JPH0515229B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Object of the Invention [Field of Industrial Application] The present invention relates to a device for measuring the flow velocity distribution of a liquid flowing through a pipe. A liquid flow velocity distribution measuring device can be used, for example, to measure the flow state of a liquid flowing in a pipe used in a chemical plant, an LNG transport pipe, a heat transfer device, or the like.

[Prior Art] In order to know the flow state of a liquid in a pipe, it is necessary to measure the distribution of its flow velocity.

Conventionally, in order to measure the flow velocity distribution of liquid in a pipe,
Probe methods such as laser probe method and electric probe method,
Ultrasonic meters, electromagnetic flow meters, etc. have been developed.

[Problems to be solved by the invention] The laser probe method detects the flow velocity and measures the flow velocity distribution by using Doppler shift of the light reflected by the bubbles flowing along with the liquid towards the probe in the pipe. Also, in the electric probe method, two probes are placed in the flow of a pipe and the flow velocity is determined from the time difference of the bubbles flowing between the probes, but it is necessary to place a large number of probes in each pipe. , the equipment is quite large,
Moreover, these probe methods cannot measure distribution in real time. Further, those using ultrasonic waves and those using electromagnetic flowmeters can measure the average flow rate in the pipe, but cannot measure the flow velocity distribution.

This invention was made in view of the above circumstances, and it is possible to measure the flow velocity distribution easily and in real time, and also enables high-speed measurement with small-scale equipment. The object is to provide a distribution measuring device.

(B) Structure of the Invention [Means for Solving the Problem] In response to this objective, the liquid flow velocity distribution measuring device of the present invention includes a plurality of electrodes each consisting of a pair of electrode elements located opposite to each other with a gap between them. are arranged in a matrix in the flow of the liquid to be measured parallel to the axis of the pipe, and a nozzle for generating air bubbles is arranged upstream of the sensor in the same plane as the sensor. an excitation device that excites one electrode element of each of the electrodes, and a processing device that processes the output from the other electrode element of each of the electrodes; It is characterized by being configured to detect the dielectric constant of the object to be measured.

Hereinafter, details of the present invention will be explained with reference to the drawings showing one embodiment.

In FIG. 1, reference numeral 1 denotes a liquid flow velocity distribution measuring device, and the liquid flow velocity distribution measuring device 1 is provided with a nozzle 3 and an electrode grid 4 serving as a sensor in a conduit 2.

The nozzle 3 is a long tubular body, and is provided with a plurality of air blowing holes 5 in the longitudinal direction. Nozzle 3
are located in the diametrical direction of the conduit 2, so that a plurality of air blowing holes 5 open in a plane perpendicular to the axis of the conduit 2. Air bubbles 6 can be blown out from each of the air blowing holes 5 into the liquid 7 that is the object to be measured and flowing inside the pipe 2 . The operation of this nozzle 3 is controlled by a processing device 27, which will be described later.

The electrode grid 4 is arranged downstream of the nozzle 3 and
As shown in FIGS. 3 and 4, the virtual first
It consists of a plurality of horizontal shield wires 13a arranged in parallel in the horizontal direction in the second plane, and a plurality of vertical shield wires 13b arranged in parallel in the vertical direction in the second plane. There is. A plurality of horizontal shield wires 13a and a plurality of vertical shield wires 13b
are each molded into a flat plate shape with resin to constitute an electrode plate. By molding the resin into a flat plate shape, it is possible to reduce disturbance of the flow of the liquid 7 when the electrode grid 4 is disposed within the conduit 2. The first plane and the second plane are located parallel to each other with a distance S between them. The horizontal shield wire 13a and the vertical shield wire 13b have a plurality of intersections when viewed from opposite directions at each pitch of the arrangement, as shown by the symbol A in FIG. This constitutes one electrode 18.

Horizontal shield wire 13a and vertical shield wire 13
Both lines b are composed of coaxial shielded wires with a conducting wire 15 at the center and an insulating layer 16 and a shielding layer 17 provided on the outside, but at the intersection,
The insulating layer 16 and the shield layer 17 are peeled off and removed on opposite sides of both the shield wires 13a and 13b to expose the conductive wire 15. The exposed conductive wires 15 facing each other constitute electrodes 18 facing each other as electrode elements. Further, as shown in FIG. 5, the electrode plate 20 is
An electrode layer 15a and an insulating layer 1 are disposed on two insulating plates 10.
6a and the shield layer 17a may be formed by overlapping printing.

The electrode grid 4 configured in this way is arranged, for example, in the flow of liquid in the conduit 2 parallel to the axis of the conduit 2 . The vertical shield wires 13b of the electrode grid 4 are connected to a multiplexer 22, and the multiplexer 22 is connected to an oscillator 23.

On the other hand, the shield wire 13a next to the electrode grid 4 is
Detectors 2 constituting the detector array 24, respectively.
Connect to 5. The output of the detector 25 is input to a processing device 27 via a multi-channel high-speed AD converter 26. The processing device 27 is attached with an external storage device 28 and a CRT display 31.

[Operation] In the liquid flow velocity distribution measuring device configured as described above, the operation when detecting the flow velocity distribution of the object to be measured is as follows.

Air bubbles 6 are discharged into the liquid 7 from the air blowing hole 5 of the nozzle 3 in response to a trigger signal from the processing device 27 . Due to the difference in the release position in the radial direction within the conduit 2, the many released bubbles 6 reach the electrode 18 on the downstream side with a slow velocity depending on the flow velocity distribution of the liquid. At this time, the oscillator 23 is set to 10M, for example.
Excite at frequencies higher than Hz. The multiplexer 22 selects one of the plurality of vertical shield wires 13b and excites it. Switching of multiplexer 22 is controlled by a switching signal from processing unit 27. When the selected vertical shield wire 13b is excited, the crossed electrodes 18 of the vertical shield wire 13b
An alternating current electric field is formed near the exposed conductor 15 at the portion , and is received by the exposed conductor 15 of the corresponding horizontal shield wire 13a. This received voltage includes information on the capacitance of the electrode 18, which changes depending on the object to be measured interposed between the electrode elements of the electrode 18.

The signals received by the plurality of horizontal shielded wires 13 a are simultaneously detected by a wave detector 25 , sent to a multi-channel high-speed AD converter 26 for AD conversion, and input to a processing device 27 . A heterodyne detector is used as the detector 25, and amplification detection is performed by filtering at an intermediate frequency using a heterodyne method. Each detector integrates the detected signal for 10 to several tens of cycles and outputs it. However, a phase detector can also be used as the detector 25.

Similarly, by switching the multiplexer 22, all the vertical shield wires 13b are sequentially excited, and when the capacitance at the electrode 18 is measured, these signals are input to the processing device 27 and used for calculation. Therefore, from the capacitance at each electrode 18,
The dielectric constant of the object to be measured in each electrode 18 is calculated, the bubbles 6 interposed between the electrode elements of each electrode 18 are specified from the dielectric constant, and the flow velocity distribution is specified from the distribution. This flow velocity distribution is drawn on the CRT display 31.

(C) Effects of the Invention According to the liquid flow velocity distribution measuring device of the present invention, when a gas-liquid multiphase flow passes between orthogonal grid electrodes, changes in capacitance of the electrodes that differ depending on the phase can be accurately measured. Since detection can be performed at high speed, based on this, the flow velocity distribution of bubbles and, in turn, the flow velocity distribution of liquid can be detected from the distribution of permittivity that differs depending on the phase. Accurately and rapidly detecting changes in the dielectric constant distribution in minute spaces has traditionally been considered difficult due to the extremely large impedance, but with this invention, everything except the lattice points that form the electrodes are shielded. By constructing the electrode grid using shielded wires, it has become possible to suppress electrostatic induction noise from the outside and detect local changes in dielectric constant as changes in capacitance. Moreover, it is easy to handle and can measure flow distribution in real time with the same ease as the probe method, and on a much smaller scale compared to methods that use ultrasonic waves or electromagnetic flowmeters. A measurement system can be constructed.

[Brief explanation of the drawing]

Fig. 1 is a perspective explanatory diagram of a liquid flow velocity distribution measuring device;
Fig. 2 is a circuit diagram of the liquid flow velocity distribution measuring device, Fig. 3 is a perspective explanatory view showing the electrode, Fig. 4 is an enlarged side view of part A in Fig. 3, and Fig. 5 shows another example of the electrode plate. FIG. 1...Liquid flow velocity distribution measuring device, 2...Pipe line, 3
... Nozzle, 4 ... Electrode grid, 13a ... Horizontal shield wire, 13b ... Vertical shield wire, 15 ... Conductor wire, 16 ... Insulating layer, 17 ... Shield layer, 18
... Electrode, 20 ... Electrode plate, 22 ... Multiplexer, 23 ... Oscillator, 24 ... Detector array, 25 ... Detector, 26 ... Multi-channel high speed
AD converter, 27...processing device, 28...external storage device, 31...CRT display.

Claims (1)

[Claims] 1. An in-plane sensor comprising a plurality of electrodes arranged in a matrix, each consisting of a pair of electrode elements facing each other with a space between them, is disposed within the flow of the liquid to be measured parallel to the axis of the conduit, and an excitation device that is provided with a nozzle that generates bubbles in a plane that intersects the axis of the conduit on the upstream side of the in-plane sensor, and that excites one electrode element of each electrode; A processing device for processing the output from the other electrode element of the electrode, and configured to detect the dielectric constant of the object to be measured between the electrode elements of each of the electrodes. Device.