CN1963402A - A differential pressure type flow measuring method and flow apparatus thereof - Google Patents

Abstract

The invention relates to a flow measuring method and a flow device, and aims to provide a flow measuring method and a flow measuring device of an orifice throttling differential pressure type with low pressure drop and wide range ratio. The method includes: respectively transmitting the fluid pressure signals of the pressure measuring nozzle at the high pressure end and the pressure measuring nozzle at the low pressure end to the differential pressure sensor through the pressure guiding tube; detecting the differential pressure signal through the differential pressure sensor; Square operation transmitter, or intelligent controller, or computer, and obtain the fluid flow value from the received differential pressure signal. The present invention also provides a measuring device for realizing the aforementioned flow measuring method. The differential pressure flow measuring method and the flow device of the present invention have the advantages of wide measuring range, small throttling resistance loss, low cost, convenient processing and manufacture, and the like. The flow measurement device of the present invention can be widely used in flow measurement of various fluid flows, such as water, air, steam, gas and the like.

Description

A kind of differential pressure type flow measurement method and flow apparatus

Technical field

The present invention relates to a kind of measuring method and flow apparatus of flow.More particularly, the present invention relates to a kind of orifice plate throttling differential pressure type flow measurement method and flow measurement device of low pressure loss wide-range ratio.

Background technology

Differential pressure flowmeter is a most frequently used flow instrument device during fluids such as present measurement gas, liquid and high-temperature steam flow, and it does not need the real advantage such as fixed of failing to be sold at auction when having simple in structure, stable, processing and using conformance with standard.With orifice plate, nozzle and Venturi tube is that the differential pressure flowmeter maturation of representative is applied to industrial circle, wherein the standard orifice plate flowmeter be research both at home and abroad the earliest, test figure at most, use experience is the abundantest, standardization level is the highest measurement means.

It is constant that traditional orifice plate or blast tube flow apparatus can only be provided with coefficient of flow, when fluctuations in discharge scope more especially low discharge is measured, because coefficient of flow will cause very big substantial measurement errors because of Reynolds number (Re) influence, thereby the range ratio relative narrower of definition.After adopting ISO 5167 (2003) standards in the world, to having proposed harsher requirement on the installation of classical orifice plate, the working service, as not requiring longer upstream straight tube to guarantee the abundant development in flow field with the orifice plate of screens, and orifice plate belongs to the restriction device of center sudden contraction formula, and its crushing is very big.

At present some publications all be intended to orifice plate installation, measure on computing formula or the version and improve design.Because standard orifice plate requires installation accuracy height, the pressure loss big, in actual engineering, not too meet the demands fully easily, the series of patents technology that has occurred standard orifice plate remodeling thus is (as the monoblock type throttle orifice plate apparatus, built-in orifice plate measurement mechanism etc.), so that being carried out integrated standard design, orifice plate measurement mechanism, pressure obtaning device, mounting flange make.

On the flow rate calculation formula of orifice differential pressure formula principle, some patented technology or computing method about flow correction have been proposed also.Present standard orifice plate measurement range is about 4: 1 (rangeability of definition orifice plate is 4) generally, and its reason is that coefficient of flow is subjected to the influence of Reynolds number (Re) variation too big.The patented technology that adopts intelligent transducer or computer technology that coefficient of flow is dynamically revised in different range is also arranged recently, and this has improved the orifice plate measurement range to a certain extent; Formal in AND DEWATERING FOR ORIFICE STRUCTURE, in order to reduce the pressure loss, also there are many patented technologies to concentrate on the sharp edge that changes the orifice plate upstream, perhaps be designed to eccentric orifice, segmental orifice plate etc.These patents mostly stop standard orifice plate and calibrating nozzle carries out innovative design in form.

Standard orifice plate corresponding pressure loss value inherent shortcoming bigger than normal is difficult to avoid always, therefore differential flow-measuring method and the measurement mechanism that breaks away from the orifice plate pattern fully also arranged, as Annubar flow apparatus, Verabar flow apparatus, tapered hydrodynamic form flow measurement device or the like.

Being based upon flowmeter extension product based on orifice plate differential pressure type principle has simple in structure, easy to use, highly versatile, advantage such as cheap equally and is used widely.Become stream remodeling if standard orifice plate is carried out Transform Type design, can obviously reduce the pressure loss of flow apparatus, the range ratio of raising flow measurement.

The known streamlined orifice plate flow apparatus of also not finding utilizes this device can realize the orifice plate differential pressure type flow measurement method of low pressure loss, wide-range ratio at present.

Summary of the invention

Fundamental purpose of the present invention is to overcome deficiency of the prior art, and a kind of implementation method of flow measurement is provided.Further object of the present invention is to provide the streamlined orifice plate differential pressure type flow measurement method and the flow measurement device of a kind of low pressure loss, wide-range ratio.

In order to solve the problems of the technologies described above, the present invention is achieved by the following technical solutions:

The invention provides a kind of differential pressure type flow measurement method, may further comprise the steps:

(1) by connecting pipe the fluid pressure signal that pressure survey is chewed with low pressure end is chewed in the high-pressure side pressure survey respectively and be passed to differential pressure pickup;

Described high-pressure side pressure survey is chewed and is installed on the tested pipeline wall or the going on the head piece wall of streamlined orifice plate, and described low pressure end pressure survey is chewed and is installed on the going out on the head piece wall of streamlined orifice plate;

(2) by differential pressure pickup detected pressures difference signal;

(3) differential pressure pickup passes to extracting operation transmitter or intelligent controller or computing machine with pressure difference signal, and obtains flow values according to following manner by the pressure difference signal of receiving:

$Q_M=C_{\mathrm{\ϵ}}\·\mathrm{\α}\·C_R\·A\·\sqrt{2\·\mathrm{\ΔP}\·\mathrm{\ρ}}$

$Q_V=C_{\mathrm{\&epsiv;}}\&CenterDot;\mathrm{\&alpha;}\&CenterDot;C_R\&CenterDot;A\&CenterDot;\sqrt{2\&CenterDot;\mathrm{\&Delta;P}/\mathrm{\&rho;}}$ Perhaps $Q_V=C_{\mathrm{\&tau;}}\&CenterDot;\mathrm{\&alpha;}\&CenterDot;C_R\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="A20061015476200101.png,A20061015476200111.png"\; state="\{\{state\}\}">d</figure-callout>}}^2\&CenterDot;\sqrt{2\&CenterDot;\mathrm{\&Delta;P}/\mathrm{\&rho;}}$

Wherein:

C _R: definition efflux coefficient (or coefficient of flow) is the important parameter that characterizes the throttle orifice plate apparatus discharge characteristic.

Q _M: the mass rate of flow apparatus, units/h;

Q _V: the volumetric flow rate of flow apparatus, the m of unit ³/ h;

D: the minimum through bore diameter of streamlined orifice plate, the m of unit;

D: the pipeline drift diameter of orifice plate flow apparatus (diameter), the m of unit;

α: the blockage factor of streamlined orifice plate, mainly the aperture by orifice fitting determines than β=d/D, influenced by the orifice plate physical dimension, specifically can decide by real failing to be sold at auction;

C _ε: the correction factor when measuring the different fluid flow, the influence of fluid media (medium) can just flow to the rower periodical repair by real;

A: the flow area of measured pipeline;

Δ P: the output differential pressure value of streamline throttle orifice plate apparatus, Pa of unit or kPa;

Experimental study found that, efflux coefficient C _RInfluence factor comprise: the blockage factor α of (1) orifice plate, (2) orifice plate throttling install pattern, the ways of measure pressure of (3) orifice differential pressure, (4) incoming flow reynolds number Re.

Wherein three aspects, front are mainly determined by the physical construction of streamlined orifice plate flow apparatus.For given orifice plate measurement mechanism, when Re surpasses certain limit, its efflux coefficient (coefficient of flow) C _RSubstantially be tending towards constant, this moment Q with Linear, utilize differential pressure pickup to carry out becoming behind differential pressure measurement and the mathematics extracting operation and send into the standard electric signal, just can realize the measurement of differential flow.

As a kind of improvement, this method also comprises adjusts streamlined orifice plate installation site, makes the streamlined orifice plate be positioned at the tested pipeline center.

As a kind of improvement, this method also comprises adjusts streamlined orifice plate installation site, makes the streamlined orifice plate be arranged in the position of tested pipeline incoming flow average velocity.

The present invention further provides a kind of realization one measurement device for above flow measurement, comprise that the high-pressure side pressure survey that links to each other with differential pressure pickup respectively by connecting pipe chews with low pressure end pressure survey and chew, also comprise a streamlined orifice plate with hollow barrel-type structure, its inner longshore current body flow direction is followed successively by orifice plate goes into head piece, streamlined throttle orifice and orifice plate and goes out head piece, and the edge of streamlined throttle orifice is streamlined and longshore current body flow direction shrinks to the center; Described low pressure end pressure survey is chewed and is installed on the going out on the head piece wall of streamlined orifice plate.

As a kind of improvement, described high-pressure side pressure survey is chewed and is installed on the tested pipeline wall or the going on the head piece wall of streamlined orifice plate.

As a kind of improvement, described differential pressure pickup links to each other with the extracting operation transmitter by signal wire, the standard electric signal that pressure difference signal is directly proportional with flow by extracting operation transmitter 7 output is (as DC 4～20mA, DC0～10V), constituted the direct differential pipe flow meter of a kind of streamlined orifice plate.。

As a kind of improvement, described differential pressure pickup directly links to each other with intelligent controller or computing machine by signal wire, utilizes the conversion of higher level lanquage to realize flow output.

As a kind of improvement, described streamlined orifice plate is installed on the tested pipeline center by support, and the high-pressure side measurement is chewed 2 and can be directly connected on the relatively more uniform inner-walls of duct face of incoming flow.With the high-pressure side pressure survey chew 2, the low pressure end pressure survey chews 4 and is connected to differential pressure pickup 6 by connecting pipe 8, the standard electric signal that is directly proportional with flow by 7 outputs of extracting operation transmitter (as DC 4～20mA), constitutes a kind of bigbore pipe flow meter.

As a kind of improvement, described streamlined orifice plate is installed on the position of tested pipeline incoming flow average velocity by support, by the correction of coefficient, constitutes the flow measurement device of another kind of large-diameter pipe.

As another kind of improvement the of the present invention, described extracting operation transmitter 7 can be unworthy of, be directly inputted to intelligent controller or computing machine by pressure difference signal and carry out output stream value behind extracting operation and the range designation, constituted a kind of pipe flow meter of streamlined orifice differential pressure formula differential pressure pickup 6.

Compare with background technology, beneficial effect of the present invention is that differential flow-measuring method of the present invention and flow apparatus have advantages such as the broad quantum of measurement, the throttle resistance loss is little, cost is low, processing and fabricating is convenient.Flow measurement device of the present invention can be widely used in the flow measurement that various fluids flow, as water, air, steam, coal gas etc.

Description of drawings

Fig. 1 is a streamlined AND DEWATERING FOR ORIFICE STRUCTURE synoptic diagram in the embodiment of the invention.

Fig. 2 is the another kind of structural representation of streamlined orifice plate in the embodiment of the invention.

Fig. 3～Fig. 4 is the measurement mechanism synoptic diagram that the streamlined orifice plate is assemblied in the pipeline center position in the embodiment of the invention.

Symbol in the legend: 1 orifice plate goes into that head piece, 2 high-pressure side pressure surveys are chewed, 3 streamlined throttle orifices, 4 low pressure end pressure surveys are chewed, 5 orifice plates go out head piece, the mounting bracket of 6 differential pressure pickups, 7 extracting operation transmitters, 8 connecting pipes, 9 streamlined orifice plates, 10 orifice fittings,

Embodiment

1～accompanying drawing 4 with reference to the accompanying drawings, will describe the present invention below.

Specific embodiment 1 is as shown in Fig. 1,3.Flow apparatus comprise the high-pressure side pressure survey that links to each other with differential pressure pickup 6 respectively by connecting pipe 8 chew 2 and the low pressure end pressure survey chew 4, differential pressure pickup 8 links to each other with extracting operation transmitter 7 by signal wire.Streamlined orifice plate 9 with hollow barrel-type structure is installed on the tested pipeline center by support 10, its inner longshore current body flow direction is followed successively by orifice plate goes into head piece 1, streamlined throttle orifice 3 and orifice plate and goes out head piece 5, and the edge of streamlined throttle orifice 3 is streamlined and longshore current body flow direction shrinks to the center; The low pressure end pressure survey is chewed 4 and is installed on the going out on head piece 5 walls of streamlined orifice plate 9, and the high-pressure side pressure survey is chewed 2 and is installed on the tested pipeline wall.

Extracting operation transmitter 7 with pressure difference signal carry out evolution become send after, the standard electric signal that output is directly proportional with the flow (measurement mechanism that as DC 4～20mA), streamlined orifice plate 9, high-pressure side pressure survey chew 2, the low pressure end pressure survey chews 4, connecting pipe 8, differential pressure pickup 6, extracting operation transmitter 7 have constituted a kind of direct differential pipeline flow jointly.

Embodiment 1 as shown in Figure 3, the method that flow apparatus carries out differential pressure type flow measurement is as follows:

(1) respectively by connecting pipe 8 with the high-pressure side pressure survey chew 2 and the low pressure end pressure survey chew 4 fluid pressure signal and be passed to differential pressure pickup 6;

Described high-pressure side pressure survey is chewed 2 and is installed on the tested pipeline wall, and described low pressure end pressure survey is chewed 4 and is installed on the going out on head piece 5 walls of streamlined orifice plate 9;

(2) by differential pressure pickup 6 detected pressures signals to obtain pressure difference signal;

(3) differential pressure pickup 6 passes to extracting operation transmitter 7 with pressure difference signal, and obtains the fluid flow value according to following manner by the pressure difference signal of receiving:

$Q_M=C_{\mathrm{\&epsiv;}}\&CenterDot;\mathrm{\&alpha;}\&CenterDot;C_R\&CenterDot;A\&CenterDot;\sqrt{2\&CenterDot;\mathrm{\&Delta;P}\&CenterDot;\mathrm{\&rho;}};$ Or

$Q_V=C_{\mathrm{\&epsiv;}}\&CenterDot;\mathrm{\&alpha;}\&CenterDot;C_R\&CenterDot;A\&CenterDot;\sqrt{2\&CenterDot;\mathrm{\&Delta;P}/\mathrm{\&rho;}};$

Wherein:

C _R: the definition efflux coefficient;

Q _M: the mass rate of flow apparatus, units/h;

Q _V: the volumetric flow rate of flow apparatus, the m of unit ³/ h;

D: the minimum through bore diameter of streamlined throttle orifice, the m of unit;

D: the pipe diameter of orifice plate flow apparatus, the m of unit;

α: the blockage factor of streamlined orifice plate;

C _ε: the correction factor when measuring the different fluid flow;

Δ P: the output differential pressure of flow apparatus, Pa of unit or kPa.

A: the flow area of measured pipeline.

Embodiment 2 as shown in Figure 4, in the present embodiment, the high-pressure side pressure survey is chewed 2 and is installed on the going on head piece 1 wall of streamlined orifice plate 9.Streamlined orifice plate 9 is installed to pipeline location near incoming flow average velocity by mounting bracket 10, by revising coefficient C _RCorrection demarcate, constitute the measurement mechanism of another kind of large diameter pipeline flow.

Embodiment 3 as shown in Figure 2, in the present embodiment, the high-pressure side pressure survey is chewed 2 and is installed on the going on head piece 1 wall of streamlined orifice plate 9, the low pressure end pressure survey is chewed 4 and is installed on the going out on head piece 5 walls of streamlined orifice plate 9, and it is the pipe diameter D of orifice plate flow apparatus is identical with the through-flow diameter of tested pipeline, and be assembled into integral structure, and constituting another kind of small-bore pipeline flow measurement device, the calibration formula of this moment is as follows:

$Q_V=C_{\mathrm{\&tau;}}\&CenterDot;\mathrm{\&alpha;}\&CenterDot;C_R\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="A20061015476200101.png,A20061015476200111.png"\; state="\{\{state\}\}">d</figure-callout>}}^2\&CenterDot;\sqrt{2\&CenterDot;\mathrm{\&Delta;P}/\mathrm{\&rho;}}$

Described extracting operation transmitter 7 can dispose, be directly inputted to intelligent controller or computing machine carries out exporting behind extracting operation and the range designation by pressure difference signal, constituted a kind of measurement mechanism of streamline orifice differential pressure formula pipeline flow differential pressure pickup 6.

Obviously, the above-mentioned streamlined orifice plate measurement mechanism pressure loss is very little, measurement range wide ranges.When this flow measurement device is applied to measuring water flow, experiment is found all can realize high-precision flow measurement in water flow velocity 0.25m/s～5.0m/s scope, according to international standard ISO11631:1998 latest definition, the rangeability of this flow measurement device (Range ability) reaches 20.

Obviously, the invention is not restricted to above embodiment, many distortion can also be arranged.All distortion that those of ordinary skill in the art can directly derive or associate from content disclosed by the invention all should be thought protection scope of the present invention.

Claims (9)

1. A differential pressure flow measurement method, characterized in that, comprising the following steps: (1) Transmit the fluid pressure signals of the pressure measuring nozzle at the high pressure end and the pressure measuring nozzle at the low pressure end to the differential pressure sensor through the pressure guiding tube respectively; The pressure measuring nozzle at the high-pressure end is installed on the wall of the pipeline under test or the inlet wall of the streamlined orifice plate, and the pressure measuring nozzle at the low-pressure end is installed on the outlet wall of the streamlined orifice plate; (2) Detecting the pressure signal by the differential pressure sensor to obtain the differential pressure signal; (3) The differential pressure sensor transmits the differential pressure signal to the square root operation transmitter, intelligent controller or computer, and obtains the fluid flow value from the received differential pressure signal according to the following methods: ${\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; \&Delta;P</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; \&rho;</span>}}<span\; class="notranslate">\; ;</span>$ $Q_V=C_{\mathrm{\&epsiv;}}\&CenterDot;\mathrm{\&alpha;}\&CenterDot;C_R\&CenterDot;A\&CenterDot;\sqrt{2\&CenterDot;\mathrm{\&Delta;P}/\mathrm{\&rho;}};$ or $Q=C_{\mathrm{\&tau;}}\&Center\; Dot;\mathrm{\&alpha;}\&CenterDot;C_R\&Center\; Dot;d^2\&Center\; Dot;\sqrt{2\&Center\; Dot;\mathrm{\&Delta;}/\mathrm{\&rho;}};$ in: C _R : defines the outflow coefficient; Q _M : the mass flow rate of the flow device, in kg/h; Q _V : the volumetric flow rate of the flow device, in m ³ /h; d: the through-hole diameter of the streamlined orifice, in m; D: The diameter of the pipe under test, in m; α: blocking coefficient of streamlined orifice; C _ε : Correction coefficient when measuring different fluid flows; ΔP: The output differential pressure of the flow device, in Pa or kPa; A: The flow area of the pipe to be measured. 2. The differential pressure flow measurement method according to claim 1, further comprising adjusting the installation position of the streamlined orifice plate so that the streamlined orifice plate is located at the center of the pipeline to be measured. 3. The differential pressure flow measurement method according to claim 1, further comprising adjusting the installation position of the streamlined orifice plate so that the streamlined orifice plate is located at the position of the average velocity of incoming flow in the pipeline under test. 4. A flow device for measuring fluid flow according to the orifice plate differential pressure method according to claim 1, comprising a pressure measuring nozzle at the high pressure end and a pressure measuring nozzle at the low pressure end respectively connected to the differential pressure sensor through a pressure guiding tube, characterized in that , also includes a streamlined orifice plate with a hollow cylindrical structure, the inside of which along the fluid flow direction is the orifice inlet, the streamlined orifice and the orifice outlet, and the edge of the streamlined orifice It is streamlined and shrinks toward the center along the direction of fluid flow; the pressure measuring nozzle at the low-pressure end is installed on the wall of the outlet of the streamlined orifice plate. 5. The flow device according to claim 4, characterized in that the pressure measuring nozzle at the high pressure end is installed on the wall of the pipeline to be measured or on the wall of the inlet port of the streamlined orifice plate. 6. The flow device according to claim 4, wherein the differential pressure sensor is connected to the square root operation transmitter through a signal line. 7. The flow device according to claim 4, wherein the differential pressure sensor is connected to an intelligent controller or a computer through a signal line. 8. The flow device according to claim 4, wherein the streamlined orifice plate is installed in the center of the pipeline to be tested through a bracket. 9. The flow device according to claim 4, characterized in that, the streamlined orifice plate is installed at the position of the average velocity of incoming flow in the measured pipeline through a bracket.

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