CN100538307C - A kind of wind tunnel calibration method for large flow gas pipeline averaging velocity tube flowmeter - Google Patents
A kind of wind tunnel calibration method for large flow gas pipeline averaging velocity tube flowmeter Download PDFInfo
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- CN100538307C CN100538307C CNB2007100667369A CN200710066736A CN100538307C CN 100538307 C CN100538307 C CN 100538307C CN B2007100667369 A CNB2007100667369 A CN B2007100667369A CN 200710066736 A CN200710066736 A CN 200710066736A CN 100538307 C CN100538307 C CN 100538307C
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Abstract
The invention discloses a kind of wind tunnel calibration method for large flow gas pipeline averaging velocity tube flowmeter.Tested in test chamber by the school flowmeter, obtain the flowmeter efflux coefficient, obtain the flowmeter coefficient of flow in conjunction with the velocity distribution correction factor then.In this method of calibration, regardless of flowmeter length, as long as less than the wind-tunnel sectional dimension, just can insert and carry out verification in the verification section, equipment interoperability is good.The velocity distribution correction factor need be measured by experiment on special experimental system with database and accumulate.Be provided with test chamber in the velocity distribution correction factor experimental system and fully develop two verification sections of pipe stream test section, under the situation of same traffic, in test chamber and abundant development pipe stream test section, measured respectively by the school flowmeter, thereby obtain the velocity distribution correction factor.The velocity distribution correction factor accuracy height that the present invention obtains, data credibility height.
Description
Technical field
The present invention relates to the flowmeter calibration technology, particularly a kind of wind tunnel calibration method that is suitable for large flow gas pipeline averaging velocity tube flowmeter.
Background technology
The method of calibration of plug-in type mean velocity tube flowmeter can be divided into two kinds: flowmeter method and current meter method.The flowmeter method is to whole sensor, comprises that measuring head, insertion rod, insertion mechanism, converter and measuring channel (instrument housing) test.General gas flow standard device is by the design of flowmeter method, and its experimental technique can be divided into volumetric method, mass method, proving flowmeter method and velocity-area method.Wherein for the bigger situation of flow, comparatively typical devices has bell-jar gas flow meter, PVTt method gas flow standard device, Mt method gas flow standard device and sonic nozzle.
The bell-jar gas flow meter is that the calibrating gas flow transmits one of major equipment of standard and gas flow instrument, at home and abroad uses in a large number.The working pressure of this device is generally less than 10000Pa, and maximum flow is by the volume and the measuring technology decision of bell jar, and the bell jar volume of present domestic approved product has plurality of specifications between 50～10000L, and the maximum flow of measurement can reach 4500m
3/ h, the device uncertainty generally is better than ± and 0.5%, reach as high as ± 0.2%.PVTt and Mt method gas flow standard device are commonly used to examine and determine the sonic nozzle as the standard of transmission, also can examine and determine other high-precision flowmeter, and flow range is about 2.3 * 10
-5～5kg/s, the device uncertainty be better than ± 0.1%.Proving flowmeter method gas flow meter is the usual means of verification gas meter, because it is easy to use, the verification cost saving so be subjected to user's welcome deeply, is a kind of rising flow standard device.Sonic nozzle is a kind of of standard scale, because its precision height, repdocutbility are good, is that development in recent years is transmitted standard faster.Sonic nozzle flow calibration equipment many sonic nozzles in parallel often come the checking flow instrument.PTB (German physical technique research institute) adopts 16 velocity of sound Venturi nozzles in parallel to come verification industrial gas table and other gas flow instrument.It has the input head flange of 5 bores from 100mm to 400mm can be connected to the experiment pipeline, can produce thousands of kinds of 50～5500m
3The different flow of/h is with total amount instrument or the flow instrument on the verification test pipeline.The relative uncertainty of device is ± 0.06%.These several gas flow standard devices all are not suitable as the verification standard set-up of heavy caliber, large flow pipe road gas meter from its purposes, parameter (flow) scope and cost.
For the verification of big flow gas pipe flowmeter, be feasible as the flow standard device with wind-tunnel.Flow velocity can be thought even distribution in test chamber/active section, and therefore the flow velocity that needs only with pitot tube uniform flow measuring method surveying work section point just can obtain flow accurately according to the product of flow velocity and circulation area.The wind-tunnel outlet connects the verification pipeline, and the length that this pipe design is enough is managed the formation of stream to guarantee fully development.Inserted fully development pipe stream test section by the school flowmeter, the normal flow in the pipeline is determined by the wind-tunnel of front portion, just can carry out the flowmeter verification.But several problems are arranged here: (1) uses this method, and the experimental channel diameter should be corresponding with actual pipeline, will change experimental channel during the flowmeter of verification different size, very trouble; (2) so many experimental channel needs a large amount of investments, and need take very big laboratory area; (3) for the super large caliber pipeline, for example diameter 2.8m for guaranteeing the fully development of flowing in the pipe, needs flow development length to surpass 100m, all is unpractical from place and investment.
Current meter method is another method of flow verification, and the measuring head of check sensor only in this method comes verification to measuring head as a velocimeter.At first record the flow velocity instrument coefficient of measuring head, then the instrument coefficient (flow instrument coefficient) of determining several correction factors (velocity distribution correction factor, blockage factor and interference coefficient) and cross-section of pipeline area reckoning flowmeter according to the fluid and the pipeline condition (being mainly velocity flow profile) at scene.The advantage of this method is: (1) calibration equipment more easily solves.Daily verification expense is cheap.Under the accumulation of long-term verification data, may give standardization; (2) each correction factor of current meter method has many data can reference.The calibration equipment of current meter method is a low-speed wind tunnel.Low-speed wind tunnel is made up of contraction section, test section, diffuser and drive unit (fan) etc.Measuring head inserts in the test section transfixion.Blower fan produces the air-flow of certain flow rate and blows over measuring head.The air-flow standard flow rate is generally determined with pitot tube.Change air-flow velocity and try to achieve the flow velocity instrument coefficient that flow velocity and instrument signal relation can be determined measuring head.
Summary of the invention
The objective of the invention is to solve the check problem of heavy caliber, large flow gas pipeline averaging velocity tube flowmeter.A kind of wind tunnel calibration method for large flow gas pipeline averaging velocity tube flowmeter is provided, relate to a checking wind tunnel and a velocity distribution correction factor test macro that contains test chamber and fully develop two verification sections of pipe stream test section, finish the mensuration of coefficient of flow.
The technical solution used in the present invention is:
1, a kind of wind tunnel calibration method for large flow gas pipeline averaging velocity tube flowmeter is tested in test chamber by the school flowmeter, obtains the flowmeter efflux coefficient, obtains the flowmeter coefficient of flow in conjunction with the velocity distribution correction factor then;
2, calibration equipment is a low-speed wind tunnel, and model bay is as the test section of flowmeter verification; Air is gone into the wind-tunnel test section through wind-tunnel inlet, honeycomb, damping screen, stable section and the rectification of wind-tunnel contraction section are laggard, and test chamber cross section velocity distribution is very even, therefore, inserts test chamber simultaneously with a pitot tube with by the school flowmeter.Owing to can obtain accurate wind speed with pitot tube, according to differential pressure transmitter export by school flowmeter differential pressure, just can obtain by the efflux coefficient of school flowmeter; After obtaining efflux coefficient, determine pipeline velocity distribution correction factor, just can calculate the coefficient of flow of flowmeter in conjunction with internal diameter of the pipeline that flowmeter is surveyed according to actual pipeline Reynolds number.
3, the velocity distribution correction factor determine it is a key issue in this method, in this method of calibration implementation process, need set up velocity distribution correction factor curve or database to the mean velocity tube flowmeter of each type; Velocity distribution correction factor curve determination process is carried out on flowmeter velocity distribution correction factor test macro; The wind-tunnel main body also provides test chamber simultaneously as the flow standard device in the flowmeter velocity distribution correction factor test macro; Air enters system by the wind-tunnel inlet, and flow velocity is even distribution in test chamber, just can obtain flow accurately according to the flow velocity area-method as long as measure flow velocity; Under the identical flow situation, measured at test chamber and abundant development pipe stream test section respectively, obtain to be obtained the velocity distribution correction factor by the differential pressure output of school flowmeter in two test sections by the school flowmeter; The flowmeter of geometric similarity, its velocity distribution correction factor is identical under identical Reynolds number.
The beneficial effect that the present invention has is:
(1) the wind-tunnel cross section can also can be a rectangle for circle among the present invention, the flowmeter of can verification pipe diameter 300mm above (even the above super large pipeline of diameter 3m), flow can reach 100 ten thousand steres/hour more than, can satisfy the requirements of the big traffic engineering pipeline flowmeter verifications of great majority.And, in this method,,, just can insert in the verification section and test as long as less than the wind-tunnel sectional dimension regardless of flowmeter length, equipment interoperability is fabulous.
(2) be provided with test chamber and two verification sections of abundant development pipe stream test section in the velocity distribution correction factor experimental system, under identical flow velocity (the being flow) situation, measured at test chamber and abundant development pipe stream test section respectively by the school flowmeter, thereby obtain the velocity distribution correction factor.The velocity distribution correction factor accuracy height that adopts this method to obtain, data credibility height.
Description of drawings
Fig. 1 is a large flow gas pipeline averaging velocity tube flowmeter wind-tunnel check system synoptic diagram:
Fig. 2 is a flowmeter velocity distribution correction factor test macro synoptic diagram
Among the figure: the 1-honeycomb; The 2-damping screen; The 3-stable section; 4-wind-tunnel contraction section; The 5-test chamber; The 6-pitot tube; The 7-differential pressure transmitter; 8-is by the school flowmeter; 9-wind-tunnel expansion segment; The 10-safety net; The 11-axial flow blower; The 12-test chamber; 13-pitot tube and differential pressure transmitter; The 14-straight length; 15-fully develops pipe stream test section; 16-is by the school flowmeter; The 17-proving flowmeter; 18-wind-tunnel main body.
Embodiment
The present invention proposes a kind of heavy caliber, big flow gas pipe flowmeter wind tunnel calibration method.Specific implementation process is as follows:
Set up wind-tunnel according to flowmeter checking dimension needs, this wind-tunnel is identical with general single flow low velocity fluid mechanics wind-tunnel requirement, and model bay is as the test section of flowmeter verification.As shown in Figure 1, under the effect of axial flow blower 11, air enters wind-tunnel goes into wind-tunnel test section 5 after honeycomb 1, damping screen 2, stable section 3 and 4 rectifications of wind-tunnel contraction section are laggard.Test chamber 5 cross section velocity distribution are very even, therefore, insert test chamber simultaneously with a pitot tube 6 with by school flowmeter 8, just can measure the differential pressure of output, thereby obtain air velocity and obtain by the efflux coefficient of school flowmeter by differential pressure transmitter 7.Wherein, the effect of wind-tunnel expansion segment 9 is to guarantee mobile stability, and safety net 10 is in order to prevent that foreign matter from entering into axial flow blower 11.
Wind-tunnel is different with actual pipeline section velocity flow profile, even distribution can be thought in the flow field in the wind-tunnel, and flow in the actual pipeline is full-blown turbulent flow, its velocity flow profile meets the velocity flow profile that abundant development pipe stream flows, and this influence adopts the velocity distribution correction factor to revise.Like this, just can determine the flowmeter coefficient of flow, thereby realize the verification of flowmeter according to efflux coefficient, the velocity distribution correction factor of flowmeter.Adopt this scheme,,, just can insert in the verification section and test as long as less than the wind-tunnel sectional dimension regardless of flowmeter length.Like this, when the model bay diameter be D
Wind-tunnelThe time (if wind-tunnel cross section be circular), just can verification join 2D
Wind-tunnelFlowmeter (because in the large diameter pipeline, flowmeter is half to insert).Compare with traditional gas flow calibration technology, this method checking flow improves greatly, has solved a difficult problem in the flow verification.
It is as follows that the velocity distribution correction factor is measured process: velocity distribution correction factor experimental system as shown in Figure 2, this system is by wind-tunnel main body 18 and connect straight length two parts thereafter and form.Wind-tunnel also provides test chamber simultaneously as the flow standard device.Be that system is provided with test chamber 12 and fully develops 15 two test sections of pipe stream test section.Air enters system by the wind-tunnel inlet, and flow velocity evenly distributes in test chamber 12, as long as the flow velocity of measuring in the test chamber 12 with pitot tube and differential pressure transmitter 13 just can obtain flow accurately according to the flow velocity area-method.Subsequently, air-flow enters straight length 14, and forms that fully development section flows in the pipe.Under identical flow velocity (the being flow) situation, by school flowmeter 16 respectively at test chamber 12 (shown in dotted line by the school flowmeter) with fully measure in the development pipe stream test section 15, obtain the differential pressure output of flowmeter in two test sections, can obtain the velocity distribution correction factor.Proving flowmeter 17 can provide the checking work of velocity-area method wind tunnel flow rate accuracy of measurement.The flowmeter of geometric similarity (comprising that position of opening is similar), its velocity distribution correction factor is identical under identical Reynolds number.
After obtaining efflux coefficient and velocity distribution correction factor, just can calculate the coefficient of flow of flowmeter in conjunction with the measured internal diameter of the pipeline of flowmeter.
Claims (1)
1, a kind of wind tunnel calibration method for large flow gas pipeline averaging velocity tube flowmeter is characterized in that: tested in test chamber by the school flowmeter, obtain the flowmeter efflux coefficient, obtain the flowmeter coefficient of flow in conjunction with the velocity distribution correction factor then;
Determining of velocity distribution correction factor is a key issue in this method, in this method of calibration implementation process, needs set up velocity distribution correction factor curve or database to the mean velocity tube flowmeter of each type; Velocity distribution correction factor curve determination process is carried out on flowmeter velocity distribution correction factor test macro; Wind-tunnel main body (18) also provides first test chamber (12) simultaneously as the flow standard device in the flowmeter velocity distribution correction factor test macro; Air enters system by the wind-tunnel inlet, and flow velocity is even distribution in first test chamber (12), just can obtain flow accurately according to the flow velocity area-method as long as measure flow velocity; Under the identical flow situation, measured at first test chamber (12) and abundant development pipe stream test section (15) respectively, obtain to be obtained the velocity distribution correction factor by the differential pressure output of school flowmeter in two test sections by the school flowmeter; The flowmeter of geometric similarity is identical with its velocity distribution correction factor under the pipeline relative roughness at identical Reynolds number;
Calibration equipment is a low-speed wind tunnel, and model bay is as the test section of flowmeter verification; Air enters second test chamber (5) after wind-tunnel inlet, honeycomb (1), damping screen (2), stable section (3) and wind-tunnel contraction section (4) rectification, the second test chamber cross section velocity distribution is very even, therefore, insert second test chamber simultaneously with a pitot tube (6) with by school flowmeter (8), obtain accurate wind speed by pitot tube (6), according to differential pressure transmitter (7) output by school flowmeter differential pressure, just obtain by the efflux coefficient of school flowmeter; Obtain by behind the efflux coefficient of school flowmeter, the pipeline of being surveyed in conjunction with the velocity distribution correction factor with by the school flowmeter i.e. internal diameter of second test chamber (5) just calculates the coefficient of flow of flowmeter.
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| CNB2007100667369A CN100538307C (en) | 2007-01-16 | 2007-01-16 | A kind of wind tunnel calibration method for large flow gas pipeline averaging velocity tube flowmeter |
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| CNB2007100667369A CN100538307C (en) | 2007-01-16 | 2007-01-16 | A kind of wind tunnel calibration method for large flow gas pipeline averaging velocity tube flowmeter |
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| CN100538307C true CN100538307C (en) | 2009-09-09 |
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