance between the sound transmitter 510a and the sound receiver 512a, and t 2 It is the signal transmission time between the acoustic transmitter 510a and the acoustic receiver 512a.

[0093] Now for reference Figure 5B Assuming the control volume (fluid) is opposite to the direction in which sound travels from the sound transmitter 510b to the sound receiver 512b, as represented by line 502b. The speed at which the sound wave travels through the fluid will change relative to the velocity of the fluid.

[0094] in L 3 t3 is the distance between the acoustic transmitter 510b and the acoustic receiver 512b, and t3 is the signal transmission time between the acoustic transmitter 510b and the acoustic receiver 512b.

[0095] 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 上 = L 下 = L = distance between transmitters; D = diameter; therefore, the area of ​​the fluid control conduit 520. A = Cross-sectional area; C 流体 =Speed ​​of sound in a fluid; V 流体 =Fluid velocity; ρ 流体 =Fluorite density; Z 流体 =Acoustic impedance of the fluid.

[0096] By utilizing the aforementioned shared characteristics, the time difference between upstream and downstream signals will allow for the calculation of various fluid properties.

[0097] The upstream and downstream transmission times become: Solve t 上 、t 下 and C 流体 ： Since the speed of sound is the same across the transducers, the speeds of sound are equal to each other, allowing the fluid velocity to be derived: Knowing the velocity of the fluid allows us to determine the volumetric fluid flow rate. Q 流体 ),in C d It is the predetermined discharge coefficient of the fluid in the fluid control conduit 520: It is also possible to determine the properties of fluid sound velocity. Because the fluid velocity is shared between a pair of transducers, the fluid velocity can be solved. (Recall:) and: Solve for V 流体 of t 上 and t 下 : Since the fluid velocity is the same across the sensors, the first two equations are equal to each other, allowing the solution for the fluid sound velocity: Figure 6A and 6B It is shown Figure 1 Example incident wave and echo curves in an ultrasonic flow measurement system. Figure 6A A graph 600 showing the change of sound amplitude over time is shown, including sub-durations 601. Figure 6B The graph 602 is shown, in which the sub-duration 601 has been expanded for visibility.

[0098] Graph 600 shows a representation of the transmission of the initial incident wave 610 (e.g., when the acoustic transceiver element 230 is activated to transmit an acoustic “sound pulse”). An echo 620 is received a few milliseconds later. In some embodiments, the echo 620 may be… Figure 3 The echo 320 is a reflection of a portion of the incident wave 310 leaving the surface 262 of the cavity 260.

[0099] Echo 630 is received a few milliseconds later. In some implementations, echo 630 may be echo 340, which is a reflection of a portion of the incident wave 330 leaving the axial end 254, which is also the interface to the fluid. Echoes 640, 650, and 660 represent echoes within the buffer rod 250. In operation, echoes 640-660 may be filtered out or otherwise ignored.

[0100] Incident wave 670 represents a portion of the incident wave received by an acoustic sensor (e.g., an acoustic transceiver element 230 located downstream or opposite to the emitting incident wave). The amount of time taken for incident wave 670 to arrive is influenced by several variables, such as the fluid density, velocity, and direction of the fluid in the fluid control conduit 130, and the distance 150 from the acoustic sensor. The amount of time taken for incident wave 670 to arrive can be used as t. 上 or t 下 (For example, depending on whether the wave travels upstream or downstream in the fluid control conduit 130).

[0101] like Figure 4As shown, the buffer rod 250 is designed to transmit pressure-sensitive forces to surface 210 of the sensor housing 202. This is achieved through a dual-diameter configuration of the buffer rod 250, where the smaller cross-sectional area is sized to accommodate the acoustic transceiver element 230 and decouple the thermal expansion of the sensor housing 202 from the acoustic path. The larger cross-sectional area of ​​the axial buffer portion 256b is sized to accommodate the pressure-sensitive forces acting on the buffer rod 250. Transmitting the force to the sensor housing 202 essentially eliminates the pressure-sensitive forces acting on the acoustic transceiver element 230 and essentially eliminates the need for pressure compensation (e.g., piezoelectric ceramics) to adjust the magnitude of the pressure-sensitive forces, and essentially avoids the constraints of wet transducer design.

[0102] Several advantages can be 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 sensing force, 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 magnitude of the acoustic transducer frequency can be set for acoustic optimization and low flow measurement accuracy.

[0103] For aircraft turbine fuel systems, the mass fuel flow rate can be determined to understand the combustion energy content. This can be achieved using a buffer bar 250. The internal design of the buffer bar 250 enables additional acoustic benefits that can be intentionally incorporated into the USFM system 100. For example, the configuration of the buffer bar 250 allows the controller 190 to determine the reflection coefficient for fuel acoustic impedance measurements. This is achieved by introducing a transducer emission amplitude response (e.g., echo 320 or 620) using the cavity 260, 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 bar. In some embodiments, the matching layer 280 further enhances the sensitivity of the axial end 254; however, this will be ignored for the sake of simplicity in the equations below.

[0104] The fluid acoustic 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 regions 209a and 209c. In some embodiments, the areas may not be equal, and mathematical compensation can be integrated into the process. However, for clarity, the areas are assumed to be 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 262 is equivalent to the echo from axial end 254.

[0105] The reflection coefficient was obtained using a short-time Fourier transform (STFT). A fast Fourier transform (FFT) was then performed on the two echoes to determine the peak values ​​of the returned echoes. therefore: in: Echo 1 is respectively Figure 3 and 6A -6B echoes are either 320 or 620, echo 2 are respectively Figure 3 and 6A The echo of -6B is either 340 or 630, and f and f0 are the transducer drive frequencies. The reflection coefficient is obtained from the following formula: Furthermore, it is assumed that the buffer bar 250 is in direct interface contact with the fluid or fuel (e.g., in this case, there is no mating layer 280): Where R is the reflection coefficient.

[0106] The impedance of the buffer rod 250 can be determined through sensor-level characterization. The fluid impedance can be solved using the known buffer rod impedance and the measured reflection coefficient. From the equation above, 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.

[0107] Clearly: Given the volumetric fluid flow rate and density, the mass fluid flow rate can be obtained: Figure 7 This is a flowchart illustrating an example of a process 700 for determining the fluid reflection coefficient. In some embodiments, process 700 can be performed by... Figure 1-2B The example ultrasonic sensor module 200 is used.

[0108] At 710, the first transmitter is activated to transmit at least one incident wave. For example, the example acoustic transceiver element 230 can be activated to transmit an incident wave.

[0109] At 720, the incident wave propagates along a buffer rod having a first axial end adjacent to the first transmitter and a second axial end opposite to the first axial end. For example, the incident wave can propagate through the buffer rod 250.

[0110] At 730, the first echo of the incident wave is reflected along a gap defined by a portion of the buffer rod. For example, a portion of the incident wave 310 may encounter surface 262 of cavity 260 and be reflected as echo 320.

[0111] At 740, the first echo is detected. For example, it can be detected... Figure 6A and 6B The echo is 620.

[0112] 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).

[0113] At 760, the second axial end reflects a second echo of the incident wave. For example, a portion of the incident wave 330 is reflected as echo 340 away from the axial end 254. In some embodiments, the second echo can be reflected by a 1 / 4λ matching layer fixed to the second axial end, for example, matching layer 280 at the axial end 254.

[0114] At 770, the second echo is detected. For example, it can be detected... Figure 6A and 6B The echo is 630.

[0115] 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).

[0116] At 790, the reflection coefficient can be determined based on the first and second amplitudes. For example: Figure 8 This is a flowchart illustrating an example of a process 800 for determining mass fluid flow rate. In some embodiments, process 800 can be performed by... Figure 1 Example USFM system 100 is used.

[0117] At 805, the reflection coefficient value is received. For example, the reflection coefficient R determined at 790 can be received.

[0118] In step 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, as described above, the reflection coefficient R can be related to the predetermined buffer rod impedance Z. 缓冲 Together used to determine Z 流体.

[0119] At 815, a portion of the incident wave is transmitted to a sensor via fluid at the second axial end. This sensor is positioned at a predetermined distance from and opposite the first transmitter, wherein the fluid is contained 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 through the fluid to the downstream ultrasonic sensor module 200.

[0120] At 820, the second sensor detects a portion of the incident wave. For example, the downstream ultrasonic sensor module 200 can detect the incident wave 670.

[0121] At 825, the first flight time of the incident wave is determined based on the detected incident wave portion. For example, t can be determined. 下 .

[0122] At 830, the second transmitter transmits another incident wave to the first sensor via fluid. For example, the downstream ultrasonic sensor module 200 can be activated to transmit another incident wave upstream.

[0123] At 835, the first sensor detects another incident wave, and at 840, based on the detected other incident wave, the second time of flight of the other incident wave is determined. For example, t can be determined. 上 .

[0124] In 845, determine the fluid velocity within the tubular fluid conduit. For example, V 流体 It can be determined as follows: At 850, determine the speed of sound within the fluid. For example, C 流体 It can be determined as follows: At 855, the mass fluid flow rate is determined based at least on a predetermined cross-sectional area, a defined fluid velocity, a defined fluid acoustic impedance, and a defined sound velocity. For example: In some embodiments, one or both of the first transmitter and the first sensor may be a piezoelectric element. In some embodiments, 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.

[0125] Figure 9 This shows the resistance to fluid exposure. Figure 1-4A flowchart illustrating an example of the process of the effect of the acoustic transceiver element 230 of an example ultrasonic sensor module 200 is provided at 900. 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 cavity 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 perpendicular to the sensor axis smaller than the first cross-sectional area; and an acoustic transceiver element acoustically mated to the first end. For example, an ultrasonic sensor module 200 can be provided.

[0126] At 920, fluid is provided at the second axial end. For example, fluid 301, such as fuel, may be provided in fluid chambers 120a or 120b to contact the axial end 254.

[0127] In 930, the buffer rod and sensor housing obstruct fluid flow from the acoustic transceiver element at the second end. For example, as in Figure 4 As discussed in the description, the transceiver element 230 is separated from the fluid 301 by the sensor housing 202 and the buffer rod 250, and the sensor housing 202 and the buffer rod 250 are configured to prevent the fluid 301 from flowing to the transceiver element 230.

[0128] In some embodiments, fluid flow from the second end to the transceiver element can be blocked by the sensor housing and the second axial buffer portion. For example, the flow of fluid 301 to the transceiver element 230 is prevented by the interference between the sensor housing 202 and the axial buffer portion 256b.

[0129] 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.

[0130] 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.

[0131] At 960, the sensor housing prevents axial forces from being transmitted to the transceiver element. In some embodiments, process 900 may further include transmitting the axial force to a surface via a second axial portion, wherein the surface interferes with axial movement of the buffer rod toward the transceiver element. For example, a reaction force 430 generated by contact between the axial buffer portion 256b and the surface 210 prevents any movement of the buffer rod 250 into the sensor cavity 204.

[0132] Figure 10 This is a schematic diagram of an example of a general-purpose computer system 1000. According to one implementation, system 1000 can be used for the operations described in conjunction with processes 700, 800, and / or 900. For example, system 1000 may be included in controller 190.

[0133] 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 using a system bus 1050. The processor 1010 is capable of processing instructions that execute within system 1000. In one embodiment, the processor 1010 is a single-threaded processor. In another embodiment, the processor 1010 is a multi-threaded processor. The processor 1010 is capable of processing instructions stored in the memory 1020 or the storage device 1030 to display graphical information for a user interface on the input / output device 1040.

[0134] The memory 1020 stores information within the system 1000. In one embodiment, the memory 1020 is a computer-readable medium. In one embodiment, the memory 1020 is a volatile memory cell. In another embodiment, the memory 1020 is a non-volatile memory cell.

[0135] Storage device 1030 provides large-capacity storage for system 1000. In one embodiment, storage device 1030 is a computer-readable medium. In various other embodiments, storage device 1030 may be a floppy disk device, a hard disk device, an optical disk device, or a magnetic tape device.

[0136] Input / output device 1040 provides input / output operations for system 1000. In one embodiment, input / output device 1040 includes a keyboard and / or a pointing device. In another embodiment, input / output device 1040 includes a display unit for displaying a graphical user interface.

[0137] The described features can be implemented in digital electronic circuits or computer hardware, firmware, software, or combinations thereof. The device can be implemented in a computer program product tangibly contained in an information carrier, such as a machine-readable storage device, for execution by a programmable processor; and the method steps can be executed by a programmable processor executing an instruction program to perform the functions of the described embodiments by manipulating input data and generating output. The described features can advantageously be implemented in one or more computer programs that can be executed on a programmable system including at least one programmable processor coupled to receive and send data and instructions from a data storage system, at least one input device, and at least one output device. A computer program is a set of instructions that can be used directly or indirectly in a computer to perform a specific activity or produce a specific 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.

[0138] As an example, suitable processors for executing instruction programs include both general-purpose and special-purpose microprocessors, as well as one or more processors in any kind of computer. Typically, 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 containing computer program instructions and data include all forms of non-volatile memory, such as semiconductor storage devices, such as EPROM, EEPROM, and flash memory devices; disks, such as internal hard disks and removable disks; magneto-optical disks; and DVD-ROM disks. The processor and memory may be supplemented or incorporated into ASICs (Application-Specific Integrated Circuits).

[0139] To provide interaction with the user, these features can be implemented on a computer that has a display device for displaying information to the user, such as a CRT (cathode ray tube) or LCD (liquid crystal display) monitor, and a keyboard and pointing device, such as a mouse or trackball, that the user can use to provide input to the computer.

[0140] 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 digital data communication of any form or medium, such as a communication network. Examples of communication networks include, for example, LANs, WANs, and the computers and networks that form the Internet.

[0141] Computer systems can include clients and servers. Clients and servers are typically geographically separated and usually interact via networks such as those described. The client-server relationship arises from computer programs running on their respective computers and having a client-server relationship with each other.

[0142] While some implementations have been described in detail above, other modifications are possible. Furthermore, the logical flow shown in the figures does not require the specific or sequential order to achieve the desired result. Additionally, other steps may be provided, or steps may be removed from the described flow, and other components may be added to or removed from the described system. Therefore, other implementations are also within the scope of the following claims.

Claims

1. A sensor, comprising: A sensor housing having a first inner surface defining a sensor axis and an axially internal sensor housing cavity, comprising: The first axial sensor housing portion has a first cross-sectional area perpendicular to the sensor axis; The second axial sensor housing portion is arranged adjacent to the first axial sensor housing portion along the sensor axis and has a second cross-sectional area larger than the first cross-sectional area perpendicular to the sensor axis; and A first surface extending from the first inner surface of the first axial sensor housing portion to the first surface of the second inner surface of the second axial sensor housing portion; A buffer rod having a first axial end and a second axial end opposite to the first axial end, and comprising: A first axial buffer portion is disposed within a first axial sensor housing portion and includes a first axial end portion; A second axial buffer portion, disposed within and adjacent to the second inner surface of the second axial sensor housing portion, and including a second axial end portion; and A third axial buffer portion extends axially between the first axial buffer portion and the second axial buffer portion, and has a third cross-sectional area perpendicular to the sensor axis, the third cross-sectional area being smaller than the first cross-sectional area. A cavity, defined between the first inner surface and the third axial buffer portion, and partially defined by a second surface defined between the first axial buffer portion and the third axial buffer portion; and An acoustic transceiver element that is acoustically fitted to the first axial end.

2. The sensor according to claim 1, wherein, The transceiver element is configured to emit vibrations with a predetermined wavelength λ, and the buffer rod has an axial length that is an integer multiple of approximately n / 2λ.

3. The sensor according to claim 1 or 2, wherein, The third cross-sectional region is approximately half the size of the first cross-sectional region.

4. The sensor according to claim 1 or 2 further includes a tubular fluid conduit having a first conduit end and a second conduit end opposite to the first conduit end, and defining a conduit axis arranged such that the conduit axis is aligned with the sensor 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 cavity, includes: Another first axial sensor housing portion has another first cross-sectional area perpendicular to another sensor axis; Another second axial sensor housing portion, arranged adjacent to another first axial sensor housing portion along another sensor axis, and having another second cross-sectional area, said second cross-sectional area being larger than the other first cross-sectional area perpendicular to the other sensor axis; and On the other hand, it extends from another inner surface of another first axial sensor housing portion to another inner surface of another second axial sensor housing portion; Another buffer rod, having another first axial end and another second axial end opposite to the other first axial end, and comprising: Another first axial buffer portion is disposed within another first axial sensor housing portion and includes another first axial end portion; Another second axial buffer portion, which is disposed within another second axial sensor housing portion and adjacent to another face, and includes another second axial end; and Another third axial buffer portion extends axially between another first axial buffer portion and another second axial buffer portion, and has another third cross-sectional area that is perpendicular to the axis of another sensor and smaller than the other first cross-sectional area; Another cavity is defined between another inner surface and another third axial buffer portion; and Acoustically fitted to another acoustic transceiver element at the other first axial end; The axis of another sensor is aligned with the axis of the conduit.

6. The sensor according to claim 4, further comprising: Fluid housing, comprising: The inner surface of the fluid housing that defines the axial fluid housing cavity; A first fluid port in fluid communication with the axial fluid housing cavity; and A second fluid port that is in fluid communication with the axial fluid housing cavity; 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 end of the first conduit. The sensor housing is disposed within the fluid housing such that the sensor axis is aligned with the conduit axis.

7. The sensor according to claim 6, further comprising: Another sensor housing, having another inner surface defining another sensor axis and another axial internal sensor housing cavity, includes: Another first axial sensor housing portion has another first cross-sectional area perpendicular to another sensor axis; Another second axial sensor housing portion, arranged adjacent to another first axial sensor housing portion along another sensor axis, and having another second cross-sectional area, said second cross-sectional area being larger than the other first cross-sectional area perpendicular to the other sensor axis; and On the other hand, it extends from another inner surface of another first axial sensor housing portion to another inner surface of another second axial sensor housing portion; Another buffer rod, having another first axial end and another second axial end opposite to the other first axial end, and comprising: Another first axial buffer portion is disposed within another first axial sensor housing portion and includes another first axial end portion; Another second axial buffer portion, which is disposed within another second axial sensor housing portion and adjacent to another face, and includes another second axial end; and Another third axial buffer portion extends axially between another first axial buffer portion and another second axial buffer portion, and has another third cross-sectional area that is perpendicular to the axis of another sensor and smaller than the other first cross-sectional area; Another cavity is defined between another inner surface and another third axial buffer portion; Acoustically coupled to another transceiver element at the other first axial end; and Another fluid housing includes: Another fluid housing inner surface that defines another axial fluid housing cavity; Another first fluid port in fluid communication with another axial fluid housing cavity; and Another second fluid port is in fluid communication with another axial fluid housing cavity; The tubular fluid conduit is in fluid communication with another second fluid port and extends axially away from another fluid housing along the conduit axis at the end of the second conduit. Another sensor housing is disposed within the other fluid housing such that the axis of the other sensor is aligned with the axis of the conduit.

8. The sensor according to claim 1 or 2, wherein, The acoustic transceiver components include piezoelectric elements.

9. The sensor according to claim 1 or 2, further comprising a matching layer fixed to the second axial end and having a thickness of approximately 1 / 4λ (an odd multiple of the thickness).

10. The sensor according to claim 1 or 2, further comprising a backing, the backing being adjacent to the acoustic transceiver element and axially opposite to the first axial end.

11. The sensor according to claim 5, further comprising: Fluid housing, comprising: The inner surface of the fluid housing that defines the axial fluid housing cavity; A first fluid port in fluid communication with the axial fluid housing cavity; and A second fluid port that is in fluid communication with the axial fluid housing cavity; 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 end of the first conduit. The sensor housing is disposed within the fluid housing such that the sensor axis is aligned with the conduit axis.

12. The sensor according to claim 11, Another sensor housing, having another inner surface defining another sensor axis and another axial internal sensor housing cavity, includes: Another first axial sensor housing portion has another first cross-sectional area perpendicular to another sensor axis; Another second axial sensor housing portion is arranged adjacent to another first axial sensor housing portion along another sensor axis and has another second cross-sectional area, which is larger than the other first cross-sectional area perpendicular to the other sensor axis; and On the other hand, it extends from another inner surface of another first axial sensor housing portion to another inner surface of another second axial sensor housing portion; Another buffer rod, having another first axial end and another second axial end opposite to the other first axial end, and comprising: Another first axial buffer portion is disposed within another first axial sensor housing portion and includes another first axial end portion; Another second axial buffer portion, which is disposed within another second axial sensor housing portion and adjacent to another face, and includes another second axial end; and Another third axial buffer portion extends axially between another first axial buffer portion and another second axial buffer portion, and has another third cross-sectional area that is perpendicular to the axis of another sensor and smaller than the other first cross-sectional area; Another cavity is defined between another inner surface and another third axial buffer portion; Acoustically coupled to another transceiver element at the other first axial end; and Another fluid housing includes: Another fluid housing inner surface that defines another axial fluid housing cavity; Another first fluid port in fluid communication with another axial fluid housing cavity; and Another second fluid port is in fluid communication with another axial fluid housing cavity; The tubular fluid conduit is in fluid communication with another second fluid port and extends axially away from another fluid housing along the conduit axis at the end of the second conduit. Another sensor housing is disposed within the other fluid housing such that the axis of the other sensor is aligned with the axis of the conduit.

13. The sensor according to claim 4, wherein, The acoustic transceiver components include piezoelectric elements.

14. The sensor according to claim 6, wherein, The acoustic transceiver components include piezoelectric elements.

15. A sensor system, comprising: Fluid housing, comprising: A first fluid housing portion defines a first axial fluid housing cavity and includes a first fluid port in fluid communication with the first axial fluid housing cavity; The second fluid housing portion defines a second axial fluid housing cavity and includes a second fluid port in fluid communication with the second axial fluid housing cavity; and A tubular fluid conduit, which is in fluid communication with a first fluid port at a first end and with a second fluid port at a second end opposite to the first end, and defines the conduit axis; A first sensor is disposed within the first axial fluid housing cavity and axially aligned with the conduit axis; and The second sensor is disposed within the second axial fluid housing cavity and axially aligned with the conduit axis. Wherein, one or both of the first sensor or the second sensor include: A sensor housing having a first inner surface defining a sensor axis and an axially internal sensor housing cavity, 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 larger than a first cross-sectional area perpendicular to the sensor axis; and A first surface extending from the first inner surface of the first axial sensor housing portion to the second inner surface of the second axial sensor housing portion; A buffer rod having a first axial end and a second axial end opposite to the first axial end, and comprising: A first axial buffer portion is disposed within the first axial sensor housing portion and includes a first axial end portion; A second axial buffer portion, disposed within and adjacent to the second inner surface of the second axial sensor housing portion, and including the second axial end portion; and A third axial buffer portion extends axially between the first axial buffer portion and the second axial buffer portion, and has a third cross-sectional area perpendicular to the sensor axis, the third cross-sectional area being smaller than the first cross-sectional area. A cavity, defined between the first inner surface and the third axial buffer portion, and partially defined by a second surface defined between the first axial buffer portion and the third axial buffer portion; and An acoustic transceiver element that is acoustically fitted to the first axial end.

16. The sensor system of claim 15, further comprising circuitry configured to: Activate the first sensor to emit the first incident wave; Activate the second sensor to emit the second incident wave; The echo of the first incident wave is detected by the first sensor; The fluid acoustic impedance of the fluid in the tubular fluid conduit is determined based on the echo. At least a first portion of the first incident wave is detected by the second sensor; Determine the first flight time of the first part; At least a second portion of the second incident wave is detected by the first sensor; Determine the second flight time for the second part; and The mass fluid flow rate is determined based on the determined fluid acoustic impedance, the determined first flight time, and the determined second flight time.

17. The sensor system according to claim 15 or 16, wherein, The transceiver element is configured to emit vibrations with a predetermined wavelength λ, and the buffer rod has an axial length that is an integer multiple of approximately n / 2λ.

18. The sensor system according to claim 15 or 16, wherein, The third cross-sectional region is approximately half the size of the first cross-sectional region.

19. The sensor system according to claim 15 or 16, wherein, The acoustic transceiver components include piezoelectric elements.

20. The sensor system of claim 15 or 16 further comprises a matching layer fixed to the second axial end and having a thickness that is an odd multiple of approximately 1 / 4λ.

21. The sensor system of claim 15 or 16, further comprising a backing, the backing being adjacent to the acoustic transceiver element and axially opposite to the first axial end portion.

22. The sensor system according to claim 18, wherein, The third cross-sectional region is approximately half the size of the first cross-sectional region.

23. The sensor system according to claim 18, wherein, The acoustic transceiver components include piezoelectric elements.

24. The sensor system according to claim 19, wherein, The acoustic transceiver components include piezoelectric elements.

25. A sensing method, comprising: Activate the first transmitter to emit at least one incident wave; The transmitted wave is transmitted along the buffer rod in the sensor of claim 1, the buffer rod having a first axial end adjacent to the first transmitter and a second axial end opposite to the first axial end; The first echo of the incident wave is reflected by a gap defined along a portion of the buffer rod; Detect the first echo; Determine the first amplitude of the first echo; The second echo of the incident wave is reflected by the second axial end; Detect the second echo; Determine the second amplitude of the second echo; as well as The reflection coefficient is determined based on the first amplitude and the second amplitude.

26. The method of claim 25, further comprising 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.

27. The method of claim 26, further comprising: At the second axial end, a portion of the incident wave is transmitted to a sensor by fluid, the sensor being arranged at a predetermined distance away from and opposite to the first transmitter, wherein the fluid is in a tubular fluid conduit having a predetermined cross-sectional area; The first sensor detects the portion of the incident wave; Based on the detected portion of the incident wave, the first flight time of that portion of the incident wave is determined; Another incident wave is emitted from the second transmitter towards the first sensor via fluid; Another incident wave is detected by a second sensor; and Based on the detected other incident wave, the second flight time of the other incident wave is determined.

28. The method of claim 27, further comprising determining at least one of the fluid velocity 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.

29. The method of claim 28, further comprising determining the mass fluid flow rate based on a predetermined cross-sectional area and a determined sound velocity.

30. The method according to any one of claims 25 to 28, wherein, The second echo, which reflects the incident wave through the second axial end, also includes the reflection of the second echo through a 1 / 4λ matching layer fixed to the second axial end.

31. The method according to claim 27 or 28, wherein, One or both of the first transmitter and the first sensor are piezoelectric elements.

32. The method according to any one of claims 25 to 28, wherein, The piezoelectric element includes a first transmitter and a first sensor.

33. A method for protecting a sensor element, comprising: Provide a sensor, the sensor comprising: A sensor housing having a first inner surface defining a sensor axis and an axially internal sensor housing cavity, comprising: The first axial sensor housing portion has a first cross-sectional area perpendicular to the sensor axis; The second axial sensor housing portion is arranged adjacent to the first axial sensor housing portion along the sensor axis and has a second cross-sectional area larger than the first cross-sectional area perpendicular to the sensor axis; and A first surface extending from the first inner surface of the first axial sensor housing portion to the first surface of the second inner surface of the second axial sensor housing portion; A buffer rod having a first axial end and a second axial end opposite to the first axial end, and comprising: A first axial buffer portion is disposed within a first axial sensor housing portion and includes a first axial end portion; A second axial buffer portion, disposed within and adjacent to the second inner surface of the second axial sensor housing portion, and including a second axial end portion; and The third axial buffer portion extends axially between the first axial buffer portion and the second axial buffer portion, and has a third cross-sectional area perpendicular to the sensor axis, the third cross-sectional area being smaller than the first cross-sectional area. A cavity, defined between the first inner surface and the third axial buffer portion, and partially defined by a second surface defined between the first axial buffer portion and the third axial buffer portion; and An acoustic transceiver element, acoustically fitted to the first axial end; and Fluid is provided at the second axial end; and The buffer rod and sensor housing prevent fluid from flowing from the second axial end to the acoustic transceiver element.

34. The method according to claim 33, wherein, Fluid flow from the second axial end to the acoustic transceiver element is blocked by the sensor housing and the second axial buffer portion.

35. The method according to claim 33 or 34, further comprising: Fluid pressure is applied to the second axial end to generate an axial force on the buffer rod; The axial force is transmitted to the sensor housing via the buffer rod; and The sensor housing prevents axial force from being transmitted to the acoustic transceiver element.

36. The method according to claim 35, wherein, It also includes transmitting axial force to the first surface through the second axial buffer portion, wherein the first surface interference buffer rod moves axially toward the acoustic transceiver element.

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