CN102538912A - Method for analyzing additive errors of flow field of ultrasonic flowmeter - Google Patents

Abstract

The invention relates to a method for analyzing additive errors of a flow field of an ultrasonic flowmeter, which is characterized in that fluid dynamic numerical simulation is performed to liquid flow of a flowmeter in a pipeline within a certain range of upstream and downstream. Splash flow velocity information of the flow field in the pipeline is acquired by utilizing the fluid dynamic numerical simulation, the flow velocity is interpolated onto each sound channel of the flowmeter, sound channel speed of each sound channel is calculated according to the fundamental principle of the flowmeter, and weighted summation is further performed to obtain an indicating flow. Surface integral is performed to main flow velocity of flowmeter cross section flow field splashes, or weighted summation is performed to sound channel speed main flow contributions of a plurality of sound channels collected in a cross section flow field so as to obtain a standard flow of the flow field. Difference of the indicating flow and the standard flow is analyzed to obtain the additive errors of the flow field. By means of the method, quick and accurate evaluation of the additive errors of the flow field is achieved, and the fact that the flow measurement problem is solved by utilizing a numerical method has good reference significance.

Description

Ultrasonic flowmeter flow field additive error analytical approach

Technical field

The present invention relates to a kind of analytical approach, especially, relate to a kind of ultrasonic flowmeter flow field additive error analytical approach.

Background technology

Ultrasonic flowmeter is a kind of novel flow measurement instrument that developed recently gets up; Since have the big more accuracy of no crushing, bore high more, can on existing pipeline, installation, multichannel can adapt to many advantages such as complex flowfield; Bring into play more and more important effect in the flow measurement field, particularly in the super large caliber flow measurement, having outstanding advantage.Forward and reverse mistiming that ultrasonic flowmeter utilizes ultrasound wave in flow media, to propagate is measured the line mean flow rate on the sound channel, and utilizes face mean flow rate and flow on line mean flow rate on the different sound channels (below be called sound channel speed) the weighted calculation cross section to be measured.The accuracy of measurement of flow and the flow field of position are in close relations; This is because cross flow is disturbed the reach the standard grade measurement of mean flow rate of sound channel easily on the one hand, then is because the weighted calculation accuracy of face mean flow rate receives the influence of sound channel velocity distribution on the other hand.Therefore, ultrasonic flowmeter requires to keep sufficiently long front and back straight length, does not have cross flow to guarantee its interior flow field, and the sound channel velocity distribution is also fairly simple.

The accuracy of measurement of ultrasonic flowmeter and its interior flow field are in close relations; The upstream and downstream choked flow piece all can influence its interior flow field and then produce the flow field additive error with probe localized indentation male structure; The flow development length of 5D behind the 10D before the installation of regulation multichannel flowmeter need guarantee among the measurement verification regulations JJG1030-2007, otherwise need flow field additive error of extra consideration during uncertainty evaluation.The flow field additive error is relevant with the complexity in flowmeter flow field of living in; Also relevant with the flowmeter channel configuration; Analyze the flow field additive error though spend the real stream of the flowmeter calibration experiments that a large amount of manpower and materials carry out under the different mounting conditions; Obtained a lot of achievements, but, can not cover all mounting conditions and flowmeter configuration through experiment because the influence factor of flow field additive error is numerous and ten minutes is complicated; Therefore, seek suitable method and analyze the major issue that the flow field additive error becomes the accuracy of measurement that improves ultrasonic flowmeter.

Summary of the invention

The purpose of this invention is to provide a kind of can be low-cost and obtain the pipeline flow field under the different condition fast, and then analyze the method for flow field additive error through the difference of flowmeter indication flow and normal flow relatively.

The invention provides a kind of ultrasonic flowmeter flow field additive error analytical approach, it carries out the fluid dynamics numerical simulation for the liquid flow in the flowmeter upstream and downstream certain limit in the pipeline; Utilize the fluid dynamics numerical simulation to obtain the diffusing some flow rate information in pipe interior flow field, flow velocity is interpolated on each sound channel of flowmeter, and according to the sound channel speed of each sound channel of flowmeter first principles computations, and then weighted sum obtains the indication flow; The loose main flow flow velocity of point of flowmeter xsect flow field is carried out area minute, and perhaps gathering the sound channel speed main flow contribution amount of abundant sound channel in the xsect flow field carries out weighted sum, obtains the normal flow in flow field; Obtain the additive error in flow field through the difference of analyzing indication flow and normal flow.

Wherein, utilize the particular location of direction, unique definite each sound channel of flowmeter in sound channel angle on the centre coordinate, main flow direction, sound channel face of flowmeter in the pipeline flow field.

Wherein, based on the diffusing point of a pipeline flow velocity, adopt the pchip interpolation method of conformal shape to calculate the sound channel speed on the ultrasonic flowmeter sound channel.

Wherein, utilize vector operation that sound channel speed is decomposed into main flow contribution amount and crossing current contribution amount.

Wherein, the area separating method of normal flow is: at first the diffusing point of xsect is carried out the triangularization subdivision, then the product of average velocity on all triangles and area is sued for peace.

Wherein, the Gauss integration algorithm of normal flow is: in the xsect flow field, gather the sound channel speed main flow contribution amount of a plurality of sound channels, carry out weighted mean then and obtain the standard mean flow rate and then obtain normal flow.Said a plurality of number of channels is 36.

Wherein, the flow field additive error comprises the integral error that produces owing to the flow that utilizes the whole cross section of limited sound channel velocity information integral and calculating and because the crossing current error that cross flow forms the interference of flow measurement.

The problem that possibly occur in the stream field additive error assessment of the present invention is analyzed; Set up the flow field additive error analytical approach of ultrasonic flowmeter; Realized the assessment quick and precisely of flow field additive error, this analytical approach has good reference significance to utilizing numerical method to solve the flow metering problem.

Description of drawings

Fig. 1 flowmeter sound channel numbering and A/B sound channel face nomenclature principle;

The trigonometric ratio integration method of Fig. 1 normal flow;

The relation of Fig. 3 virtual channels number and relative difference;

Fig. 4 flow field additive error computing method;

Cross flow on Fig. 5 flowmeter center cross-sectional

The sound channel velocity distribution of Fig. 6 flowmeter;

The flow field additive error assessment result of Fig. 7 flowmeter.

Embodiment

The development of Along with computer technology and computing technique, numerical simulation become a kind of important research means gradually, are penetrated into each field of engineering technology relevant with fluid gradually based on the numerical simulation of computational fluid dynamics (CFD).Numerical simulation has the advantage that cost is low and can quick and precisely simulate with respect to traditional test method, and the hydrodynamics numerical simulation is combined with the measurement of ultrasonic flowmeter, helps to improve the measurement accuracy of fluid flow.

The flow field additive error refers to normal flow poor that flowmeter is installed in the indication flow that obtains in certain specific flow field and this flow field; After diffusing some flow rate information utilizing this flow field of CFD technology acquisition; Need flow rate information be interpolated on the sound channel of flowmeter; And calculating the sound channel speed of each sound channel, the mean flow rate in cross section to be measured is calculated in weighted sum then, and multiplies each other with area and to obtain indicating flow; Normal flow then needs to divide acquisition through at tested point flow velocity being carried out area.

In order to calculate the flowmeter indication flow in the specific flow field, at first need solve the sound channel orientation problem, obtain the coordinate of two end points on the sound channel line.Ultrasonic flow rate although flowmeter producer adopts different sound channel naming methods, need be unified the nomenclature principle of sound channel numbering and A/B sound channel face in respect of monophony face or the configuration of two-channel face when handling based on the numerical value flow field.Nomenclature principle is as shown in Figure 2; Define direction that two sound channels hand-delivers line points to the sound channel Base Serial Number and be main flow direction that last direction

definition pipeline flows for

people the downstream head of flowmeter up direction

upstream so see; The downstream sound channel of probe on the right side is the A face; The downstream sound channel of probe in the left side is the B face; The sound channel numbering is followed successively by 1 to n from top to bottom; Corresponding sound channel height is from just bearing; As shown in Figure 1, with sound channel A-Path1, A-Path2, A-Path3, A-Path4 and B-Path1, B-Path2, B-Path3, B-Path4 as an example.Sound channel angle φ is another key parameter in the flowmeter configuration; Refer to the acute angle angle of sound channel and main flow direction, the center position coordinates

of adding flowmeter totally four parameters

φ,

just can be confirmed in the three-dimensional flow field flowmeter sound channel position of attitude arbitrarily.

Definition sound channel direction

is the direction that sound channel line upper reaches probe points to the downstream probe; Then the sound channel direction is identical in the sound channel face, and monophony flow meter has only a sound channel direction

two-channel face flowmeter to have two sound channel directions

and so the coordinate of two end points of sound channel line does

${\stackrel{\→}{P}}_{d,u}=\stackrel{\→}{x}+\stackrel{\→}{u}\·{\mathrm{Rt}}_i\±\stackrel{\→}{l}\·R\sqrt{1-t_i^2}/\sin \mathrm{\φ}---\left(1\right)$

R is the pipeline section radius in the formula, t _iBe relative sound channel height, Rt _iBe actual sound channel height, Be half length of this sound channel, sign is the downstream and the upper reaches end points of corresponding sound channel respectively.The integration scheme that ultrasonic flowmeter adopts is different, relatively the sound channel height t _iDifference, Gauss-Jaccobi integration scheme is the integration scheme of appointment among international rules IEC60041 and the ASME PTC18, the form with tabulation in the rules has provided t _iNumerical value, in fact also can be formulated as

$t_i=\mathrm{Cos}\frac{\mathrm{I\π}}{N+1},i=\mathrm{1,2},...,N---\left(2\right)$ In the formula, N is the channel number of flowmeter.

Any calculating more complicated of attitude flowmeter sound channel direction vector can be found the solution through the relative position relation of it and known direction.At first the sound channel direction is vertical with last direction; Then the angle of its secondary channel direction and main flow direction is the sound channel angle; Then

to go up direction in addition vertical with main flow direction; Then

considers that again three vectors are unit vector, then

thus six formula simultaneous solution equations can obtain

its three components and do

${\mathrm{<figure-callout\; id="1"\; label="l"\; filenames="DEST\_PATH\_HSB00000736197300032.png,DEST\_PATH\_HSB00000736197300041.png"\; state="\{\{state\}\}">l</figure-callout>}}_1=((f_1(u_2^2+u_3^2)-u_1(f_2{u}_2+f_3{u}_3))\cos \mathrm{\&phi;}+(f_2{u}_3-f_3{u}_2){\mathrm{\&sigma;}}_2)/{\mathrm{\&sigma;}}_2$

${\mathrm{<figure-callout\; id="2"\; label="l"\; filenames="DEST\_PATH\_HSB00000736197300041.png"\; state="\{\{state\}\}">l</figure-callout>}}_2=((f_2(u_1^2+u_3^2)-u_2(f_1{u}_1+f_3{u}_3))\cos \mathrm{\&phi;}-(f_1{u}_3-f_3{u}_1){\mathrm{\&sigma;}}_1)/{\mathrm{\&sigma;}}_2---\left(3\right)$

${\mathrm{<figure-callout\; id="3"\; label="l"\; filenames="DEST\_PATH\_HSB00000736197300041.png"\; state="\{\{state\}\}">l</figure-callout>}}_3=((f_3(u_1^2+u_2^2)-u_3(f_1{u}_1-f_2{u}_2))\cos \mathrm{\&phi;}+(f_1{u}_2-f_2{u}_1){\mathrm{\&sigma;}}_1)/{\mathrm{\&sigma;}}_2$

In the formula, parameter σ ₂=(f ₁u ₂-f ₂u ₁) ²+ (f ₁u ₃-f ₃u ₁) ²+ (f ₂u ₃-f ₃u ₂) ², parameter

That sign is corresponding is two sound channel face A/B.Can utilize multiplication cross to judge σ ₁Sign and the corresponding relation of sound channel A/B face since multiplication cross corresponding be right-handed system,

Point to the left side, so according to the nomenclature principle utilization of front $(\stackrel{\&RightArrow;}{f}\&times;\stackrel{\&RightArrow;}{u})\&CenterDot;\stackrel{\&RightArrow;}{l}=(f_2{u}_3-f_3{u}_2){\mathrm{<figure-callout\; id="1"\; label="l"\; filenames="DEST\_PATH\_HSB00000736197300032.png,DEST\_PATH\_HSB00000736197300041.png"\; state="\{\{state\}\}">l</figure-callout>}}_1+(f_3{u}_1-f_1{u}_3){\mathrm{<figure-callout\; id="2"\; label="l"\; filenames="DEST\_PATH\_HSB00000736197300041.png"\; state="\{\{state\}\}">l</figure-callout>}}_2+(f_1{u}_2-f_2{u}_1)l_3---\left(4\right)$ Judge, make

For on the occasion of direction vector

Corresponding is the B sound channel,

For negative value

Then corresponding is the A sound channel.

Flowmeter for liquid medium; Flow velocity is much smaller than the velocity of sound; Sound channel is a straight line; If on the sound channel the line mean flow rate is

then

projection on sound channel direction

equate in the projection of sound channel direction with sound channel speed

, so the sound channel velocity magnitude can be expressed as with the form of vector dot product

$v_{m,i}=({\stackrel{\&RightArrow;}{v}}_i\&CenterDot;\stackrel{\&RightArrow;}{l})/(\stackrel{\&RightArrow;}{f}\&CenterDot;\stackrel{\&RightArrow;}{l})---\left(5\right)$

Therefore; The extraction of sound channel speed is most important to be exactly to obtain after line mean flow rate

sound channel line position on the sound channel line confirmed by the two-end-point coordinate; Diffusing spot speed in the three-dimensional flow field can be interpolated on the sound channel line; Line mean flow rate

is not the arithmetic mean of each point three-dimensional flow on the sound channel line, but need carry out formula fitting and ask its line integral to obtain it.Fit procedure has adopted the PCHIP method of conformal shape, and problem is over-evaluated or underestimated in the part of having avoided linear fit to bring.

Formula (5) shows the contribution that has not only comprised axia flow in the sound channel speed, has also comprised the contribution of cross flow, and when no cross flow, sound channel speed is exactly the flow velocity of main flow direction, and this also is the ideal situation that ultrasonic flowmeter is measured flow.So can be with the sound channel speed v _{M, i}Be divided into the main flow contribution amount artificially

With crossing current contribution amount v _{C, i}=v _{M, i}-v _{A, i}Two parts, the former is the flow velocity that flowmeter will be measured, the latter then is the interference volume of cross flow to the flowmeter survey flow.In the sound channel speed v that obtains different sound channels _{M, i}Afterwards, according to the ultimate principle of ultrasonic flowmeter, indication flow Q can obtain according to the mode of weighted sum,

$Q=A\&CenterDot;\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{\mathrm{\&omega;}}_i\&CenterDot;v_{m,i}---\left(6\right)$

In the formula, A is the cross-sectional area of pipeline, ω _iBe weight coefficient, with relative sound channel height t _iCorresponding one by one, the weight coefficient of Gauss-Jaccobi integration scheme does in the rules

${\mathrm{\&omega;}}_i=\frac{2}{N+1}{\sin }^2\frac{\mathrm{i\&pi;}}{N+1},i=\mathrm{1,2},...,N---\left(7\right)$

Because sound channel speed v _{M, i}Can be decomposed into main flow contribution amount v _{A, i}With crossing current contribution amount v _{C, i}So indication flow Q also can be decomposed into main flow contribution amount Q _aWith crossing current contribution amount Q _cTwo parts.

Normal flow refers to the corresponding actual flow in this flow field, in other words carries out area minute resultant flow for the diffusing point of each xsect of a flow field main flow flow velocity.When utilizing CFD method simulation flow field additive error; The speed inlet adopts equally distributed flow conditions; And, possibly cause normal flow to have certain deviation with this velocimeter basis of calculation flow, the flow field that enters the mouth in addition need can attain full development through tens times of diameter distances; Also there are differences, so the inlet velocity flow profile is appointed as full-blown velocity flow profile or other given flow rate are distributed as good with the expectation flow field.

In order to calculate the area branch of mainstream speed on the xsect of flow field; Can the diffusing point on the cross section be carried out the trigonometric ratio subdivision; As shown in the figure; Average velocity on each triangle area is the arithmetic mean of its three summit mainstream speeds, and leg-of-mutton area can be calculated by the multiplication cross of its both sides vector, is the flow on the xsect so the product of average velocity on all triangles and area sued for peace.In addition; In the xsect flow field, get abundant virtual channels according to Gauss-Jaccobi integration scheme, calculate the main flow contribution amount of sound channel speed, and the weighted average calculation flow; Figure has provided the flow that Gauss (Gauss) integration that utilizes different channel number obtains and the relative difference of trigonometric ratio integration flow; It is thus clear that 36 sound channel can be approached the area shunt volume, its difference can be directly as normal flow less than 0.05%.

The flow field additive error is indication flow Q and normal flow Q _SPoor, obtaining Q and Q _SCan directly calculate the flow field additive error afterwards.Because indication flow Q can be decomposed into main flow contribution amount Q _aWith crossing current contribution amount Q _cTwo parts are so the flow field additive error also can be decomposed into integral error (Q _a-Q _s)/Q _sWith crossing current error Q _c/ Q _sTwo parts, the former is called integral error is owing to the flow that utilizes the whole cross section of limited sound channel velocity information integral and calculating produces, what the latter was called crossing current error representes is the interference of cross flow to flow measurement.Ultrasonic flow rate can calculate the integral error of two sound channel faces, the sum of errors total error of flowing in respect of configuration of monophony face and the configuration of two-channel face respectively based on the CFD flow field, and its arithmetic mean is the corresponding error of two-channel face configuration, and concrete computing method are seen Fig. 4.

FLUENT is one of most widely used commercial CFD software; Utilize FLUENT can obtain the pipeline flow field under the specified conditions more accurately and easily; Analyzing and processing through data; Generate, draw and derive the sound channel velocity distribution of any flowmeter parameter based on FLUENT, and calculate the flow field additive error under the relevant parameter.

As stated; Utilize any attitude that four parameters such as

φ,

can unique definite flowmeter sound channel; When the flowmeter level is installed in the practical application; The sound channel attitude obtains around α angle of main flow direction

rotation on the direction vertically upward in physical space

basis often; This angle is called established angle α, and with from downstream upstream so see and be rotated counterclockwise to just.So plug-in unit is used for the convenience of the user, also can pass through Form actual last direction is set

Rotation matrix wherein $S\left(\mathrm{\&alpha;}\right)=(1-\mathrm{Cos}\mathrm{\&alpha;})\left[\begin{array}{ccc}{\mathrm{<figure-callout\; id="1"\; label="f"\; filenames="DEST\_PATH\_HSB00000736197300032.png,DEST\_PATH\_HSB00000736197300041.png"\; state="\{\{state\}\}">f</figure-callout>}}_1^2& f_1{f}_2& f_1{f}_3\\ f_1{f}_2& {\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="DEST\_PATH\_HSB00000736197300041.png"\; state="\{\{state\}\}">f</figure-callout>}}_2^2& f_2{f}_3\\ f_1{f}_3& f_2{f}_3& {\mathrm{<figure-callout\; id="3"\; label="f"\; filenames="DEST\_PATH\_HSB00000736197300041.png"\; state="\{\{state\}\}">f</figure-callout>}}_3^2\end{array}\right]+\left[\begin{array}{ccc}\mathrm{Cos}\mathrm{\&alpha;}& {\mathrm{<figure-callout\; id="3"\; label="f"\; filenames="DEST\_PATH\_HSB00000736197300041.png"\; state="\{\{state\}\}">f</figure-callout>}}_3\mathrm{Sin}\mathrm{\&alpha;}& -{\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="DEST\_PATH\_HSB00000736197300041.png"\; state="\{\{state\}\}">f</figure-callout>}}_2\mathrm{Sin}\mathrm{\&alpha;}\\ -{\mathrm{<figure-callout\; id="3"\; label="f"\; filenames="DEST\_PATH\_HSB00000736197300041.png"\; state="\{\{state\}\}">f</figure-callout>}}_3\mathrm{Sin}\mathrm{\&alpha;}& \mathrm{Cos}\mathrm{\&alpha;}& {\mathrm{<figure-callout\; id="1"\; label="f"\; filenames="DEST\_PATH\_HSB00000736197300032.png,DEST\_PATH\_HSB00000736197300041.png"\; state="\{\{state\}\}">f</figure-callout>}}_1\mathrm{Sin}\mathrm{\&alpha;}\\ {\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="DEST\_PATH\_HSB00000736197300041.png"\; state="\{\{state\}\}">f</figure-callout>}}_2\mathrm{Sin}\mathrm{\&alpha;}& -{\mathrm{<figure-callout\; id="1"\; label="f"\; filenames="DEST\_PATH\_HSB00000736197300032.png,DEST\_PATH\_HSB00000736197300041.png"\; state="\{\{state\}\}">f</figure-callout>}}_1\mathrm{Sin}\mathrm{\&alpha;}& \mathrm{Cos}\mathrm{\&alpha;}\end{array}\right]---\left(8\right)$ New last direction after the rotation

Participate in the sound channel location Calculation.In the formula (1) sound channel half length be

at this moment the sound channel two-end-point just in time on tube wall; In order to adapt to the situation that there is the probe indentation in flowmeter; Half length of sound channel multiply by one greater than 1 Coefficient m,

the indentation flow field partly that guarantees pop one's head in also cover the computational analysis territory.In fact m all is taken as 1.2 and gets final product, bigger slightly can not influence the location of sound channel line.Settings when pipeline section radius R value possibly make up with grid in the numerical value flow field is slightly variant; Specify radius R possibly cause indicating flow to have deviation here; Need to calculate through the actual grid cross section; At first obtain the flowmeter xsect by flowmeter center

and main flow direction

; Utilize Graham convex closure algorithm to ask its convex polygon then, justify match again and can obtain radius R by the diffusing point coordinate information on this face.In addition, at present except Gauss-Jaccobi integration scheme, partial discharge meter manufacturer has also adopted the integration scheme of oneself, such as OWICS scheme etc.,

Generate after the sound channel line, diffusing some flow velocity on every sound channel is saved in data file, and from data file, read these some flow rate information of loosing and calculate sound channel line mean flow rate

Diffusing point coordinate vector on the same sound channel (x, y, z) direction upwards

Projection value xu ₁+ yu ₂+ zu ₃Identical, can come in view of the above the different sound channels in the identical file are distinguished.

Obtain sound channel speed main flow contribution amount with 36 virtual channels during the flow field additive error is calculated and come basis of calculation flow Q _s, and be interpolated into the sound channel speed of 36 virtual channels on the actual sound channel of flowmeter and calculate indication flow Q, calculate integral error, crossing current error, total error on two sound channel faces of A/B thus.Interpolation still adopts the PCHIP method of conformal shape, and the deviation of as far as possible avoiding linear interpolation to bring can obtain more near actual sound channel velocity distribution curve.

To the flow field additive error that typical choked flow piece (elbow, butterfly valve, reducer, increaser) possibly cause, utilize the CFD method to analyze.The flowmeter of installing with 1D position, elbow downstream (as shown in Figure 2) is an example, and the flowmeter bore is 1m.

Cross flow result of calculation on the flowmeter center cross-sectional is as shown in Figure 5, and cross flow is stronger, and the centre flows downward and by returning both sides, forms the fluidal texture of a binary vortices; Flowmeter established angle α=90 °, sound channel angle φ=45 °, the straight line among Fig. 5 is the projection of sound channel, in the flow field, locatees sound channel and extracts 36 sound channel speed v on the virtual channels _{A, i}And v _{C, i}Component, as shown in Figure 6.Can find, under violent crossing current effect, the sound channel speed v on A, B two sides _mWidely different, after both are average near the main flow contribution amount v of sound channel speed _a, explain that two-sided configuration can offset the interference that parts transversely flows.

The further flow field additive error assessment result of quadraphonic flowmeter from Fig. 7; Because sound channel velocity distribution profile is with evenly distributional difference is bigger; Therefore the integral error on AB two sides all bigger and be on the occasion of, though and crossing current error numeric ratio has obtained good counteracting than AB two sides greatly positive is negative.Under 1D place, elbow downstream complicated flox condition like this, the flow field additive error of the vertical two-sided flowmeter of installing of sound channel is about 1.2%, and visible multichannel flowmeter has flow field adaptability preferably.

The flow field additive error assessment of ultrasonic flowmeter is the work of a complicacy; Set up the additive error appraisal procedure of a cover based on the CFD flow field; Can carry out data processing to any configuration ultrasonic flowmeter of optional position and attitude layout, improve the speed and the reliability of evaluation process greatly.In addition, the problem that possibly occur in indication flow and the normal flow calculating process is analyzed, the processing of similar problem is had reference very much.

Although illustrate and described the present invention with reference to embodiments of the invention; But those skilled in the art should understand that; Specific embodiments of enumerating in this instructions or embodiment; Only in order to understand technology contents of the present invention, under the situation that does not deviate from purport of the present invention and scope, the present invention can carry out multiple change in form with on the details.

Claims (8)

1. ultrasonic flowmeter flow field additive error analytical approach, it is characterized in that: the liquid flow in the flowmeter upstream and downstream certain limit in the pipeline carries out the fluid dynamics numerical simulation; Utilize the fluid dynamics numerical simulation to obtain the diffusing some flow rate information in pipe interior flow field, flow velocity is interpolated on each sound channel of flowmeter, and according to the sound channel speed of each sound channel of flowmeter first principles computations, and then weighted sum obtains the indication flow; The loose main flow flow velocity of point of flowmeter xsect flow field is carried out area minute, and perhaps gathering the sound channel speed main flow contribution amount of a plurality of sound channels in the xsect flow field carries out weighted sum, obtains the normal flow in flow field; Obtain the additive error in flow field through the difference of analyzing indication flow and normal flow.

2. analytical approach as claimed in claim 1 is characterized in that: the particular location that utilizes direction, unique definite each sound channel of flowmeter in sound channel angle on the centre coordinate, main flow direction, sound channel face of flowmeter in the pipeline flow field.

3. analytical approach as claimed in claim 1 is characterized in that: utilize vector operation that sound channel speed is decomposed into main flow contribution amount and crossing current contribution amount.

4. analytical approach as claimed in claim 1 is characterized in that: the area separating method of normal flow is: at first the diffusing point of xsect is carried out the triangularization subdivision, then the product of average velocity on all triangles and area is sued for peace.

5. analytical approach as claimed in claim 1; It is characterized in that: the Gauss integration algorithm of normal flow is: in the xsect flow field, gather the sound channel speed main flow contribution amount of a plurality of sound channels, carry out weighted mean then and obtain the standard mean flow rate and then obtain normal flow.

6. analytical approach as claimed in claim 5 is characterized in that: said a plurality of number of channels are 36.

7. analytical approach as claimed in claim 1 is characterized in that: based on the diffusing point of a pipeline section flow velocity, adopt the pchip interpolation method of conformal shape to calculate the sound channel speed on the ultrasonic flowmeter sound channel.

8. analytical approach as claimed in claim 1 is characterized in that: the flow field additive error comprises the integral error that produces owing to the flow that utilizes the whole cross section of limited sound channel velocity information integral and calculating and because the crossing current error that cross flow forms the interference of flow measurement.

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