CN206339270U - A kind of inside and outside tubular type gas flowmeter - Google Patents

Abstract

The utility model provides a kind of inside and outside tubular type gas flowmeter.The inside and outside tubular type gas flowmeter is set and the isometric inner tube of outer tube in outer tube, and sets support at the two ends of inner tube, to ensure that inner tube is fixed in measurement process, reduces the disturbing phenomenon of inner tube；Simultaneously uniformly four pressure taps are opened on the same section of inner tube, the foil gauge of normal stress is set in two relative pressure taps, the foil gauge of negative sense stress is set in two other pressure tap, four foil gauges constitute full-bridge difference structure, equivalent to built in pressure sensor on inner pipe.When gas flows through, foil gauge is changed due to strain effect resistance, the on-load voltage on foil gauge, and magnitude of voltage is collected by signal acquisition and amplifying circuit, the magnitude of voltage collected reflects the differential pressure information between inner and outer pipes, and the flow of gas can be calculated by differential pressure information.The utility model is simple in construction, reasonable in design, and final measurement is accurate, reliable.

Description

A kind of inside and outside tubular type gas flowmeter

Technical field

The utility model is related to two-phase flow technical field, specifically a kind of inside and outside tubular type gas flowmeter.

Background technology

Differential pressure flowmeter is one of flowmeter for being most widely used in two-phase flow measurement, is generally acknowledged in two-phase at present Flow under each flow pattern can steady operation a kind of flowmeter.

Differential pressure flowmeter sets up the relation of flow and pressure drop based on split-phase or homogeneous model.Wherein research is gone through History is most long for throttle differential flowmeter, and the method for differential pressure type all sees throttle differential flowmeter substantially.The flowmeter has There is easy for installation, reliable operation, and form during years of researches the international standard of maturation, at present many factories All contain throttle differential flowmeter in the multiphase flow measurement system that family releases.Wide variety of throttle differential flowmeter has hole Plate, Venturi tube and V cone flow meters.

For orifice flowmeter, fluid flows through the throttle orifice plate apparatus in pipeline, and local contraction is caused near orifice plate, section Pressure drop, i.e. differential pressure are just generated before and after stream part, differential pressure signal is relevant with uninterrupted.Had in the design of orifice flowmeter Many to improve, Japanese SONIC companies have designed and developed a kind of scope on flow computer to range ratio and have carried out the hole of selection Flowmeter, compared with traditional orifice flowmeter, is extended to measurement range；The novel intelligent orifice flow of recent studies on Meter, temperature and pressure signal is sent directly among live flow computer, and temperature and pressure is acted certainly according to changes in flow rate Go out compensation.

For differential pressure type flowmeter, the Xu Lijun of BJ University of Aeronautics ＆ Astronautics proposes to be based on using long throat Venturi tube The wet gas measurement model of Separating Flow Pattern；Strong waits for University Of Tianjin utilizes long larynx footpath Venturi tube to be surveyed for biphase gas and liquid flow Amount, establishes double difference pressure flux of moisture measurement model.Other sensors are coordinated to be combined measurement using a kind of throttling arrangement Method has also obtained substantial amounts of research, and yellow will Yao etc. is entered using Venturi tube combination electrical capacitance tomography to oil-gas two-phase flow Row effectively measurement；The mode that Xu Ying etc. is combined using inner cone and venturi proposes wet gas measurement virtual height model.

V cone flow meters are a kind of new differential pressure flowmeters that last century the eighties are released, with other differential pressure type streams Gauge design concept is different, and fluid is gradually tapered up tube wall by V cone throttling elements, by measuring differential pressure fluid flow before and after cone Etc. measuring.Relative to the Traditional differential pressure formula flowmeter such as orifice plate, Venturi tube, V cone flow meters have that crushing is small, structure is steady Gu, anti-contamination, the advantages of range ratio is wide.But it still has some shortcomings to be difficult to overcome, for example, V cone flow meters afterbody is bluff body Structure, flow of fluid produces separation, forms a large amount of whirlpools and causes the larger pressure loss；Compared with electromagnetic flowmeter, its range Compare relative narrower；L-type cantilever design is in big flow, it is possible to create vibration etc..

For above-described orifice plate, Venturi tube and V cone flow meters, its throttle style is all by changing fluid Total circulation area will certainly so produce disturbance in itself come what is realized to fluid, and differential pressure signal is unstable.Therefore design inside and outside The design of reducer pipe make it that biphase gas and liquid flow can not change when flowing through medium circulation tube in pipe differential pressure flowmeter, flow sensor Differential pressure is obtained under the situation for becoming circulation area；Same section of the flow sensor in flow of media sets pressure tap, therefore disappears Influence except frictional resistance to media flow data, solves prior art and differential pressure flow transducer is applied on vertical pipeline Existing impulse problem.

Utility model content

The purpose of this utility model is just to provide a kind of inside and outside tubular type gas flowmeter, and the flowmeter is poor in existing inner and outer pipes Design is optimized on the basis of pressure type flowmeter, disturbing phenomenon of the inner tube in experimentation is eliminated.

What the purpose of this utility model was realized in：A kind of inside and outside tubular type gas flowmeter, including：

Outer tube, is horizontally disposed round straight tube structure；

Inner tube, is placed in the outer tube, and on the axial line of the outer tube；Said inner tube is big including what is be sequentially connected Bore pipe, collapsible tube and small-bore pipe；The two ends of the end of the large-diameter pipe and the small-bore pipe respectively with the outer tube Alignment；Four pressure taps uniformly are opened up on same cross section on large-diameter pipe or small-bore pipe, are divided in four pressure taps A circular sheet that can be blocked to pressure tap is not set；The medial surface of two relative circular sheets is pasted with respectively wherein The foil gauge of normal stress, the foil gauge of negative sense stress is pasted with the medial surface of two other relative circular sheet respectively； Four foil gauges are connected by wire with power supply and signal acquisition with amplifying circuit；

Support, is arranged on the two-end part between the outer tube and said inner tube, for being supported to said inner tube and It is fixed；The support includes band and the support floor being arranged on the band lateral wall, and the band is socketed in described On the lateral wall at pipe two ends, the end of the support floor is rabbeted on the inwall of the outer tube；

Power supply, for providing operating voltage to four foil gauges；

Signal acquisition and amplifying circuit, for gathering the voltage signal of four foil gauge output and being amplified；And

Data processing circuit, the voltage signal for signal acquisition and amplifying circuit to be exported is converted into differential pressure signal, and The flow of gas is calculated according to differential pressure signal；

The computing formula that voltage signal is converted into differential pressure signal is：

In formula (1), Δ P is the differential pressure between the inner and outer pipe after conversion, C_SFor correction factor, h is the thickness of circular sheet, E For the Young's modulus of foil gauge, U_OThe voltage exported for signal acquisition and amplifying circuit, K is the gage factor of foil gauge, R For the radius of circular sheet, μ is the Poisson's coefficient of circular sheet, and U is applied to the operating voltage on foil gauge for power supply；

The flow of gas is calculated according to differential pressure signal, specific formula for calculation is：

In formula (2), Q_mIt is the mass flow of gas, C is efflux coefficient, and ε is the inflatable coefficient of gas, and β is Throttling ratio, A is the cross-sectional area of outer tube bore, and ρ is the density of upstream gas, and Δ P is between the inner and outer pipe obtained by being calculated according to formula (1) Differential pressure.

It is preferred that, four pressure taps are elliptical openings；When gas flows along large-diameter pipe to small-bore pipe direction, Four pressure taps are opened on large-diameter pipe, and four pressure taps are more than away from large-diameter pipe and the distance of collapsible tube junction And be less thanWhen gas flows along small-bore pipe to large-diameter pipe direction, four pressure taps are opened on small-bore pipe, Four pressure taps are more than away from small-bore pipe and the distance of collapsible tube junctionAnd be less thanD is the internal diameter of outer tube.

It is preferred that, it is provided with the inwall of said inner tube along its axial wire lead-out groove, the wire being connected with foil gauge Connected by the wire lead-out groove with the power supply and signal acquisition of pipeline external with amplifying circuit.

It is preferred that, three support floors are evenly equipped with the lateral wall of the band.

It is preferred that, the distance between inwall of the outer wall of the large-diameter pipe and the outer tube is more than 1mm；Throttling ratio β is big In 0.4 and less than 0.7.

Design is optimized on the basis of existing inner and outer pipes differential pressure flowmeter in the utility model, eliminates inner tube throttling Disturbing phenomenon of the part in experimentation, and the enterprising promoting the circulation of qi phase dynamic test of inner and outer pipes differential flow device after optimization, are obtained To the measurement model of gas phase flow rate.Inner tube can only be fixed by two pressure ports in existing inner and outer pipes differential pressure flowmeter, Inner tube throttling element can not be made to be remained stationary in the measurement process of actual flow, can thus make pressure inaccurate；Together When, the flow channel between inner and outer pipe is asymmetric, also causes flowing instability, and the utility model passes through the gas of pipe throttling element inside Body flows into the port position with outflow, and an axisymmetric support is added respectively, inner tube throttling element and outer tube are consolidated by support It is fixed, reduce the disturbing phenomenon of inner tube throttling element, and ensure gas in inner and outer pipe gap, except the obstruction of support at import and export Outside, can fully it be flowed；The large-diameter pipe of inner tube and small-bore pipe are extended to the port of outer tube simultaneously, gas is existed During into and out of pipeline section, sufficient transition is obtained, change of flow is gentler, reduce the error that fluid impact tube wall is brought.Pressure tap Elliptical openings (or pancake opening) are optimized for by original circular open, the design can obtain pressure tap position Average pressure, make measurement more accurate.Four foil gauges are embedded in corresponding four pressure taps by circular sheet, and four Individual pressure tap is opened on large-diameter pipe or small-bore pipe, so that realizing pressure in internal tube, reduces pressure process The loss of middle pressure, makes pressure result sensitiveer, accurate.Inside and outside tubular type gas flowmeter provided by the utility model can be with The acceleration error for coming from axial direction and radial direction is eliminated, also the acceleration for coming from other directions is influenceed to play alleviation or even disappeared Remove so that measurement result is more accurate.

The utility model is on the basis of theory analysis and previous work experience, according to gas phase flow mechanism, to inside and outside Pipe differential pressure flowmeter carries out pipeline mechanism design, the design of optimization.By the test of the flow regime to gas phase, extraction has The signal of value, and carry out signal characteristic abstraction, the measuring method of the inside and outside tubular type gas flow measuring amount device of research, checking pipe The reasonability and feasibility in road.Specifically：By being set and the isometric inner tube of outer tube in outer tube, and in the port at inner tube two ends Place sets axisymmetric support, and support is embedded at inner tube lateral wall and is connected with outer tube madial wall, inner tube is supported, can Ensure that inner tube is remained stationary in measurement process, so that pressure result is accurate, it is ensured that the reliability that the later stage calculates；Inside Four pressure taps are provided with pipe, circular sheet is set in each pressure tap, and in wherein two relative circular sheets The foil gauge of normal stress is pasted in side, and the foil gauge of negative sense stress is pasted in the inner side of two other relative circular sheet, and four should Become piece formation full-bridge difference structure, equivalent to built in pressure sensor on inner pipe.When gas flows through, foil gauge is due to strain Effect, foil gauge resistance is changed, the on-load voltage on foil gauge, and strain is collected by signal acquisition and amplifying circuit The magnitude of voltage of piece output, the magnitude of voltage collected reflects the differential pressure information between inner and outer pipe, can counted by differential pressure information Calculate the flow for drawing gas.

Brief description of the drawings

Fig. 1 is the structural representation of inside and outside tubular type gas flowmeter provided by the utility model.

Fig. 2 is the structural representation of Fig. 1 middle outlets end support.

In figure：1st, outer tube, 2, large-diameter pipe, 3, collapsible tube, 4, small-bore pipe, 5, arrival end support, 6, port of export support, 6-1, band, 6-2, support floor, the 7, first foil gauge, the 8, second foil gauge, the 9, the 3rd foil gauge.

Embodiment

Embodiment 1, a kind of inside and outside tubular type gas flowmeter.

As shown in figure 1, inside and outside tubular type gas flowmeter provided by the utility model include outer tube 1, inner tube, support, by Full-bridge difference structure, power supply, signal acquisition and the amplifying circuit of four foil gauge compositions, data processing circuit.

Outer tube 1 is the cylindrical straight tubular construction of horizontal positioned；The internal diameter of outer tube 1 represents that length is represented with L with D.It is interior Manage as throttling element, inner tube is arranged in outer tube 1, and inner tube is located on the axial line of outer tube 1, i.e. the axial line of outer tube 1 and inner tube axle Heart line is overlapped.Inner tube length is identical with the length L of outer tube 1, and two ends of the two ends respectively with outer tube 1 of inner tube are alignd.Inner tube includes Large-diameter pipe 2, collapsible tube 3 and the small-bore pipe 4 being sequentially connected.Large-diameter pipe 2 and small-bore pipe 4 are straight tube structure, big mouth The internal diameter d of footpath pipe 2₁To represent, length L₁To represent；The internal diameter d of small-bore pipe 4₂To represent, length L₂To represent； Collapsible tube 3 connects large-diameter pipe 2 and small-bore pipe 4, and collapsible tube 3 is round table-like pipe, the horizontal length of collapsible tube 3 (i.e. collapsible tube 3 The length of axial line) it is (L-L₁-L₂), angle of throat is usedTo represent, angle of throatTypically between 11 ° to 21 ° (i.e.).Angle of throatComputing formula it is as follows：

Inner and outer tubes 1 are isometric in the utility model so that gas is before collapsible tube 3 is flowed into and flows out after collapsible tube 3, All there is the sufficient flowing space, make variations in flow patterns gentler, reduce the impact phenomenon of the internal pipe throttling element of gas.

Support is arranged on the two-end part between outer tube 1 and inner tube, and support includes axisymmetric arrival end support 5 and outlet Support 6 is held, the support and fixation to inner tube can be realized by two supports, to remain stationary as inner tube in measurement process, Reduce the disturbing phenomenon of inner tube throttling element.When gas flows through the gap location of inner and outer pipe, the obstruction that two supports flow to gas Effect is also smaller.Arrival end support 5 is identical with the structure of port of export support 6, is illustrated by taking port of export support 6 as an example.Such as Fig. 2 Shown, port of export support 6 includes band 6-1 and be uniformly arranged on band 6-1 lateral walls three support floor 6-2, three Support floor 6-2 is respectively perpendicular to the lateral wall of the band 6-1 with each connecting.Band 6-1 is socketed in the lateral wall of small-bore pipe 4 End, band 6-1 lateral wall flushes with the lateral wall of small-bore pipe 4, specifically can be by the end of the lateral wall of small-bore pipe 4 Open with band 6-1 thickness identical breach to realize in portion.Three support floor 6-2 end is rabbeted on the inwall of outer tube 1, can Three grooves corresponding with support floor 6-2 are opened on the inwall of outer tube 1, are respectively embedded into three support floor 6-2 corresponding In groove.End of each groove from outer tube 1 is opened up, so that port of export support 6 can be socketed in from gas outflow end On the small-bore pipe 4 of inner tube, and three support floor 6-2 end is set just to be connected in three grooves of the inwall of outer tube 1.Enter Mouth end support 5 is identical with the structure of port of export support 6, repeats no more.

On same cross section on the large-diameter pipe 2 or small-bore pipe 4 of inner tube it is uniform open up four it is of the same size ellipse Circular pressure tap, sets a circular sheet in each pressure tap, the radius all same of four circular sheets, thickness also phase Together, the thickness of circular sheet is generally the 1/3~1/2 of inner tube wall thickness, and the radius of circular sheet is more than the length of oval pressure tap Semiaxis, i.e.,：Circular sheet is embedded in pressure tap and blocks pressure tap completely.The inner side of two relative circular sheets wherein The foil gauge (i.e. when the pressure was increased, resistance value becomes big) of normal stress is pasted respectively, in two other relative circular sheet The foil gauge (i.e. when the pressure was increased, resistance value diminishes) of negative sense stress, size and the ellipse of four foil gauges are pasted respectively in inner side The size of shape pressure tap is identical.Four foil gauges constitute a full-bridge difference structure, equivalent in interior outer pipe type gas flowmeter A upper built-in pressure sensor.Four foil gauges are typically provided to upper and lower, forward and backward structure type, as shown in figure 1, figure In show the first foil gauge 7 above, the second following foil gauge 8 and the 3rd foil gauge 9 above.At four foil gauges In on the same cross section of large-diameter pipe 2 or small-bore pipe 4, the influence of frictional resistance can be eliminated.Four foil gauges are uniform simultaneously It is embedded in inner tube, this modes of emplacement can eliminate the influence of the acceleration of gravity of each radial direction vertical with flow direction, make Obtain measurement result more accurate.

Four foil gauges are connected by wire with power supply and signal acquisition with amplifying circuit.Power supply is used for four foil gauges Operating voltage is provided, power supply is also that signal acquisition and amplifying circuit provide operating voltage simultaneously., should when gas flows through foil gauge Become piece due to strain effect, its resistance is changed, and the on-load voltage on foil gauge can be adopted by signal acquisition with amplifying circuit Collection obtains the magnitude of voltage of foil gauge output, and the magnitude of voltage collected reflects the differential pressure information between inner and outer pipe, passes through differential pressure Information can calculate the flow of gas.

When measuring gas flow, gas can be flowed into from one end of outer tube 1, along the large-diameter pipe 2 of inner tube to the side of small-bore pipe 4 To flowing (direction as shown by the arrows in Figure 1)；Also it can be flowed into from the other end of outer tube 1, along the small-bore pipe 4 of inner tube to heavy caliber The flowing of the direction of pipe 2 (with Fig. 1 shown in arrow it is in opposite direction).For prevent particulate matter block pipeline, the lateral wall of large-diameter pipe 2 with Gap between the madial wall of outer tube 1 should be greater than 1mm, that is, meet：

When gas flows in outer tube 1 from large-diameter pipe 2 to the direction of small-bore pipe 4, it should ensure that four pressure taps are opened up On the same cross section of large-diameter pipe 2, and four pressure taps are more than away from large-diameter pipe 2 and the distance of the joint of collapsible tube 3 And be less than(pressure tap is so set, is in order to before pressure measurement, it is ensured that gas can sufficiently be flowed in pipeline)； And along its axial direction convince line lead-out groove by patient analysis in the inwall of large-diameter pipe 2, the wire connected with four foil gauges passes through wire lead-out groove Connect with the power supply and signal acquisition of pipeline external with amplifying circuit.When gas is interior from small-bore pipe 4 to large-diameter pipe in outer tube 1 When 2 directions are flowed, it should ensure that four pressure taps are opened on the same cross section of small-bore pipe 4, and four pressure taps are away from osculum Footpath pipe 4 and the distance of the joint of collapsible tube 3 are more thanAnd be less thanAnd along its axial direction convince line by patient analysis in the inwall of small-bore pipe 4 Lead-out groove, power supply and signal acquisition and amplification electricity that the wire connected with four foil gauges passes through wire lead-out groove and pipeline external Road connects.

Signal acquisition is used to gather the voltage signal of four foil gauge output and is amplified with amplifying circuit, after amplification Voltage signal is exported to data processing circuit, the voltage signal that data processing circuit first exports signal acquisition and amplifying circuit The differential pressure signal between inner and outer pipe is converted into, the flow of gas is then calculated further according to differential pressure signal.

The voltage signal that signal acquisition and amplifying circuit are exported is converted into the computing formula of the differential pressure signal between inner and outer pipe For：

In formula (1), Δ P is the differential pressure between the inner and outer pipe after conversion, C_SFor correction factor, dimensionless, by testing really It is fixed, it is ensured that the accuracy of formula；H is the thickness of circular sheet, and E is the Young's modulus of foil gauge (i.e. flexible member), U_OFor The voltage that signal acquisition is exported with amplifying circuit, K is the gage factor of foil gauge, and R is the radius of circular sheet, and μ is circle The Poisson's coefficient of shape thin plate, U is applied to the operating voltage on foil gauge for power supply.

The flow of gas is calculated according to differential pressure signal, specific formula for calculation is：

In formula (2), Q_mIt is the mass flow (unit is Kg/s) of gas, C is efflux coefficient, is determined by testing；ε is gas The inflatable coefficient of body, generally for these compressible fluids such as gas, steam, ε ＜ 1；β is Throttling ratio, the utility model Middle β is between 0.4 to 0.7；A be outer tube bore cross-sectional area, ρ be working condition pressure under, the density of throttling element upstream gas (unit K g/m³)；Δ P is the differential pressure (or pressure differential, unit is Pa) between the inner and outer pipe according to obtained by being calculated formula (1).

Throttling ratio β specific formula for calculation is：

In above formula, K₁For the annular space between the annular space area and small-bore pipe 4 and outer tube 1 between large-diameter pipe 2 and outer tube 1 Area ratio, K₂For the lumenal cross-section area of large-diameter pipe 2 and the lumenal cross-section area ratio of small-bore pipe 4.K₁And K₂It is specific Computing formula is as follows：

Embodiment 2, a kind of inside and outside tubular type detection of gas flow rate method.

As shown in Fig. 1~Fig. 2, inside and outside tubular type detection of gas flow rate method provided by the utility model includes following step Suddenly：

Inner tube is set on a, the axial line in outer tube 1.

Outer tube 1 is the circle straight tube structure of horizontal positioned.Inner tube is set on axial line in outer tube 1；Inner tube is included successively Large-diameter pipe 2, collapsible tube 3 and the small-bore pipe 4 of connection；Collapsible tube 3 is round table-like structure；Large-diameter pipe 2 and small-bore pipe 4 Two ends of the end respectively with outer tube 1 are alignd, i.e.,：Inner tube and outer tube 1 are isometric.Between the outer wall of large-diameter pipe 2 and the inwall of outer tube 1 Distance be more than 1mm.Uniformly four sizes are offered on same cross section on the large-diameter pipe 2 or small-bore pipe 4 of inner tube Consistent oval pressure tap, sets a circular sheet in each pressure tap, and the radius all same of four circular sheets is thick Degree is also identical, and the radius of circular sheet is more than the major semiaxis of oval pressure tap.In two wherein relative circular sheets The foil gauge of normal stress is pasted in side respectively, and the strain of negative sense stress is pasted respectively in the inner side of two other relative circular sheet Piece, the size of four foil gauges is identical with the size of oval pressure tap.Four foil gauges constitute a full-bridge difference structure, phase When in a built-in pressure sensor on interior outer pipe type gas flowmeter.Four foil gauges pass through wire and power supply and signal Collection is connected with amplifying circuit.

B, the support for being provided for being supported inner tube and fixing at the two ends of inner tube.

Support includes symmetrical arrival end support 5 and port of export support 6.Arrival end support 5 and port of export support 6 Structure is identical.As shown in Fig. 2 port of export support 6 includes band 6-1 and three branch being uniformly arranged on band 6-1 lateral walls Stake rib plate 6-2, band 6-1 are socketed in the end of the lateral wall of small-bore pipe 4, band 6-1 lateral wall and the outside of small-bore pipe 4 Wall is flushed, and three support floor 6-2 end is rabbeted on the groove of the inwall of outer tube 1.

C, gas is flowed into from one end of outer tube 1, and apply operating voltages from power supply to four foil gauges.

When gas flows in outer tube 1, it can be flowed along large-diameter pipe 2 to the direction of small-bore pipe 4, also can be from small-bore pipe 4 Flowed to the direction of large-diameter pipe 2.When gas flows in outer tube 1 from large-diameter pipe 2 to the direction of small-bore pipe 4, four are should ensure that Individual pressure tap is opened on the same cross section of large-diameter pipe 2, and four pressure taps are away from large-diameter pipe 2 and the joint of collapsible tube 3 Distance be more thanAnd be less thanWhen gas flows in outer tube 1 from small-bore pipe 4 to the direction of large-diameter pipe 2, Ying Bao Four pressure taps of card are opened on the same cross section of small-bore pipe 4, and four pressure taps are away from small-bore pipe 4 and the phase of collapsible tube 3 The distance at the place of connecing is more thanAnd be less than

D, the voltage signal by the four foil gauges output of signal acquisition and amplifying circuit collection are simultaneously amplified, after amplification Voltage signal is exported to data processing circuit.

The voltage signal that e, data processing circuit first export signal acquisition and amplifying circuit is changed between inner and outer pipe Differential pressure signal, the flow of gas is calculated further according to differential pressure signal.

The voltage signal that signal acquisition and amplifying circuit are exported is changed into the computing formula of the differential pressure signal between inner and outer pipe For：

In formula (1), Δ P is the differential pressure between the inner and outer pipe after conversion, C_SFor correction factor, dimensionless, by testing really It is fixed, it is ensured that the accuracy of formula；H is the thickness of circular sheet, and E is the Young's modulus of foil gauge (i.e. flexible member), U_OFor The voltage that signal acquisition is exported with amplifying circuit, K is the gage factor of foil gauge, and R is the radius of circular sheet, and μ is circle The Poisson's coefficient of shape thin plate, U is applied to the operating voltage on foil gauge for power supply.

The flow of gas is calculated according to differential pressure signal, specific formula for calculation is：

In formula (2), Q_mIt is the mass flow (unit is Kg/s) of gas, C is efflux coefficient, is determined by testing；ε is gas The inflatable coefficient of body, generally for these compressible fluids such as gas, steam, ε ＜ 1；β is Throttling ratio, the utility model Middle β is between 0.4 to 0.7；A be outer tube bore cross-sectional area, ρ be working condition pressure under, the density of throttling element upstream gas (unit K g/m³)；Δ P is the differential pressure (or pressure differential, unit is Pa) between the inner and outer pipe according to obtained by being calculated formula (1).

In the utility model, it is fitted through CFD emulation and test data of experiment, obtains the inflatable coefficient ε of gas in formula (2) Computing formula be：

In formula (3), τ is pressure correcting coefficient, and computing formula is：

In formula (4), P_bFor the background pressure during gas flow measurement, Δ P be according to obtained by being calculated formula (1) it is interior, Differential pressure between outer tube, P₀For a standard atmospheric pressure.

Throttling ratio β, the physical dimension of inner and outer pipes meet following condition in the utility model：

In formula (5), D is the internal diameter of outer tube 1, d₁For the internal diameter of large-diameter pipe 2, d₂For the internal diameter of small-bore pipe 4, L is pipeline Total length (i.e. outer tube, the length of inner tube), L₁For the horizontal length of large-diameter pipe 2, L₂For the horizontal length of small-bore pipe 4,For The angle of throat of collapsible tube 3, K₁For the annular space face between the annular space area and small-bore pipe and outer tube between large-diameter pipe and outer tube The ratio between product, K₂For large-diameter pipe lumenal cross-section area and small-bore pipe lumenal cross-section area ratio.Typically require heavy caliber The length L of pipe 2₁With the length L of small-bore pipe 4₂It is all higher than 10cm.

Embodiment 3, Throttling ratio β and angle of throatPreferred embodiment.

The rule of thumb consideration of theoretical and total duct size, by the angle of throat of collapsible tubeIt is set to 15 °, then asks for difference Large-diameter pipe inner diameter values and small-bore pipe inner diameter values under Throttling ratio, the physical dimension further according to determination in entrance velocity is Emulated in the case of 10.27m/s, flowmeter many places pressure value is obtained according to simulation result, be specifically：1. draw inside and outside Differential pressure between pipe, 2. show that outer tube (or inner tube) flows into 10D (D is outer tube diameter) places and the pressure at 5D after outflow end before end Difference, this is the pressure loss.Pressure Loss Ratio is produced with the pressure loss divided by differential pressure.It finally found that when Throttling ratio β is 0.5892, it is poor Pressure is big, the pressure loss is small, and Pressure Loss Ratio is small.

Gas can have two kinds of different flow directions in outer tube 1 in the utility model, through CFD emulation draw, no matter gas Body flows from large-diameter pipe to small-bore pipe direction, or is flowed from small-bore pipe to large-diameter pipe direction, and gaseous fluid is not Influenceed by acceleration of gravity.But, from simulation result as can be seen that gas is from small-bore pipe to large-diameter pipe direction mobile phase For being flowed than gas from large-diameter pipe to small-bore pipe direction, the differential pressure of acquisition is big, and crushing is small, and Pressure Loss Ratio is small.User Ke Gen The suitable type of flow and corresponding physical dimension are selected according to actual demand.

According to simulation result it has also been found that, with L₁、L₂Increase, the differential pressure value between inner and outer pipe is increased, but corresponding pressure Power loss is consequently increased, on the premise of coincidence formula (5), L₁And L₂Can be according to actual conditions value.

Embodiment 4, efflux coefficient C determination.

Efflux coefficient C is asked for according to the formula (2) in embodiment 2.Coefficient ε, Throttling ratio β (throttlings are may expand in formula (2) Calculated than β by 0.5892), outer tube bore cross-sectional area A and gas density ρ be fixed known quantity, therefore utilize differential pressure Δ P (can be tried to achieve by formula (1)) and flow value Q_mAsk for efflux coefficient C.In four flow points, (a flow point is correspondence below One flow value) under calculated.The efflux coefficient under the flow point is asked for using differential pressure value under each flow point, four are obtained Individual different value.Efflux coefficient is determined first with the mode averaged, the stream drawn after averaging is then utilized Go out coefficient and ask for mass flow, the mass flow tried to achieve is compared with known flow, it is found that error is larger.Therefore can not Efflux coefficient C is sought with the method.

During due to seeking efflux coefficient under each flow point above, only one variable of differential pressure, therefore efflux coefficient with it is poor There is certain quantitative relation in pressure, so carrying out formula fitting to differential pressure and efflux coefficient in the utility model, obtain fitting public Formula is shown in formula (6), and the goodness of fit is up to 0.994.

C=0.73145+0.01023 (Δ PK ') -0.00304 (Δ PK ')²+2.70121×10⁴(ΔP·K′)³ (6)

In formula (6), K ' is correction factor, and computing formula is：

K '=Δ P/P_b+T/T₀ (7)

In formula (7), P_bFor the background pressure during gas flow measurement, T is the background during gas flow measurement Temperature, T₀For mark condition temperature (temperature i.e. under the status of criterion, 273.15K), it is contemplated that the influence of temperature and pressure.

Efflux coefficient after being fitted using formula (6).The efflux coefficient obtained according to fitting carries out the calculating of flow, As a result find error within 0.7%.Concrete numerical value is shown in Table 1.

The efflux coefficient computational chart of table 1

Claims (6)

1. a kind of inside and outside tubular type gas flowmeter, it is characterized in that, including：

Outer tube, is horizontally disposed round straight tube structure；

Inner tube, is placed in the outer tube, and on the axial line of the outer tube；Said inner tube includes the heavy caliber being sequentially connected Pipe, collapsible tube and small-bore pipe；Align at two ends of the end of the large-diameter pipe and the small-bore pipe respectively with the outer tube； Four pressure taps uniformly are opened up on same cross section on large-diameter pipe or small-bore pipe, are set respectively in four pressure taps One can to pressure tap block circular sheet；The medial surface of two relative circular sheets is pasted with positive answer respectively wherein The foil gauge of power, the foil gauge of negative sense stress is pasted with the medial surface of two other relative circular sheet respectively；Four should Become piece by wire with power supply and signal acquisition with amplifying circuit to connect；

Support, is arranged on the two-end part between the outer tube and said inner tube, for being supported and fixing to said inner tube； The support includes band and the support floor being arranged on the band lateral wall, and the band is socketed in said inner tube two ends Lateral wall on, it is described support floor end rabbet on the inwall of the outer tube；

Power supply, for providing operating voltage to four foil gauges；

Signal acquisition and amplifying circuit, for gathering the voltage signal of four foil gauge output and being amplified；And

Data processing circuit, the voltage signal for signal acquisition and amplifying circuit to be exported is converted into differential pressure signal, and according to Differential pressure signal calculates the flow of gas；

The computing formula that voltage signal is converted into differential pressure signal is：

$\mathrm{\Δ}P=C_S\frac{8h^2{\mathrm{EU}}_O}{3{\mathrm{KR}}^2(1-{\mathrm{\μ}}^2)U}---\left(1\right)$

In formula (1), Δ P is the differential pressure between the inner and outer pipe after conversion, C_SFor correction factor, h is the thickness of circular sheet, and E is should Become the Young's modulus of piece, U_OThe voltage exported for signal acquisition and amplifying circuit, K is the gage factor of foil gauge, and R is circle The radius of shape thin plate, μ is the Poisson's coefficient of circular sheet, and U is applied to the operating voltage on foil gauge for power supply；

The flow of gas is calculated according to differential pressure signal, specific formula for calculation is：

$Q_m=\frac{{\mathrm{C\ϵ\β}}^{2}A}{\sqrt{1-{\mathrm{\β}}^4}}\×\sqrt{2\mathrm{\Δ}P\×\mathrm{\ρ}}---\left(2\right)$

In formula (2), Q_mIt is the mass flow of gas, C is efflux coefficient, and ε is the inflatable coefficient of gas, and β is Throttling ratio, and A is outer The cross-sectional area of tube cavity, ρ is the density of upstream gas, and Δ P is the differential pressure between the inner and outer pipe according to obtained by being calculated formula (1).

2. inside and outside tubular type gas flowmeter according to claim 1, it is characterized in that, four pressure taps are ellipse and opened Mouthful；When gas flows along large-diameter pipe to small-bore pipe direction, four pressure taps are opened on large-diameter pipe, four pressure measurement Pitch-row large-diameter pipe and the distance of collapsible tube junction are more thanAnd be less thanWhen gas is along small-bore pipe to large-diameter pipe When direction is flowed, four pressure taps are opened on small-bore pipe, and four pressure taps are away from small-bore pipe and collapsible tube junction Distance is more thanAnd be less thanD is the internal diameter of outer tube.

3. inside and outside tubular type gas flowmeter according to claim 1, it is characterized in that, it is provided with edge on the inwall of said inner tube Its axial wire lead-out groove, the wire being connected with foil gauge passes through the wire lead-out groove and the power supply and signal of pipeline external Collection connects with amplifying circuit.

4. inside and outside tubular type gas flowmeter according to claim 1, it is characterized in that, it is uniform on the lateral wall of the band There are three support floors.

5. inside and outside tubular type gas flowmeter according to claim 1, it is characterized in that, the outer wall of the large-diameter pipe with it is described The distance between inwall of outer tube is more than 1mm.

6. inside and outside tubular type gas flowmeter according to claim 1, it is characterized in that, Throttling ratio β is more than 0.4 and less than 0.7.