JPS62231175A - Measuring instrument for fluid velocity distribution - Google Patents

Abstract

PURPOSE:To easily measure a flow velocity distribution in real time by detecting variation in the electrostatic capacity of an electrode which is different with phases when a vapor-liquid mixed phase flow passes between orthogonal grating type electrodes. CONSTITUTION:Air bubbles 6 are discharged into liquid 7 from the air blowout hole of a nozzle in response to a trigger signal from a processor 27. Many blown-out air bubbles 6 reach a downstream-side electrode 18 while reduced in speed according to the flow velocity distribution of the liquid owing to the radial difference in the discharge position in the duct 2. All lateral shield lines 13a are excited in order through the switching of a multiplexer 22 to measure the electrostatic capacity at the electrode 18 and then their signals are inputted to the processor 27; and the dielectric constant of the objective liquid at each electrode 18 is measured through arithmetic operation to specify an air bubble 6 interposed between electrode element of each electrode 18, thereby specifying the flow velocity distribution from the distribution of the air bubbles.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Object of the Invention [Industrial Field of Application 1 This invention relates to a flow velocity distribution measuring device for a liquid flowing through a pipe. The liquid flow velocity distribution measuring device can be used, for example, when measuring 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 a liquid in a pipe, probe methods such as a laser probe method and an electric probe method, an ultrasonic meter, an electromagnetic flow probe, and the like 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 towards the probe along with the liquid in the pipe. In addition, 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. It is necessary to do this, and the equipment becomes quite large.
Moreover, these probe methods cannot measure distribution in real time. Further, those using ultrasonic waves and those using electromagnetic side u1 can measure the average flow base in the pipe, but cannot measure the flow velocity distribution.

This invention was made in view of the above-mentioned 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 Problem c] Corresponding to this object, the liquid flow velocity distribution measuring device of the present invention has a plurality of electrodes each consisting of a pair of electrode elements positioned opposite to each other with a gap. A sensor having a matrix of sensors is disposed in the flow of the liquid to be measured parallel to the axis of the pipe, and a nozzle for generating air bubbles is disposed upstream of the sensor in the same plane as the sensor. an excitation device that excites one electrode element of each electrode, and a processing device that processes output from the other electrode element of each electrode,
The present invention is characterized in that it is configured to detect the dielectric constant of the object to be measured between the electrode elements of each of the electrodes.

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 has a solid tubular shape and is provided with a plurality of air blowing holes 5 in its longitudinal direction. The nozzle 3 is located in the diametrical direction of the conduit 2, so that a plurality of air blowing holes 5 are opened in a plane perpendicular to the axis of the conduit 5. 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 is shown in FIGS.
As shown in the figure and FIG. 4, a plurality of shield wires 13 are arranged in parallel in the lateral direction within the imaginary first plane.
a, and a plurality of shield wires 13b arranged in parallel in the vertical direction within the second plane. The plurality of shielded wires 13a and the plurality of shielded wires 13b are each molded into a flat plate shape with resin 19 to constitute an electrode plate 20. By molding the resin 19 into a flat plate shape, it is possible to reduce the disturbance of the flow of the liquid 7 when the grid electrode 4 is disposed within the conduit 2. The first plane and the second plane are located parallel to each other with a distance maintained between them. Horizontal shield wire 13a and vertical shield wire 13
As shown by the symbol A in FIG. 2, the bits intersect with each other at an interval S when viewed from opposite directions.

Both the horizontal shield wire 13a and the vertical shield wire 13b are composed of coaxial shield wires with a conductor 15 at the center and an insulation wA 16 and a shield layer 17 on the outside. Lines 13a, 13
The insulating layer 16 and the shield layer 17 are peeled off and removed on the opposite sides of b to expose the conductive wire 15. The exposed conductive wires 15 facing each other constitute electrodes 18 facing each other as electrode elements. Alternatively, the electrode plate 20 may be formed by overprinting an electric m layer 15a, an insulating layer 16a, and a shield layer 17a on two insulating plates 10, as shown in FIG.

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 . electrode grid 4
The shielded wire 13a next to is connected to a multiplexer 22, and the multiplexer 22 is connected to an oscillator 23.

On the other hand, the vertical shield wires 13b of the electrode grid 4 are respectively connected to detectors 25 constituting a detector array 24.

The output of the detector 25 is sent to the multi-channel high-speed AD converter 2.
6 to the processing device 27. The processing device 27 is attached with an external storage device 28 and a CRT display 31.

[Function] 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 outlet 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 excited at a frequency of 10 MH2 or higher, for example. The multiplexer 22 selects and excites one of the plurality of horizontal shields a13a. Switching of multiplexer 22 is controlled by a switching signal from processing device 27. When the selected horizontal shield wire 13a is excited, an alternating current electric field is formed near the conductor 1115 exposed at the part of the electrode 18 that intersects with the vertical shield wire 13b, and the corresponding vertical shield wire 13b is exposed. The conductor 15 that is connected receives the signal. 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 vertical shield wires 13b are
The signal is then 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 the signal is dissipated at an intermediate frequency by a hetero gain method.
Perform amplification detection. Each detector performs 10 to several rifle integrals on the detected signal and outputs it. However, a phase detector can also be used as the detector 25.

Similarly, by switching the multiplexer 22, all the horizontal shield wires 13a are sequentially excited, and the electrode 18
When the capacitance at is measured, those signals are input to the processing device 27, and the dielectric constant of the object to be measured at each electrode 18 is calculated from the capacitance at each electrode 18 by calculation. From this, the bubbles 6 interposed between the electrode elements of each electrode 18 are identified, and the flow velocity distribution is identified 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 mixed flow passes between orthogonal grid-like electrodes, changes in the zero capacitance of the electrodes, which differ depending on the phase, can be measured accurately and at high speed. Based on this, it is possible to detect the flow velocity distribution of bubbles and, in turn, the flow velocity distribution of liquid, 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.
A measurement system can be constructed on a much smaller scale than those using ultrasonic waves or current flowmeters.

[Brief explanation of drawings]

Fig. 1 is a perspective explanatory diagram of the 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 diagram showing the electrodes, and Fig. 4 is similar to Fig. 3. The enlarged side view of part A and FIG. 5 are cross-sectional explanatory views showing other examples of the electrode plate. 1...Liquid flow velocity distribution measuring device 2...Pipeline 3
...Nozzle 4...Electrode grid 13a...Horizontal shield M 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 △D converter 27... Processing device 2
8... External storage device 31... CRT display designated agent Yoshigebe Shimizu, Director of Mechanical Technology Research Institute, Agency of Industrial Science and Technology Figure 1 Figure 2

Claims (1)

[Claims] 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 gap therebetween, is disposed within the flow of the liquid to be measured parallel to the axis of the conduit, and an excitation device that excites one electrode element of each electrode; and an excitation device that excites one electrode element of each electrode, and includes a nozzle that generates bubbles in a plane that intersects the axis of the pipe on the upstream side of the in-plane sensor; a processing device for processing output from the electrode elements of the respective electrodes, and configured to detect the dielectric constant of the object to be measured between the electrode elements of the respective electrodes.