SU1476436A1 - Method and apparatus for adjusting flow rate of gas - Google Patents

Abstract

The invention relates to methods for determining, measuring, controlling or controlling the flow of gases in the main lines of automatic systems. The aim of the invention is to expand the scope and increase accuracy. The method consists in measuring pressures in a narrow and wide sections of the restriction device, carried out with an interval depending on the pulsation of the flow, and calculating the flow rate as a function of pressure in the flow and pressure drops in the narrow and wide sections of the restriction device. A device for carrying out the method comprises a restriction device 2, selection nipples 3 and 4, a pneumatic switch 10, a pressure sensor 5, first 7, second 8 and third 9 electric switches, first 11 and second 12 memory blocks, algebraic adder 13, multiplication unit 6. 1 hp f-ly, 1 ill.

Description

The invention is inclined to methods for determining, measuring, controlling or controlling the flow of gases in main lines, for example, automatic systems or air conditioning systems. The purpose of the invention is to expand the scope of application of the method and improve the accuracy of determining the gas flow.

The drawing shows a schematic diagram of an apparatus for implementing a method for determining a gas flow rate. The device comprises a pipeline 1, a narrowing device 2 with fittings 3 and 4 for selecting pressure from narrow and wide sections, respectively, pressure sensor 5, multiplying unit 6, two on-off with synchronized wires, the first 7, second 8 and third 9 electrical switches and pneumatic switch 10, The first inlet is connected to the pressure tapping nozzle 3 from a narrow section, the second inlet is connected to the pressure tapping nozzle 4 from a wide section, and the output is connected to the input of the pressure sensor 5, the output of which is connected to the input of the first a switch 7, a first output coupled to an input of the first block memory 11 and per- vym input of the third electric switches 9, a second output connected to the input of the second block memory 12 and the second input of the second electric switches 8.

The output of the third electric switch 9 is connected to the first input of the algebraic adder 13 and to the first input of the multiplying unit 6, the second input of which is connected to the output of the algebraic adder 13. The output of the second auxiliary switch 8 is connected to the second input of the algebraic adder 13.

If the device is intended for 2, a differential pressure is determined.

controlling the flow rate of the gas, the regulator 14 is located in the pipeline 1 and is connected either to the toggle switch 15 or to the command unit 16, the input of which is connected to the output of the multiplying unit 6.

A temperature sensor 17 may also be installed in the device, the output of which is connected to the third input of the multiplying unit 6. In this case, the flow rate is calculated as a function of flow pressure and pressure drop across wide and narrow sections of the restriction device and the gas temperature. At50

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on it, and use this parameter as a measure of the flow rate of controlled stress. For this, using the pressure sensor 5 connected to the pressure tapping nozzle via the open first / pneumatic switch 10 input, the static pressure Rf) is measured in a narrow section.

After the end of the measurement of pressure Pn, the pneumatic switch TO automatically or manually transfers to the second, opposite position in which the first input is closed, and the second input is open and through it is 5 0 5 0

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Water 18 contains an electric motor with a transmission mechanism and an indicator of the duration of a half-cycle, i.e. switching frequencies, depending on the pulsations of the gas flow, appearing during the operation of the source 19 (compressor, fan, etc.). For visual observations, a flow indicator 20 and a periodicity and pressure amplitude monitor 21 are installed.

The first 11 and second 12 blocks of memory are electronic amplifying and converting computing devices on the microcircuits, which fix, store and reset the previous signal when they are turned on again.

The multiplication unit 6 is an electronic operational amplifier on chips, performing the following operations: addition, inversion, multiplication, division, extraction of the roots.

The device works as follows.

When the source 19 of the compressed air is turned on by the manual control switch 15, the regulator 14 is opened and the flow of the controlled medium is passed through the constriction device 2. Air under pressure rushes through the pipeline to the consumer.

In the constriction device 2, the part of the potential energy of the pressure transforms into kinetic energy, while the average flow velocity in the narrow section where the pressure fitting 3 is installed rises, and the static pressure Py in it becomes less than the static pressure Rc in the wide section where the fitting is installed 4 pressure selection. Pass flow through constriction device.

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on it and use this parameter as a measure of the flow rate of the controlled medium. To do this, using a pressure sensor 5 connected to pressure fitting 3 through an open first / pneumatic switch 10 input, the static pressure Rf) is measured in a narrow section.

After the end of the measurement of pressure Pn, the pneumatic switch TO is automatically or manually transferred to the second, opposite position, in which the first input is closed and the second input is opened and through it the fitting 4 of the restriction device 2 is connected to the input of the pressure sensor 5, by which the measurement There is a static pressure Рц, flow in a wide section, which has a lower speed and more pressure.

Measurements of the pressure of Py and Psh are performed in alternate order, then a pair of measurements of the pressure of Py and Psh are repeated cyclically: RU-RSH, PV-PW, etc. at a rate dependent on the stability of the operation of the source 19 of compressed gas. When implementing the method of determining the gas flow, if necessary, the flow temperature is also measured with a temperature sensor 17, in order to more accurately determine the flow rate. Using the data obtained listed measurements determined

Air flow in line 1 is calculated by calculating its value as a function of pressure in the flow, pressure drops at the restriction device, and temperatures. In the method of controlling the gas flow, depending on the deviation of the flow rate found from a given value, the flow area of the regulator 14 is changed, including opening or closing the engine, for example, manually controlling the flow rate of the toggle switch 15 until the current flow rate is equal to the set value.

In a device for carrying out the proposed method, the determination and control of the flow rate is carried out automatically.

The subtraction operation is performed automatically by the electronic algebraic adder 13 as follows.

The diagram shows the position of the device when the pneumatic switch 10 and the electric switch 7-9 are in the position at which the pressure P is fed through the pneumatic switch 10 to the input of the pressure sensor 5. In this case, the electrical voltage signal corresponding to

from the output of the pressure sensor 5 is fed to the first input of the multiplying unit 6, as well as to the input of the first pressure memory unit 11 of Py and to the first input of the algebraic adder 13. In this position, the device lasts for half a cycle, which is necessary

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It is necessary to obtain data characterizing the controlled flow according to the pressure value Py.

Measuring the pressure of Ru, corresponding to its instantaneous, integral value during the period of the half-cycle, the pneumatic switch 10 and the electric switches 7-9 are simultaneously translated. c to the second position at which the pressure Ry is supplied to the input of the pressure sensor 5. In this case, an electrical voltage signal corresponding to the pressure Psh in a wide section of the restriction device 2, from the output of the pressure sensor 5, is fed to the second input of the algebraic adder 13, as well as the input of the second memory block 12

pressure

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The next half cycle of pressure measurement Ry is equal to the previous one (for example, 2.5.10, etc., seconds). In the same position, from the first memory block 11, an electrical voltage signal corresponding to the pressure Pn measured in the immediately preceding half cycle is fed to the first inputs of the multiplying block 6 and the algebraic adder 13, which compares the electrical voltage signals received at its inputs corresponding to the actual pressure Psh of the given half cycle and the stored pressure P of the previous half cycle, calculates the difference between them, the magnitude of the signal increment, and amplifies the algebraic difference obtained s The signal thus obtained is proportional to the difference between two successively

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and Rsha va 2 lah, torus

in sections of a narrowing device, in two consecutive semi-cycles, from the output of the algebraic sum, 13 goes to the second input of the multiple

The unit 6, which automatically determines the actual air flow rate in the pipe 1, calculates its value as a function of the flow pressure and the pressure drop across the restriction device.

Claims (2)

1. A method for determining the flow rate of a gas, consisting in measuring pressures in a wide and narrow cross section of a restriction device, measuring pressure in a flow, and calculating the flow as a function of pressure in a flow and differential pressure. pressures in wide and narrow sections of the restriction device, which is used in order to expand the field of application and increase accuracy, pressure measurements in the narrow and wide sections of the restriction device are carried out at intervals proportional to the ripple flow. 2. A device for determining gas flow, comprising a pipeline in which a restriction device is installed with wide-narrow and narrowing selection nozzles, an algebraic adder with two inputs and an output connected to the first input of the multiplying unit, and a pressure sensor having that, in order to broaden the field of application and increase the accuracy, a pneumatic switch, two-position with synchronized drives, and the first, second and third electric switches, the first and second blocks na MP, the inputs of which are connected, respectively, with the first and second outputs of the first electric switch, the second input of the multiplying unit and the first input of the algebraic adder connected to the output of the third electric switch, the first and second inputs of which are connected respectively to the first output of the first electric switch and the output of the first block memory, and the second input of the algebraic adder is connected to the output of the second electric switch, the first and second inputs of which are connected respectively to the output of the second on the memory block and the second output of the first electric switches having an input coupled with the pressure sensor output, the input coupled to the output of the pneumatic switch, the first and second inputs of which are connected with fittings selection respectively in narrow and wide x secheni5 five 0