JPH0226033Y2 - - Google Patents

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to an electromagnetic flowmeter transmitter (hereinafter abbreviated as a transmitter if necessary), and is particularly concerned with improving small diameter transmitters. Regarding.

<Prior Art> FIG. 1 shows a vertical cross-sectional view of a conventional micro-diameter transmitter. 1 is a conduit with a flange portion 11 on the upstream side;
It has a flange portion 12 on the downstream side. The fluid to be measured flows in from arrow F. Flange parts 11, 12
is connected to the flange of the mating pipe to be connected.
The inner surface of the conduit 1 is lined with a lining 2, and together with the conduit 1 constitutes a conduit 3 through which the fluid to be measured flows. An enlarged portion 21 at the upstream end of the lining 2,
There is an enlarged portion 22 at the downstream end. Enlarged section 21,
The inner diameter of the outer end of 22 is configured to match the inner diameter of the mating pipe. This is because it is not possible to obtain an appropriate flow velocity for an electromagnetic flowmeter with the same inner diameter as the mating pipe, so the inner diameter is narrowed to obtain a predetermined flow velocity. 4 is an electrode that detects a signal voltage corresponding to the flow rate. The distance L from the inner end of the enlarged portion 21 to the electrode 4 is a run-up distance necessary to stabilize the flow velocity distribution, and is generally set to several times to several tens of times the inner diameter d. Numerals 51 and 52 are cores for concentrating magnetic flux, and excitation coils 53 and 54 are wound around these cores 51 and 52, respectively, to constitute a magnetic flux generating device 5 for applying magnetic flux to the fluid to be measured.

In general, an electromagnetic flowmeter has the characteristic that if the flow is axially symmetrical, the flow rate and signal voltage are proportional regardless of the flow velocity distribution, assuming that the magnetic field is uniform, the flow velocity distribution is axially symmetrical, and the contact area of the electrode is negligible. . but,
As shown in Figure 1, the micro diameter (for example, diameter 2.5
The above assumption generally does not hold true for transmitters with a diameter of about 100 mm (mm) and is affected by the flow velocity distribution. In other words, in such a micro-diameter transmitter, the size of the contact part of the electrode 4 cannot be ignored compared to the inner diameter d, and the proportion of the electrode 4 protruding into the flow is larger than in a normal-diameter transmitter. This tends to cause non-linearity in the signal voltage with respect to the flow rate. In particular, with a micro-diameter transmitter, the flow changes from laminar to turbulent, and the flow velocity profile seen in the cross section of the pipe 3 in the flow direction changes significantly from a parabolic shape to an almost flat shape. Linearity tends to deteriorate. Furthermore, since the run-up distance is generally long, pressure loss also increases.

<Purpose of the invention> In view of the above-mentioned prior art, the object of the present invention is to obtain a transmitter with good linearity of signal voltage with respect to flow rate even in a micro-diameter transmitter.

<Configuration of the invention> The configuration of the invention that achieves this objective consists of a conduit equipped with an electrode that extracts a signal voltage corresponding to the flow rate of the fluid to be measured, and a magnetic flux generator that applies a magnetic field to the conduit. In the electromagnetic flowmeter transmitter, a first straight pipe portion is formed in a straight pipe shape from one end face of the pipe line toward the inside, and a lapper shape is formed continuously to the first straight pipe portion. a second straight pipe part that is formed in a straight pipe shape following the truss-like sudden reduction part and to which the electrode is attached;
The pipe line has an enlarged part that gradually expands from the straight pipe part toward the other end surface of the pipe line, and the flow velocity distribution is made almost uniform in the rapid contraction part in the shape of a bulge, so that a straight line of the signal voltage with respect to the flow rate is obtained. This feature is characterized by ensuring sex.

<Example> Hereinafter, an example of the present invention will be described in detail based on the drawings. Note that parts having the same functions as those in the prior art are given the same numbers, and redundant explanations will be omitted.

FIG. 2 is a longitudinal sectional view showing an embodiment of the present invention. Reference numeral 6 denotes a conduit that can withstand the internal pressure of the fluid to be measured and is connected to a mating pipe. The conduit 6 is provided with connection parts 61 and 62 on both sides thereof, and the central part of the conduit 6 is constricted to match the diameter d. The inner surface of the conduit 6 is lined with a lining 7 for preventing short-circuiting of the signal voltage generated inside the fluid to be measured, and together with the conduit 6 constitutes a conduit 8 . The lining 7 has a straight pipe part 71 formed from the connecting part 61 of the conduit 6 toward the inside of the transmitter.
Continuing from this straight pipe part 71, a rapidly contracting part 72 is provided which is constricted in a rattling shape, and further, following this rapidly contracting part 72, a straight pipe part 73 extending for about 1 d is formed on the upstream and downstream sides of the electrode 4. It has an enlarged portion 74 that gradually expands to the connecting portion 62 of the conduit 6 at an angle θ. The reason why the straight pipe portion 73 of about 1 d is provided upstream and downstream of the electrode 4 is because it is within this range that the signal voltage generated in the fluid to be measured contributes to the electrode.

The operation of the micro-diameter transmitter constructed in this manner will be explained using FIG. 3. Figure 3 shows conduit 9
shows the profiles of various flow velocity distributions when the fluid to be measured flows. First, in a laminar flow state (parabolic velocity distribution profile shown by a solid line), the straight pipe section 9 of the conduit 9
When the fluid to be measured flows into the tube 1 from the direction of the arrow F, the rapid contraction section 92 of the conduit 9 tends to accelerate the flow velocity near the tube wall. The pipe portion 93 has a substantially uniform flow velocity distribution as shown by the solid line. Next, when the fluid to be measured flows into the straight pipe section 91 of the conduit 9 from the direction of the arrow in a turbulent flow state (a nearly uniform velocity distribution profile shown by the dotted line), the pipe flows in the same way as in the laminar flow state. There is a tendency for the flow velocity near the wall to accelerate, but the degree of this is not as pronounced as in the laminar flow state, and in the straight pipe section 93 there is a slight roundness in the center of the pipe as shown by the dotted line, but it is quite noticeable. Shows a flat flow velocity distribution. Therefore, even if the flow velocity distribution at the time of flowing into the conduit 9 changes significantly, in the straight pipe section 93 where the electrodes are attached, the flow becomes almost uniform with little change in the flow velocity distribution. Thereafter, it flows away without peeling off due to the gradual expansion part 94. This state of flow is the second
Since the embodiment shown in the figure is exactly the same, the flow velocity distribution near the straight pipe section 73 to which the electrode 4 is attached is a substantially uniform flow regardless of the flow state of the mating pipe. Therefore, even if the contact portion of the electrode 4 has a certain size, or even if the electrode slightly protrudes into the flow, a signal voltage proportional to the flow rate can be obtained.

<Effects of the invention> As explained above in detail with the examples, according to the invention, even if the flow velocity changes significantly, the flow velocity distribution near the electrode becomes almost uniform, so that the fluid to be measured at the electrode The flow rate and signal voltage are accurately proportional without being limited by the protrusion into the electrode or the size of the electrode, improving accuracy. Further, since processing of the electrode portion and attachment of the electrode are extremely easy, costs are reduced. Furthermore, since the length of the straight pipe where the electrode is attached can be approximately one time the inner diameter upstream and downstream from the electrode, the overall axial length of the transmitter conduit can be shortened compared to conventional transmitters, making it compact and compact. Contributes to weight reduction.
Furthermore, since the part that restricts the inner diameter is shorter, the overall pressure loss can be reduced compared to conventional transmitters.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of a conventional micro-diameter transmitter.
FIG. 2 is a longitudinal sectional view showing an embodiment of the present invention, and FIG. 3 is an explanatory diagram for explaining the profile of flow velocity distribution. 1... Conduit, 2... Lining, 3 ... Conduit,
4... Electrode, 6... Conduit, 7... Lining, 7
1... Straight pipe section, 72... Rapidly reduced section, 73... Straight pipe section, 74... Enlarged section, 8 ... Pipe line.

Claims (1)

[Scope of utility model registration request] In an electromagnetic flowmeter transmitter comprising a conduit equipped with an electrode that extracts a signal voltage corresponding to the flow rate of the fluid to be measured, and a magnetic flux generator that applies a magnetic field to the conduit, the internal a first straight pipe portion formed in a straight pipe shape toward the first straight pipe portion, a truss-like rapidly decreasing portion formed in a truss-like shape continuously from the first straight pipe portion, and a truss-like rapidly decreasing portion continuing from the truss-like rapidly decreasing portion. The pipe line is characterized in that the pipe line includes a second straight pipe part formed in a straight pipe shape and to which the electrode is attached, and an enlarged part that gradually expands from the second straight pipe part toward the other end surface of the pipe pipe. An electromagnetic flowmeter transmitter.