CN103808381A - Temperature influence eliminating method for time difference ultrasonic flowmeter - Google Patents

Abstract

The invention discloses a temperature influence eliminating method for a time difference ultrasonic flowmeter. The temperature influence eliminating method comprises the following steps: measuring the propagation speeds of ultrasonic waves in a fluid and the fluid kinematic viscosity, at a plurality of temperature points; carrying out segmentation fitting to obtain a temperature modifier formula v=f(T) of the propagation speed of the ultrasonic waves in the fluid and a temperature modifier formula of the fluid kinematic viscosity, shown in the specification; respectively calculating the actual sound velocity of the sound channel where a probe is positioned and the actual kinematic viscosity of the fluid according to the fluid temperature during measuring, sound velocity temperature modifier formula, and the temperature modifier formula of the fluid kinematic viscosity; calculating the fluid velocity of the sound channel where the probe is positioned according to the actual sound velocity and the time difference obtained by measurement; judging in which state the measured fluid is positioned, a laminar flow state or turbulent flow state, according to the fluid velocity of the sound channel where the probe is positioned, the measured size of pipe diameter and the fluid kinematic viscosity after the influence from temperature is eliminated; calculating the flow by using a corresponding laminar flow speed-flow modifier formula or turbulent flow speed-flow modifier formula, according to the flow state of the measured flow and the arrangement position of the sound channel.

Description

A kind of temperature influence eliminating method of transit-time ultrasonic flow meter

Technical field

The present invention relates to ultrasonic flow rate measuring field, relate in particular to the temperature influence eliminating method of transit-time ultrasonic flow meter.

Background technology

Propagate time difference method and carry out one of main method of flow metering as using ultrasound ripple, its principle is in fluid, to calculate flow velocity along the difference in journey travel-time and flyback travel-time by measuring ultrasonic signal, in ultrasonic type flow metering field, is widely used.

Can find according to its measuring principle, the velocity of propagation of ultrasound wave in fluid is to participate in calculating flow rate information directly as known constant, and the velocity of propagation of ultrasound wave in fluid is along with the variation of temperature changes, in the time that the range of temperature of fluid is larger, the impact that the variation of the velocity of sound brings is also by very important, if the velocity of sound is not revised, the measurement result of the flow velocity finally calculating has larger deviation, makes the measurement result of flow comprise unnecessary error.

During due to mobile in pipeline of fluid, low flow velocity and high flow condition Fluid field velocity distribution complexity very.From flow dynamics analysis, different for the laminar flow velocity flow profile under the low flow velocity of same acoustic poth arrangement mode and velocity distribution under high flow rate, make need to use different computing formula while calculating pipeline flow with sound channel flow velocity.And the kinematic viscosity of the judgement of fluid flow state and pipe diameter, fluid and flow velocity size are closely related, for actual flowmeter, pipe diameter is invariant, the size of flow velocity can be measured from measuring sound channel again, so the size of kinematic viscosity is to judging the flow state effect key of certain flow velocity.And the kinematic viscosity characteristic of known fluid varies with temperature and changes the physical property of fluid, if kinematic viscosity is not revised according to temperature level, may false judgment flow field flow condition, cause adopting wrong computing formula to carry out computation and measurement pipeline flow, make the measurement result of flow comprise unnecessary error.

Summary of the invention

For solving the problem and blemish of above-mentioned middle existence, the object of this invention is to provide a kind of simple, effect and eliminate significantly the method for transit-time ultrasonic flow meter temperature impact.The technical scheme adopting is as follows:

A temperature influence eliminating method for transit-time ultrasonic flow meter, the method comprises:

Measure velocity of propagation and the fluid motion viscosity of ultrasound wave in fluid under some temperature spots;

Obtain the temperature correction formula v=f (T) of ultrasonic propagation velocity in fluid and the temperature correction formula of fluid motion viscosity by piecewise fitting

Fluid temperature (F.T.) during according to measurement and the temperature correction formula of velocity of sound temperature correction formula and fluid motion viscosity, calculate respectively the real velocity of sound of probe place sound channel and the actual motion viscosity of fluid;

Calculate the rate of flow of fluid of probe place sound channel according to real velocity of sound and the time difference measuring;

According to the fluid motion viscosity after the rate of flow of fluid of probe place sound channel, measurement pipe diameter size and the impact of elimination temperature, judge that detected fluid is in Laminar Flow state or in Turbulence Flow state;

According to the flow state of detected fluid and sound channel position, utilize corresponding laminar flow flow velocity-flow correction formula or turbulent flow rate-flow correction formula to calculate uninterrupted.

Compared with prior art, one or more embodiment of the present invention can have the following advantages by tool:

Thereby cause the flow state of detected fluid with temperature change by eliminating respectively the impact of the velocity of sound in temperature convection body and fluid motion viscosity property, substantially eliminated the flow measurement error that fluid temperature variations causes, improve flow measurement precision, improved the adaptive capacity to environment of flowmeter.The present invention is not only applicable to the temperature impact of transit-time ultrasonic flow meter and eliminates, and the pressure influence that is also applicable to transit-time ultrasonic flow meter is eliminated.

Accompanying drawing explanation

Accompanying drawing is used to provide a further understanding of the present invention, and forms a part for instructions,, is not construed as limiting the invention jointly for explaining the present invention with embodiments of the invention.In the accompanying drawings:

Fig. 1 is the specific works flow process figure in the invention process process;

Fig. 2 is the segmentation velocity of sound temperature correction schematic diagram in the invention process process;

Fig. 3 is the temperature correction intention of the segmentation fluid motion viscosity in the invention process process.

Embodiment

Below in conjunction with embodiment and accompanying drawing, the present invention is described in further detail.

Fig. 1 is the temperature influence eliminating method of transit-time ultrasonic flow meter, and the method comprises:

Measure velocity of propagation and the fluid motion viscosity of ultrasound wave in fluid under some temperature spots;

Obtain the temperature correction formula v=f (T) of ultrasonic propagation velocity in fluid and the temperature correction formula of fluid motion viscosity by piecewise fitting

(as shown in Figure 2);

Fluid temperature (F.T.) during according to measurement and the temperature correction formula of velocity of sound temperature correction formula and fluid motion viscosity, calculate respectively the real velocity of sound of probe place sound channel and the actual motion viscosity of fluid;

Calculate the rate of flow of fluid of probe place sound channel according to real velocity of sound and the time difference measuring;

According to the fluid motion viscosity after the rate of flow of fluid of probe place sound channel, measurement pipe diameter size and the impact of elimination temperature, judge that detected fluid is in Laminar Flow state or in Turbulence Flow state;

According to the flow state of detected fluid and sound channel position, utilize corresponding laminar flow flow velocity-flow correction formula or turbulent flow rate-flow correction formula to calculate uninterrupted.

Above-mentioned laminar flow flow velocity-flow correction formula is:

$v=\frac{\mathrm{\&pi;}{R}^4{\mathrm{<figure-callout\; id="0"\; label="V"\; filenames="HDA0000472399180000012.png,HDA0000472399180000021.png"\; state="\{\{state\}\}">V</figure-callout>}}_0}{2(R^2-{{\mathrm{<figure-callout\; id="0"\; label="r"\; filenames="HDA0000472399180000012.png,HDA0000472399180000021.png"\; state="\{\{state\}\}">r</figure-callout>}}_0}^2)}$

Above-mentioned turbulent flow rate-flow correction formula is:

$v=2\mathrm{\&pi;}{V}_0{\left(\frac{1}{R-r_0}\right)}^{\frac{1}{7}}{\&Integral;}_0^{R}r{(R-r)}^{\frac{1}{7}}\mathrm{dr}$

Wherein, R is measuring channel radius, r ₀for the distance of the sound channel range observation conduit axis that is arranged in parallel with axis, V ₀for the rate of flow of fluid in sound channel.

Above-mentioned steps specifically comprises: measure the ultrasonic propagation velocity of some temperature spots and the kinematic viscosity size of fluid in detected fluid, computing formula and the kinematic viscosity of obtaining the each section of corresponding velocity of sound by software segments calculate formula.Then calculate the measurement sound channel flow velocity size of reynolds number Re=2300 o'clock of fluid flow fields under different temperatures according to the measuring channel diameter of flowmeter self design and the segmentation of kinematic viscosity correction formula.

In actual measurement process, first calculate the ultrasonic propagation velocity of sound of correction according to fluid temperature (F.T.) value, and use the time difference size of revising the velocity of sound and measure to calculate the rate of flow of fluid of measuring in sound channel; Then the flow velocity size when rate of flow of fluid relatively calculating and Re=2300, judges and the flow field state of fluid adopts correct flow rate calculation formula, calculates uninterrupted.

As Fig. 2 and Fig. 3 have shown the segmentation velocity of sound temperature correction figure of above-described embodiment in implementation process and the temperature correction intention of segmentation fluid motion viscosity.

Above the temperature influence eliminating method of a kind of transit-time ultrasonic flow meter providing in the embodiment of the present invention is described in detail; for one of ordinary skill in the art; according to the thought of the embodiment of the present invention; all will change in specific embodiments and applications; this description should not be construed as limitation of the present invention in sum, and all any changes of making according to design philosophy of the present invention are all within protection scope of the present invention.

Claims (3)

1. a temperature influence eliminating method for transit-time ultrasonic flow meter, is characterized in that, described method comprises:

Measure velocity of propagation and the fluid motion viscosity of ultrasound wave in fluid under some temperature spots;

Obtain the temperature correction formula v=f (T) of ultrasonic propagation velocity in fluid and the temperature correction formula of fluid motion viscosity by piecewise fitting

Fluid temperature (F.T.) during according to measurement and the temperature correction formula of velocity of sound temperature correction formula and fluid motion viscosity, calculate respectively the real velocity of sound of probe place sound channel and the actual motion viscosity of fluid;

Calculate the rate of flow of fluid of probe place sound channel according to real velocity of sound and the time difference measuring;

According to the fluid motion viscosity after the rate of flow of fluid of probe place sound channel, measurement pipe diameter size and the impact of elimination temperature, judge that detected fluid is in Laminar Flow state or in Turbulence Flow state;

According to the flow state of detected fluid and sound channel position, utilize corresponding laminar flow flow velocity-flow correction formula or turbulent flow rate-flow correction formula to calculate uninterrupted.

2. the temperature influence eliminating method of transit-time ultrasonic flow meter according to claim 1, is characterized in that, described detected fluid is to be in laminar condition or in Turbulence Flow state:

In reynolds number Re=2300 o'clock of fluid flow fields, go out flow speed value in the sound channel that under different temperatures, fluid kinematic viscosity is corresponding according to given PIPE DIAMETER CALCULATION, described flow speed value and the actual flow speed value recording are compared, judge the flow state of fluid.

3. the temperature influence eliminating method of time difference type ultrasonic flowmeter according to claim 1, is characterized in that,

Described laminar flow flow velocity-flow correction formula is:

$v=\frac{\mathrm{\&pi;}{R}^4{V}_0}{2(R^2-{r_0}^2)}$

Described turbulent flow rate-flow correction formula is:

$v=2\mathrm{\&pi;}{V}_0{\left(\frac{1}{R-r_0}\right)}^{\frac{1}{7}}{\&Integral;}_0^{R}r{(R-r)}^{\frac{1}{7}}\mathrm{dr}$

Wherein, R is measuring channel radius, r ₀for the distance of the sound channel range observation conduit axis that is arranged in parallel with axis, V ₀for the rate of flow of fluid in sound channel.

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