CN103808381B - A kind of temperature influence eliminating method of transit-time ultrasonic flow meter - Google Patents

Abstract

The invention discloses the temperature influence eliminating method of a kind of transit-time ultrasonic flow meter, the method includes: measure the spread speed in a fluid of ultrasound wave under some temperature spots and fluid dynamic viscosity; Temperature adjustmemt formula v=f (T) of ultrasonic propagation velocity in fluid and the temperature adjustmemt formula of fluid dynamic viscosity is obtained by piecewise fittingTemperature adjustmemt formula according to fluid temperature (F.T.) when measuring and velocity of sound temperature adjustmemt formula and fluid dynamic viscosity, calculates the real velocity of sound of probe place sound channel and the actual motion viscosity of fluid respectively; According to real velocity of sound with measure time difference of obtaining and calculate the rate of flow of fluid of probe place sound channel; According to the fluid dynamic viscosity after the rate of flow of fluid of probe place sound channel, measurement pipe diameter size and elimination temperature impact, it is judged that detected fluid is in Laminar Flow state and is in Turbulence Flow state; Flow regime according to detected fluid and sound channel position, utilize corresponding linear flow rate-flow correction formula or turbulent flow rate-flow correction formula to calculate uninterrupted.

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, particularly relate to the temperature influence eliminating method of transit-time ultrasonic flow meter.

Background technology

Propagation time difference method is one of main method carrying out flow measurement as using ultrasound ripple, its principle is to calculate flow velocity by measuring ultrasonic signal difference along journey propagation time and flyback propagation time in a fluid, is widely used in ultrasonic type flow measurement field.

According to its measuring principle it appeared that, ultrasound wave spread speed in a fluid is directly to participate in as known constant calculating flow rate information, and the spread speed that ultrasound wave is in a fluid is as the change of temperature and changes, when the range of temperature of fluid is relatively larger time, the impact that the change of the velocity of sound brings is also by very important, if the velocity of sound is not modified, the measurement result of the flow velocity finally calculated has relatively larger deviation so that the measurement result of flow comprises unnecessary error.

During due to fluid flowing in pipeline, low flow velocity and high flow condition Fluid field velocity distribution complexity very. By flow dynamics analysis it can be seen that be distributed different from the velocity distribution under high flow rate for the linear flow rate under same acoustic poth arrangement mode low flow velocity so that need when calculating pipeline flow with sound channel flow velocity to use different computing formula. And the judgement of fluid flow state and pipe diameter, the dynamic viscosity of fluid and flow velocity size are closely related, for actual effusion meter, pipe diameter is invariant, the size of flow velocity can be measured again measurement sound channel, so the size of dynamic viscosity is crucial to the flow regime effect judging certain flow velocity.And vary with temperature from the dynamic viscosity characteristic of fluid known the physical property of fluid and change, if dynamic viscosity is not modified according to temperature level, may false judgment flow field flow situation, cause that the computing formula adopting mistake carrys out computation and measurement pipeline flow so that the measurement result of flow comprises unnecessary error.

Summary of the invention

For solving above-mentioned middle Problems existing and defect, it is an object of the invention to provide a kind of method that simple, effect eliminates the impact of transit-time ultrasonic flow meter temperature significantly. The technical scheme adopted is as follows:

A kind of temperature influence eliminating method of transit-time ultrasonic flow meter, the method includes:

Measure the spread speed in a fluid of ultrasound wave under some temperature spots and fluid dynamic viscosity;

Temperature adjustmemt formula v=f (T) of ultrasonic propagation velocity in fluid and the temperature adjustmemt formula of fluid dynamic viscosity is obtained by piecewise fitting

Temperature adjustmemt formula according to fluid temperature (F.T.) when measuring and velocity of sound temperature adjustmemt formula and fluid dynamic viscosity, calculates the real velocity of sound of probe place sound channel and the actual motion viscosity of fluid respectively;

According to real velocity of sound with measure time difference of obtaining and calculate the rate of flow of fluid of probe place sound channel;

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

Flow regime according to detected fluid and sound channel position, utilize corresponding linear flow rate-flow correction formula or turbulent flow rate-flow correction formula to calculate uninterrupted;

Described linear flow rate-flow correction formula is:

$Q=\frac{{\mathrm{\πR}}^4{V}_0}{2(R^2-r_0^2)}$

Described turbulent flow rate-flow correction formula is:

$Q=2{\mathrm{\πV}}_0{\left(\frac{1}{R-r_0}\right)}^{\frac{1}{7}}\underset{0}{\overset{R}{\∫}}r{(R-r)}^{\frac{1}{7}}dr$

Wherein, R is for measuring pipe radius, r₀The distance of the sound channel range measurement conduit axis for being arranged in parallel with axis, V₀For the rate of flow of fluid in sound channel.

Compared with prior art, one or more embodiments of the invention can have the advantage that

By eliminating in temperature convection body velocity of sound impact and fluid dynamic viscosity characteristic respectively with temperature change thus causing the flow regime of detected fluid, essentially eliminate the flow measurement error that fluid temperature variations causes, improve flow measurement precision, improve the adaptive capacity to environment of effusion meter. The present invention is applicable not only to the temperature impact of transit-time ultrasonic flow meter and eliminates, and the pressure influence applying also for transit-time ultrasonic flow meter eliminates.

Accompanying drawing explanation

Accompanying drawing is for providing a further understanding of the present invention, and constitutes a part for description, is provided commonly for explaining the present invention with embodiments of the invention, is not intended that limitation of the present 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 adjustmemt schematic diagram in the invention process process.

Detailed description of the invention

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 includes:

Measure the spread speed in a fluid of ultrasound wave under some temperature spots and fluid dynamic viscosity;

Temperature adjustmemt formula v=f (T) of ultrasonic propagation velocity in fluid and the temperature adjustmemt formula of fluid dynamic viscosity is obtained by piecewise fitting(as shown in Figure 2);

Temperature adjustmemt formula according to fluid temperature (F.T.) when measuring and velocity of sound temperature adjustmemt formula and fluid dynamic viscosity, calculates the real velocity of sound of probe place sound channel and the actual motion viscosity of fluid respectively;

According to real velocity of sound with measure time difference of obtaining and calculate the rate of flow of fluid of probe place sound channel;

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

Flow regime according to detected fluid and sound channel position, utilize corresponding linear flow rate-flow correction formula or turbulent flow rate-flow correction formula to calculate uninterrupted.

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

$Q=\frac{{\mathrm{\πR}}^4{V}_0}{2(R^2-r_0^2)}$

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

$Q=2{\mathrm{\πV}}_0{\left(\frac{1}{R-r_0}\right)}^{\frac{1}{7}}\underset{0}{\overset{R}{\∫}}r{(R-r)}^{\frac{1}{7}}dr$

Wherein, R is for measuring pipe radius, r₀The distance of the sound channel range measurement conduit axis for being arranged in parallel with axis, V₀For the rate of flow of fluid in sound channel.

Above-mentioned steps specifically includes: measure the ultrasonic propagation velocity of some temperature spots in detected fluid and the dynamic viscosity size of fluid, is obtained computing formula and the dynamic viscosity calculating formula of the velocity of sound each section corresponding by software segments. Then measurement sound channel flow velocity size during reynolds number Re=2300 of fluid flow fields under different temperatures is calculated according to the measurement pipe diameter size of effusion meter self design and dynamic viscosity correction formula segmentation.

In actual measurement process, it is first depending on fluid temperature values and calculates the ultrasonic propagation velocity of sound of correction, and use the time difference size that the correction velocity of sound and measurement obtain to calculate the rate of flow of fluid measured in sound channel; Flow velocity size when then comparing the rate of flow of fluid calculated with Re=2300, it is judged that the flow field state of fluid, adopts correct flow rate calculation formula, calculates uninterrupted.

As Fig. 2 illustrates above-described embodiment segmentation velocity of sound temperature adjustmemt figure in implementation process.

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

Claims (2)

1. the temperature influence eliminating method of a transit-time ultrasonic flow meter, it is characterised in that described method includes:

Measure the spread speed in a fluid of ultrasound wave under some temperature spots and fluid dynamic viscosity;

Temperature adjustmemt formula v=f (T) of ultrasonic propagation velocity in fluid and the temperature adjustmemt formula of fluid dynamic viscosity is obtained by piecewise fitting

Temperature adjustmemt formula according to fluid temperature (F.T.) when measuring and velocity of sound temperature adjustmemt formula and fluid dynamic viscosity, calculates the real velocity of sound of probe place sound channel and the actual motion viscosity of fluid respectively;

According to real velocity of sound with measure time difference of obtaining and calculate the rate of flow of fluid of probe place sound channel;

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

Flow regime according to detected fluid and sound channel position, utilize corresponding linear flow rate-flow correction formula or turbulent flow rate-flow correction formula to calculate uninterrupted;

Described linear flow rate-flow correction formula is:

$Q=\frac{{\mathrm{\πR}}^4{V}_0}{2(R^2-r_0^2)}$

Described turbulent flow rate-flow correction formula is:

$Q=2{\mathrm{\πV}}_0{\left(\frac{1}{R-r_0}\right)}^{\frac{1}{7}}\underset{0}{\overset{R}{\∫}}r{(R-r)}^{\frac{1}{7}}dr$

Wherein, R is for measuring pipe radius, r₀The distance of the sound channel range measurement conduit axis for being arranged in parallel with axis, V₀For the rate of flow of fluid in sound channel.

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

When reynolds number Re=2300 of fluid flow fields, go out flow speed value in the sound channel that under different temperatures, fluid dynamic viscosity is corresponding according to given PIPE DIAMETER CALCULATION, described flow speed value and actually measured flow speed value are compared, it is judged that the flow regime of fluid.