CN201858993U - Device for measuring flow quantity of double-directional unstable fluid flow - Google Patents

Abstract

The utility model relates to a device for measuring flow quantity of double-directional unstable fluid flow, comprising a measuring pipe (1), a device for determining the pressure difference of the fluid, a device for determining the density of the fluid and an analyzing and evaluating unit; the flow quantity is computed in the analyzing and evaluating unit based on the determined pressure difference of the fluid and the determined density of the fluid; the analyzing and evaluating unit comprises a computing unit for timely solving a non-linear and normal differential equation of the flow speed under the condition of considering the pressure difference and the accelerated speed of the flow speed to measure the total pressure of two flowing directions; the device is provided with two detectors which are basically in parallel with each other reversely and which are in parallel with the fluid flowing direction; one detector (2) senses the total pressure and the other detector (3) senses the static pressure; the analyzing and evaluating unit is used for determining the pressure difference between the total pressure and the static pressure sensed by the detector. Through the utility model, the flow quantity can be timely measured highly precisely under the condition of quick fluctuation.

Description

Be used to measure the equipment of the flow of two-way non-stable fluid stream

Technical field

The utility model relates to a kind of equipment that is used to measure the flow of two-way astable fluid stream.

Background technology

Disclose a kind of flow measurement of the above-mentioned type in EP1716393A1, relate to a kind of quick differential pressure type method at this, the wherein contraction that exists according to measurement point adopts Throttle Principle in conjunction with astable Bernoulli equation.

The utility model content

Therefore the purpose of this utility model is, a kind of equipment and a kind of method are provided, and can measure flow in real-time high-precision ground so as to the stream for rapid fluctuation.

In order to realize this purpose, by the equipment that is used to measure the flow of two-way non-stable fluid stream of the present utility model, comprise: a measuring tube, the device of the device of a definite fluid pressure difference and a definite fluid density, and assay unit, in this assay unit, calculate flow based on determined fluid pressure difference and fluid density, wherein, this assay unit comprises a computing unit, be used for the differential equation of under the situation of the acceleration item of considering pressure reduction and flow velocity, finding the solution the nonlinear routine of flow velocity in real time, this equipment is characterised in that, in measuring tube, be provided with two (substantially) antiparallel each other (antiparallel: antiparallel), and be parallel to the detector that fluid flow direction is arranged, one of them detector sensing (Aufnehmen) general pressure and another detector sense static pressures power, and described assay unit is used for determining the general pressure that sensed by described detector and the pressure reduction between the static pressure.Even it is can realize the flow of the fixed astable fluid stream of side real-time and accurately,, the most direct and be flow direction and rate conversion measurable pressure most accurately because by considering that dynamic head guarantees by this equipment.By the layout of symmetry, for the situation that flow direction changes, two detectors also can exchange its function.

In order particularly to eliminate the influence of gravity from equation under the situation of measuring flow of liquid, another form of implementation of the present utility model is characterised in that described measuring tube and detector (substantially) are flatly arranged.

In order further to improve precision by equipment of the present utility model, the feature of this equipment can be, be provided with an other device, be used to measure the flow of unsteady fluid flow, wherein, in described assay unit, implement to be used for by the algorithm of separating the coefficient of relatively calibrating astable Bernoulli equation of the mean value of separating of the astable Bernoulli equation of unsteady fluid flow and steady flow.

Also has a kind of form of implementation, it is characterized in that, be provided with a stabilising arrangement and an other device that is used for unsteady fluid flow is stabilized to steady flow, this other device is used to measure the flow of steady flow, wherein, implement to be used in described assay unit by the algorithm of separating the coefficient of relatively calibrating astable Bernoulli equation of the mean value of separating of the astable Bernoulli equation of unsteady fluid flow and steady flow, this form of implementation is used for further improving the precision of flow measurement.

In order to realize this purpose,, comprising: determine pressure reduction by the method that is used for the flow of the fixed two-way non-stable fluid stream of side of the present utility model; With under the situation of the density of the acceleration item of the pressure reduction of consider determining, flow velocity and fluid, come calculated flow rate by the astable Bernoulli equation of finding the solution flow velocity in real time; The method is characterized in that, determine the pressure reduction between general pressure and the static pressure and this pressure reduction introduced Bernoulli equation.

According to a kind of favourable enforcement flexible program, calibrate the coefficient of astable Bernoulli equation constantly with steady flow at some.Thus, can calibrate the coefficient of the differential equation for the item of stablizing component at least by frame of reference, this frame of reference needn't necessarily also will be applicable to unsteady fluid flow.

Press another or the enforcement flexible program regulation of replenishing of the utility model method, after unsteady fluid flow stabilizes to steady flow, by the mean value of separating of the astable Bernoulli equation of unsteady fluid flow and the reference value that steady flow is recorded relatively being calibrated the coefficient of astable Bernoulli equation.There is stabilising arrangement front in frame of reference, makes the mean value that frame of reference need not (misst) unsteady fluid flow.The differential equation can be adjusted to like this for the coefficient of unstable component so, makes that the mean value that is calculated by the unsteady fluid flow of measuring is consistent with the measured value of frame of reference.Frame of reference needn't necessarily also will be applicable to unsteady fluid flow in this case equally.

Certainly, under any circumstance can for example carry out time delay, compare and measure and be suitable for unsteady fluid flow equally by carrying out the particularly calibration of the coefficient of unstable component with comparing and measuring of frame of reference based on ultrasound wave.

The beneficial effect that can reach by the utility model is: the stream for rapid fluctuation can be measured flow in real-time high-precision ground.

Description of drawings

To be described in greater detail with reference to the attached drawings the utility model below.

Fig. 1 illustrates the equipment that comprises the two-way pitot tube of symmetry by of the present utility model with synoptic diagram, is used to measure the flow of unsteady fluid flow.

Embodiment

At the measuring tube 1 that is used for fluid stream, the distance that is spaced apart from each other is provided with two oppositely oriented each other pressure detectors 2,3, preferred parallel is orientated in flow direction, wherein, the detector 3 of corresponding sensing flow direction transmits static pressure and transmits general pressure with the detector 2 of (direction) opposed orientation that flows to the input end of a pressure transducer to the input end of a pressure transducer.The input end of these two pressure transducers is connected with an assay unit 4, in this assay unit, as first step, determines the pressure reduction between the value of two sensors, and it is corresponding to dynamic head (Staudruck).

Not only for measuring volumetric flow rate but also all needing to know density at the fluid that flows for the quality measurement flow.In this common setting, the density between two measurement points is approximate constant.Be not as prerequisite in the derivation of the equation that the time constancy of density is implemented in this equipment, but the time constancy can be set certainly equally for approximation method.Therefore, for density, can be by (being quasi-steady) average value measured on certain time interval or pre-determine density value by given fixed value (especially this can be highly significant for liquid) at all.

Draw the formula of in the assay unit, implementing based on the non-vortex Eulerian equation of a peacekeeping:

$\frac{\∂v}{\∂t}+\frac{\∂}{\∂s}\left(\frac{v^2}{2}\right)=F_s-\frac{1}{\mathrm{\ρ}}\frac{\∂p}{\∂s}---\left(1\right)$

Also comprise an item (Term) for external force in this formula, for example, according to following formula (2), gravity is as the gradient of gravity potential.

$F_s=-\frac{\∂}{\∂s}(g\·z)---\left(2\right)$

Wherein,

V... flow velocity

P... pressure

ρ ... density

S... the position coordinates on flow direction

Z... the position coordinates that is parallel to external force (for example gravity)

T... time

Fs... the component of external force on flow direction

G... gravity field strength

Assert under local (oertlich) constant density situation, obtaining following equation thus:

$\frac{\∂}{\∂t}+\frac{\∂}{\∂s}(\frac{v^2}{2}+g\·z+\frac{p}{\mathrm{\ρ}})=0---\left(3\right)$

Carry out the position integration by position with respect to the position of another pressure detector 3 or 2, obtain following equation a pressure detector 2 or 3:

$\underset{1}{\overset{2}{\∫}}\frac{\∂v}{\∂t}\mathrm{ds}+{(\frac{v^2}{2}+g\·z+\frac{p}{\mathrm{\ρ}})}_2-{(\frac{v^2}{2}+g\·z+\frac{p}{\mathrm{\ρ}})}_1=0---\left(4\right)$

By pipe 1 that adopts basic horizontal and/or the detector of on equal height, arranging substantially 2,3, can from formula, eliminate the influence of gravity, this is favourable for liquid especially, and for gas, the influence of universal gravitation (gravity) was exactly negligible originally.

For the speed of the fluid stream of the porch of the pressure detector 2 of general pressure, its value is considered to equal zero, and owing to set local constant density, the item dv/dt between the position of two pressure detectors 2,3 also is considered to constant.With Δ p as the pressure reduction p between two pressure detectors 2,3 ₁-p ₂Symbol, and with Δ s as the distance between two opening, then obtain following equation (5) for the instantaneous value of flow velocity v:

$\frac{\mathrm{dv}}{\mathrm{dt}}\·\mathrm{\Δs}+\frac{v^2}{2}-\frac{\mathrm{\Δp}}{\mathrm{\ρ}}=0---\left(5\right)$

For stable situation, acceleration item dv/dt=0 wherein then has known formula:

$v=\sqrt{\frac{2\·\mathrm{\Δp}}{\mathrm{\ρ}}}---\left(6\right)$

Then forward non-stable mass rate to, the processing of non-stable volumetric flow rate is carried out in a comparable manner.

For mass rate, make q=A. ρ .v, wherein A is the pipe cross-sectional area, is obtained by equation (5):

$\frac{\mathrm{dq}}{\mathrm{dt}}\&CenterDot;\frac{\mathrm{\&Delta;s}}{A}+\frac{{\mathrm{<figure-callout\; id="2"\; label="q"\; filenames="HDA0000027229590000011.png"\; state="\{\{state\}\}">q</figure-callout>}}^2}{2\mathrm{\&rho;}{A}^2}-\mathrm{\&Delta;p}=0---\left(7\right)$

For the application of reality with considering under the situation of bidirectional flow, obtain by equation (7):

$C_1\&CenterDot;\frac{\mathrm{dq}}{\mathrm{dt}}+\frac{{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HDA0000027229590000011.png"\; state="\{\{state\}\}">C</figure-callout>}}_2}{\mathrm{\&rho;}}\&CenterDot;q\&CenterDot;\left|q\right|-\mathrm{\&Delta;p}=0---\left(8\right)$

Coefficient C ₁And C ₂Can be optimized by test/experience.

By known method (numerical value, analog computer) own this differential equation is carried out integration, in the hope of instantaneous q (t) and average mass rate.

In order to optimize and/or to calibrate equation (8) for the coefficient C that stablizes component ₂, observe the moment that steady flow is arranged.By a kind of measuring method that optionally, also is applicable to unsteady fluid flow, for example based on the (Laufzeit: flow measurement working time) time delay of ultrasonic signal, obtain flow value and such matching factor, the feasible value that is drawn by finding the solution of the differential equation is equivalent to directly use the value of reference system measurements.

In order also to optimize and/or calibrate the second coefficient C ₁, for example can set a kind of optional, high dynamic measuring method, by this measuring method, after calibration and optimizing another coefficient, make again by matching factor C ₁Be consistent by finding the solution of the differential equation value that obtains and the value of directly measuring.

Can set according to a kind of other form of implementation, the stable (Beruhigung: calmness) be steady flow of unsteady fluid flow, then, by the measured value of the mean value of separating of the astable Bernoulli equation of unsteady fluid flow with the frame of reference that is used for steady flow compared, calibrate the coefficient of astable Bernoulli equation.For stable then stream, also can measure flow, with the coefficient C of the calibration differential equation here, for the item of unstable component by a kind of optional measuring method ₁

Claims (5)

1. equipment that is used to measure the flow of two-way non-stable fluid stream, comprise: a measuring tube (1), the device of the device of a definite fluid pressure difference and a definite fluid density, and assay unit, in this assay unit, calculate flow based on determined fluid pressure difference and fluid density, wherein, this assay unit comprises a computing unit, be used for the differential equation of under the situation of the acceleration item of considering pressure reduction and flow velocity, finding the solution the nonlinear routine of flow velocity in real time, it is characterized in that, in measuring tube (1), be provided with two antiparallel each other, and be parallel to the detector (2 that fluid flow direction is arranged, 3), one of them detector (2) sensing general pressure and another detector (3) sense static pressures power, and described assay unit is used for determining the general pressure that sensed by described detector and the pressure reduction between the static pressure.

2. equipment as claimed in claim 1 is characterized in that, described measuring tube (1) and detector (2,3) are flatly arranged.

3. equipment as claimed in claim 1 or 2, it is characterized in that, be provided with an other device, be used to measure the flow of unsteady fluid flow, wherein, in described assay unit, implement to be used for by the algorithm of separating the coefficient of relatively calibrating astable Bernoulli equation of the mean value of separating of the astable Bernoulli equation of unsteady fluid flow and steady flow.

4. equipment as claimed in claim 1 or 2, it is characterized in that, be provided with a stabilising arrangement and an other device that is used for unsteady fluid flow is stabilized to steady flow, this other device is used to measure the flow of steady flow, wherein, in described assay unit, implement to be used for by the algorithm of separating the coefficient of relatively calibrating astable Bernoulli equation of the mean value of separating of the astable Bernoulli equation of unsteady fluid flow and steady flow.

5. equipment as claimed in claim 3, it is characterized in that, be provided with a stabilising arrangement and an other device that is used for unsteady fluid flow is stabilized to steady flow, this other device is used to measure the flow of steady flow, wherein, in described assay unit, implement to be used for by the algorithm of separating the coefficient of relatively calibrating astable Bernoulli equation of the mean value of separating of the astable Bernoulli equation of unsteady fluid flow and steady flow.

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