SU1732163A1 - Flowmeter - Google Patents

Abstract

The invention relates to flow rate and allows to increase the measurement volume and expand the flow measurement range. When the flow rate on the diaphragm 1 changes, the pressure drop changes, which is detected by sensor 3. The output signal of sensor 3 is fed to summing amplifier optimizer k, at the output of which the error signal arises. Under the influence of this signal, the actuator 6 changes the flow area of the diaphragm 1. The counting unit 5 processes the signals and outputs the measurement result. 1 hp ff, 2 ill. 3 (/

Description

This invention relates to the measurement of liquid and gas flow.

A known system for measuring the flow rate of a fluid, containing a flow divider, in each bypass pipe is a flowmeter of the appropriate measurement limit, as well as a comparison selective switching device and a measuring device.

 The flow measurement system operates as follows.

The flow rate is recorded by the flow sensor and the result is processed in the comparing selective switching device and when the flow rate reaches the maximum flow rate through the sensor, the device switches the flow of liquid to another sensor with a different range. A further increase in flow will lead to switching the flow to the next sensor, and so on.

A disadvantage of the known system is its large size due to the presence of switching devices, pipelines and flow sensors, as well as the lack of information at the time of switching from one sensor to another.

Closest to the proposed invention, the technical essence is a flow meter that contains a metering line with a flow sensor installed in it and a diaphragm in parallel with which a differential sensor is connected.

The flow meter works as follows. The flow of liquid or gas passing through the diaphragm creates a pressure drop, which is recorded with a differential pressure gauge on the recorder. A piezoelectric sensor mounted behind the diaphragm detects the presence of flow. The electric signal from the piezoelectric sensor is fed through the trigger system to the additional pen drive mechanism on the recorder.

Thus, according to the chart of the recorder, you can separately determine the amount of liquid and gas flowing through the line.

The disadvantage is the narrow range of measurement of the flow rate of the fluid, as well as the low accuracy of the measurement at low flow rates, since the flow rate of the fluid is proportional to the product of the cross section of the diaphragm and root

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square of the pressure drop over it. The aperture area of the diaphragm is constant, which limits the range of measurable flow rates. In addition, the differential pressure sensor has the smallest relative error at the maximum differential, which means that at the minimum flow rate, the measurement was made with the highest error.

The purpose of the invention is to improve the accuracy of measuring the flow of liquid and gas and the expansion of the measurement range.

The goal is achieved by additionally introducing a diaphragm area sensor connected to a diaphragm, pressure and temperature sensors installed on the metering line, a differential pressure optimizer, an actuator and a calculating unit connected by inputs to the outputs of the differential sensor, pressure sensors , the temperature of the flow and the area of the diaphragm, the output of the differential sensor through the pressure differential optimizer is connected to the actuator associated with the diaphragm.

FIG. 1 is a block diagram of a liquid and gas flow meter; Fig. 2 is a block diagram of a pressure differential optimizer.

The flow meter contains a diaphragm 1 installed in the chamber main 2, a differential sensor 3, an optimizer L pressure differential, a calculating unit 5) an actuator 6, a diaphragm area sensor 7, a pressure sensor 8, a flow sensor 9 and a medium temperature sensor 10 .

The diaphragm 1, the actuator 6 and the diaphragm area sensor 7 constitute the bore adjuster 11.

The optimizer + pressure differential consists of a summing amplifier 12 and a non-linearity type 15 dead band.

The flow meter works as follows.

Measured medium (liquid ntin gas), passage through metering line 2 creates pressure difference on diaphragm 1, which is recorded by differential sensor 3. Voltage proportional to this pressure from sensor 3 enters calculating unit 5 and to the first input of sums5

power amplifier 12 optimizer k pressure drop. The second input of the summing amplifier 12 is supplied with a reference voltage equal to the voltage received from the differential sensor 3 at the maximum differential pressure across the diaphragm, but with the opposite sign. At the output of summing amplifier 12, the error voltage is obtained, so if ITp-} is a positive signal, a UJC ,. - negative, and in absolute value they are equal, then the output of SU 12 will be zero.

Changing the%) to a greater or lesser side from this value will result in a change in the amount, which will be positive or negative.

The error signal enters the nonlinearity block 13, at the output of which a signal of a different sign is obtained depending on the mismatch sign and taking into account the insensitivity.

A dead band nonlinearity unit 13 is inserted to prevent the actuator 6 from processing a certain range of pressure drop across the diaphragm.

The actuator 6 changes the flow area of the diaphragm 1 to such a level that the diaphragm 1 will have a maximum differential pressure.

The change in the flow area of the diaphragm 1 is recorded by the sensor 7 of the diaphragm area, the electrical signal from which is fed to the counting unit 5 for determining the flow rate of the medium being measured. When receiving a signal from sensor 9, the measured medium is a liquid, the counting unit 5 processes the results from the differential sensor 3, the diaphragm area sensor 7 and the medium temperature sensor 10, and if the measured medium is gas, block 5 processes the electrical signal pressure sensor 8.

Consider the operation of the flow meter with increasing fluid flow. As the flow rate on the diaphragm increases, the pressure drop (D.P.) increases, which is recorded by sensor 3, the output () of which increases in proportion to the voltage. This voltage enters the summing amplifier 12 of the optimizer h, at the output of which we receive the signal

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matching D U. If this signal is in the zone D1) of the nonlinearity unit 12, then the controller 11 does not and -,. changing its flow area, if the DI with amplifier 12 is larger than & U of block 13, then the actuator 6 increases the flow area of the diaphragm 1. Increasing the flow area reduces the difference in the diaphragm, and, accordingly, the voltage from the sensor 3 The diaphragm flow section increases to as long as with amplifier 12, the signal UU will be in zone 13 Di nonlinearity.

Similarly, we consider the operation of the circuit with a decrease in the flow of the medium.

When the flow rate decreases, the difference in diaphragm 1 decreases and, accordingly, Ujjg decreases, which will reduce AU amplifier 12. If U amp 12 is smaller than Di 13, then actuator 6 decreases the orifice plate 1. Decreased cross section causes an increase in Д Р and an increase in Di 12. A reduction in the flow area occurs as long as with amplifier 12 the signal AU falls into the zone UU of nonlinearity 13.

The counting unit 5 in all cases leads to the processing of electrical

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signals UD1), uD7, ig8, L with the corresponding sensors.

Performing a flow measurement system with a variable cross-sectional area allows you to increase the flow measurement range by several times, and creating a maximum pressure drop across the diaphragm increases the flow measurement accuracy.

Claims (2)

1. A flow meter comprising a metering line with a flow sensor installed therein and a diaphragm, in parallel with which a differential sensor is connected, characterized in that, in order to improve the accuracy of measurement and expansion of the range. a measurement zone, a diaphragm area sensor connected to the diaphragm, pressure and temperature sensors installed on the metering line, a differential pressure optimizer, an actuator and a calculating unit connected to one inputs with outputs of the differential sensor, pressure sensors, temperature, the presence of flow and aperture area, the output of the differential sensor through the pressure differential optimizer is connected to the actuator associated with the diaphragm. 2. The flow meter according to claim. the differential pressure torus contains successively connected summing amplifier and nonlinearity unit, output which is the output of the differential pressure optimizer, the input of which is connected to the first input of a summing amplifier connected by a second input to a source of the driving voltage. FIG. 2