JPH03197821A - Ultrasonic flowmeter - Google Patents

Abstract

PURPOSE:To obtain the accurate predicted flow rate of even an unsteady flow by substituting the flow velocity signal which is outputted with a flow velocity detecting means for the mean flow velocity part of a conduit model which is calculated by a predictive arithmetic means, and calculating and outputting the unsteady flow rate. CONSTITUTION:Ultrasonic wave pulses which are sent out of an ultrasonic wave pulse transmitter 2 are made incident at an angle alpha to the flow direction through a tube wall 1', received by an ultrasonic wave receiver 2' through a slanting wedge 3' at the facing position, and sent from the transmitter 2 again through an amplification device 4 and a pulse transmitter 5. This operation is repeated to equalize the cycles of ultrasonic wave pulses to a propagation time t1, and its frequency is represented as f1=1/t1. Then when a switch 7 is changed over by a timing circuit 6, the path of the ultrasonic wave pulses is inverted and a pulse frequency f2 is represented as f2=1/t2, where t2 is the current propagation time; and the mean flow velocity V is found from the difference DELTAf in pulse frequency by using V=DELTAf.D/sin2alpha (D: conduit internal diameter) and outputted from a converter 8. Then a predictive arithmetic means 10 inputs the mean flow velocity signal and the estimated value of an instantaneous flow rate is displayed 16 as an actual flow rate signal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention approximates a pipe model based on an ultrasonic flow meter, more specifically, a turbulence model of unsteady flowing fluid, and adds parts to the pipe model. The present invention relates to a technique that combines a model paste method for predicting and calculating a flow rate by substituting a measured value of the flow velocity at a viewpoint, and a flow rate detection means.

The present inventor first developed a model paste measurement method for estimating and measuring the flow velocity distribution and instantaneous flow rate based on a pipeline model that evaluates the arterial behavior of the flow in response to unsteady turbulent flow of fluid flowing in the pipeline. We proposed this and reported it at the 31st Automatic Control Association Conference (October 25, 1986). In this model paste method, flow velocity is observed at multiple locations on a pipe cross section, and the obtained flow velocity observations are substituted into a pipe model calculated from a turbulence equation to estimate the flow velocity distribution and flow rate. In the experiment, a laser current meter was used to measure the flow velocity. This laser anemometer uses a differential optical system to irradiate laser light onto suspended particles passing through a pipe cross section, detects a beat signal from the irradiated light and reflected light, and detects a beat signal from this beat signal. The purpose was to determine the flow velocity, and He-Ne light was used as a laser.

The beat signal obtained from the current meter is sent to a period counting circuit via a filter band. Since the frequency of the obtained beat signal is proportional to the flow velocity, the period was measured by a counting circuit, and the flow velocity was determined by a microcomputer.

Problems with the conventional technology Although this method allows the point flow velocity to be determined with high accuracy, in the experiment, in order to compare it with the theoretical value, an optical system was set up that scanned the pipe diameter using a beam scanner at the observation point, so it was complicated. In addition, there was the problem that pulse-like noise was mixed into the measurement data due to period counting errors, and the laser current meter could not be used in conditions where it was opaque to light.

The present invention was made to solve the above-mentioned problems, and it substitutes the actual flow velocity signal of the average flow velocity into the average flow velocity position using a propagation time difference method using ultrasonic waves. The purpose of this is to provide a highly accurate ultrasonic flowmeter with an improved S/N ratio that is affected by flow rate fluctuations by predicting and calculating the current flow. An ultrasonic average flow velocity detection means for detecting the average flow velocity of an unsteady fluid, a turbulence model using a partial differential equation that includes an eddy viscosity coefficient, and a turbulence model that captures the flow phenomenon of the turbulence model as a distributed constant system. a prediction calculation means for estimating the flow velocity distribution in the pipeline and calculating the flow rate by approximating a model and substituting measured values of arbitrary partial observations into the pipeline model; This is an ultrasonic flowmeter that calculates and outputs an unsteady flow rate by substituting it into the average flow velocity point of a pipe model using a prediction calculation means.

Regarding the measurement of the flow of fluid flowing unsteadily in a pipe,
A model of the fluid flow velocity distribution of unsteady flow in the pipe is obtained, and the flow velocity Il! is added to the model. There is a model paste measurement method that calculates the flow rate by substituting the actual flow velocity value at a measurement point.The present invention introduces the concept of turbulent viscosity to evaluate the well-developed axisymmetric turbulent flow flowing through a circular pipe. The method is based on the Reynolds equation. The Reynolds equation is:

Hail to you. Here, U: time average velocity component in the tube axis direction p: time average pressure r: tube radial coordinate X: tube axis coordinate t: time ρ: fluid density ν: fluid kinematic viscosity coefficient S1: eddy viscosity coefficient And the boundary condition is U a 〒=v −” at the pipe center r=o, U at the pipe wall r=a (a: pipe radius)
=ν, =0. In order to obtain the flow velocity distribution based on the Reynolds equation (1), the flow velocity U is measured at m observation points in the pipe, and the flow velocity value at the m points is taken as the measured value. However, since the measured value is a probability value, the estimated value Y(r,,t) is y(r++t)=ciu(r,,t)+v(rt+t)
(2) Here, u(r,, t): true flow velocity V (r+-t): second-order stochastic process CI: observation matrix 1=1121...9m.

In addition, in equation (1), it is necessary to determine the eddy viscosity coefficient y, but in order to apply it to the turbulent flow region, the inventor has determined the velocity distribution of turbulent flow using the empirical formula % formula % (3): and the average mixing The average mixing distance nm is calculated using the N1 kuradse equation, which is known as an experimental equation for determining the distance Ωm, and the eddy viscosity coefficient ν is obtained by substituting this average mixing distance Qm into the following equation (4).

v, (r, t)=C:w Q m”(1-r/a)
−”Um(t) (4) However, to C! A finite approximation model of the conduit with output is obtained.The finite approximation model is as follows (5).

(6) Expression is used.

X=A (Um)X+B Y (
5) u=c (r)X
(6) where, An observation system is obtained.By considering the pressure gradient term γ as an unknown input and incorporating it into the state variable, the observation system is expanded as follows.

Z=f (Z)+GW Y , = HZ > + V* (7) (8) However, z=(xTγ)7 H= (C0) WER: [Normal with dynamic noise White process VkER: Normal with observation noise white process ω: parameter-dependent coefficient subscript k: is the th sampling time, and by applying the extended Kalman filter to equations (7) and (8), the following flow velocity distribution and flow rate estimation filter equations (9) ~ (13
) is obtained.

2=f (2) (9
) p (t) = F ('2) P (t) + p (
t)FT(2)+G QvGT(10) 2 to/to = 2 to/) knee t”Kx (Yx-H2x
z, -0] (11) PK/N = [I-KrH) PK/X-(12
)Kx”PK/ni-□HT(HPK/X-xH+Qv)
(13) The estimated value U of flow velocity distribution and the estimated value q of flow rate are respectively ancient = C
Cross (15)q =
f 2 πrcdrX (1
6) Hail upon you.

However, Q v E R1 and QvER"' are each W
, is the covariance of V*.

FIG. 1 is a block diagram showing the configuration of an embodiment of an ultrasonic flowmeter of the present invention. In the figure, 1 is a pipe through which an unsteady fluid to be measured flows, and 2 is an outer wall of the pipe 1. This is an ultrasonic pulse transmitter in which an inclined wedge (shoe) 3 is interposed in the part, and the ultrasonic pulse is incident from the transmitter 2 through the tube wall 1' at an angle α in the flow direction, and is transmitted to the tube at the opposite position. The waves pass through an inclined wedge 3' installed in the wall and are received by an ultrasonic receiver 2'. When the pulse reaches the receiver 2', the pulse is amplified by the amplification bag @4, and the next pulse is triggered and transmitted from the ultrasonic transmitter 2 again via the pulse oscillator 5. When such an event is repeated, the period of the ultrasonic pulse becomes the propagation time t1
, and its frequency, f□=1/l□. Next, when the timing circuit 6 switches the switch 7 and switches 2' to the transmitter and 2 to the receiver, the path of the ultrasonic pulse is reversed, so if the propagation time at this time is t2, the pulse The frequency f2 is f2=1/12.

Since the obtained pulse frequency difference Δf is given by the following equation, the average flow velocity V can be obtained.

Δf=f1-f,=1/11-1/1z=sin2α/
D·V,', v = Δf-D/5in2α where D is the inner diameter of the conduit.

The output of the transducer 8 therefore represents the average flow rate of the liquid flowing through the conduit 1. Reference numeral 10 denotes a prediction calculation means, which is a calculation means such as a computer that calculates a predicted flow rate based on the above-mentioned model paste method. 11 is the above-mentioned Reynolds equation (1) that generates a sufficiently developed axisymmetric turbulent flow in a circular pipe, and 12 is a calculation unit that calculates the hyperviscosity coefficient ν8 in equation (1), which approximates the flow velocity distribution. Exponent law formula (3) as a formula and N i k u r a d
213, which is calculated by calculating the mixing distance Qm obtained from the e equation and substituting that value into equation (4), is expressed by equation (4) of the Reynolds equation (1) and the hyperviscosity coefficient ν. The calculation unit converts the distributed constant system into lumped constants using the finite element method.The pipe radius area is divided into a predetermined number of elements, four nodes are established in each element, and the flow velocity U in each element is calculated from the node. A finite-dimensional approximation model of a pipe (5), which outputs the flow velocity distribution U as the vector product of the shape function vector associated with the vector and the velocity vector at the node in the element, and as a simultaneous equation with the weighted residual equation. 6) It is a calculation unit that calculates the formula. 14 expresses the flow velocity value at the velocity point on the pipe radius using equation (2) and finite dimensional approximation model (5)
Find the estimated value of the flow velocity distribution equation (15) from the established linear system including unknown parameters obtained by simultaneously calculating the equation (9
) to (14), and the output estimated flow rate is numerically calculated based on equation (16), and the flow rate is displayed on the display 16.

In the prediction calculation means 10 described above, the estimated value of the instantaneous flow rate is converted into an actual flow signal by inputting the average flow velocity portion outputted from the current detection means 2 as a flow velocity signal of the average flow velocity portion of the finite model 13 of the pipe. It is displayed as follows. According to the ultrasonic flowmeter of the present invention, the instantaneous flow rate of a non-constantly flowing fluid can be displayed in real time without being affected by fluctuations in flow velocity distribution.

As described above, according to the ultrasonic flowmeter of the present invention, the ultrasonic flow rate signal detected at predetermined time intervals is used as the average instantaneous flow rate signal of the unsteady fluid flowing in the fluid pipe. Since the flow rate is estimated and displayed by inputting it into the average flow velocity part of the model, an accurate predicted flow rate can be obtained even in an unsteady flow, and furthermore, the flow rate can be displayed in real time.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an ultrasonic flowmeter according to the present invention. 1...Flow path piping, 2...Ultrasonic pulse transmitter, 3.
... Inclined wedge (shoe), 4... Amplifier, 5...
・Pulse transmitter, 6. Timing circuit, 7. Changeover switch, 8. Converter, 10. Prediction calculation means, 11. Turbulence equation, 12. Eddy viscosity coefficient, 13.
・Finite pipe model, 14...Extended Kalman filter, 1
5...Flow rate calculator, 16...Display device. Figure 1 0 1. Display of the case Applicant Address: 3-110-8 Kamiochiai, Shinjuku-ku, Tokyo Name: Representative of Oval Equipment Industry Co., Ltd. High School: 1
) Mei 4, Substitute address: 1001 Chuo Dai-6 Kannai Building, 1-2-1 Furocho, Naka-ku, Yokohama, 231 6. Column 7 for detailed explanation of the invention in the specification to be amended, Contents of the amendment (1) , "the measured value of the flow velocity from a partial viewpoint" described in the 20th line of the first page of the specification to the first line of the second page is corrected to "the measured value of the flow velocity of one partial observation". (2) "and flow rate detection means" stated in the second line of page 2 of the same
is corrected to "and ultrasonic flow velocity detection means". (3) Correct "the arterial behavior of the flow" written in the sixth line of the second page to "the pulsating behavior of the flow". (4), "required" written on page 2, line 12 of the same is amended to "required". (5) The "obtainable beat signal" described in the first and second lines of page 3 is corrected to "this beat signal". (6), "required." written on page 3, line 4 of the same is amended to "required." (7) Correct "point flow velocity with high precision" in line 6 of page 3 to "flow velocity at point #R with high precision". (8), "Scan pipe diameter" written on page 3, line 8.
Correct to "scan on pipe diameter". (9), "turbulent viscosity to cause turbulence" written on page 4, line 18 of the same is corrected to "turbulent viscosity to cause turbulence". (10), ``S1=Machi'' written in the first line of page 5 of the same (1) is corrected to ``δt''. (11), "(a: pipe radius)" written in the 12th line of page 5 is corrected to "(a: pipe radius)". (12), "To determine the flow velocity value" stated on page 5, lines 14 to 15, "In order to determine the flow velocity value, m representative flow velocities U in the pipe are detected." Then, the m representative flow velocity values are corrected to ``. (13), 'y (rt. . . . (2))' written on page 5, line 18 of the same page, as rY(rt, t) = Ctu (rt+ t) +V
(r++ t) (2) Correct to J. (14), "It is done. Also, formula (1)" written in the fourth to fifth lines of page 6 is corrected to "It is done. Also, formula (1)." (15), "It will not happen, but... turbulent flow" written in the 6th line and 7th line of the same page will be corrected to "It will not happen. The inventor of the present invention will cause turbulent flow." (16), "u=..." written on page 6, line 8 of the same
・(3)" is ru=αu, (a r)"'" (3
)”. (17), rum:J described on page 6, line 9 of the same is corrected to rTJ,:J. (18), rflmJ described on page 6, lines 10, 11, and 12 is corrected to rQ,J. (19), page 6, line 14, “ν,...dan...
(4) "rv t(r I t ) = Cfu w"
(1-r/a)-”'U+n(t) (4)J
Correct to. (20), "L is calculated" on page 6, line 19 of the same document is amended to "L is calculated." (21), "Cross=...(5)" written in the first line of page 7 of the same
rx=A(tJ,) x+13y (5) J(
22), (23), Correct as follows. ``(5)'' written in page 7, line 8 of the same page is r (5),
Correct equation (6) to ``. "Yk=......(8
)” as rYk=H2m+Vi+ (8) J(25
), on page 9, lines 4 and 5, the phrase ``It will be. However,'' will be amended to ``It will be. However,''. (26), "2m" written on page 10, line 20 is corrected to rQ and to J. (27), "the flow velocity value at the flow velocity point" written on page 11, line 12 is corrected to "representative flow velocity value". (28) Correct the "probability linear" described in the 14th line of page 11 to "probability linear". (29), r(16) stated on page 11, line 17 of the same
The numerical value "is corrected to the numerical value J by the arithmetic unit 15 of the r(16) formula based on the formula. (30), page 12, lines 10-11, “
The fluid average instantaneous flow rate signal is corrected to the fluid instantaneous average flow velocity signal. (31), ``In some cases, the flow rate'' stated in the 12th line of page 12 is corrected to ``In some cases, the instantaneous flow rate.''

Claims (1)

[Claims] 1. An ultrasonic average flow velocity detection means that is installed in a pipe and detects the average flow velocity of an unsteady fluid passing through a cross section of the pipe, and the flow is expressed by a turbulence model of a partial differential equation including an eddy viscosity coefficient,
Prediction calculation means for approximating a pipe model by approximating the flow phenomenon of the turbulent flow model as a distributed constant system, estimating the flow velocity distribution in the pipe by substituting an average flow velocity value into the pipe model, and calculating the flow rate. An ultrasonic flowmeter characterized in that the flow velocity signal output from the flow velocity detection means is substituted into the average flow velocity portion of the pipeline model calculated by the prediction calculation means to calculate and output an unsteady flow rate.