RU2644457C1 - Device for gas volumetric flow rate measurement - Google Patents

Device for gas volumetric flow rate measurement Download PDF

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Publication number
RU2644457C1
RU2644457C1 RU2017108061A RU2017108061A RU2644457C1 RU 2644457 C1 RU2644457 C1 RU 2644457C1 RU 2017108061 A RU2017108061 A RU 2017108061A RU 2017108061 A RU2017108061 A RU 2017108061A RU 2644457 C1 RU2644457 C1 RU 2644457C1
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RU
Russia
Prior art keywords
flow
gas
label
measured
volume
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RU2017108061A
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Russian (ru)
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Александр Степанович Леонов
Дмитрий Александрович Леонов
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Общество с ограниченной ответственностью "Современное лабораторное оборудование"
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01FMEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F25/00Testing or calibrating apparatus for measuring volume, volume flow or liquid level, or for metering by volume

Abstract

FIELD: measuring equipment.
SUBSTANCE: device for determination of the volumetric flow rate of the measured gas flow contains a flow label gas pressure regulator, which is executed with an ability to be connected to the flow label gas source input; a thermostat; a flow switch executed with an ability to switch the direction of the measured gas flow; at least two measuring channels, each of made with a possibility of measurement of the volumetric flow rate of the measured gas flow with partially overlapping ranges of flow rate measurement of adjacent channels and containing a flow line, which is made with a possibility of placement in the inner volume of the thermostat with a possibility of transmission of the measured gas flow, as well as of the flow gas label of the specified volume and contains the following components arranged along the flow in the order of mentioning: a gas delay line, the first detector made wih a possibility of flow label gas concentration measurement in the measured gas flow, a measuring volume, the second detector made with a possibility of flow label gas concentration measurement in the measured gas flow; as well as a flow label gas pulse input unit, connected to the gas delay line input; a temperature sensor, executed with an ability to measure temperature in the measured gas flow and connected to the gas delay line output; the first absolute pressure sensor, which is connected to the first detector; the second absolute pressure sensor, which is connected to the second detector. The flow switch is placed in the internal volume of the thermostat, one of the flow switch outputs is connected to the flow measuring line in the junction point of the flow label gas pulse input unit output with the delay line, and the flow label gas pressure regulator output is connected to the input of each flow label gas pulse input unit.
EFFECT: provision of a possibility of measurement of volumetric flow rates of any gases, gas mixtures of arbitrary composition, including gas mixtures with a condensation temperature below the thermostat temperature, in volumetric flow rate determination with a low error.
12 cl, 1 dwg

Description

The invention relates to the field of measuring equipment, and in particular to devices that allow measurements of the volumetric flow rate of not only gas, but also gas mixtures of any composition. The invention can find application in instrumentation for the creation of laboratory gas flow meters.

Terms Used

Measured gas stream — a gas stream or a multicomponent gas mixture that is in a gaseous state at the measurement temperature and is directed to a device to measure the volumetric flow rate.

The volumetric flow rate of the measured gas stream is reduced to normal conditions (0 ° C, 760 mm Hg) the volume of gas or multicomponent gas mixture flowing through the cross section of the stream per unit time.

Gas flow label - heterogeneity of the measured gas flow created by pulsed input into the given flow of a given volume of gas of the flow label, which differs in physical properties from the properties of the gas medium of the measured gas flow, such as thermal, optical, magnetic and others.

Marked gas flow meters are known that are based on creating an indicator heterogeneity in the gas stream, called a flow mark, and measuring the time of moving the flow mark on the control section of the path and consist, as a rule, of a device that creates a flow mark, a device that controls the movement of the flow mark in a certain section paths and devices that measure any characteristic associated with the speed of the flow, for example, the transit time of the flow label between two control points (Kremlevsky P.P. Ras odomery. Mashgiz, 1964). The difference in the numerous modifications of the tagged flow meters is the way to create the flow tag and the device for its registration at the control points of the measuring section of the track.

A technical solution is known in which the measurement of the gas flow rate is based on the property of the soap film to move along the inner surface of the measuring burette or some other transparent tube with a known volume under the pressure of the measured gas flow, and the device for measuring the gas flow contains the measuring volume in the form of a glass tube , a device for creating a soap film, while the position of the soap film is controlled by two optical sensors, sensor signals carrying information about travel time film waits between control points are processed by a microprocessor control and control unit, and taking into account information about the tube volume between sensors, the flow rate is calculated, http://www.ooo-monitoring.ru/products/eauip/qasflow/potok/ (accessed date 20.02. 2017).

The disadvantages of the known technical solutions are low accuracy, the inability to measure the flow rates of gases and gas mixtures that destroy the soap film, the low strength of the soap film, the need for humidification of the gas to reduce the measurement error of the volumetric flow rate.

A technical solution is known in which a piston is used as a flow mark, which freely moves in a glass pipe in the direction of the measured gas flow, the piston is controlled by two optical sensors located on the pipe at a fixed distance between the sensors, the flow rate is determined by measuring the piston travel time between sensors with a known volume of the pipe segment between the sensors (Patent US 5684246 A, IPC G01F 25/00, priority from 04/11/1997).

The disadvantages of the known technical solutions are the need to use for measuring the flow rate of highly pure gases, the impossibility of measuring the flow rate of mixtures of several gases, the need to take into account the dynamic viscosity in the flow of the measured gas, the high cost of the piston flow meter. For these reasons, a piston flow meter is mainly used as calibrators for other flow meters and flow controllers.

The objective of the proposed technical solution is to develop a device that allows you to determine the volumetric flow rate of the measured gas flow, while ensuring the accuracy of the measurement is not worse than ± 1% of the measured value.

The problem is solved in that the device for determining the volumetric flow rate of the measured gas stream contains a gas pressure regulator of the flow label, which is configured to connect a flow label to the gas source; thermostat; a flow switch, which is configured to switch the direction of the measured gas flow; at least two measuring channels, each of which is capable of measuring the volumetric flow rate of the measured gas flow with partially overlapping ranges of flow measurement of adjacent channels and containing a flow line that is configured to fit into the internal volume of the thermostat, with the possibility of passing the measured gas flow, and the gas label of the flow of a given volume and contains the gas delay line, arranged in the direction of flow in the order of mention, the first detector, which is made with the possibility of measuring the gas concentration of the label flow in the measured gas stream, a measuring volume, a second detector, which is configured to measure the gas concentration of the label gas flow in the measured gas stream; as well as a block of pulse input of gas flow labels, the output of which is connected to the input of the gas delay line; a temperature sensor that is configured to measure the temperature in the measured gas flow and is connected to the output of the gas delay line; a first absolute pressure sensor that is connected to the first detector; a second absolute pressure sensor that is connected to the second detector; in this case, the flow switch is placed in the internal volume of the thermostat, one of the outputs of the flow switch is connected to the flow line at the junction of the output of the pulse mark gas supply unit with the delay line, and the output of the pressure mark gas pressure regulator is connected to the input of each pulse mark gas input unit . In this case, the block of gas pulse input of the flow mark is configured to introduce into the flow the gas volume of the flow mark necessary for a given measured volume flow of the measured gas flow. The block of pulse input of the gas of the flow label is based on a two-way electro-pneumatic valve and gas throttle. The flow switch is based on two-way electro-pneumatic valves. The thermostat is made in the form of a closed volume with the ability to maintain the set temperature value inside the volume. The flow line is configured to allow gas to pass through a flow mark significantly different from the thermal conductivity of the measured gas flow. The first as well as the second detectors are made either in the form of sensitive elements of thermal conductivity detectors with small geometric dimensions of the spirals of sensitive elements, or in the form of planar microelectronic sensitive elements of thermal conductivity detectors. The gas delay line is made either in the form of a metal tube, the diameter of which is much less than its length, or in the form of a plastic tube, the diameter of which is much less than its length. The measuring volume is made either in the form of a metal tube, the diameter of which is much less than its length, or in the form of a plastic tube, the diameter of which is much less than its length. Delay lines and measuring volumes of adjacent measuring channels are made of tubes with different inner diameters. The delay line and the measuring volume are made in the form of tubes rolled into a spiral. The gas source of the flow label is made in the form of a cylinder with gas flow label.

The technical effect of the proposed technical solution is to expand the funds for this purpose. In addition, it is possible to measure the volumetric flow rates of any gases, gas mixtures of arbitrary composition, including gas mixtures with a condensation temperature below the temperature of the thermostat, in determining the volumetric flow rate with an error of not more than 1% of the measured value.

The claimed technical solution is illustrated in FIG. 1, which shows a block diagram of the claimed technical solution, in the case of its execution having three measuring channels, where 1 is a cylinder with gas flow mark, 2 is a pressure regulator gas pressure flow mark, 3 is a block of pulse input gas flow mark, 4 - gas delay line, 5 - temperature sensor, 6 - first detector, 7 - first absolute pressure sensor, 8 - measuring volume, 9 - second detector, 10 - second absolute pressure sensor, 11 - thermostat, 12 - flow switch.

A device for implementing the claimed technical solution is assembled by methods known in the art.

The input of the gas pressure regulator of the flow label 2 is connected to the gas source of the flow label, for example, to the gas cylinder of the flow label 1. The output of the gas pressure regulator of the flow label 2 is connected to the input of the pulse input of the gas of flow label 3, the output of the pulse input of the gas of flow label 3 is connected to the input of the gas delay line 4. The temperature sensor 5 is configured to measure the temperature of the measured gas flow and is connected to the output of the gas delay line. The first absolute pressure sensor 7 is hermetically connected to the first detector 6, the second absolute pressure sensor 10 is hermetically connected to the second detector 9. The flow switch 12 is placed in the internal volume of the thermostat 11, one of the outputs of the flow switch 12 is connected to the measuring line of the flow 8 at the junction of the output unit pulse input gas label flow 3 with a gas delay line 4, and the output of the gas pressure regulator gas label flow 2 is connected to the input of each unit pulse input gas gas label 3. One of the flow lines, for example p first, located in the direction of movement of the measured gas flow and hermetically connected to one of the outputs of the flow switch 12, while in the flow line are located in the order of mention and tightly interconnected gas delay line 4, the first detector 6, the measuring volume 8, the second detector 9.

At the junction of one of the outputs of the flow switch with the input of the delay line, the impulse input unit for the gas flow label 3 is hermetically connected, at the junction of the delay line with the first detector, the temperature sensor 5 is hermetically connected, the first absolute pressure sensor 7 is hermetically connected to the first detector, the second absolute pressure sensor 10 is hermetically connected to the second detector. The flow switch 12, the gas delay line 4, the first detector 6, the measuring volume 8, the second detector 9 are located in the thermostat.

The measurements are carried out as follows. The operating temperature for measuring the flow rate is set and set in the thermostat 11, while the operating temperature exceeds the condensation temperature of the components in the measured gas flow. The gas pressure regulator of the flow label 2 sets the pressure value at the inlet of the pulse input device of the gas flow label 3. The gas flow is fed to the input of the flow switch 12 and directed by the switch 12 to the flow line with the maximum value of the measuring volume. Purge the flow line with a measured gas flow. Using the pulsed gas inlet unit, flow labels introduce a predetermined volume of gas flow labels into the measured gas flow, and a volume of gas flow labels is selected such that the gas concentration of the flow mark in the measured gas flow is in the linear range of the first and second detectors, and the peak shape of the gas flow label was close to Gaussian with a well-defined apex, while the volume of the introduced gas flow label is controlled by changing the pressure of the gas flow label using pressure regulator 2 and the duration of the input . The change in time of gas concentration of the flow label in the measured gas stream is monitored by the first and second detectors. The time separation of the peaks and spurious oscillations of the detector signal is provided by the gas delay line. The time interval between the peaks of the recorded peaks corresponding to the time the gas marks travel the distance between the first and second detectors is measured with a time meter. If the specified time interval between the peaks exceeds the maximum allowable, switch the measured gas flow by the switch 12 to the flow line with a smaller value of the measuring volume and a smaller volume of the gas delay line and repeat the procedure for entering the gas of the flow mark, selecting the gas pressure of the flow mark and the duration of the input. The pressure in the measured gas flow at the inlet of the measuring volume is measured by the first absolute pressure sensor 7 and at the output of the measuring volume by the second absolute pressure sensor 10. The temperature in the measured gas stream is measured by the temperature sensor 5.

The volumetric flow rate of the measured gas flow reduced to normal conditions (0 ° C and 760 mm Hg) is calculated by the formula W = V⋅P⋅T 0 / (P 0 ⋅T⋅t), where V is the value of the measuring volume between control points, P = (P 1 + P 2 ) / 2 is the arithmetic mean of the gas pressure in the measuring volume in mm Hg, T is the temperature of the gas in the stream in K, T O = 273.15 K, P O is the normal atmospheric pressure (760 mm Hg), t is the transit time of the gas mark of the flow between the first and second detectors.

The proposed device has the following advantages.

1) The ability to determine the volumetric flow rates of gases and gas mixtures of various compositions in a wide range of costs, including low costs.

This possibility is associated with the properties of the gas flow label and the design of the device. First, a wide variety of gases can be used to create a gas flow label, including inert gases that differ in physical characteristics from the measured gas or gas mixture. In this case, the inert gas of the flow label does not chemically interact with the measured gas flow and the composition of the gas of the flow label does not change. Secondly, the delay line and the measuring volume are made in the form of tubes of small diameter and large length, which provides a “piston” mode of propagation of the gas flow mark, while the diffusion velocity of the gas flow mark along the direction of motion of the measured gas flow is limited by the small cross-section of the tubes. These two features of the proposed device for measuring the volumetric flow rate provide high stability of the gas flow mark and allow measurements in a wide range of linear velocities of the measured gas flow, corresponding to the passage of the gas flow mark between the control points corresponding to the first and second gas flow meter sensors from 1 to 200 seconds . The absence of special restrictions on the purity of the measured gases is ensured by the absence of mechanical moving parts in the device for measuring volumetric flow and high stability of the gas flow label.

2) The ability to measure the volumetric flow rates of gas mixtures with a condensation temperature of components above room temperature.

The presence of a thermostat used to heat the measured gas flow and maintain the set temperature allows the volumetric flow rate of multicomponent gas mixtures to be measured with a condensation temperature of the components of the measured gas flow not exceeding the temperature of the thermostat. When used as detectors of sensitive elements of thermal conductivity detectors, a permissible operating temperature in the thermostat of up to 180 ° C can be ensured.

3) The ability to achieve high accuracy measurement of volumetric flow.

High accuracy of flow measurement is due to the following factors:

a) high accuracy in determining the magnitude of the measuring volume between the control points, which is provided by a special calibration procedure;

b) by preheating the measured gas flow in the gas delay line, providing high uniformity and temperature stability in the measured gas flow in the direction of flow;

c) measuring with high accuracy the pressure distribution in the measured stream along the direction of flow using microelectronic pressure sensors;

d) high accuracy of measuring the transit time of the gas flow mark between the control points, which is ensured by high-frequency gating of the signal of the first and second detectors, mathematical processing of the peak shape, averaging of the measurement results over a specified number of implementations of the measurement procedure.

The limits of permissible relative error when measuring the volume flow in the claimed technical solution do not exceed ± 1% in the flow range from 5 to 2500 cm 3 / min (Certificate of approval of the type of measuring instruments RU.C.29.001.A No. 53871 dated 04/04/2014 ; description of the type of measuring instrument).

Claims (12)

1. The device for determining the volumetric flow rate of the measured gas stream contains a gas pressure regulator of the flow label, which is configured to connect a flow label to the gas source; thermostat; a flow switch, which is configured to switch the direction of the measured gas flow; at least two measuring channels, each of which is capable of measuring the volumetric flow rate of the measured gas flow with partially overlapping ranges of flow measurement of adjacent channels and containing a flow line that is configured to fit into the internal volume of the thermostat, with the possibility of passing the measured gas flow, and the gas label of the flow of a given volume and contains the gas delay line, arranged in the direction of flow in the order of mention, the first detector, which is made with the ability to measure the gas concentration of the flow label in the flow of the measured gas stream, a measuring volume, a second detector, which is configured to measure the gas concentration of the flow label in the measured gas stream; as well as a block of pulse input of gas flow labels, the output of which is connected to the input of the gas delay line; a temperature sensor that is configured to measure the temperature in the measured gas flow and is connected to the output of the gas delay line; a first absolute pressure sensor that is connected to the first detector; a second absolute pressure sensor that is connected to the second detector; in this case, the flow switch is placed in the internal volume of the thermostat, one of the outputs of the flow switch is connected to the flow line at the junction of the output of the pulse mark gas supply unit with the delay line, and the output of the pressure mark gas pressure regulator is connected to the input of each pulse mark gas input unit .
2. The device according to claim 1, characterized in that the pulse input unit of the gas flow label is configured to introduce into the flow the measured volume of gas flow of the gas flow label necessary for a given volume flow.
3. The device according to claim 1, characterized in that the pulse input unit of the gas flow mark is made on the basis of a two-way electro-pneumatic valve and a gas throttle.
4. The device according to claim 1, characterized in that the flow switch is based on two-way electro-pneumatic valves.
5. The device according to p. 1, characterized in that the thermostat is made in the form of a closed volume with the ability to maintain the set temperature value inside the volume.
6. The device according to p. 1, characterized in that the flow line is configured to transmit gas flow labels with thermal conductivity significantly different from the thermal conductivity of the measured gas stream.
7. The device according to claim 1, characterized in that the first as well as the second detectors are made either in the form of sensitive elements of thermal conductivity detectors with small geometric dimensions of the spirals of sensitive elements, or in the form of plenary microelectronic sensitive elements of thermal conductivity detectors.
8. The device according to p. 1, characterized in that the gas delay line is made either in the form of a metal tube, the diameter of which is much less than its length, or in the form of a polymer tube, the diameter of which is much less than its length.
9. The device according to p. 1, characterized in that the measuring volume is made either in the form of a metal tube, the diameter of which is much less than its length, or in the form of a polymer tube, the diameter of which is much less than its length.
10. The device according to claim 1, characterized in that the delay lines and the measuring volumes of the adjacent measuring channels are made of tubes with different inner diameters.
11. The device according to p. 1, characterized in that the delay line and the measuring volume are made in the form of tubes rolled into a spiral.
12. The device according to p. 1, characterized in that the gas source of the flow label is made in the form of a cylinder with gas flow label.
RU2017108061A 2017-03-10 2017-03-10 Device for gas volumetric flow rate measurement RU2644457C1 (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3614892A (en) * 1969-04-11 1971-10-26 M & J Valve Co Flowmeter temperature compensation system and method
US4253156A (en) * 1979-06-22 1981-02-24 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Automatic flowmeter calibration system
US5684246A (en) * 1992-04-30 1997-11-04 Sierra Instruments, Inc. Method and apparatus for improved flow rate measurement and calibration
CN103278220A (en) * 2013-06-05 2013-09-04 中国计量学院 Method for rapidly verifying intrinsic errors of membrane type gas meter and device thereof

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3614892A (en) * 1969-04-11 1971-10-26 M & J Valve Co Flowmeter temperature compensation system and method
US4253156A (en) * 1979-06-22 1981-02-24 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Automatic flowmeter calibration system
US5684246A (en) * 1992-04-30 1997-11-04 Sierra Instruments, Inc. Method and apparatus for improved flow rate measurement and calibration
CN103278220A (en) * 2013-06-05 2013-09-04 中国计量学院 Method for rapidly verifying intrinsic errors of membrane type gas meter and device thereof

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