CN111337071A - Natural gas measurement evaluation system - Google Patents
Natural gas measurement evaluation system Download PDFInfo
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- CN111337071A CN111337071A CN201911285684.3A CN201911285684A CN111337071A CN 111337071 A CN111337071 A CN 111337071A CN 201911285684 A CN201911285684 A CN 201911285684A CN 111337071 A CN111337071 A CN 111337071A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D21/00—Measuring or testing not otherwise provided for
- G01D21/02—Measuring two or more variables by means not covered by a single other subclass
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D18/00—Testing or calibrating apparatus or arrangements provided for in groups G01D1/00 - G01D15/00
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F25/00—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume
- G01F25/10—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume of flowmeters
Abstract
The invention provides a natural gas metering and evaluating system, which comprises a flow metering device arranged in a natural gas pipeline and a flow computer arranged outside the natural gas pipeline; the flow metering device comprises a flow meter, a temperature transmitter, a pressure transmitter and a gas chromatographic analysis instrument, wherein the flow meter, the temperature transmitter, the pressure transmitter and the gas chromatographic analysis instrument are used as primary measuring instruments to measure the flow, the temperature, the pressure and the gas components of the natural gas respectively; the flow computer is used as a secondary metering instrument, the uncertainty of the system is calculated by collecting the measured value of the primary metering instrument on the spot, the measurement accuracy of the field metering system is evaluated by using the uncertainty of the system, and the larger the uncertainty is, the worse the measurement accuracy of the field metering system is. The invention calculates the calculation method verification and the system uncertainty of the metering system by calling a natural gas physical property calculation dynamic calculation calling library and a measurement uncertainty calculation calling library, and the calculation method verification result is compared with the actual measurement result to directly obtain the calculation deviation of the field metering system; and the measurement accuracy of the field metering system can be directly evaluated according to the result of measurement uncertainty calculation.
Description
Technical Field
The invention relates to an evaluation system, in particular to a natural gas metering evaluation system.
Background
Natural gas has become an important development trend for world energy application as a high-quality, efficient and clean low-carbon energy and chemical raw material. Since the 21 st century, the natural gas consumption in our country has increased rapidly, from 1509 billions of cubic meters in 2012 to 1884 billions of cubic meters in 2014. The natural gas industry development is accelerated, the proportion of natural gas in primary energy consumption is improved, and the method has important strategic significance for adjusting the energy structure, improving the living standard of people, promoting energy conservation and emission reduction and coping with climate change in China. The increase speed of the natural gas demand of China will obviously exceed that of coal and petroleum in the next 20 years, and the proportion of the natural gas in the total energy demand will exceed 10% in 2020, and the demand amount is estimated to reach 2517 billion cubic meters. With the rapid increase of natural gas trade volume, international natural gas trade is increasingly frequent, and the measurement of natural gas is concerned and valued by trade parties. In order to meet the requirements of high-pressure, large-flow and high-accuracy measurement development directions of natural gas trade, various natural gas flowmeters of different types such as an ultrasonic flowmeter, a turbine flowmeter, a vortex shedding flowmeter, a Coriolis flowmeter, a standard orifice plate flowmeter and the like are applied to a measurement system of natural gas trade handover and process measurement.
Since the strategy of 'natural gas big development' is implemented in China petrochemical industry, the China has completed the east China gas supply pipeline, Yuji natural gas pipeline and Qingdao LNG, and has started to build the Guangxi LNG, Tianjin LNG, Zhongyuan and Jintan gas storage, and other important projects, and gradually forms a gas supply market taking 'two lines and three zones' as the main parts in the whole country. In the aspect of natural gas development, key capacity construction projects are accelerated, management of old gas fields such as plain light is strengthened, marketing strategies are reasonably adjusted, the total amount of operation is enlarged, and economic benefits are improved; in the aspect of shale gas development, 50 billion square of capacity construction in the first stage of Fuling is efficiently promoted, the daily production level of a production well exceeds the design scheme, and a good situation of large development is formed. In 2014, China petrochemical industry produces about 202.88 billion cubic meters of natural gas, the year is 8.5 percent of natural gas, 183.1 billion cubic meters of natural gas are sold, the year is 8.7 percent of natural gas, the market area of the natural gas is expanded to more than 20 provinces in China, and the natural gas becomes a new economic growth point. In the heavy-spot projects such as the new natural gas pipeline of the petrochemical industry in China, LNG (liquefied natural gas) and the like, the ultrasonic flowmeter becomes a main handover metering instrument and is widely applied. In 2014, the number of natural gas flow meters used in high-pressure natural gas metering systems by China main petrochemical natural gas pipeline enterprises is nearly 800.
In the natural gas metering system at present, the popularity of primary instruments such as a flowmeter, a temperature transmitter, a pressure transmitter, a differential pressure transmitter, a gas chromatography analyzer is quite high, the popularity of secondary instruments such as a flow computer, a volume calculator and the like is higher and higher, most natural gas trade handing-over units can carry out effective periodic traceability/verification work on the primary instruments, but in the aspect of verification of the secondary instruments, because of no mandatory verification category, a part of secondary instruments are not subjected to effective periodic verification.
In a typical natural gas metering system, the configuration of a metering device of a primary meter, the management of the primary meter, and the configuration parameter configuration of a flow computer all affect the measurement accuracy of the whole natural gas metering system. At present, no matter the overall evaluation of the whole natural gas metering system in China is mainly guided by GBT 35186 and 2017 'natural gas metering system performance evaluation', but because compulsory verification is not included, basically no evaluation work is executed, a user level mainly focuses on one-time instrument periodic verification and trade transmission difference, and a corresponding evaluation system or execution specification is not available.
Disclosure of Invention
Aiming at the technical problem, the invention provides a natural gas metering and evaluating system which comprises a flow metering device arranged in a natural gas pipeline and a flow computer arranged outside the natural gas pipeline; the flow metering device comprises a flow meter, a temperature transmitter, a pressure transmitter and a gas chromatographic analysis instrument, wherein the flow meter, the temperature transmitter, the pressure transmitter and the gas chromatographic analysis instrument are used as primary measuring instruments to measure the flow, the temperature, the pressure and the gas components of the natural gas respectively; the flow computer is used as a secondary metering instrument, the uncertainty of the system is calculated by collecting the measured value of the primary metering instrument on the spot, the measurement accuracy of the field metering system is evaluated by using the uncertainty of the system, and the greater the uncertainty is, the poorer the measurement accuracy of the field metering system is.
The system further comprises a working condition instantaneous flow meter arranged in the natural gas pipeline, wherein the working condition instantaneous flow meter collects working condition instantaneous flow in the natural gas pipeline; the flow computer is used as a secondary metering instrument, the measured value of the primary metering instrument on the site is collected to calculate, the instantaneous flow of the standard condition is also calculated, and the instantaneous flow of the standard condition is compared with the instantaneous flow of the working condition, so that the flow deviation of the on-site metering system is obtained.
Further, the flowmeter is an ultrasonic flowmeter, a turbine flowmeter, a waist wheel flowmeter, a mass flowmeter or a vortex shedding flowmeter, and the uncertainty comprises volume flow uncertainty, pressure uncertainty, temperature uncertainty and compression factor uncertainty;
the uncertainty formula is:
analyzing the uncertainty of each parameter item by item, wherein:
ur(qs,s) The working condition volume flow uncertainty; read from the nameplate of the flow meter apparatus.
ur(ps) Working condition pressure uncertainty; read from the nameplate of the flow meter apparatus.
ur(Ts) Working condition temperature uncertainty; read from the nameplate of the flow meter apparatus.
ur(Zs) Compression factor uncertainty for the operating conditions; read from the nameplate of the flow meter apparatus.
ur(pf) The standard condition pressure uncertainty;
ur(Tf) Is standard condition temperature uncertainty;
ur(Zsf) The standard condition compression factor uncertainty;
the uncertainty function in the uncertainty formula is derived from a calculation formula of the volume flow of the standard meter method gas flow standard device, and the calculation formula of the volume flow of the standard meter method gas flow standard device is as follows:
in the formula: -standard volumetric flow rate at standard conditions of the flowmeter;
-volumetric flow rate under the conditions of the flowmeter; the natural gas pipeline is internally provided with a working condition flowmeter device, the working condition flowmeter device comprises a working condition flowmeter, and the volume flow under the working condition of the flowmeter is from the measured value of the working condition flowmeter;
-pressure under standard conditions, constant, 101.325 kPa;
-temperature under standard conditions, constant, 20 ℃;
-compression factor under standard conditions;
-pressure under flow meter conditions; the natural gas pipeline is internally provided with a working condition flowmeter device, the working condition flowmeter device comprises a working condition pressure transmitter, and the pressure of the flowmeter under the working condition is from the measured value of the working condition pressure transmitter;
-temperature under flow meter conditions; the natural gas pipeline is internally provided with a working condition flowmeter device, the working condition flowmeter device comprises a working condition temperature transmitter, and the temperature of the flowmeter under the working condition is obtained from the measured value of the working condition temperature transmitter;
-compression factor under flowmeter conditions; the compression factor at the flow meter is calculated according to the method in AGA NO.8 report or GB/T17747.2-1999 standard, and the method for calculating the compression factor at the flow meter in AGA NO.8 report and GB/T17747.2-1999 standard is a standard and belongs to the known technology, and is not described in a repeated way;
further, the flow meter is a sonic nozzle and orifice plate flow meter, and the uncertainty comprises the uncertainty of the sectional area of the throat part of the boundary flow Venturi nozzle, the uncertainty of the outflow coefficient, the uncertainty of the critical flow function, the uncertainty of stagnation pressure, the uncertainty of the gas constant and the uncertainty of stagnation temperature;
when a single critical flow venturi nozzle participates in flow measurement, the mass flow measurement uncertainty formula of the metering system is as follows:
the mass flow calculation formula measured by the metering system is as follows:
the uncertainty of each parameter is analyzed item by item.
The flow meter, the temperature transmitter, the pressure transmitter and the gas chromatographic analysis instrument are respectively connected with the switch, data exchange is carried out through a TCP/IP protocol, the flow computer is connected with the switch, and data in the flow meter, the temperature transmitter, the pressure transmitter and the gas chromatographic analysis instrument are collected through the TCP/IP protocol.
The flow computer is connected with the diagnosis terminal, and collects data in the flow meter, the temperature transmitter, the pressure transmitter and the gas chromatography analyzer through the TCP/IP protocol.
The calculation method of each metering system checks the uncertainty evaluation calculation of the system, and the dynamic calculation call library of natural gas physical property calculation is called for calculation in the calculation process.
The instantaneous flow and the accumulated flow of the flow meters are calculated by the following methods:
1) ultrasonic flowmeter flow velocity calculation
The gas ultrasonic flowmeter is a flow meter comprising a flowmeter body, an electronic element, a microprocessor system, an ultrasonic transducer and the like. Ultrasonic transducers are typically mounted along the wall of a pipe and are in direct contact with the gas and are subject to the pressure of the gas. Ultrasonic pulses emitted by one ultrasonic transducer are received by the other ultrasonic transducer and vice versa. In some flow meters, a reflected acoustic channel is used, where the acoustic pulse undergoes one or more reflections at the tube wall.
The ultrasonic pulses travel through the pipeline like a ferry through a river. If the gas is not flowing, the sound waves will propagate in both directions at the same speed. When the gas flow velocity in the pipe is not zero, the downstream propagating pulses in the direction of the gas flow will increase in speed, while the upstream propagating pulses will slow down. Thus, the forward flow propagation time tD will be shortened and the reverse flow propagation time tU will be increased relative to the absence of gas flow, both propagation times being measured by the electronic components. From these two travel times, the measured flow velocity can be calculated
In the formula:
v-average flow velocity of gas in meters per second (m/s);
l-vocal tract length in meters (m);
x-track distance in meters (m);
tU — the time of acoustic pulse counter-current propagation in seconds(s);
tD-the time for the downstream propagation of the acoustic pulse in seconds(s).
2) Instantaneous operating condition flow calculation of ultrasonic flowmeter
In a multi-channel gas ultrasonic flow meter, ultrasonic transducers are arranged in various ways. The channels may be parallel to each other or may be otherwise oriented. The flow meter may propagate acoustic waves directly or via reflection along two or more angled strings. The method used to combine the measurements of the individual channels into an average flow velocity also varies depending on the particular configuration of the flow meter. It is particularly worth mentioning that not all methods use the aforementioned k-factor to calculate the mean flow rate.
In a multi-channel gas ultrasonic flowmeter, a calculation is made from a series of discrete y values
Since V can be expressed as:
here the average flow velocity along the vocal tract (the lateral position of the chord line is Y) and the above equation can be integrated using a suitable digital integration technique, such as gaussian integration. Thus, it is possible to obtain a channel-by-channel basis
An approximation of the axial average flow velocity V is calculated. The expression is as follows:
here, the
Is the weighting factor associated with the integration technique used, yi is the chord line transverse position of the ultrasound transducer. This is a widely used digital integration technique that can be implemented in a number of ways in a flow meter. The channel positions chosen should be such that the weighting coefficients are treated as constants, without requiring assumptions on the velocity profile, but depending on the method used.
The product of the axial average flow velocity and the flow area a is the volume flow qf at the operating conditions:
qf＝VA………………(23)
the flowmeter is designed and manufactured by using an ultrasonic propagation principle and a digital integration technology, and the measured value according to the formula (5) is the natural gas flow under the working condition. The flow rate under the standard reference condition is calculated according to the gas state equation according to the airflow static pressure and the temperature which are actually measured on line.
3) Instantaneous flow calculation under standard reference condition of ultrasonic flowmeter
In a multi-channel gas ultrasonic flow meter, ultrasonic transducers are arranged in various ways. The channels may be parallel to each other or may be otherwise oriented. The flow meter may propagate acoustic waves directly or via reflection along two or more angled strings. The method used to combine the measurements of the individual channels into an average flow velocity also varies depending on the particular configuration of the flow meter. It is particularly worth mentioning that not all methods use the aforementioned k-factor to calculate the mean flow rate.
In a multi-channel gas ultrasonic flowmeter, a calculation is made from a series of discrete y values
Since V can be expressed as:
here the average flow velocity along the vocal tract (the lateral position of the chord line is Y) and the above equation can be integrated using a suitable digital integration technique, such as gaussian integration. Thus, it is possible to obtain a channel-by-channel basis
An approximation of the axial average flow velocity V is calculated. The expression is as follows:
here, the
Is the weighting factor associated with the integration technique used, yi is the chord line transverse position of the ultrasound transducer. This is a widely used digital integration technique that can be implemented in a number of ways in a flow meter. The channel positions chosen should be such that the weighting coefficients are treated as constants, without requiring assumptions on the velocity profile, but depending on the method used.
The product of the axial average flow velocity and the flow area a is the volume flow qf at the operating conditions:
qf＝VA………………(26)
the flowmeter is designed and manufactured by using an ultrasonic propagation principle and a digital integration technology, and the measured value according to the formula (5) is the natural gas flow under the working condition. The flow rate under the standard reference condition is calculated according to the gas state equation according to the airflow static pressure and the temperature which are actually measured on line.
4) Cumulative flow calculation under standard reference conditions for ultrasonic flow meters
The instantaneous flow under standard reference conditions of the flowmeter is calculated as follows:
in the formula: qn-instantaneous flow rate under standard reference conditions, in cubic meters per hour (m 3/h);
qf-instantaneous flow under operating conditions, in cubic meters per hour (m 3/h);
pn-absolute pressure under standard reference conditions, having a value of 0.101325 MPa;
pf-the absolute static pressure under operating conditions, in megapascals (MPa);
tn-the thermodynamic temperature under standard reference conditions, with a value of 293.25K;
tf-thermodynamic temperature under operating conditions in Kelvin (K);
zn, a compression factor under standard reference conditions, is calculated according to GB/T17747;
zf is the compression factor under the working condition and is calculated according to GB/T17747.
4. Turbine flow metering system calculation model
The typical turbine metering system comprises a turbine flowmeter, a temperature transmitter, a pressure transmitter, a gas chromatographic analyzer and a flow computer, wherein the turbine flowmeter, the temperature transmitter, the pressure transmitter and the gas chromatographic analyzer are used as primary measuring instruments to respectively measure the working condition flow, the temperature, the pressure and the gas components of natural gas, the flow computer is used as a secondary measuring instrument, and the working condition compression factor and the standard condition compression factor of the natural gas are calculated by collecting the measured value of the primary measuring instrument on site, so that the instantaneous standard condition flow of the natural gas is calculated.
The specification mainly used by the turbine flow metering system is as follows:
JJG 1037 turbine flowmeter verification procedure
GB _ T21391-
ISO 9951Measurement of Gas Flow in Closed Conduits–Turbine Meters
1) Turbine flowmeter instantaneous operating condition flow calculation
The turbine flowmeter is a measuring device in which an impeller rotates under the action of measured gas flow in a pipeline, the rotating speed of the impeller and the volume flow of gas are in a functional relation, and the measured gas flow passing through the flowmeter is obtained on the basis of measuring the number of pulses generated by the rotation of the impeller.
The turbine flowmeter volumetric flow is calculated by:
in the formula: qV-turbine flow meter volumetric flow rate, cubic meters per hour (m 3/h).
The value measured according to equation (8) is the natural gas flow rate under the operating conditions. The flow rate under the standard reference condition is calculated according to the gas state equation according to the airflow static pressure and the temperature which are actually measured on line.
2) Instantaneous flow calculation under standard reference condition of turbine flowmeter
The instantaneous flow under standard reference conditions of the flowmeter is calculated as follows:
in the formula: qn-instantaneous flow rate under standard reference conditions, in cubic meters per hour (m 3/h);
qf-instantaneous flow under operating conditions, in cubic meters per hour (m 3/h);
pn-absolute pressure under standard reference conditions, having a value of 0.101325 MPa;
pf-the absolute static pressure under operating conditions, in megapascals (MPa);
tn-the thermodynamic temperature under standard reference conditions, with a value of 293.25K;
tf-thermodynamic temperature under operating conditions in Kelvin (K);
zn, a compression factor under standard reference conditions, is calculated according to GB/T17747;
zf is the compression factor under the working condition and is calculated according to GB/T17747.
3) Cumulative flow calculation for turbine flow meter under standard reference conditions
The cumulative flux at standard reference conditions is calculated as:
in the formula: qn-cumulative amount over a period of time from t0 to t under standard reference conditions, in cubic meters (m 3);
dt — integral increment of time.
5. Calculating model of waist wheel flow measuring system
The typical waist wheel metering system consists of a waist wheel flowmeter, a temperature transmitter, a pressure transmitter, a gas chromatographic analyzer and a flowmeter computer, wherein the waist wheel flowmeter, the temperature transmitter, the pressure transmitter and the gas chromatographic analyzer are used as primary measuring instruments to respectively measure the working condition flow, the temperature, the pressure and the gas components of natural gas, the flowmeter computer is used as a secondary measuring instrument, and the working condition compression factor and the standard condition compression factor of the natural gas are calculated by collecting the measured value of the primary measuring instrument on site, so that the instantaneous standard condition flow of the natural gas is calculated.
The main used regulation specification of the waist wheel flow metering system is as follows:
SY _ T6660-2006 method for measuring natural gas flow by using rotary volumetric gas flowmeter
JJG 633-once 2005 gas volumetric flowmeter
3.EN 12480 64_e_stfGas meters-Rotary displacement gas meters
1) Instantaneous operating condition flow calculation of waist wheel flowmeter
A roots meter is a typical positive displacement meter, which is a measuring device in which a rotor is forced to rotate by a flow of gas to be measured in a pipe, the rotational speed of the impeller of the roots meter being a function of the volumetric flow of the gas, the flow of gas through the roots meter being measured based on the number of pulses generated by the rotation of the rotor.
The volumetric flow rate of the waist wheel flowmeter is calculated by the following formula:
in the formula: qV-Roots flowmeter volumetric flow, cubic meters per hour (m 3/h).
The value measured according to equation (8) is the natural gas flow rate under the operating conditions. The flow rate under the standard reference condition is calculated according to the gas state equation according to the airflow static pressure and the temperature which are actually measured on line.
2) Instantaneous flow calculation under standard reference conditions of a Roots flowmeter
The instantaneous flow under standard reference conditions of the flowmeter is calculated as follows:
in the formula: qn-instantaneous flow rate under standard reference conditions, in cubic meters per hour (m 3/h);
qf-instantaneous flow under operating conditions, in cubic meters per hour (m 3/h);
pn-absolute pressure under standard reference conditions, having a value of 0.101325 MPa;
pf-the absolute static pressure under operating conditions, in megapascals (MPa);
tn-the thermodynamic temperature under standard reference conditions, with a value of 293.25K;
tf-thermodynamic temperature under operating conditions in Kelvin (K);
zn, a compression factor under standard reference conditions, is calculated according to GB/T17747;
zf is the compression factor under the working condition and is calculated according to GB/T17747.
3) Cumulative flow calculation under Roots flowmeter standard reference conditions
The cumulative flux at standard reference conditions is calculated as:
in the formula: qn-cumulative amount over a period of time from t0 to t under standard reference conditions, in cubic meters (m 3);
dt — integral increment of time.
6. Calculation model of vortex street flow metering system
Similar to ultrasonic flowmeter, turbine flowmeter and waist wheel flowmeter, the vortex flowmeter is a typical speed flowmeter, a typical vortex metering system is composed of a vortex flowmeter, a temperature transmitter, a pressure transmitter, a gas chromatographic analyzer and a flowmeter computer, wherein the vortex flowmeter, the temperature transmitter, the pressure transmitter and the gas chromatographic analyzer are used as primary measuring instruments to respectively measure the working condition flow, the temperature, the pressure and the gas components of natural gas, the flow computer is used as a secondary metering instrument, and the working condition compression factor and the standard condition compression factor of the natural gas are calculated by collecting the measured value of the primary metering instrument on site, so that the instantaneous standard condition flow of the natural gas is calculated.
The main used regulation specification of the vortex street flow metering system is as follows:
JJG 1029-2007 vortex street flowmeter
Method for measuring fluid flow in GB _ T25922-2010 closed pipeline by using vortex shedding flowmeter installed in circular-section pipeline filled with fluid
ISO TR12764:1997Measurement of fluid flow in closed conduits—Flowrate measurement by means of vortex shedding
1) Instantaneous working condition flow calculation of vortex shedding flowmeter
The vortex shedding flowmeter is a measuring device which generates vortex under the action of measured gas flow in a pipeline, the frequency generated by the vortex is in a functional relation with the volume flow of the gas, and the measured gas flow passing through the flowmeter is obtained on the basis of measuring the number of pulses generated by the rotation of an impeller.
After the fluid passes through a vortex generator (see fig. 1) consisting of helical blades, the fluid is forced to rotate vigorously around the generator axis, forming a vortex. When the fluid enters the diffusion section, the vortex flow starts to rotate for the second time under the action of backflow, and a gyro type vortex precession phenomenon is formed. The precession frequency is proportional to the flow rate and is not influenced by the physical properties and density of the fluid. The flow rate is known by measuring the secondary rotational precession frequency of the fluid by the detection element. And good linearity can be obtained over a wide range of flow rates. The flow calculation formula is:
K＝f/q………………(34)
in the formula: k is the flow meter coefficient l/m 3;
f-vortex frequency Hz
q-volume flow m3/h
The meter coefficient of the flowmeter is independent of the temperature, pressure, composition and physical properties (density, viscosity) of the fluid within certain structural parameters and specified reynolds number ranges.
The value measured according to equation (11) is the natural gas flow rate under the operating conditions. The flow rate under the standard reference condition is calculated according to the gas state equation according to the airflow static pressure and the temperature which are actually measured on line.
2) Instantaneous flow calculation under standard reference condition of vortex shedding flowmeter
The instantaneous flow under standard reference conditions of the flowmeter is calculated as follows:
in the formula: qn-instantaneous flow rate under standard reference conditions, in cubic meters per hour (m 3/h);
qf-instantaneous flow under operating conditions, in cubic meters per hour (m 3/h);
pn-absolute pressure under standard reference conditions, having a value of 0.101325 MPa;
pf-the absolute static pressure under operating conditions, in megapascals (MPa);
tn-the thermodynamic temperature under standard reference conditions, with a value of 293.25K;
tf-thermodynamic temperature under operating conditions in Kelvin (K);
zn, a compression factor under standard reference conditions, is calculated according to GB/T17747;
zf is the compression factor under the working condition and is calculated according to GB/T17747.
3) Cumulative flow calculation under vortex shedding flowmeter standard reference conditions
The cumulative flux at standard reference conditions is calculated as:
in the formula: qn-cumulative amount over a period of time from t0 to t under standard reference conditions, in cubic meters (m 3);
dt — integral increment of time.
7. Calculation model of orifice plate flow metering system
The standard orifice plate flowmeter consists of a standard orifice plate, an orifice plate clamping device, a pressure taking pipeline, a front straight pipe section, a rear straight pipe section, a differential pressure transmitter, a gauge pressure transmitter, a temperature transmitter and a flow computer which are seen just before, wherein the flow computer is used as a secondary metering instrument, and the working condition compression factor and the standard condition compression factor of natural gas are calculated by collecting the measured value of a primary metering instrument on site, so that the instantaneous standard condition flow of the natural gas is calculated.
The orifice plate flow metering system mainly uses the following regulation specifications:
SYT6143-2004 measurement of Natural gas flow with a Standard orifice flowmeter
GBT 21446-
3.ISO 5167Orifice
1) Orifice flowmeter instantaneous operating condition flow calculation
The measuring principle of the orifice plate flowmeter is simple, namely when air flows through a standard orifice plate, differential pressure is generated on the upstream side and the downstream side of the orifice plate, the larger the air flow is, the larger the generated differential pressure is, and the magnitude of the air flow can be determined by measuring the differential pressure according to the relation between the differential pressure and the flow.
Specifically, then, the flow calculation for a standard orifice meter is such and virtually all standard differential pressure meters follow the calculation:
in this connection, it is possible to use,
qm-mass flow rate, kg/s;
c-outflow coefficient, dimensionless;
β -the ratio of the diameter of the opening of the standard orifice plate to the inner diameter of the upstream pipeline, which is called the diameter ratio for short and is dimensionless;
epsilon-coefficient of expandability, dimensionless;
d, the diameter of the opening of the standard orifice plate, m;
Δ p-differential pressure, Pa;
ρ1the air density at the upstream tapping, kg/m3, under operating conditions.
2) Instantaneous flow calculation under standard reference conditions of orifice plate flowmeter
The flow calculation utility formula derived by pushing down under the natural gas condition is as follows:
the value measured according to equation (8) is the natural gas flow rate under the operating conditions. The flow rate under the standard reference condition is calculated according to the gas state equation according to the airflow static pressure and the temperature which are actually measured on line.
3) Cumulative flow calculation under standard reference conditions for orifice plate flowmeters
The cumulative flux at standard reference conditions is calculated as:
in the formula: qn-cumulative amount over a period of time from t0 to t under standard reference conditions, in cubic meters (m 3);
dt — integral increment of time.
8. Nozzle flow metering system calculation model
The typical standard nozzle metering system consists of a standard nozzle, a temperature transmitter, a pressure transmitter, a gas chromatographic analyzer and a flow computer, wherein the standard nozzle, the temperature transmitter, the pressure transmitter and the gas chromatographic analyzer are used as primary measuring instruments to respectively measure the working condition flow, the temperature, the pressure and the gas components of natural gas, the flow computer is used as a secondary measuring instrument, and the working condition compression factor and the standard condition compression factor of the natural gas are calculated by collecting the measured value of the primary measuring instrument on site, so that the instantaneous standard condition flow of the natural gas is calculated.
The protocol specifications used primarily for standard nozzle flow metering systems are as follows:
ISO 9300-
GB _ T21188-
JJG 620 + 2008 critical flow venturi nozzle verification procedure
BS ENISO 5167.3-2003 fluid flow measurement with a differential pressure device inserted into a circular section pipe nozzle and a Venturi nozzle
1) Mass flow calculation for critical flow venturi nozzle instantaneous operating conditions
The theoretical mass flow at critical flow venturi nozzle metering is calculated by:
in the formula: a-nozzle throat area, cubic meters (m 3);
c — critical flow function;
p 0-stagnation pressure at the nozzle throat, megapascals (MPa);
t0-stagnation temperature at the throat of the nozzle, on (K).
2) Critical flow venturi nozzle transient condition volumetric flow calculation
The critical flow venturi nozzle volume is calculated by the following formula:
in the formula: qV-critical flow Venturi nozzle volumetric flow, cubic meters per hour (m 3/h);
z0-stagnation natural gas compression factor at the throat of the nozzle.
3) Instantaneous flow calculation under critical flow Venturi jet standard reference condition
The instantaneous flow under standard reference conditions of the flowmeter is calculated as follows:
in the formula: qn-instantaneous flow rate under standard reference conditions, in cubic meters per hour (m 3/h);
qf-instantaneous flow under operating conditions, in cubic meters per hour (m 3/h);
pn-absolute pressure under standard reference conditions, having a value of 0.101325 MPa;
pf-the absolute static pressure under operating conditions, in megapascals (MPa);
tn-the thermodynamic temperature under standard reference conditions, with a value of 293.25K;
tf-thermodynamic temperature under operating conditions in Kelvin (K);
zn, a compression factor under standard reference conditions, is calculated according to GB/T17747;
zf is the compression factor under the working condition and is calculated according to GB/T17747.
4) Cumulative flow calculation under critical flow venturi jet standard reference conditions
The cumulative flux at standard reference conditions is calculated as:
in the formula: qn-cumulative amount over a period of time from t0 to t under standard reference conditions, in cubic meters (m 3);
dt — integral increment of time.
Calculation model of 9 Coriolis flow metering system
The Coriolis flowmeter is a mass flowmeter, a typical Coriolis metering system comprises a Coriolis flowmeter, a temperature transmitter, a pressure transmitter, a gas chromatography analyzer and a flowmeter computer, wherein the Coriolis flowmeter, the temperature transmitter, the pressure transmitter and the gas chromatography analyzer are used as primary measuring instruments for respectively measuring the working condition flow, the temperature, the pressure and the gas components of natural gas, the flowmeter computer is used as a secondary measuring instrument, and the working condition compression factor and the standard condition compression factor of the natural gas are calculated by collecting the measured value of the primary measuring instrument on site, so that the instantaneous standard condition flow of the natural gas is calculated.
The protocol specification mainly used by the coriolis flow metering system is as follows:
SYT 6659-2006 uses a Coriolis mass flowmeter to measure natural gas flow
JJG 1038-
ISO 10790:2015gives guidelines for the selection,installation,calibration,performance,and operation of Coriolis flowmeters for themeasurement of mass flow and density
1) Coriolis flowmeter transient operating condition flow calculation
The flowmeter is a novel instrument for directly and precisely measuring the mass flow of fluid, and two parallel U-shaped pipes are adopted as a structural main body, so that the bent parts of the two pipes vibrate slightly in opposite directions, the straight pipes on the two sides vibrate along with each other, namely, the straight pipes can be closed or opened simultaneously, namely, the vibration of the two pipes is synchronous and symmetrical. Coriolis flowmeters are measuring devices in which the vibrations of two measuring tubes, which vibrate in opposite directions under the influence of a gas flow to be measured in a pipeline, are functionally related to the volumetric flow of the gas, the measurement of the gas flow through the flowmeter being based on the phase difference between the measuring tubes.
The coriolis flowmeter body instantaneous volumetric flow rate is calculated by:
in the formula: q. q.smCoriolis flowmeter mass flow rate, kilograms per hour (kg/h).
The measured value according to equation (21) is the natural gas mass flow under operating conditions. The flow rate under instantaneous volume flow and standard reference conditions should be calculated from the on-line measured static airflow pressure, temperature and composition.
2) Instantaneous flow calculation under operating conditions of coriolis flowmeter
The instantaneous flow under operating conditions of the coriolis flowmeter is calculated as follows:
in the formula: q. q.sm-instantaneous mass flow under working conditions in kilograms per hour (kg/h);
qf-instantaneous volumetric flow under operating conditions, in cubic meters per hour (m 3/h);
ρf-density under working conditions, which value is kilograms per cubic meter (kg/m 3).
3) Instantaneous flow calculation under standard reference conditions for coriolis flowmeters
The instantaneous flow under the standard reference condition of the coriolis flowmeter is calculated according to the following formula:
in the formula: q. q.sm-instantaneous mass flow under working conditions in kilograms per hour (kg/h);
qn-instantaneous volume flow in cubic meters per hour (m3/h) under standard reference conditions;
ρn-density under standard reference conditions, which value is kilograms per cubic meter (kg/m 3).
4) Cumulative flow calculation for coriolis flowmeter under standard reference conditions
The cumulative flux at standard reference conditions is calculated as:
in the formula: qn-cumulative amount over a period of time from t0 to t under standard reference conditions, in cubic meters (m)3)；
dt — integral increment of time.
The working principle of the invention is as follows: calculating the calculation method verification and the system uncertainty of the metering system by calling a natural gas physical property calculation dynamic calculation calling library and a measurement uncertainty calculation calling library, and comparing the calculation method verification result with an actual measurement result to directly obtain the calculation deviation of the field metering system; and the measurement accuracy of the field metering system can be directly evaluated according to the result of measurement uncertainty calculation.
The method comprises the steps of selecting the type of a system to be evaluated in the system, inputting field working condition conditions such as temperature, pressure and natural gas components after selecting the type and the precision grade of field metering equipment, automatically calculating by software to obtain a standard condition instantaneous flow calculation result and system uncertainty of the natural gas metering system of the type, and comparing the standard condition instantaneous flow calculation result and the system uncertainty with a measurement result of the measured flow metering system to obtain the relative deviation of the measured metering system and a theoretical metering result, thereby evaluating the calculation precision and the measurement uncertainty of the measured metering system.
The system can directly check and evaluate different types of natural gas metering systems by researching a metering system calculation method and an uncertainty evaluation method which take an ultrasonic flowmeter, a turbine flowmeter, a pore plate flowmeter, a nozzle flowmeter, a precession vortex flowmeter, a Coriolis flowmeter and a waist wheel flowmeter as main bodies and combining natural gas physical property parameters.
Drawings
Fig. 1 is a network architecture diagram of the natural gas metering and evaluating system of the present invention.
Detailed description of the preferred embodiments
Example 1: a natural gas metering and evaluating system comprises a flow metering device arranged in a natural gas pipeline and a flow computer arranged outside the natural gas pipeline; the flow metering device comprises a flow meter, a temperature transmitter, a pressure transmitter and a gas chromatographic analysis instrument, wherein the flow meter, the temperature transmitter, the pressure transmitter and the gas chromatographic analysis instrument are used as primary measuring instruments to measure the flow, the temperature, the pressure and the gas components of the natural gas respectively; the flow computer is used as a secondary metering instrument, the uncertainty of the system is calculated by collecting the measured value of the primary metering instrument on the spot, the measurement accuracy of the field metering system is evaluated by using the uncertainty of the system, and the greater the uncertainty is, the poorer the measurement accuracy of the field metering system is.
The system further comprises a working condition instantaneous flow meter arranged in the natural gas pipeline, wherein the working condition instantaneous flow meter collects working condition instantaneous flow in the natural gas pipeline; the flow computer is used as a secondary metering instrument, the measured value of the primary metering instrument on the site is collected to calculate, the instantaneous flow of the standard condition is also calculated, and the instantaneous flow of the standard condition is compared with the instantaneous flow of the working condition, so that the flow deviation of the on-site metering system is obtained.
Further, the flowmeter is an ultrasonic flowmeter, a turbine flowmeter, a waist wheel flowmeter, a mass flowmeter or a vortex shedding flowmeter, and the uncertainty comprises volume flow uncertainty, pressure uncertainty, temperature uncertainty and compression factor uncertainty;
the uncertainty formula is:
analyzing the uncertainty of each parameter item by item, wherein:
ur(qs,s) The working condition volume flow uncertainty;
ur(ps) Working condition pressure uncertainty;
ur(Ts) Working condition temperature uncertainty;
ur(Zs) Compression factor uncertainty for the operating conditions;
ur(pf) The standard condition pressure uncertainty;
ur(Tf) Is standard condition temperature uncertainty;
ur(Zsf) The standard condition compression factor uncertainty;
the uncertainty function in the uncertainty formula is derived from a calculation formula of the volume flow of the standard meter method gas flow standard device, and the calculation formula of the volume flow of the standard meter method gas flow standard device is as follows:
in the formula: -standard volumetric flow rate at standard conditions of the flowmeter;
-volumetric flow rate under the conditions of the flowmeter; the natural gas pipeline is internally provided with a working condition flowmeter device, the working condition flowmeter device comprises a working condition flowmeter, and the volume flow under the working condition of the flowmeter is from the measured value of the working condition flowmeter;
-pressure under standard conditions, constant, 101.325 kPa;
-temperature under standard conditions, constant, 20 ℃;
-compression factor under standard conditions;
-pressure under flow meter conditions; the natural gas pipeline is internally provided with a working condition flowmeter device, the working condition flowmeter device comprises a working condition pressure transmitter, and the pressure of the flowmeter under the working condition is from the measured value of the working condition pressure transmitter;
-temperature under flow meter conditions; the natural gas pipeline is internally provided with a working condition flowmeter device, the working condition flowmeter device comprises a working condition temperature transmitter, and the temperature of the flowmeter under the working condition is obtained from the measured value of the working condition temperature transmitter;
-compression factor under flowmeter conditions; the compression factor at the flow meter is calculated according to the method in the AGA NO.8 report, which is a well-known technique and is not described herein in detail;
taking ultrasonic flow meter, turbine flow meter, waist wheel flow meter, mass flow meter and vortex shedding flow meter uncertainty analysis as examples
The ultrasonic flowmeter, the turbine flowmeter, the waist wheel flowmeter, the mass flowmeter and the vortex shedding flowmeter have similar calculation methods, taking a turbine flow metering system as an example, a gas flow measuring system consists of 1 turbine flowmeter, 1 temperature transmitter, 1 pressure transmitter and 1 gas component analyzer.
In the flow measurement process, the flow measurement uncertainty of a single turbine flowmeter is taken as the flow measurement uncertainty of a flow standard device.
The calculation formula of the volume flow of the standard meter gas flow standard device is shown as the formula (48):
in the formula, qs,f-standard volumetric flow rate for standard conditions of the turbine flowmeter;
qs,s-volumetric flow rate under turbine flowmeter operating conditions;
pf-pressure under standard conditions, constant, 101.325 kPa;
Tf-temperature under standard conditions, constant, 20 ℃;
zf-compression factor under standard conditions;
ps-pressure under turbine meter conditions;
Tsturbine flowmeter behaviorTemperature under conditions;
zs-compression factor under turbine meter operating conditions.
The flow measurement uncertainty of the turbine flow metering system is calculated by adopting a method in JJF 1059.1-2012 'measurement uncertainty evaluation and expression' and an equation (48) as shown in an equation (49):
the uncertainty of each parameter is analyzed item by item:
(1) uncertainty of volume flow of turbine flow meter
Typically, taking the case that a turbine flow meter of the turbine flow metering system traces to a Nanjing substation secondary flow metering system as an example, the uncertainty of the measurement error is better than 0.24% through the previous calibration report; confidence probabilities are all 95%, including factor k 2:
the uncertainty of relative expansion of the volume flow of the turbine flowmeter is Ur(qs,s)＝0.24％，k＝2。
The relative standard uncertainty of the volumetric flow of a turbine flowmeter is: u. ofr(qs,s)＝0.12％。
(2) Uncertainty of pressure at a turbine meter
The pressure measurement uncertainty at the turbine flowmeter is mainly due to the pressure transmitter, and the pressure transmitter at the turbine flowmeter is exemplified by a 3051S pressure transmitter manufactured by Rosemount corporation, and has a maximum allowable error of ± 0.025%, and is uniformly distributed.
The relative standard uncertainty of the pressure at the turbine flow meter is:
(3) uncertainty of temperature at turbine flow meter
The uncertainty of the temperature measurement at the turbine flowmeter mainly comes from a temperature transmitter, which is manufactured by Rosemount, and is a 3144P temperature transmitter, for example, the extended uncertainty of the temperature measurement is 0.05 ℃ (K is 2), and the extended uncertainty is converted into an absolute temperature of 0.05K, and the common temperature is 293.15K.
The relative standard uncertainty of the temperature at the turbine meter is:
(4) uncertainty of compression factor at a turbine flowmeter
The compression factor at the turbine flow meter was calculated according to the method in the AGA No.8 report and had a relative expansion uncertainty of 0.1% (k ═ 2).
The relative standard uncertainty of the compression factor at the turbine meter is:
because the calculation methods are the same, the compression factor uncertainty of the turbine flowmeter under the working condition and the standard condition is the working condition, the standard condition is not repeatedly calculated, and the value is 0.
The temperature and pressure of the turbine meter at standard conditions are constant with an uncertainty of 0.
In summary, the uncertainty of the volumetric flow of the metering system is shown in table 1:
TABLE 1 turbine flow metering system volume flow uncertainty evaluation statistical table
The uncertainty of the relative expansion of the volume flow of the turbine flow metering system is as follows: u shaper(qv)＝Ur(qs,f)＝0.29％，k＝2。
Example 2: a natural gas metering and evaluating system comprises a flow metering device arranged in a natural gas pipeline and a flow computer arranged outside the natural gas pipeline; the flow metering device comprises a flow meter, a temperature transmitter, a pressure transmitter and a gas chromatographic analysis instrument, wherein the flow meter, the temperature transmitter, the pressure transmitter and the gas chromatographic analysis instrument are used as primary measuring instruments to measure the flow, the temperature, the pressure and the gas components of the natural gas respectively; the flow computer is used as a secondary metering instrument, the uncertainty of the system is calculated by collecting the measured value of the primary metering instrument on the spot, the measurement accuracy of the field metering system is evaluated by using the uncertainty of the system, and the greater the uncertainty is, the poorer the measurement accuracy of the field metering system is.
The system further comprises a working condition instantaneous flow meter arranged in the natural gas pipeline, wherein the working condition instantaneous flow meter collects working condition instantaneous flow in the natural gas pipeline; the flow computer is used as a secondary metering instrument, the measured value of the primary metering instrument on the site is collected to calculate, the instantaneous flow of the standard condition is also calculated, and the instantaneous flow of the standard condition is compared with the instantaneous flow of the working condition, so that the flow deviation of the on-site metering system is obtained.
Further, the flow meter is a sonic nozzle and orifice plate flow meter, and the uncertainty comprises the uncertainty of the sectional area of the throat part of the boundary flow Venturi nozzle, the uncertainty of the outflow coefficient, the uncertainty of the critical flow function, the uncertainty of stagnation pressure, the uncertainty of the gas constant and the uncertainty of stagnation temperature;
when a single critical flow venturi nozzle participates in flow measurement, the mass flow measurement uncertainty formula of the metering system is as follows:
the mass flow calculation formula measured by the metering system is as follows:
the uncertainty of each parameter is analyzed item by item.
The gas flow metering system composed of the critical flow Venturi nozzle or the orifice plate flowmeter has the same calculation method, and the mass flow measurement uncertainty of a single nozzle is taken as the measurement uncertainty of the metering system.
When a single critical flow venturi nozzle participates in flow measurement, the mass flow measurement uncertainty of the metering system can be expressed as:
the mass flow calculation formula measured by the metering system is as follows:
the uncertainty of each parameter is analyzed item by item:
⑴ uncertainty of cross-sectional area of throat of venturi nozzle:
the metering system critical flow venturi nozzle is in a data processing system of the metering system, the sectional area of the throat part of the critical flow nozzle is used as a constant to participate in flow calculation, and the numerical value of the critical flow venturi nozzle does not have a system error; the diameter of the throat part is used for calculating the sectional area of the throat part, and the nominal diameter adopted in the Nanjing substation for calibration is adopted, so that the measured mass flow can be corrected accurately and reliably by the outflow coefficient provided by the Nanjing substation. However, in the actual measurement process, the sectional area of the throat part changes along with the changes of pressure and temperature, and the medium components in the measurement pipeline are not completely consistent in each measurement process, so that a certain influence is generated on the measurement result of mass flow.
The simplified calculation formula of the nozzle throat diameter along with the temperature and pressure change is as follows:
the different pressure and temperature can be easily obtained according to the formula, and the calculation formula of the nozzle throat diameter variation value is as follows:
in the formula, d is a nominal throat diameter;
β is the linear expansion coefficient of steel, and the value is 10.5 × 10-6mm/(mm·℃)；
E is the Young's modulus of steel, with a value of 1.94 × 1011N/m2；
t is the nozzle wall thickness.
According to the test data of the Nanjing substation, the test pressure of the critical flow nozzle is respectively 5.5 MPa, 6.0 MPa and 6.5MPa, and the normal working pressure of the substation is (6.2-6.4) MPa; the testing temperature of the critical flow nozzle is 12-14 ℃, and the normal working temperature of the substation is 5-20 ℃. The maximum value of the change of the throat diameter of the nozzle can be calculated:
the maximum value of the variation value of the cross section area of the throat part of the nozzle is as follows:
according to even distribution, the uncertainty of the expansion of the sectional area of the throat part of the nozzle is as follows:
the relative uncertainty in the cross-sectional area of the nozzle throat is therefore:
the relative uncertainty of the nozzle throat cross-sectional area is estimated as: u. ofr(A)＝0.015％；
⑵ uncertainty of outflow coefficient:
typically, the outflow coefficient of the critical flow venturi nozzle gas flow metering system is traced from the Nanjing substation 'mt' method gas flow metering system, and the uncertainty of the outflow coefficient is better than 0.15% through the previous calibration report; the confidence probabilities are all 95%, including the factor k 2. The test data of the magnitude tracing is detailed in the calibration certificate of the critical flow venturi nozzle:
therefore, the outflow coefficient traceability uncertainty of the critical flow Venturi nozzle throat diameter nozzle of the critical flow Venturi nozzle gas flow metering system is better than that of the critical flow Venturi nozzle gas flow metering system
k＝2；
The data processing system of the critical flow Venturi nozzle gas flow metering system adopts a linear fitting method to calculate the outflow coefficient of the nozzle in an interpolation mode, and the numerical value of the outflow coefficient participating in calculation is determined by calculating the Reynolds number of the throat part of the nozzle.
The relationship between the outflow coefficient and the reynolds number can be determined according to the outflow coefficient at the reynolds number corresponding to each nozzle in the detection process provided in the nozzle report.
The Reynolds number of the throat part of the nozzle is calculated by the formula:
natural gas viscosity is a parameter related to temperature and gas composition, and the related data gives an uncertainty estimate of 0.75% for its calculated results, but in the flow measurement, its sensitivity coefficient is very small,
the resulting mass flow measurement changes are negligible.
The uncertainty of the outflow coefficient of the critical flow venturi nozzle is as follows:
k＝2；
⑶ uncertainty of critical flow function:
the critical flow function is a function of stagnation pressure, stagnation temperature, and gas composition. The numerical value is slightly influenced by temperature and pressure, and the sensitivity coefficients are as follows:
the influence of stagnation pressure and stagnation temperature on the critical flow function can be ignored, and the uncertainty of the method mainly comes from a mathematical model for calculating the critical flow function by using gas components. The data processing system of the metering system adopts the state equation provided by AGA-NO.8 report to calculate the gas, the ideal state equation of the gas is error-free, but the deviation of the actual gas calculation result is 0.05%, and the critical flow function has the expansion uncertainty according to the uniform distribution:
⑷ uncertainty of stagnation pressure:
the stagnation pressure at the upstream inlet of the critical flow Venturi nozzle is obtained by measuring the static pressure at the inlet of the nozzle by using a pressure transmitter and calculating by using a thermodynamic formula, wherein the calculation formula is as follows:
the isentropic index is determined by the working condition pressure, temperature and the measured natural gas components; the Mach number is calculated through the nominal volume flow of the nozzle and the diameter of the pipeline at the upstream inlet, the influence of the two parameters on the calculation result of the stagnation pressure is about 0.002%, the influence can be ignored, and the uncertainty of the stagnation pressure is considered to be mainly derived from the uncertainty of the pressure measurement at the upstream inlet of the nozzle.
The uncertainty of pressure measurement mainly comes from the sum of a gauge pressure transmitter and an absolute atmospheric pressure transmitter, and the gauge pressure transmitter is a 3051S pressure transmitter produced by Rosemount CorpThe indication error of the absolute pressure transmitter is better than 0.025 percent through debugging and field verification, the model produced by Rosemount company is 3051C, the indication error of the absolute pressure transmitter is better than 0.05 percent, and the maximum contribution value of the uncertainty of the absolute pressure transmitter is less than 0.05 percent/50 to 0.001 percent considering that the actual use pressure is about more than 50 times of the atmospheric pressure, and the expansion uncertainty of the stagnation pressure is as follows according to uniform distribution:
⑸ uncertainty of gas constant:
the general gas constant is introduced as a constant in the data processing system, and the value of the general gas constant is not changed in the process of participating in calculation, so that the general gas constant is considered to have no error; the molar mass of the gas is calculated according to the components of the natural gas, during the detection process, the components of the natural gas are obtained by on-line chromatographic analysis, the molar mass measurement accuracy is 0.1%, and according to uniform distribution, the relative uncertainty of the obtained gas constant is as follows:
⑹ uncertainty of stagnation temperature:
the stagnation temperature at the upstream inlet of the critical flow Venturi nozzle is obtained by calculating a thermodynamic formula through a static pressure measured by a temperature transmitter, wherein the calculation formula is as follows:
the error of the stagnation temperature calculation result introduced by the errors of the two parameters of the isentropic index and the Mach number is 0.004%, the uncertainty of the stagnation temperature is considered to be mainly derived from the uncertainty of the measurement of the static temperature, the indication error of the temperature transmitter is superior to 0.1K, the common working temperature is 293.15K, and the expansion uncertainty of the stagnation temperature according to uniform distribution is as follows:
in summary, the uncertainty of the flow measurement of the metering system is as follows:
| serial number | Symbol | Relative uncertainty |
| 1 | A | 0.015％ |
| 2 | Cd | 0.15％ |
| 3 | C* | 0.058％ |
| 4 | P0 | 0.029％ |
| 5 | R/M | 0.115％ |
| 6 | T0 | 0.039％ |
The mass flow measurement uncertainty of the critical flow Venturi gas flow measurement system is better than that of the mass flow measurement:
the confidence probability is 95%, including the factor k 2.
Example 3:
as shown in fig. 1, a natural gas metering and evaluating system includes a flow metering device disposed in a natural gas pipeline and a flow computer 6 disposed outside the natural gas pipeline; the flow metering device comprises a flow meter 1, a temperature transmitter 2, a pressure transmitter 3 and a gas chromatographic analysis instrument 4, wherein the flow meter 1, the temperature transmitter 2, the pressure transmitter 3 and the gas chromatographic analysis instrument 4 are used as primary measuring instruments to measure the flow, the temperature, the pressure and the gas components of the natural gas respectively; the flow computer is used as a secondary metering instrument, the uncertainty of the system is calculated by collecting the measured value of the primary metering instrument on the spot, the measurement accuracy of the field metering system is evaluated by using the uncertainty of the system, and the greater the uncertainty is, the poorer the measurement accuracy of the field metering system is.
The system further comprises a working condition instantaneous flow meter arranged in the natural gas pipeline, wherein the working condition instantaneous flow meter collects working condition instantaneous flow in the natural gas pipeline; the flow computer is used as a secondary metering instrument, the measured value of the primary metering instrument on the site is collected to calculate, the instantaneous flow of the standard condition is also calculated, and the instantaneous flow of the standard condition is compared with the instantaneous flow of the working condition, so that the flow deviation of the on-site metering system is obtained.
Further, still include switch 5, flowmeter 1, temperature transmitter 2, pressure transmitter 3, gas chromatography analytical instrument 4 are connected with switch 5 respectively, carry out data interchange through the TCP/IP protocol, flow computer 6 is connected with switch 5, gathers the data in flowmeter 1, temperature transmitter 2, pressure transmitter 3, the gas chromatography analytical instrument 4 and carries out the computing system uncertainty and the instantaneous flow of standard condition through the TCP/IP protocol.
Further, the flow meter device further comprises a PLC (programmable logic controller) 7, a communication network 8 and a diagnosis terminal 9, wherein the flow meter 1, the temperature transmitter 2, the pressure transmitter 3 and the gas chromatography analyzer 4 are respectively connected with the PLC 7 and exchange data through a TCP/IP (transmission control protocol/Internet protocol) protocol, the communication network 8 is responsible for network communication between the PLC 7 and the diagnosis terminal 9, the flow computer 6 is connected with the diagnosis terminal 9, and data in the flow meter 1, the temperature transmitter 2, the pressure transmitter 3 and the gas chromatography analyzer 4 are collected through the TCP/IP protocol and system uncertainty and standard condition instantaneous flow are calculated.
Further, the flowmeter is an ultrasonic flowmeter, a turbine flowmeter, a waist wheel flowmeter, a mass flowmeter or a vortex shedding flowmeter, and the uncertainty comprises volume flow uncertainty, pressure uncertainty, temperature uncertainty and compression factor uncertainty;
the uncertainty formula is:
analyzing the uncertainty of each parameter item by item, wherein:
ur(qs,s) The working condition volume flow uncertainty;
ur(ps) Working condition pressure uncertainty;
ur(Ts) Working condition temperature uncertainty;
ur(Zs) Compression factor uncertainty for the operating conditions;
ur(pf) The standard condition pressure uncertainty;
ur(Tf) Is standard condition temperature uncertainty;
ur(Zsf) Is a standard condition compression factorDetermining degree;
the uncertainty function in the uncertainty formula is derived from a calculation formula of the volume flow of the standard meter method gas flow standard device, and the calculation formula of the volume flow of the standard meter method gas flow standard device is as follows:
in the formula: q. q.ss,f-standard volumetric flow rate at standard conditions of the flowmeter;
qs,s-volumetric flow rate under the conditions of the flowmeter; the natural gas pipeline is internally provided with a working condition flowmeter device, the working condition flowmeter device comprises a working condition flowmeter, and the volume flow under the working condition of the flowmeter is from the measured value of the working condition flowmeter;
pf-pressure under standard conditions, constant, 101.325 kPa;
Tf-temperature under standard conditions, constant, 20 ℃;
zf-compression factor under standard conditions;
ps-pressure under flow meter conditions; the natural gas pipeline is internally provided with a working condition flowmeter device, the working condition flowmeter device comprises a working condition pressure transmitter, and the pressure of the flowmeter under the working condition is from the measured value of the working condition pressure transmitter;
Ts-temperature under flow meter conditions; the natural gas pipeline is internally provided with a working condition flowmeter device, the working condition flowmeter device comprises a working condition temperature transmitter, and the temperature of the flowmeter under the working condition is obtained from the measured value of the working condition temperature transmitter;
zs-compression factor under flowmeter conditions; the compression factor at the flow meter is calculated according to the method in the AGA NO.8 report, which is a well-known technique and is not described herein in detail;
further, the flow meter is a sonic nozzle and orifice plate flow meter, and the uncertainty comprises the uncertainty of the sectional area of the throat part of the boundary flow Venturi nozzle, the uncertainty of the outflow coefficient, the uncertainty of the critical flow function, the uncertainty of stagnation pressure, the uncertainty of the gas constant and the uncertainty of stagnation temperature;
when a single critical flow venturi nozzle participates in flow measurement, the mass flow measurement uncertainty formula of the metering system is as follows:
the mass flow calculation formula measured by the metering system is as follows:
the uncertainty of each parameter is analyzed item by item.
Claims (6)
1. A natural gas measurement evaluation system is characterized in that: the flow meter comprises a flow metering device arranged in a natural gas pipeline and a flow computer arranged outside the natural gas pipeline; the flow metering device comprises a flow meter, a temperature transmitter, a pressure transmitter and a gas chromatographic analysis instrument, wherein the flow meter, the temperature transmitter, the pressure transmitter and the gas chromatographic analysis instrument are used as primary measuring instruments to measure the flow, the temperature, the pressure and the gas components of the natural gas respectively; the flow computer is used as a secondary metering instrument, the uncertainty of the system is calculated by collecting the measured value of the primary metering instrument on the spot, the measurement accuracy of the field metering system is evaluated by using the uncertainty of the system, and the greater the uncertainty is, the poorer the measurement accuracy of the field metering system is.
2. The natural gas metering and evaluating system according to claim 1, wherein: the natural gas pipeline working condition instantaneous flow meter is arranged in the natural gas pipeline and used for collecting working condition instantaneous flow in the natural gas pipeline; the flow computer is used as a secondary metering instrument, the measured value of the primary metering instrument on the site is collected to calculate, the instantaneous flow of the standard condition is also calculated, and the instantaneous flow of the standard condition is compared with the instantaneous flow of the working condition, so that the flow deviation of the on-site metering system is obtained.
3. The natural gas metering and evaluating system according to claim 1, wherein: the flowmeter is an ultrasonic flowmeter, a turbine flowmeter, a waist wheel flowmeter, a mass flowmeter or a vortex shedding flowmeter, and the uncertainty comprises volume flow uncertainty, pressure uncertainty, temperature uncertainty and compression factor uncertainty;
the uncertainty formula is:
analyzing the uncertainty of each parameter item by item, wherein:
ur(qs,s) The working condition volume flow uncertainty;
ur(ps) Working condition pressure uncertainty;
ur(Ts) Working condition temperature uncertainty;
ur(Zs) Compression factor uncertainty for the operating conditions;
ur(pf) The standard condition pressure uncertainty;
ur(Tf) Is standard condition temperature uncertainty;
ur(Zsf) The standard condition compression factor uncertainty;
the uncertainty function in the uncertainty formula is derived from a calculation formula of the volume flow of the standard meter method gas flow standard device, and the calculation formula of the volume flow of the standard meter method gas flow standard device is as follows:
in the formula: q. q.ss,f-standard volumetric flow rate at standard conditions of the flowmeter;
qs,s-volumetric flow rate under the conditions of the flowmeter; the natural gas pipeline is internally provided with a working condition flowmeter device, the working condition flowmeter device comprises a working condition flowmeter, and the volume flow under the working condition of the flowmeter is from the measured value of the working condition flowmeter;
pf-pressure under standard conditions, constant, 101.325 kPa;
Tf-temperature under standard conditions, constant, 20 ℃;
zf-compression factor under standard conditions;
ps-pressure under flow meter conditions; the natural gas pipeline is internally provided with a working condition flowmeter device, the working condition flowmeter device comprises a working condition pressure transmitter, and the pressure of the flowmeter under the working condition is from the measured value of the working condition pressure transmitter;
Ts-temperature under flow meter conditions; the natural gas pipeline is internally provided with a working condition flowmeter device, the working condition flowmeter device comprises a working condition temperature transmitter, and the temperature of the flowmeter under the working condition is obtained from the measured value of the working condition temperature transmitter;
zs-compression factor under flowmeter conditions; the compression factor at the flow meter is calculated according to the method in the AGA No.8 report, which is a well-known technique and not described in further detail herein.
4. The natural gas metering and evaluating system according to claim 1, wherein: the flow meter is a sonic nozzle and an orifice plate flow meter, and the uncertainty comprises uncertainty of sectional area of a throat part of a boundary flow Venturi nozzle, uncertainty of outflow coefficient, uncertainty of critical flow function, uncertainty of stagnation pressure, uncertainty of gas constant and uncertainty of stagnation temperature;
when a single critical flow venturi nozzle participates in flow measurement, the mass flow measurement uncertainty formula of the metering system is as follows:
the mass flow calculation formula measured by the metering system is as follows:
the uncertainty of each parameter is analyzed item by item.
5. The natural gas metering and evaluating system according to claim 1, wherein: the flow meter, the temperature transmitter, the pressure transmitter and the gas chromatography instrument are respectively connected with the switch, data exchange is carried out through a TCP/IP protocol, the flow computer is connected with the switch, and data in the flow meter, the temperature transmitter, the pressure transmitter and the gas chromatography instrument are collected through the TCP/IP protocol.
6. The natural gas metering and evaluating system according to claim 1, wherein: the flow computer is connected with the diagnosis terminal and collects data in the flow meter, the temperature transmitter, the pressure transmitter and the gas chromatography analyzer through the TCP/IP protocol.
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| CN112733304A (en) * | 2020-08-25 | 2021-04-30 | 濮阳市新宝自动化科技开发有限公司 | Multi-transmission-difference cooperative computing model for urban gas pipe network and application method |
| CN113531395A (en) * | 2021-06-29 | 2021-10-22 | 佛燃能源集团股份有限公司 | Real-time monitoring method for purchase-sale gas difference rate of natural gas pipe network |
| CN113551744A (en) * | 2021-08-10 | 2021-10-26 | 中国石油大学(北京) | Ultrasonic flowmeter performance online monitoring method and system |
| CN113570475A (en) * | 2021-07-26 | 2021-10-29 | 成都秦川物联网科技股份有限公司 | Cross-network sharing method and system for energy metering data of intelligent pipe network |
| CN114740159A (en) * | 2022-04-14 | 2022-07-12 | 成都秦川物联网科技股份有限公司 | Natural gas energy metering component acquisition method and Internet of things system |
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2019
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112733304A (en) * | 2020-08-25 | 2021-04-30 | 濮阳市新宝自动化科技开发有限公司 | Multi-transmission-difference cooperative computing model for urban gas pipe network and application method |
| CN113531395A (en) * | 2021-06-29 | 2021-10-22 | 佛燃能源集团股份有限公司 | Real-time monitoring method for purchase-sale gas difference rate of natural gas pipe network |
| CN113531395B (en) * | 2021-06-29 | 2022-11-22 | 佛燃能源集团股份有限公司 | Real-time monitoring method for purchase-sale gas difference rate of natural gas pipe network |
| CN113570475A (en) * | 2021-07-26 | 2021-10-29 | 成都秦川物联网科技股份有限公司 | Cross-network sharing method and system for energy metering data of intelligent pipe network |
| CN113570475B (en) * | 2021-07-26 | 2023-10-27 | 成都秦川物联网科技股份有限公司 | Intelligent pipe network energy metering data cross-network sharing method and system |
| CN113551744A (en) * | 2021-08-10 | 2021-10-26 | 中国石油大学(北京) | Ultrasonic flowmeter performance online monitoring method and system |
| CN114740159A (en) * | 2022-04-14 | 2022-07-12 | 成都秦川物联网科技股份有限公司 | Natural gas energy metering component acquisition method and Internet of things system |
| CN114740159B (en) * | 2022-04-14 | 2023-09-19 | 成都秦川物联网科技股份有限公司 | Natural gas energy metering component acquisition method and Internet of things system |
| CN114777011A (en) * | 2022-04-20 | 2022-07-22 | 中国石油化工股份有限公司 | Multifunctional fair metering system and metering method based on LNG tank car |
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