CN2434647Y - Reducing rectifier for measuring - Google Patents

Abstract

The utility model belongs to the field of metering flow, and particularly relates to a reducing rectifier for measure, which is used for a vortex shedding flowmeter. The inner diameter of a tube of the reducing rectifier for measure is diminished in the direction of the flow of a medium in the tube. The longitudinal cross-section of the inner wall of the tube from an inlet to an outlet is in the shape of a circular arc. The center of circle of the circular arc is positioned on the cross section at the point of an outlet of the reducing rectifier. The flow speed of a fluid is enabled to be increased after the fluid enters the reducing tube. Moreover, flow guidance is carried out by the inner wall in the shape of the circular arc. Therefore, the flow speed at the point of the outlet of the reducing tube is more uniformly distributed. The flow speed is closer to the condition of the uniform flow field which is required by the vortex shedding flowmeter. The lower limit value of flow measurement is lowered. The ratio of a measuring range is increased. The utility model does not need to be provided with a straight tube section.

Description

The measurement reducing rectifier

The utility model belongs to the flow metering field, is specifically related to a kind of measurement reducing rectifier that is used for vortex shedding flow meter.

Used vortex shedding flow meter in the present flow metering 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 flux lower limit 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 worked under low discharge, 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 because this reducer pipe will produce the stagnant area in the exit, forms vortex, 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 very inconveniently, and be difficult for commercialization.

The purpose of this utility model is: for addressing the above problem, the measurement reducing rectifier that a kind of length is little, processing is simple, easy for installation is provided, it directly is connected with measurement instrument, or be integral with instrument, need not add straight length in addition, the lower limit of present measurement flow is significantly reduced, range ratio improves, be very suitable for being used to improve in-situ velocity on the engineering, reach the purpose of improving the low discharge measurement performance.

The utility model is achieved in that to measure uses reducing rectifier, and its bore is along managing interior media flow direction from large to small, and the longitudinal cross-section of the inside pipe wall that exports by entering the mouth to is a circular arc.

The center of circle of described circular arc can be positioned on the transversal section in reducing rectifier exit.

The utility model is because the inner wall section of reducing rectifier is set to circular arc, flow velocity improves gradually after making fluid enter reducer pipe, and carry out water conservancy diversion by the circular arc inwall, make the velocity flow profile in reducer pipe exit more even, more near the desired uniform flow field condition of vortex shedding flow meter, select the less instrument of bore for use, reduced measurement flux lower limit value, improved range ratio, need not add straight length in addition, be very suitable for being used to improve in-situ velocity on the engineering, reach the purpose of improving the low discharge measurement performance.

Below in conjunction with embodiment the utility model is described in detail:

Fig. 1 measures vertical cross-sectional schematic of using reducing rectifier for the utility model;

Fig. 2 is a scheme of installation of the present utility model.

With reference to figure 1, measuring with reducing rectifier is to be made of cylindrical tube 1, its bore along the tube fluid flow direction from large to small, the diameter D of body 1 porch B-B ₁Maximum, the diameter minimum of body 1 exit A-A, the longitudinal cross-section of body 1 inwall is to be that the circular arc 3,4 of R constitutes by radius, fluid enters tube cavity 2 and carries out water conservancy diversion by circular arc 3,4, because the maximum dimension D of body 1 internal diameter porch ₁Progressively carry out the transition to the minimum diameter D in exit ₂So the sectional velocity of tube cavity 2 strengthens 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 increase few 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, 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 vortex, it self is exactly a rectifier, so need not add the straight length rectification in addition.

Radius R and circular arc 3,4 pairing central angle θ by selecting suitable circular arc 3,4 can reduce physical dimension greatly, and the length of reducing rectifier only is 1/3rd of process duct internal diameter, also promptly is no more than reducer pipe inlet diameter D ₁1/3rd, 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 °, as (D ₁-D ₂)/D ₂〉=0.5 o'clock, circular arc 3,4 pairing central angle θ were 35 °-48 °; As (D ₁-D ₂)/D ₂≤ 0.5 o'clock, circular arc 3,4 pairing central angle θ were 42 °-57 °.

For the selection of the radius R of circular arc 3,4, can adopt following relational expression [R-(D ₁-D ₂)/2]/R=COS θ, also be R=(D ₁-D ₂)/2 (1-COS θ).

Reducing rectifier of the present utility model porch joins porch diameter D by flange 7 and process pipe 5 ₁Equate that with process pipe 5 internal diameters exit and measurement instrument 6 join, exit diameter D ₂Equate that with instrument 6 internal diameters as shown in Figure 2, reducing rectifier both can make independently product, be installed between process duct and the measurement instrument, also can make one with measurement instrument.

Claims (3)

1. measurement reducing rectifier, its bore is characterized in that from large to small along media flow direction in the pipe: the longitudinal cross-section by the inside pipe wall of the outlet that enters the mouth is a circular arc.

2. measurement reducing rectifier as claimed in claim 1 is characterized in that: the center of circle of described circular arc is positioned on the transversal section in reducing rectifier exit.

3. measurement reducing rectifier as claimed in claim 1 or 2 is characterized in that: the pairing central angle of described circular arc is 35 °-57 °.

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