CN100375891C - Electromagnetic flow sensor for measuring non-full pipe flow and method for measurement - Google Patents

Abstract

The invention relates to a measuring method for measuring the flow of a partially filled pipe. Its electromagnetic flow sensor consists of a measuring tube, a pair of electrodes installed on the tube wall of the measuring tube and a magnetic field excitation unit that can generate a magnetic field B in the measuring tube. The measurement method is that a pair of electrodes are long arc-shaped electrodes extending along the circumference of the measuring tube wall respectively. In the two states of generating and not generating magnetic field B by the magnetic field excitation unit, the electrodes can be used to measure the flow of the non-full tube respectively. The measurement of the fluid induction potential value E and the measurement of the fluid impedance value Z under the partial liquid level H; The corresponding relationship of the value H, the geometric relationship between the cross-sectional area S of the partly filled pipe fluid, the liquid level value H and the inner diameter D of the measuring tube determines the partly filled pipe flow rate Q=V×S in the measuring pipe. The sensor provided by the invention is simple in structure and easy to use.

Description

Measuring method for measuring partial pipe flow

technical field

The invention relates to a measuring method for measuring the flow rate of a partially filled pipe.

technical background

The traditional electromagnetic flow sensor measures the flow velocity V of the fluid filled with the measuring tube of the sensor, corresponding to the cross-sectional area S of the measuring tube, there is flow Q=S×V. For the measurement of partial pipe flow, the liquid level H of the partial pipe fluid must be measured at the same time as the fluid flow rate V. The existing partial pipe flow measurement methods include adding multi-electrode liquid level measurement, capacitive liquid level measurement, and magnetic field conversion liquid level measurement to the electromagnetic flow sensor. These methods make the structure and measurement process of the electromagnetic flow sensor more complicated.

At present, there are patents 200510028473.3 and 200510110182.9 for double excitation electromagnetic flow technology, so that the traditional electromagnetic flowmeter sensor can not only measure the fluid velocity V but also the impedance Z of the fluid at both ends of the electrodes. Based on the multi-parameter measurement method and technology of double excitation electromagnetic flow technology, the partial pipe flow measurement can use the electrode terminal impedance of the electromagnetic flowmeter sensor to measure the liquid level H of the partial pipe flow. It provides a technical means for the method of measuring the partial flow of the electromagnetic flow sensor.

Contents of the invention

The object of the present invention is to provide an electromagnetic flow sensor and a measuring method for measuring partial pipe flow. The sensor structure is simple, the measurement method is simple and can meet the flow measurement of partial pipe flow.

To achieve the above object, the present invention adopts the following technical solutions:

An electromagnetic flow sensor for measuring the flow of a part-filled pipe is composed of a measuring pipe, a pair of electrodes installed on the pipe wall of the measuring pipe and a magnetic field excitation unit for generating a magnetic field in the measuring pipe, and is characterized in that:

(a) the axis of the measuring tube is set horizontally;

(b) The pair of electrodes described in is installed on both sides of the horizontal direction of the measuring tube inner wall, and the two electrodes extend into a pair of long arc-shaped electrodes along the circumferential direction of the measuring tube wall in an arc shape, and the arc length of each electrode corresponds to that of the measuring tube. The arc length covered by the variation range of the partially filled liquid value H;

(c) The magnetic field excitation unit is arranged at the upper and lower positions of the measuring tube to generate a magnetic field perpendicular to the magnetic field lines, that is, the plane formed by a pair of electrodes is perpendicular to the magnetic field B and the fluid flow velocity V.

A method for measuring a partially filled pipe flow, using the above-mentioned electromagnetic flow sensor, is characterized in that the measuring steps are:

(a) Under the condition that the magnetic field excitation unit generates a magnetic field B, the induced potential value E is measured on a pair of electrodes;

(b) by the following relationship:

E=K×D×B×V

Find the flow velocity V of the fluid in the measuring tube,

In the formula, K is the calculation coefficient, which is measured by experiment; D is the inner diameter of the measuring tube;

(c) In the case that the magnetic field excitation unit does not generate a magnetic field, E=0, and the voltage U generated by measuring the current I through the electrode is determined by the following relationship:

U=I×Z

Obtain the impedance value Z of the fluid in the measuring tube;

(d) According to the experimental measurement, the liquid level value H of the partial pipe flow and the impedance value Z have a monotone corresponding relationship

H=f(Z)

Obtain the liquid level value H;

(e) Obtain the cross-sectional area S of the non-full pipe flow in the measuring pipe according to the following formula

$\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; D.</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; arccos</span>}\frac{\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; D.</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; D.</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span>\sqrt{\frac{{\mathrm{<span\; class="notranslate">\; D.</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; -</span>{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; D.</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

(f) Finally, according to the obtained flow velocity V and cross-sectional area S, obtain the partial pipe flow Q

Q=V×S

Compared with the prior art, the present invention has the following obvious outstanding substantive features and significant advantages: as long as the electrode of the traditional electromagnetic flow sensor is transformed into a long arc electrode, the electromagnetic flow sensor can be used in different non-full pipe flow states. The measured fluid impedance value Z and the induced potential value E, and using the monotone corresponding relationship between the impedance on the electrode and the liquid level value H of the partly filled pipe, the non-full pipe can be obtained through the impedance value Z, the induced potential value E and the diameter D of the measuring tube The flow value Q of the full pipe fluid.

Description of drawings

Fig. 1 is a structural principle block diagram of an embodiment of the present invention, among the figure (a) is the situation that produces magnetic field B, (b) is the situation that does not produce magnetic field.

Figure 2 Impedance-liquid level curve of long arc electrode sensor

Detailed ways

A preferred embodiment of the present invention is described in detail as follows in conjunction with accompanying drawing:

Referring to Fig. 1, the electromagnetic flow sensor used to measure the flow rate of a partially filled pipe consists of a measuring tube 1, a pair of electrodes 2 installed on the tube wall of the measuring tube 1 and a magnetic field excitation unit 3 for generating a magnetic field in the measuring tube 1 , characterized by:

(a) The axis of the measuring tube 1 is arranged horizontally;

(b) The pair of electrodes 2 described are installed on both sides of the horizontal direction of the measuring tube 1 inner wall. Corresponding to the arc length covered by the variation range of the liquid value H of the part of the measuring tube 1;

(c) The magnetic field excitation unit 3 is arranged at the upper and lower positions of the measuring tube 1 to generate a magnetic field perpendicular to the magnetic field lines, that is, the plane formed by a pair of electrodes 2 is perpendicular to the magnetic field B and the fluid velocity V.

The measurement method of the part-filled pipe flow is to adopt the above-mentioned electromagnetic flow sensor, which is characterized in the measurement steps as follows:

(a) Under the condition that the magnetic field excitation unit generates a magnetic field B, the induced potential value E is measured on a pair of electrodes 2;

(b) by the following relationship:

E=K×D×B×V

Obtain the flow velocity V of the fluid in the measuring tube 1,

In the formula, K is a calculation coefficient, which is measured by experiments; D is the inner diameter of the measuring tube 1;

(c) Under the condition that the magnetic field excitation unit does not generate a magnetic field, E=0, the voltage U generated by the current I is measured through the electrode 2, by the following relational formula:

U=I×Z

Obtain the impedance value Z of the fluid in the measuring tube 1;

(d) According to the experimental measurement, the liquid level value H of the partial pipe flow and the impedance value Z have a monotone corresponding relationship

H=f(Z)

Obtain the liquid level value H;

(e) Obtain the cross-sectional area S of the partial flow in the measuring tube 1 according to the following formula

$\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; D.</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; arccos</span>}\frac{\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; D.</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; D.</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span>\sqrt{\frac{{\mathrm{<span\; class="notranslate">\; D.</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; -</span>{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; D.</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

(f) Finally, according to the obtained flow velocity V and cross-sectional area S, obtain the partial pipe flow Q

Q=V×S

The arc length of each electrode 2 in Fig. 1 is determined by the minimum value H of the liquid level being 0.1×D. The arc length of each electrode 2 is from the intersection point of H=0.1×D to the intersection point of H=(1-0.1)×D=0.9×D.

Figure 2 is a curve of the impedance value Z on the electrode measured by the long-arc electrode sensor and the liquid level value H of the partial flow in the measuring tube when the inner diameter of the measuring tube is D=50mm.

Claims (1)

1. A method of measuring a partially filled pipe flow, which uses a partially filled pipe flow electromagnetic flow sensor to measure, is characterized in that the measuring steps are: (a) Under the condition that the magnetic field excitation unit generates a magnetic field B, the induced potential value E is measured on a pair of electrodes (2); (b) by the following relationship: E=K×D×B×V Find the flow velocity V of the fluid in the measuring tube (1), In the formula, K is a calculation coefficient, which is measured by experiments; D is the internal diameter of the measuring tube (1); (c) Under the condition that the magnetic field excitation unit does not generate a magnetic field, E=0, the voltage U that is produced by the electrode (2) is measured by the current I, by the following relational formula: U=I×Z Obtain the impedance value Z of the fluid in the measuring tube (1); (d) According to the experimental measurement, the liquid level value H of the partial pipe flow and the impedance value Z have a monotone corresponding relationship H=f(Z) Obtain the liquid level value H; (e) Obtain the cross-sectional area S of the partial pipe flow in the measuring pipe (1) according to the following formula $\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; D.</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; arccos</span>}\frac{\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; D.</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; D.</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span>\sqrt{\frac{{\mathrm{<span\; class="notranslate">\; D.</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; -</span>{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; D.</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}$ (f) Finally, according to the obtained flow velocity V and cross-sectional area S, obtain the partial pipe flow Q Q=V×S

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