The flow tube that has reducing rectifier
The utility model belongs to the flow metering field, is specifically related to a kind of flow tube that has reducing rectifier.
Used vortex shedding flow meter in the present flow field at home and abroad, because its particular performances, in industry measurement, obtained extensive employing, but in actual applications, velocity of medium in the pipeline changes with the variation of load, its flow velocity tends to be lower than the lower limit of instrument range, and flow measurement instrument all has certain limitation to the flow range of survey medium, speed mode flow measurement instrument particularly, lower limit flow velocity to medium more has strict demand, flow is lower than lower limit, accuracy of measurement will descend or energy measurement not, and instrument is in low discharge work, signal a little less than, antijamming capability descends, the microvibration of pipeline also can bring wrong metering, measure in order to solve low discharge, the reducer pipe that present industrial employing cavity shape is a round platform, by undergauge to improve flow velocity, reach the purpose of measurement, but this reducer pipe size is big, its length is 3-5 times of process duct internal diameter, and breaks away from the formation whirlpool because boundary-layer may appear in this reducer pipe in the exit, so will add length between outlet and measurement instrument is that the straight length of process duct internal diameter more than 15 times carries out rectification, simultaneously straight length inwall smooth finish requires highly, manages longly again, and processing charges is higher, install, use very inconveniently, and be difficult for commercialization.
The purpose of this utility model is: for addressing the above problem, provide a kind of process simple, error is little, the flow tube that has reducing rectifier of installation, effectively eliminate fluid whirlpool easy to use, also can reach simultaneously and improve low discharge measurement purpose.
The utility model is achieved in that a kind of flow tube that has reducing rectifier, form by upstream side parts that are connected with measurement instrument and downstream parts, the upstream side parts comprise a reducing rectifier, the round tube inside diameter of reducing rectifier along media flow direction in the pipe from large to small, the longitudinal cross-section of inside pipe wall by the outlet that enters the mouth is a circular arc, described downstream parts comprise one with the measurement instrument connection and with the identical indentical tube of measurement instrument nominal bore.Can eliminate the fluid whirlpool in measurement instrument exit like this, improve measuring accuracy, reach and improve the purpose that low discharge is measured.
Described upstream side parts also can comprise a upstream side measuring tube that is connected with the reducing rectifier inlet, and the downstream parts also can comprise a downstream measuring tube that is connected with described indentical tube.Fluid is after the upstream side measuring tube enters reducing rectifier, and flow velocity improves gradually, carries out water conservancy diversion through the circular arc inwall, and reducer pipe exit velocity flow profile is more even, more near the desired uniform flow field condition of vortex shedding flow meter.Select small-bore instrument to reach and reduce measurement flux lower limit value, improve the purpose of range ratio.Reducing rectifier matches with the upstream side measuring tube and indentical tube matches with the downstream measuring tube, can reduce greatly upstream side straight pipeline length requirement, range ratio is brought up to more than 15: 1, simultaneously under appearring in the upstream of pipeline, the situation of bend can effectively improve the precision of measurement, reduce error, further improve the accuracy of measuring.
The part of the indentical tube body of described downstream parts can stretch in the inlet end of downstream measuring tube.
The endpiece of the indentical tube of described downstream parts also can be bore and becomes big diverging shape gradually.This structure has satisfied the toll bar whirlpool and has stablized separation condition, is fit to very much be used to improve in-situ velocity in the engineering, reaches the further purpose that low discharge is measured of improving.
Described upstream side measuring tube also can be identical with the bore of downstream measuring tube.
The outside surface of described reducing rectifier and indentical tube can be the flange arrangement form.
The bore of described upstream side measuring tube is identical with reducing rectifier porch diameter, and the length of upstream side measuring tube can be 0.2-10 times of upstream side measuring tube internal diameter,
The length of described downstream measuring tube can be 0.2-5 times of downstream measuring tube internal diameter.
The length of the indentical tube of described downstream parts also can be 0.3-3 times of measurement instrument nominal bore.
The utility model since on the basis of circular arc reducing rectifier, set up one with the measurement instrument connection and with measurement instrument nominal bore identical indentical tube, can eliminate the fluid whirlpool in measurement instrument exit, improve measuring accuracy, reach and improve the purpose that low discharge is measured.Further take reducing rectifier to match and indentical tube matches with the downstream measuring tube with the upstream side measuring tube, can reduce greatly upstream side straight pipeline length requirement, range ratio is brought up to more than 15: 1, can effectively improve simultaneously the accuracy of measurement under the situation of bend appears in the upstream of pipeline.
Below in conjunction with embodiment the utility model is described in detail:
Fig. 1 is the reducing rectifier interior wall construction longitudinal sectional view of the utility model upstream side parts;
Fig. 2 is the indentical tube structure longitudinal sectional view of the utility model downstream parts;
Fig. 3 is the upstream side measuring tube structure cut-open view of the utility model upstream side parts;
Fig. 4 is the downstream measuring tube structure cut-open view of the utility model downstream parts;
Fig. 5 is the scheme of installation of the utility model flow tube
With reference to figure 1-Fig. 5, the measuring tube that has reducing rectifier is made up of upstream side parts that are connected with measurement instrument respectively and downstream parts, described upstream side parts are made of upstream side measuring tube 5 and reducing rectifier 1, the inlet of upstream side measuring tube 5 connects process pipe, its outlet is connected with the inlet of reducing rectifier 1, the outlet of reducing rectifier 1 is connected with the inlet of measurement instrument 6, the length H of upstream side measuring tube 5
1For the 0.2-10 of upstream side measuring tube 5 inside diameter D 1 doubly, i.e. H
1=0.2-10D1, the bore of upstream side measuring tube 5 is identical with reducing rectifier 1 porch diameter D1.The downstream parts are to be made of a bore indentical tube 9 and the downstream measuring tube 11 identical with measurement instrument 6 nominal bore D2.Upstream side measuring tube 5 is identical with the bore of downstream measuring tube 11.Reducing rectifier as the upstream side parts constitutes (as shown in Figure 1) by cylindrical tube 1, its bore along the tube fluid flow direction from large to small, the diameter D1 maximum of body 1 porch B-B, the diameter minimum of body 1 exit A-A, the longitudinal cross-section of body 1 inwall is to be the circular arc 3 of R by radius, 4 constitute, fluid enters tube cavity 2, by circular arc 3,4 carry out water conservancy diversion, because the maximum dimension D 1 of body 1 internal diameter inlet progressively carries out the transition to the minimum diameter D2 in exit, so tube cavity 2 sectional velocity strengthen gradually, but the flow velocity increase of transversal section each point is different, at the A-A of Fig. 1 section, increase big near A point place flow velocity, and increasing fewly near the central spot flow velocity, the velocity flow profile that is formed on the A-A end face is more even than the velocity flow profile of B-B end face, more near the uniform flow field condition of vortex shedding flow meter, select the less instrument of bore for use, reduce the purpose of measuring the flux lower limit value and improving range ratio thereby reach.Use reducing rectifier 1 and upstream side measuring tube 5 on the measuring channel, can reduce greatly upstream side straight pipeline length requirement, range ratio is brought up to more than 15: 1.Downstream parts indentical tube 9 directly is connected with the endpiece of measurement instrument 6, and bore is identical, and downstream measuring tube 11 links to each other with indentical tube 9.More than design is very suitable for being used to improve in-situ velocity on the engineering, reaches the purpose of improving the low discharge measurement performance.The center of circle of circular arc 3,4 is positioned on the section A-A in reducing rectifier exit, and promptly the flow direction is tangent with the A point, so can not form whirlpool, it self is exactly a rectifier.Length H=0.3~the 3D2 of described downstream parts indentical tube 9, the part of indentical tube 9 bodys stretches in the inlet end of downstream measuring tube 11, the endpiece of indentical tube 9 is that bore becomes big diverging shape gradually, with further raising in-situ velocity, further reach and improve the purpose that low discharge is measured.Internal diameter is D
1The length H of downstream measuring tube 11
2=0.2-5D
1
By radius R and circular arc 3, the 4 pairing central angle θ that select suitable circular arc 3,4, can reduce physical dimension greatly, the length of reducing rectifier only is 1/3rd of process duct internal diameter, also promptly be no more than 1/3rd of reducer pipe inlet diameter D1, can make the lower limit of present measurement flow be reduced to 1/3rd, range ratio is brought up to 15: 1, circular arc 3,4 pairing central angle θ are 35 °-57 °, when (D1-D2)/D2 〉=0.5, circular arc 3,4 pairing central angle θ are 35 °-48 °; When (D1-D2)/D2≤0.5, circular arc 3,4 pairing central angle θ are 42 °-57 °.
With reference to figure 5, for easy for installation, the outside surface of reducing rectifier 1 and indentical tube 9 can be respectively the flange arrangement form, be that reducing rectifier 1 porch joins with upstream side measuring tube 5 by the flange 7 that its outside surface forms, reducing rectifier 1 porch diameter D1 equates with upstream side measuring tube 5 internal diameters, exit and measurement instrument 6 directly join, the outlet of measurement instrument 6 connects downstream parts indentical tube 9, indentical tube 9 links to each other with downstream measuring tube 11 by the flange 10 that its outside surface forms, the bore D1 of downstream measuring tube 11 is identical with upstream side measuring tube 5, length H2=0.2-5D1.According to the actual conditions of pipeline, reducing rectifier also can be connected with measurement instrument by independent flange with indentical tube, and type of attachment is not unique.Equally, upstream side measuring tube, downstream measuring tube can have multiple connected mode with being connected also of process pipe.The flow tube of the utility model band reducing rectifier both can make independently product, was installed between process pipe and the measurement instrument, also can make one with measurement instrument.