Ultrasonic flowmeter and biomass gas flow measuring system and method

Abstract

The invention discloses an ultrasonic flowmeter and a biomass gas flow measuring system and method.The flowmeter comprises a biomass gas flow path pipeline, a biomass gas storage system, a transducer system and an integrating instrument, and a biomass gas inlet and a biomass gas outlet are formed in the two ends of the biomass gas flow path pipeline respectively; a circulating channel of the biomass gas is formed; the biomass gas storage system is connected and communicated with the biomass gas flow path pipeline through a gas storage tank gas inlet pipe and a gas storage tank gas outlet pipe; the transducer system is mounted on the biomass gas flow path pipeline; the integrating instrument is installed on the biomass gas flow path pipeline and electrically connected with the biomass gas storage system and the transducer system. According to the invention, the biomass gas flow can be stably and accurately measured.

Description

Technical Field

[0001] This invention relates to the field of biomass gas flow measurement technology, specifically to an ultrasonic flow meter, a biomass gas flow measurement system, and a measurement method. Background Technology

[0002] Biomass gasification produces a low-calorific-value, multi-component gas (containing various combustible gases). For biomass gasification energy supply projects, whether users directly use the biomass gas produced by gasification or use the steam generated from it, it is necessary to measure the flow rate of biomass gas produced by the gasifier in order to conduct trade settlements and analyze project operating efficiency.

[0003] However, both differential pressure flow meters and ultrasonic flow meters, which are currently widely used, have metering problems with biomass gas flow in biomass gasification energy supply projects, as detailed below:

[0004] (1) For differential pressure flow meters, the biomass gas produced by the downdraft gasifier contains a lot of solid particulate impurities. The differential pressure components (orifice plate, nozzle, and nozzle) of conventional orifice plate flow meters, nozzle flow meters, and nozzle flow meters will be blocked by particulate impurities, making it impossible to measure the biomass gas flow rate.

[0005] (2) Ultrasonic flow meters use a non-contact measurement method, which can avoid the influence of solid particulate impurities. However, on the one hand, regardless of whether the ultrasonic flow meter uses the Doppler principle or the time difference method, it is necessary to determine the speed at which ultrasonic waves propagate in the stationary biomass gas. However, due to the influence of different operating conditions of the gasifier, the composition of biomass gas will change. The speed at which ultrasonic waves propagate in the medium is closely related to the medium. Different media have different propagation speeds. Therefore, in the actual measurement process, the speed at which ultrasonic waves propagate in biomass gas is not a constant value, but varies, which leads to a large error in the measurement of ultrasonic flow meters. On the other hand, if the measurement area is single or the ultrasonic waves interfere with each other, the measurement accuracy will also be reduced.

[0006] Therefore, providing an accurate ultrasonic flow meter and biomass gas flow measurement system and method is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] In view of this, the present invention provides an ultrasonic flow meter and a biomass gas flow measurement system and method, which can improve the accuracy of flow measurement.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] An ultrasonic flow meter includes a biomass gas flow path pipeline, a biomass gas storage system, a transducer system, and an integrator. The biomass gas flow path pipeline has a biomass gas inlet and a biomass gas outlet at its two ends, forming a flow channel for the biomass gas. The biomass gas storage system is connected to the biomass gas flow path pipeline via a gas storage tank inlet pipe and a gas storage tank outlet pipe. The transducer system is installed on the biomass gas flow path pipeline. The integrator is also installed on the biomass gas flow path pipeline and is electrically connected to both the biomass gas storage system and the transducer system.

[0010] By adopting the above technical solutions, the present invention produces the following beneficial effects:

[0011] The flow rate of biomass gas is measured using the Doppler frequency shift principle of ultrasound. At the same time, the propagation speed of ultrasound in stationary biomass gas can be calibrated in real time, realizing the function of stable and accurate measurement of biomass gas flow rate. It can also realize flow rate measurement at low flow rates, improving the measurement range and accuracy, and effectively ensuring the requirements of project trade measurement and energy efficiency analysis.

[0012] Furthermore, the biomass gas storage system includes a biomass gas storage tank, a first transmitting transducer, a first receiving transducer, an electric valve, and a first temperature sensor. The biomass gas storage tank is located above and parallel to the biomass gas flow path pipeline. The gas tank inlet pipe and the gas tank outlet pipe are located near their respective ends on the bottom centerline of the biomass gas storage tank. The biomass gas storage tank and the biomass gas flow path pipeline are connected and communicated through the gas tank inlet pipe and the gas tank outlet pipe. The first transmitting transducer and the first receiving transducer are respectively installed on the two end faces of the biomass gas storage tank near the top. The electric valve is installed on the gas tank outlet pipe. The first temperature sensor is installed on the side of the biomass gas storage tank near the gas tank outlet pipe. The first temperature sensor is electrically connected to the integrator, and the integrator is electrically connected to the first transmitting transducer, the first receiving transducer, and the electric valve.

[0013] Furthermore, the transducer system includes two central zone velocity measurement transducer groups and two boundary zone velocity measurement transducer groups. The two central zone velocity measurement transducer groups are coplanarly installed on the side of the biomass gas flow path pipe near the biomass gas outlet, and are arranged diagonally in an X-shape on a plane perpendicular to the axis of the biomass gas flow path pipe. Both central zone velocity measurement transducer groups are also inclined towards the airflow direction. The two boundary zone velocity measurement transducer groups are coplanarly installed on the side of the biomass gas flow path pipe near the biomass gas inlet, and are arranged parallel to each other on a plane perpendicular to the axis of the biomass gas flow path pipe. Both boundary zone velocity measurement transducer groups are also inclined towards the airflow direction. The integrator is electrically connected to both the two central zone velocity measurement transducer groups and the two boundary zone velocity measurement transducer groups.

[0014] Furthermore, each of the central region velocity measurement transducer groups includes a second transmitting transducer and a second receiving transducer. Two second transmitting transducers are located on either side of the top of the biomass gas flow path pipeline, and two second receiving transducers are located on either side of the bottom of the biomass gas flow path pipeline. This arrangement ensures that the two second transmitting transducers and the two second receiving transducers are coplanarly installed on the side of the biomass gas flow path pipeline near the biomass gas outlet, and are arranged diagonally in an X-shape on a plane perpendicular to the axis of the biomass gas flow path pipeline. Simultaneously, both the second transmitting transducer and the second receiving transducer form a 45° angle with both the axis of the biomass gas flow path pipeline and the direction perpendicular to the axis of the biomass gas flow path pipeline. Each of the boundary region velocity measurement transducers... Each energy transducer assembly includes a third transmitting transducer and a third receiving transducer. Two of the third transmitting transducers are located on the top sides of the biomass gas flow path pipeline, and two of the third receiving transducers are located on the bottom sides of the biomass gas flow path pipeline. The two third transmitting transducers and the two third receiving transducers are coplanarly installed on the side of the biomass gas flow path pipeline near the biomass gas inlet, and are arranged parallel to each other on a plane perpendicular to the axis of the biomass gas flow path pipeline. At the same time, the third transmitting transducers and the third receiving transducers are both at a 45° angle to the axis of the biomass gas flow path pipeline. The integrator is electrically connected to the two second transmitting transducers, the two second receiving transducers, the two third transmitting transducers, and the two third receiving transducers.

[0015] A biomass gas flow measurement system includes a biomass gas pipeline, a second temperature sensor, and an ultrasonic flow meter as described above. The biomass gas inlet and outlet are respectively connected to the biomass gas pipeline via flanges, such that the gas tank inlet pipe is located upstream of the biomass gas flow, the gas tank outlet pipe is located downstream of the biomass gas flow, a first transmitting transducer is located upstream of the biomass gas flow, a first receiving transducer is located downstream of the biomass gas flow, a second transmitting transducer and a second receiving transducer are located downstream of the biomass gas flow, and a third transmitting transducer and a third receiving transducer are located upstream of the biomass gas flow. The second temperature sensor is installed on the biomass gas pipeline located downstream and away from the ultrasonic flow meter, and the second temperature sensor is electrically connected to the integrator.

[0016] A method for measuring biomass gas flow rate, using the biomass gas flow rate measurement system described above, includes the following steps:

[0017] 1) Measurement of flow velocity in the central and boundary regions:

[0018] Each central zone velocity measurement transducer group calculates the corresponding biomass gas velocity by measuring the frequency shift generated by the ultrasonic waves within the beam's effective range. The calculation formula is as follows:

[0019] Δf=f2-f1=(1.4142×v×f1) / c

[0020] Where: f2 is the ultrasonic receiving frequency, f1 is the ultrasonic transmitting frequency, Δf is the ultrasonic frequency shift, c is the propagation speed of ultrasonic waves in stationary biomass gas, and v is the biomass gas flow velocity within the ultrasonic measurement range.

[0021] The average value of the two biomass gas flow velocities measured by the two central zone velocity measuring transducer sets is taken as the measured central zone velocity V. 中心 ;

[0022] Each boundary zone velocity measurement transducer group calculates the corresponding biomass gas velocity by measuring the frequency shift generated by the ultrasonic wave within the beam's range, using the same calculation formula as above.

[0023] The average value of the two biomass gas flow velocities measured by the two boundary zone velocity measurement transducer sets is taken as the measured boundary zone velocity V. 边界 ;

[0024] 2) Average airflow velocity V across the entire cross-section of the biomass gas flow path pipeline 平均 Using the central region flow velocity V 中心 With boundary region flow velocity V 边界The weighted average is calculated using the following formula:

[0025] V 平均 =0.6V 中心 +0.4V 边界

[0026] 4) The flow rate Q of biomass gas is calculated using the following formula:

[0027] Q = V 平均 ×A

[0028] Where A is the cross-sectional area of ​​the biomass gas flow path pipeline.

[0029] Furthermore, the biomass gas storage system performs real-time verification of the propagation speed c of ultrasound in static biomass gas, as follows:

[0030] When the ultrasonic flow meter is used for the first time, the electric valve opens, and part of the gas in the biomass gas flow path pipeline enters the biomass gas storage tank through the gas tank inlet pipe. When the temperature difference between the first temperature sensor and the second temperature sensor is within ±1℃, it is considered that the biomass gas storage tank is full, and the electric valve is closed at this time. After standing for 1 minute, when the gas in the biomass gas storage tank is still, the first transmitting transducer and the first receiving transducer are activated. The first transmitting transducer emits ultrasonic waves, and the first receiving transducer receives the ultrasonic waves. Since the installation positions of the first transmitting transducer and the first receiving transducer are fixed, the ultrasonic propagation path distance is a fixed value. It is only necessary to measure the time difference between the transmitted and received ultrasonic waves to measure the propagation speed of ultrasonic waves in the biomass gas under the current biomass gas composition conditions. This information is fed back to the integrator to calculate the biomass gas flow rate.

[0031] When the gasifier's operating conditions change, in addition to the change in biomass gas composition, the temperature of the generated biomass gas also changes. The second temperature sensor records the gas temperature every minute and compares the difference with the previous temperature record. When the temperature difference is greater than 10℃ for three consecutive records, the integrator starts recording the difference between the current measurement value and the previous measurement value of the second temperature sensor. When the measurement difference of the second temperature sensor is stable within ±1℃ for three consecutive times, it is determined that the gasifier's operating conditions adjustment is complete, and the recording of the measurement difference value of the second temperature sensor stops. At this time, the change in gas composition has stabilized, and the process of the biomass gas storage system during its first operation is repeated. The propagation speed of ultrasonic waves in the biomass gas under the current biomass gas composition conditions is measured and fed back to the integrator to calculate the biomass gas flow rate.

[0032] Therefore, the present invention provides an ultrasonic flow meter and a biomass gas flow measurement system and method. Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1) The flow meter uses the ultrasonic Doppler frequency shift principle to measure the flow rate of biomass gas. It adopts a non-contact measurement method to avoid the influence of suspended particulate matter and other dirt and impurities in biomass gas on conventional flow meters, thus achieving stable measurement of biomass gasification gas.

[0034] 2) Ultrasonic measurement of biomass gas flow rate avoids the problem of differential pressure flow meters being unable to measure low flow conditions due to small differential pressure caused by low flow of the measured medium. It can improve the range ratio of the flow meter and increase the flow measurement range.

[0035] 3) Conventional ultrasonic flow meters set the propagation speed c of ultrasonic waves in static biomass gas to a fixed value. In actual measurement, the composition of biomass gas changes with the operating conditions, causing the c value to deviate from the set value, resulting in measurement error. By using a biomass gas storage system to verify the propagation speed c of ultrasonic waves in static biomass gas in real time, the measurement error can be effectively reduced.

[0036] 4) The flow meter is equipped with multiple transducer groups at different cross-sections to measure the average flow velocity in the central and boundary areas of the pipeline. The transducers measuring the flow velocity in the central and boundary areas are located at different cross-sections of the pipeline, which reduces the mutual interference of ultrasonic waves and improves the measurement accuracy. The weighted average flow velocity in the central and boundary areas is used as the average flow velocity of the pipeline cross-section, which further improves the measurement accuracy. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0038] Figure 1 The attached figure is a perspective view of an ultrasonic flow meter provided by the present invention;

[0039] Figure 2 The attached figure is a front view of an ultrasonic flow meter provided by the present invention;

[0040] Figure 3 The attached figure is a side view of an ultrasonic flow meter provided by the present invention;

[0041] Figure 4 The attached figure is a cross-sectional view of an ultrasonic flow meter provided by the present invention. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] like Figure 1-4 As shown in the figure, an embodiment of the present invention discloses an ultrasonic flow meter, including a biomass gas flow path pipeline 1, a biomass gas storage system 2, a transducer system 3, and an integrator 4. The two ends of the biomass gas flow path pipeline 1 are a biomass gas inlet 11 and a biomass gas outlet 12, respectively, to form a biomass gas flow channel. The biomass gas storage system 2 is connected to the biomass gas flow path pipeline 1 through a gas tank inlet pipe 5 and a gas tank outlet pipe 6. The transducer system 3 is installed on the biomass gas flow path pipeline 1. The integrator 4 is installed on the biomass gas flow path pipeline 1, and the biomass gas flow path pipeline 1 has an installation slot for installing the integrator 4. The integrator 4 is electrically connected to the biomass gas storage system 2 and the transducer system 3, respectively. The integrator 4 is a central controller integrating system control program writing, control communication, data storage, display, and transmission. This invention utilizes the Doppler frequency shift principle of ultrasound to measure the flow rate of biomass gas. It can also calibrate the propagation speed of ultrasound in stationary biomass gas in real time, achieving stable and accurate measurement of biomass gas flow rate. Furthermore, it can achieve flow rate measurement at low flow rates, improving the measurement range and accuracy, and effectively ensuring the requirements of project trade measurement and energy efficiency analysis.

[0044] Specifically, the biomass gas storage system 2 includes a biomass gas storage tank 21, a first transmitting transducer 22, a first receiving transducer 23, an electric valve 24, and a first temperature sensor 25. The biomass gas storage tank 21 is located above the biomass gas flow path pipeline 1 and arranged parallel to it. The storage tank inlet pipe 5 and the storage tank outlet pipe 6 are located near the two ends of the bottom centerline of the biomass gas storage tank 21, respectively. The biomass gas storage tank 21 is connected to the biomass gas flow path pipeline 1 through the storage tank inlet pipe 5 and the storage tank outlet pipe 6. The first transmitting transducer 22 and the first receiving transducer 23 are respectively installed on the two end faces of the biomass gas storage tank 21 near the top. In this embodiment, the biomass gas storage tank 21 has mounting holes for the first transmitting transducer 22 and the first receiving transducer 23 near the top of both ends; the electric valve 24 is installed on the gas outlet pipe 6 of the storage tank; the first temperature sensor 25 is installed on the side of the biomass gas storage tank 21 near the gas outlet pipe 6. In this embodiment, the side of the biomass gas storage tank 21 near the gas outlet pipe 6 has mounting holes for the first temperature sensor 25; the first temperature sensor 25 is electrically connected to the integrator 4, and the integrator 4 is electrically connected to the first transmitting transducer 22, the first receiving transducer 23 and the electric valve 24 respectively.

[0045] Specifically, the transducer system 3 includes two central zone velocity measuring transducer groups 31 and two boundary zone velocity measuring transducer groups 32. The two central zone velocity measuring transducer groups 31 are coplanarly installed on the side of the biomass gas flow path duct 1 near the biomass gas outlet 12, and are arranged diagonally in an X-shape on a plane perpendicular to the axis of the biomass gas flow path duct 1. At the same time, both central zone velocity measuring transducer groups 31 are inclined towards the airflow direction. The two boundary zone velocity measuring transducer groups 32 are coplanarly installed on the side of the biomass gas flow path duct 1 near the biomass gas inlet 11, and are arranged parallel on a plane perpendicular to the axis of the biomass gas flow path duct 1. At the same time, both boundary zone velocity measuring transducer groups 32 are inclined towards the airflow direction. The integrator 4 is electrically connected to the two central zone velocity measuring transducer groups 31 and the two boundary zone velocity measuring transducer groups 32 respectively.

[0046] Specifically, each central zone velocity measurement transducer group 31 includes a second transmitting transducer 311 and a second receiving transducer 312. The two second transmitting transducers 311 are located on both sides of the top of the biomass gas flow path pipe 1, respectively, for emitting ultrasonic waves. The two second receiving transducers 312 are located on both sides of the bottom of the biomass gas flow path pipe 1, respectively, for receiving ultrasonic waves reflected by suspended particles in the biomass gas. The two second transmitting transducers 311 and the two second receiving transducers 312 are coplanarly installed on the side of the biomass gas flow path pipe 1 near the biomass gas outlet 12, and are arranged diagonally in an X-shape on a plane perpendicular to the axis of the biomass gas flow path pipe 1. At the same time, both the second transmitting transducer 311 and the second receiving transducer 312 form a 45° angle with the axis of the biomass gas flow path pipe 1 and a 45° angle with the direction perpendicular to the axis of the biomass gas flow path pipe 1. Each boundary zone velocity measurement transducer group 32 includes a third transmitting transducer 321 and a third receiving transducer 322. The two third transmitting transducers 321 are located on the top sides of the biomass gas flow path pipe 1, and the two third receiving transducers 322 are located on the bottom sides of the biomass gas flow path pipe 1, so that the two third transmitting transducers 321 and the two third receiving transducers 322 are coplanarly installed on the side of the biomass gas flow path pipe 1 near the biomass gas inlet 11, and are arranged parallel to each other on a plane perpendicular to the axis of the biomass gas flow path pipe 1. At the same time, the third transmitting transducers 321 and the third receiving transducers 322 are both at a 45° angle to the axis of the biomass gas flow path pipe 1. The integrator 4 is electrically connected to the two second transmitting transducers 311, the two second receiving transducers 312, the two third transmitting transducers 321, and the two third receiving transducers 322.

[0047] For the installation position and orientation of each transducer (second transmitting transducer 311, second receiving transducer 312, third transmitting transducer 321 and third receiving transducer 322), an installation hole is provided on the outer wall of the biomass gas flow path pipeline 1. The installation hole penetrates the pipe wall of the biomass gas flow path pipeline 1 and is a short pipe that meets the installation length requirements of the transducer. It is fixedly connected to the pipe wall of the biomass gas flow path pipeline 1, and each transducer is installed inside the corresponding installation hole.

[0048] This invention also discloses a biomass gas flow measurement system, including a biomass gas pipeline, a second temperature sensor, and an ultrasonic flow meter as described above. The biomass gas inlet 11 and the biomass gas outlet 12 are connected to the biomass gas pipeline via flanges. A flow meter installation direction mark is set on the outer wall of the biomass gas flow path pipeline 1. During flow meter installation, each transducer probe must be facing the airflow direction, such that the gas storage tank inlet pipe 5 is located upstream of the biomass gas flow, the gas storage tank outlet pipe 6 is located downstream of the biomass gas flow, the first transmitting transducer 22 is located upstream of the biomass gas flow, the first receiving transducer 23 is located downstream of the biomass gas flow, the second transmitting transducer 311 and the second receiving transducer 312 are located downstream of the biomass gas flow, and the third transmitting transducer 321 and the third receiving transducer 322 are located upstream of the biomass gas flow. The second temperature sensor is installed on the biomass gas pipeline located downstream and away from the ultrasonic flow meter, and the second temperature sensor is electrically connected to the integrator 4.

[0049] This invention also discloses a method for measuring biomass gas flow rate, which utilizes the biomass gas flow rate measurement system described above, and includes the following steps:

[0050] Biomass gas contains suspended particulate matter such as dust. When ultrasonic waves emitted by the transmitting transducer encounter these suspended particles moving with the airflow, the waves are reflected and then received by the receiving transducer. The frequency of the ultrasonic waves after reflection from the suspended particles in the biomass gas shifts from the emitted frequency. The magnitude of this frequency shift is proportional to the velocity of the suspended particles (i.e., the flow velocity of the biomass gas). The average flow velocity of the biomass gas is measured based on the Doppler frequency shift principle of this ultrasonic wave.

[0051] 1) Measurement of flow velocity in the central and boundary regions:

[0052] Each central zone velocity measurement transducer group 31 calculates the corresponding biomass gas velocity by measuring the frequency shift generated by the ultrasonic wave within the beam's range. The calculation formula is as follows:

[0053] Δf=f2-f1=(1.4142×v×f1) / c

[0054] Where: f2 is the ultrasonic receiving frequency, which is directly measured by the receiving transducer; f1 is the ultrasonic transmitting frequency, which is a fixed value; Δf is the ultrasonic frequency shift; c is the propagation speed of ultrasonic waves in stationary biomass gas; and v is the biomass gas flow velocity within the ultrasonic measurement range.

[0055] The average value of the two biomass gas flow velocities measured by the two central zone velocity measuring transducer groups 31 is taken as the measured central zone velocity V. 中心 ;

[0056] Each boundary zone velocity measurement transducer group 32 calculates the corresponding biomass gas velocity by measuring the frequency shift generated by the ultrasonic wave within the beam's range, using the same calculation formula as above.

[0057] The average value of the two biomass gas flow velocities measured by the two boundary zone velocity measuring transducer groups 32 is taken as the measured boundary zone velocity V. 边界 ;

[0058] Due to the influence of its own viscosity, the airflow velocity distribution on the cross-section of the pipe is uneven. The airflow velocity is high in the central region near the pipe axis and low in the boundary region near the pipe wall. Therefore, this invention measures the flow velocity in the central region and the boundary region respectively, which can improve the detection accuracy.

[0059] 2) Average airflow velocity V across the entire cross-section of biomass gas flow path pipe 1 平均 Using the central region flow velocity V 中心 With boundary region flow velocity V 边界 The weighted average is calculated using the following formula:

[0060] V 平均 =0.6V 中心 +0.4V 边界

[0061] 3) The flow rate Q of biomass gas is calculated using the following formula:

[0062] Q = V 平均 ×A

[0063] Where A is the cross-sectional area of ​​biomass gas flow path pipe 1.

[0064] It is understandable that the propagation speed *c* of ultrasound in a medium is closely related to the medium, and the value of *c* varies for different media. When the fluid being measured is a stable medium such as water or a single-element gas, the propagation speed *c* of ultrasound is constant, and the flow velocity can be measured simply by measuring the ultrasound reflection frequency. However, the composition of biomass fuel gas produced by gasification changes with the operating conditions of the gasifier, which will lead to changes in *c* during actual measurement. If *c* is set to a constant in the internal system calculation of the flow meter, it will result in deviations in the measurement results.

[0065] Based on this, the biomass gas storage system of the present invention performs real-time verification of the propagation speed c of ultrasound in static biomass gas, as follows:

[0066] When the ultrasonic flow meter is used for the first time, the electric valve 24 is opened, and part of the gas in the biomass gas flow path pipeline 1 enters the biomass gas storage tank 21 through the gas tank inlet pipe 5. When the temperature measured by the first temperature sensor 25 and the second temperature sensor is within ±1℃, it is considered that the biomass gas storage tank 21 is full, and the electric valve 24 is closed at this time. After standing for 1 minute, when the gas in the biomass gas storage tank 21 is still, the first transmitting transducer 22 and the first receiving transducer 23 are activated. The first transmitting transducer 22 emits ultrasonic waves, and the first receiving transducer 23 receives ultrasonic waves. Since the installation positions of the first transmitting transducer 22 and the first receiving transducer 23 are fixed, the ultrasonic propagation path distance is a fixed value. It is only necessary to measure the time difference between the transmitted and received ultrasonic waves to measure the propagation speed of ultrasonic waves in the biomass gas under the current biomass gas composition conditions. This is fed back to the integrator 4 to calculate the biomass gas flow rate.

[0067] When the gasifier's operating conditions change, in addition to the change in biomass gas composition, the temperature of the generated biomass gas also changes. The second temperature sensor records the gas temperature once per minute and compares the difference with the previous temperature record. When the temperature difference is greater than 10℃ for three consecutive records, the integrator starts recording the difference between the current measurement value and the previous measurement value of the second temperature sensor. When the measurement difference of the second temperature sensor is stable within ±1℃ for three consecutive times, it is determined that the gasifier's operating conditions adjustment is complete, and the recording of the measurement difference value of the second temperature sensor stops. At this time, the change in gas composition has stabilized, and the process of the biomass gas storage system 2 during its first operation is repeated. The propagation speed of ultrasonic waves in the biomass gas under the current biomass gas composition conditions is measured and fed back to the integrator 4 for calculating the biomass gas flow rate.

[0068] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0069] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An ultrasonic flow meter, characterized in that, The system includes a biomass gas flow path pipeline, a biomass gas storage system, a transducer system, and an integrator. The biomass gas flow path pipeline has a biomass gas inlet and a biomass gas outlet at both ends, forming a flow channel for the biomass gas. The biomass gas storage system is connected to the biomass gas flow path pipeline via a gas tank inlet pipe and a gas tank outlet pipe. The transducer system is installed on the biomass gas flow path pipeline. The integrator is also installed on the biomass gas flow path pipeline and is electrically connected to both the biomass gas storage system and the transducer system.

2. The ultrasonic flow meter according to claim 1, characterized in that, The biomass gas storage system includes a biomass gas storage tank, a first transmitting transducer, a first receiving transducer, an electric valve, and a first temperature sensor. The biomass gas storage tank is located above and parallel to the biomass gas flow path pipeline. The storage tank inlet pipe and the storage tank outlet pipe are located near their respective ends on the bottom centerline of the biomass gas storage tank. The biomass gas storage tank and the biomass gas flow path pipeline are connected and communicated through the storage tank inlet pipe and the storage tank outlet pipe. The first transmitting transducer and the first receiving transducer are respectively installed on the two end faces of the biomass gas storage tank near the top. The electric valve is installed on the storage tank outlet pipe. The first temperature sensor is installed on the side of the biomass gas storage tank near the gas outlet pipe of the storage tank; the first temperature sensor is electrically connected to the integrator, and the integrator is electrically connected to the first transmitting transducer, the first receiving transducer and the electric valve respectively.

3. An ultrasonic flow meter according to claim 1 or 2, characterized in that, The transducer system includes two central zone velocity measurement transducer groups and two boundary zone velocity measurement transducer groups. The two central zone velocity measurement transducer groups are coplanarly installed on the side of the biomass gas flow path pipeline near the biomass gas outlet, and are arranged diagonally in an X-shape on a plane perpendicular to the axis of the biomass gas flow path pipeline. Both central zone velocity measurement transducer groups are inclined towards the airflow direction. The two boundary zone velocity measurement transducer groups are coplanarly installed on the side of the biomass gas flow path pipeline near the biomass gas inlet, and are arranged parallel on a plane perpendicular to the axis of the biomass gas flow path pipeline. Both boundary zone velocity measurement transducer groups are inclined towards the airflow direction. The integrator is electrically connected to the two central zone velocity measurement transducer groups and the two boundary zone velocity measurement transducer groups respectively.

4. An ultrasonic flow meter according to claim 3, characterized in that, Each of the central zone velocity measurement transducer groups includes a second transmitting transducer and a second receiving transducer. The two second transmitting transducers are located on either side of the top of the biomass gas flow path pipeline, and the two second receiving transducers are located on either side of the bottom of the biomass gas flow path pipeline. The two second transmitting transducers and the two second receiving transducers are coplanarly installed on the side of the biomass gas flow path pipeline near the biomass gas outlet, and are arranged diagonally in an X-shape on a plane perpendicular to the axis of the biomass gas flow path pipeline. Simultaneously, both the second transmitting transducer and the second receiving transducer form a 45° angle with both the axis of the biomass gas flow path pipeline and the direction perpendicular to the axis of the biomass gas flow path pipeline. Each of the boundary zone velocity measurement transducer groups... Each device includes a third transmitting transducer and a third receiving transducer. The two third transmitting transducers are located on the top sides of the biomass gas flow path pipeline, and the two third receiving transducers are located on the bottom sides of the biomass gas flow path pipeline. The two third transmitting transducers and the two third receiving transducers are coplanarly installed on the side of the biomass gas flow path pipeline near the biomass gas inlet, and are arranged parallel to each other on a plane perpendicular to the axis of the biomass gas flow path pipeline. At the same time, the third transmitting transducers and the third receiving transducers are both at a 45° angle to the axis of the biomass gas flow path pipeline. The integrator is electrically connected to the two second transmitting transducers, the two second receiving transducers, the two third transmitting transducers, and the two third receiving transducers.

5. A biomass gas flow measurement system, characterized in that, The system includes a biomass gas pipeline, a second temperature sensor, and an ultrasonic flow meter as described in claim 4. The biomass gas inlet and outlet are respectively connected to the biomass gas pipeline via flanges, such that the gas tank inlet pipe is located upstream of the biomass gas flow, the gas tank outlet pipe is located downstream of the biomass gas flow, the first transmitting transducer is located upstream of the biomass gas flow, the first receiving transducer is located downstream of the biomass gas flow, the second transmitting transducer and the second receiving transducer are located downstream of the biomass gas flow, and the third transmitting transducer and the third receiving transducer are located upstream of the biomass gas flow. The second temperature sensor is installed on the biomass gas pipeline located downstream and away from the ultrasonic flow meter, and the second temperature sensor is electrically connected to the integrator.

6. A method for measuring biomass gas flow rate, using the biomass gas flow rate measurement system as described in claim 5, characterized in that, Includes the following steps: 1) Measurement of flow velocity in the central and boundary regions: Each central zone velocity measurement transducer group calculates the corresponding biomass gas velocity by measuring the frequency shift generated by the ultrasonic wave within the beam's effective range. The calculation formula is as follows: Δf=f2-f1=(1.4142×v×f1) / c Where: f2 is the ultrasonic receiving frequency, f1 is the ultrasonic transmitting frequency, Δf is the ultrasonic frequency shift, c is the propagation speed of ultrasonic waves in stationary biomass gas, and v is the biomass gas flow velocity within the ultrasonic measurement range. The average value of the two biomass gas flow velocities measured by the two central zone velocity measuring transducer sets is taken as the measured central zone velocity V. 中心 ; Each boundary zone velocity measurement transducer group calculates the corresponding biomass gas velocity by measuring the frequency shift generated by the ultrasonic wave within the beam's range, using the same calculation formula as above. The average value of the two biomass gas flow velocities measured by the two boundary zone velocity measurement transducer sets is taken as the measured boundary zone velocity V. 边界 ; 2) Average airflow velocity V across the entire cross-section of the biomass gas flow path pipeline 平均 Using the central region flow velocity V 中心 With boundary region flow velocity V 边界 The weighted average is calculated using the following formula: V 平均 =0.6V 中心 +0.4V 边界 3) The flow rate Q of biomass gas is calculated using the following formula: Q=V 平均 ×A Where A is the cross-sectional area of ​​the biomass gas flow path pipeline.

7. The method for measuring biomass gas flow rate according to claim 6, characterized in that, The biomass gas storage system performs real-time verification of the propagation speed c of ultrasound in static biomass gas. The process is as follows: When the ultrasonic flow meter is used for the first time, the electric valve opens, and part of the gas in the biomass gas flow path pipeline enters the biomass gas storage tank through the gas tank inlet pipe. When the temperature difference between the first temperature sensor and the second temperature sensor is within ±1℃, it is considered that the biomass gas storage tank is full, and the electric valve is closed at this time. After standing for 1 minute, when the gas in the biomass gas storage tank is still, the first transmitting transducer and the first receiving transducer are activated. The first transmitting transducer emits ultrasonic waves, and the first receiving transducer receives the ultrasonic waves. Since the installation positions of the first transmitting transducer and the first receiving transducer are fixed, the ultrasonic propagation path distance is a fixed value. It is only necessary to measure the time difference between the transmitted and received ultrasonic waves to measure the propagation speed of ultrasonic waves in the biomass gas under the current biomass gas composition conditions. This information is fed back to the integrator to calculate the biomass gas flow rate. When the gasifier's operating conditions change, in addition to the change in biomass gas composition, the temperature of the generated biomass gas also changes. The second temperature sensor records the gas temperature every minute and compares the difference with the previous temperature record. When the temperature difference is greater than 10℃ for three consecutive records, the integrator starts recording the difference between the current measurement value and the previous measurement value of the second temperature sensor. When the measurement difference of the second temperature sensor is stable within ±1℃ for three consecutive times, it is determined that the gasifier's operating conditions adjustment is complete, and the recording of the measurement difference value of the second temperature sensor stops. At this time, the change in gas composition has stabilized, and the process of the biomass gas storage system during its first operation is repeated. The propagation speed of ultrasonic waves in the biomass gas under the current biomass gas composition conditions is measured and fed back to the integrator to calculate the biomass gas flow rate.

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