CN113203443A - Differential pressure type online micro gas flowmeter and automatic detection method - Google Patents
Differential pressure type online micro gas flowmeter and automatic detection method Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/05—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects
- G01F1/34—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by measuring pressure or differential pressure
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Abstract
A differential pressure type on-line micro gas flowmeter and an automatic detection method are disclosed, the flowmeter comprises a differential pressure measurement branch which is divided into two alternatively operated branches from a gas source inlet, a gas source inlet valve, a measurement cavity and a measurement cavity outlet valve which are connected in sequence are arranged on the two differential pressure measurement branches, and a temperature sensor and a pressure sensor are arranged on the measurement cavity; the invention applies the differential pressure monitoring technology, adopts two branches to alternately operate and switch the measurement state, can buffer the large fluctuation of the air source inlet, and can ensure the high-precision continuous real-time monitoring flow; the volume of the measuring cavity is formulated according to the measuring range of the flow, the measuring cavity is suitable for measuring micro-flow gas, the theoretical flow value is calculated through the pressure sensor and the temperature sensor, and the measurement is accurate and reliable; the requirement on the purity of the measured gas is low, the measured gas is allowed to contain oil, water or dust, and the environment adaptability is good. The flowmeter has the advantages of simple structure, low cost, easy maintenance and basically no influence of the outside world on the precision, and is suitable for various industrial fields.
Description
Technical Field
The invention relates to the technical field of trace gas online flow measurement, in particular to a differential pressure type online trace gas flowmeter and an automatic detection method.
Background
At present, micro gas flowmeters are widely applied to important fields of electric power, chemical industry, medicine, materials and the like, the online measurement of some large-flow fluids is basically mature, but for micro fluids, particularly for micro gas flowmeters, manual measurement errors are easily caused by the fact that manual reading is basically relied on, and manually read data cannot be directly applied to an equipment control system, so that the industrial automation degree is limited and the working efficiency of the equipment is influenced.
More theoretical methods appear in recent years, based on a resistance type method and a capacitance type method, the weight of a rotor can be increased, the precision of measuring trace gas is influenced, and the resistance type and capacitance type devices are electrified, so that potential safety hazards exist in the measurement; the automatic metering method based on machine vision has the advantages that the structure of the measuring device is complex, the measuring device is not easy to be applied to industrial intelligent equipment as an element, the mode of applying wireless WiFi transmission and data reading is not suitable for network signal-free industrial sites such as a thermal power plant, and the vision sensor is easy to image fuzziness and is easy to be influenced by the environment when being used for a long time in the measuring site. Flow is indirectly derived by monitoring other variables based on a soft measurement method, such as a mass flow meter, but the requirement on the cleanliness of monitored gas is very high, and if the gas contains oil, water or dust, a measurement pipeline is blocked, so that the flow meter is irreversibly damaged.
In order to solve the automation of a trace gas flowmeter containing impurities in an industrial field and realize quick and effective metering, a stable, reliable and safe flowmeter capable of automatically measuring on line becomes a new requirement of an intelligent industrial field.
Disclosure of Invention
The invention aims to provide a differential pressure type online micro gas flowmeter and an automatic detection method in combination with new requirements of the current intelligent industrial field, wherein the differential pressure monitoring technology is utilized to realize real-time flow monitoring, and the method has high data measurement precision and strong reliability. The method is simple, convenient, rapid and safe, and the measuring system has good environment adaptability and can monitor the micro-flow impurity-containing gas.
In order to achieve the purpose, the invention adopts the following technical scheme:
a differential pressure type online micro gas flowmeter comprises a differential pressure measuring branch which is divided into two alternatively operated branches from a gas source inlet, wherein a first gas source inlet valve 1, a first measuring cavity 2 and a first measuring cavity outlet valve 5 which are sequentially connected are arranged on the first differential pressure measuring branch, and a first temperature sensor 3 and a first pressure sensor 4 are arranged on the first measuring cavity 2; a second air source inlet valve 6, a second measuring cavity 7 and a second measuring cavity outlet valve 10 which are connected in sequence are arranged on the second differential pressure measuring branch, and a second temperature sensor 8 and a second pressure sensor 9 are arranged on the second measuring cavity 7; the first and second measurement chamber outlet valves 5, 10 are connected to the gas source outlet.
The automatic detection method of the pressure difference type online trace gas flowmeter comprises the following specific method of switching the measurement state in the operation process of a first pressure difference measurement branch and a second pressure difference measurement branch in the pressure difference type online trace gas flowmeter:
step 3, when the first differential pressure measuring branch circuit meets the inflation state condition, namely the pressure of the first measuring cavity 2 is reduced to the allowable minimum value P1MINAt this time, the first air source inlet valve 1 is switched to be in an open state, the first measurement cavity outlet valve 5 is switched to be in a closed state, and the second differential pressure measurement branch is switched to be in a measurement state, namely the second air source inlet valve 6 is switched to be in a closed state, and the second measurement cavity outlet valve 10 is switched to be in an open state;
when a first differential pressure measurement branch of the differential pressure type online trace gas flowmeter is in an inflation state, opening a first gas source inlet valve 1, closing a first measurement cavity outlet valve 5, monitoring a first temperature sensor 3 and a first pressure sensor 4 on a first measurement cavity 2 in real time, closing the first gas source inlet valve 1 when the first pressure sensor 4 reaches a maximum pressure value allowed by the measurement cavity 2, and ending the inflation process of the first branch; when the first differential pressure measurement branch is in a measurement state, the first air source inlet valve 1 is closed, the first measurement cavity outlet valve 5 is opened, the first temperature sensor 3 and the first pressure sensor 4 on the first measurement cavity 2 are monitored in real time, and the interval time of data acquisition is t1Setting the value of the first temperature sensor 3 to T1The value of the first pressure sensor 4 is P1The maximum pressure value allowed by the first measuring cavity 2 is P1MAXThe first measuring chamber 2 is at a maximum pressure value P1MAXThe value of the first temperature sensor 3 is T1', the minimum pressure value allowed by the first measuring chamber 2 is P1MINThe volume of the first measuring chamber 2 is V1Can calculate formula Q according to theory1＝(P1MAXV1/P1-V1)/t1-δ1(T1-T1') to obtain a gas flow value Q at the outlet of the first measuring chamber 21Wherein, delta1For measuring the temperature loss coefficient of the first measurement chamber 2, when the first pressure sensor 4 reaches the minimum pressure value P allowed for the first measurement chamber 21MINThe first measuring chamber outlet valve 5 is closed and the measuring process of the first differential pressure measuring branch is ended.
The automatic detection method of the pressure difference type online micro gas flow meter comprises the steps that when a second pressure difference measuring branch of the pressure difference type online flow meter is in an inflation state, a second gas source inlet valve 6 is opened, a second measuring cavity outlet valve 10 is closed, a second temperature sensor 8 and a second pressure sensor 9 on a second measuring cavity 7 are monitored in real time, and when the second pressure is detectedWhen the force sensor 9 reaches the maximum pressure value allowed by the second measurement cavity 9, the second air source inlet valve 5 is closed, and the second branch inflation process is finished; when the second branch is in a measuring state, the second air source inlet valve 5 is closed, the second measuring cavity outlet valve 10 is opened, the second temperature sensor 8 and the second pressure sensor 9 on the second measuring cavity 7 are monitored in real time, and the interval time of data acquisition is t2Setting the value of the second temperature sensor 8 to T2The value of the second pressure sensor 9 is P2The maximum pressure value allowed by the second measuring cavity 7 is P2MAXThe second measuring chamber 7 is at a maximum pressure value P2MAXThe value of the second temperature sensor 8 is T2E, the minimum pressure value allowed by the second measuring cavity 7 is P2MINThe volume of the second measuring chamber 7 is V2Can calculate formula Q according to theory2＝(P2MAXV2/P2-V2)/t2-δ2(T2-T2') to obtain a gas flow value Q at the outlet of the measuring chamber 22Wherein δ2When the second pressure sensor 9 reaches the minimum pressure value P allowed by the second measuring cavity 7, the temperature loss coefficient of the second measuring cavity 7 in the measuring process is measured2MINWhen the pressure difference is measured, closing the outlet valve 10 of the second measurement cavity, and ending the measurement process of the second differential pressure measurement branch;
the automatic detection method of the pressure difference type online micro gas flowmeter is characterized in that the volumes V of a first measuring cavity 2 and a second measuring cavity 7 in the pressure difference type online micro gas flowmeter1And V2The measurement range of the trace gas is set, the smaller the measurement range of the trace gas is, the V1And V2The smaller the value of (a), the more accurate the measurement of the minute flow rate of the gas becomes.
Compared with the prior art, the invention has the following advantages:
1. the pressure difference type online flow monitoring adopts two branches to operate alternatively, so that the large fluctuation of an air source inlet can be buffered, and the high-precision continuous real-time online flow monitoring can be ensured.
2. The volume of the measuring cavity is formulated according to the measuring range of the flow, the measuring cavity is suitable for measuring micro-flow gas, the theoretical flow value is calculated through the pressure sensor and the temperature sensor, and the measurement is accurate and reliable.
3. The device has low requirement on the purity of the measured gas, allows the measured gas to contain oil, water or dust, and has good environment adaptability.
4. The device has the advantages of simple structure, low cost, easy maintenance and basically no influence of the outside world on the precision, and is suitable for various industrial fields.
Drawings
Fig. 1 is a schematic view of a differential pressure type on-line flowmeter of the present invention.
Detailed Description
The working principle of the present invention will be described in more detail with reference to the accompanying drawings.
As shown in fig. 1, the pressure difference type online micro gas flow meter comprises a pressure difference measuring branch which is divided into two alternately operated branches from a gas source inlet, wherein a first gas source inlet valve 1 is arranged on the first pressure difference measuring branch, and is sequentially connected with a first measuring cavity 2 and a first measuring cavity outlet valve 5, and a first temperature sensor 3 and a first pressure sensor 4 are arranged on the first measuring cavity 2; a second air source inlet valve 6 is arranged on the second differential pressure measuring branch, and is sequentially connected with a second measuring cavity 7 and a second measuring cavity outlet valve 10, and a second temperature sensor 8 and a second pressure sensor 9 are arranged on the second measuring cavity 7; the first and second measurement chamber outlet valves 5, 10 are connected to the gas source outlet.
The method comprises the following steps of switching the measuring state of a first measuring branch and a second measuring branch in the automatic detection process of the differential pressure type online trace gas flowmeter:
And 2, when the two differential pressure measurement branches meet the measurement state condition, the second differential pressure measurement branch keeps the original state unchanged, the first differential pressure measurement branch is preferentially switched to be in the measurement state, namely the first air source inlet valve 1 keeps the closed state, and the first measurement cavity outlet valve 5 is switched to be in the open state.
Step 3, when the first differential pressure measuring branch circuit meets the inflation state condition, namely the pressure of the first measuring cavity 2 is reduced to the allowable minimum value P1MINAt this time, the first gas source inlet valve 1 is switched to be in an open state, the first measurement chamber outlet valve 5 is switched to be in a closed state, and the second differential pressure measurement branch is switched to be in a measurement state, that is, the second gas source inlet valve 6 is switched to be in a closed state, and the second measurement chamber outlet valve 10 is switched to be in an open state.
And 5, sequentially and circularly repeating the step 3 and the step 4.
Specifically, when the first differential pressure measurement branch is in an inflation state, the first air source inlet valve 1 is opened, the first measurement cavity outlet valve 5 is closed, the first temperature sensor 3 and the first pressure sensor 4 on the first measurement cavity 2 are monitored in real time, when the first pressure sensor 4 reaches the maximum pressure value allowed by the measurement cavity 2, the first air source inlet valve 1 is closed, and the inflation process of the first branch is finished.
Specifically, when the first differential pressure measurement branch is in an inflation state and the first branch is in a measurement state, the first air source inlet valve 1 is closed, the first measurement cavity outlet valve 5 is opened, the first temperature sensor 3 and the first pressure sensor 4 on the first measurement cavity 2 are monitored in real time, and the data acquisition interval time is t1Setting the value of the first temperature sensor 3 to T1The value of the first pressure sensor 4 is P1The maximum pressure value allowed by the first measuring cavity 2 is P1MAXThe first measuring chamber 2 is at a maximum pressure value P1MAXThe value of the first temperature sensor 3 is T1E, the minimum pressure value allowed by the first measuring cavity 2 is P1MINThe volume of the first measuring chamber 2 is V1Can calculate formula Q according to theory1＝(P1MAXV1/P1-V1)/t1-δ1(T1-T1') to obtain a gas flow value Q at the outlet of the first measuring chamber 21Wherein, delta1For measuring the temperature loss coefficient of the first measurement chamber 2, when the first pressure sensor 4 reaches the minimum pressure value P allowed for the first measurement chamber 21MINThe first measuring chamber outlet valve 5 is closed and the measuring process of the first differential pressure measuring branch is ended.
Specifically, when the second differential pressure measurement branch is in an inflation state, the second air source inlet valve 6 is opened, the second measurement cavity outlet valve 10 is closed, the second temperature sensor 8 and the second pressure sensor 9 on the second measurement cavity 7 are monitored in real time, when the second pressure sensor 9 reaches the maximum pressure value allowed by the second measurement cavity 9, the second air source inlet valve 5 is closed, and the inflation process of the second branch is finished.
Specifically, when the second differential pressure measurement branch is in a measurement state, the second air source inlet valve 5 is closed, the second measurement cavity outlet valve 10 is opened, the second temperature sensor 8 and the second pressure sensor 9 on the second measurement cavity 7 are monitored in real time, and the interval time of data acquisition is t2Setting the value of the second temperature sensor 8 to T2The value of the second pressure sensor 9 is P2The maximum pressure value allowed by the second measuring cavity 7 is P2MAXThe second measuring chamber 7 is at a maximum pressure value P2MAXThe value of the second temperature sensor 8 is T2E, the minimum pressure value allowed by the second measuring cavity 7 is P2MINThe volume of the second measuring chamber 7 is V2Can calculate formula Q according to theory2＝(P2MAXV2/P2-V2)/t2-δ2(T2-T2') to obtain a gas flow value Q at the outlet of the measuring chamber 22Wherein δ2For measuring the temperature loss coefficient of the second measuring chamber 7, when the second pressure sensor 9 reachesMinimum pressure value P allowed for the second measuring chamber 72MINThe second measuring chamber outlet valve 10 is closed and the measuring process of the second differential pressure measuring branch is ended.
Claims (3)
1. A differential pressure type online micro gas flowmeter comprises a differential pressure measuring branch which is divided into two alternatively operated branches from a gas source inlet, wherein a first gas source inlet valve (1), a first measuring cavity (2) and a first measuring cavity outlet valve (5) which are sequentially connected are arranged on the first differential pressure measuring branch, and a first temperature sensor (3) and a first pressure sensor (4) are arranged on the first measuring cavity (2); a second air source inlet valve (6), a second measuring cavity (7) and a second measuring cavity outlet valve (10) which are sequentially connected are arranged on the second differential pressure measuring branch, and a second temperature sensor (8) and a second pressure sensor (9) are arranged on the second measuring cavity (7); the first measuring chamber outlet valve (5) and the second measuring chamber outlet valve (10) are connected to the gas source outlet.
2. The differential pressure type on-line trace gas flowmeter according to claim 1, characterized in that: the volumes V of the first measuring chamber (2) and the second measuring chamber (7)1And V2The measurement range of the trace gas is set, the smaller the measurement range of the trace gas is, the V1And V2The smaller the value of (a) is, the more accurately the minute flow rate of the gas is measured.
3. The automatic detection method of a differential pressure type on-line trace gas flowmeter according to claim 1 or 2, characterized in that: the specific method for switching the measurement state in the operation process of the first differential pressure measurement branch and the second differential pressure measurement branch in the differential pressure type online trace gas flowmeter is as follows:
step 1, the first differential pressure measurement branch and the second differential pressure measurement branch are kept in an inflation state, so that the first differential pressure measurement branch and the second differential pressure measurement branch both meet the measurement state condition, namely the pressures of the first measurement cavity (2) and the second measurement cavity (7) respectively reach the allowable maximum value P1MAXAnd P2MAXAnd a first gas source inlet valve (1), a second gas source inlet valve (6), a first measuring chamber outlet valve (5) and a second measuring chamberThe outlet valves (10) of the measuring chambers are all in a closed state;
step 2, when the two differential pressure measurement branches meet the measurement state condition, the second differential pressure measurement branch keeps the original state unchanged, the first differential pressure measurement branch is switched to the measurement state, namely the first air source inlet valve (1) keeps the closed state, and the first measurement cavity outlet valve (5) is switched to the open state;
step 3, when the first differential pressure measuring branch circuit meets the inflation state condition, namely the pressure of the first measuring cavity (2) is reduced to the minimum value P allowed1MINAt the moment, the first gas source inlet valve (1) is switched to be in an open state, the first measurement cavity outlet valve (5) is switched to be in a closed state, the second differential pressure measurement branch is switched to be in a measurement state, namely the second gas source inlet valve (6) is switched to be in a closed state, and the second measurement cavity outlet valve (10) is switched to be in an open state;
step 4, when the second differential pressure measuring branch circuit meets the inflation state condition, namely the pressure of the second measuring cavity (7) is reduced to the allowable minimum value P2MINAt the moment, the second gas source inlet valve (6) is switched to be in an open state, the second measuring cavity outlet valve (10) is switched to be in a closed state, the first differential pressure measuring branch is switched to be in a measuring state, namely the first gas source inlet valve (1) is switched to be in a closed state, and the first measuring cavity outlet valve (5) is switched to be in an open state;
step 5, repeating the step 3 and the step 4 in sequence;
the automatic detection method comprises the following steps: when the first differential pressure measurement branch is in an inflation state, opening a first air source inlet valve (1), closing a first measurement cavity outlet valve (5), monitoring a first temperature sensor (3) and a first pressure sensor (4) on a first measurement cavity (2) in real time, closing the first air source inlet valve (1) when the first pressure sensor (4) reaches the maximum pressure value allowed by the measurement cavity (2), and ending the inflation process of the first branch;
when the first differential pressure measurement branch is in a measurement state, the first air source inlet valve (1) is closed, the first measurement cavity outlet valve (5) is opened, the first temperature sensor (3) and the first pressure sensor (4) on the first measurement cavity (2) are monitored in real time, and the interval time of data acquisition is t1Setting the value of the first temperature sensor (3) to T1First pressure transmissionThe value of the sensor (4) is P1The maximum pressure value allowed by the first measuring cavity (2) is P1MAXThe first measuring chamber (2) is at a maximum pressure value P1MAXThe value of the first temperature sensor (3) is T1', the minimum pressure value allowed by the first measuring cavity (2) is P1MINThe volume of the first measuring chamber (2) is V1According to the calculation formula Q1＝(P1MAXV1/P1-V1)/t1-δ1(T1-T1') to obtain a gas flow value Q at the outlet of the first measuring chamber (2)1Wherein, delta1In order to measure the temperature loss coefficient of the first measuring cavity (2) during the process, when the first pressure sensor (4) reaches the minimum pressure value P allowed by the first measuring cavity (2)1MINWhen the pressure difference is measured, closing an outlet valve (5) of the first measuring cavity, and ending the measuring process of the first differential pressure measuring branch; the measurement process of the second differential pressure measurement branch is the same as that of the first differential pressure measurement branch.
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Application publication date: 20210803 |