JPS59132313A - Krmn vortex flow speed meter - Google Patents

Abstract

PURPOSE:To stabilize the yield of Krmn vortex and to prevent occurrence of errors in the measurement of flow speed, by providing a means, which vibrates a Krmn vortex yielding body in the direction perpendicular to the axils center of the body. CONSTITUTION:A Krmn vortex yielding body 1 has a column shape, whose cross setion is of a pentagon shape, and is formed by a magnetic material. The Krmn vortex yielding body 1 is attached to the tip of a supporting metal 4 by a metal fitting 2 and aligned so that the axial center and a flow are crossed at a right angle. An electromagnet 3 is embedded in the metal fitting 2 and vibrates the Krmn vortex yielding body 1, which is connected to a controller 6 through a lead wire 5 in the direction perpendicular to the axial center of the body 1, at an arbitrary number of vibration. In this constitution, the yield of the Krmn vortex can be stabilized and errors do not generate in the measurement of the flow speed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in Karman vortex current meters.

As a gas flowmeter, a JIS standard L-shaped pitot tube as shown in Figure 1 or an ASII standard special pitot tube (also called a Western type) as shown in Figure 2 is generally used. .

However, all of these pitot tubes were developed as flow meters for single-phase gas flow.

For measurement of two-phase flow of solid gas or gas/liquid.

There is a drawback that powder, granules, liquid droplets, etc. enter the pressure measurement hole and clog it, making measurement impossible. For this reason.

When using a pitot tube for two-phase flow measurement, it is necessary to pour air or steam into the pressure measurement hole and purge it frequently, resulting in a long measurement time. Additionally, in high concentration areas, pitot tubes can become clogged instantly.

It has a major drawback that it cannot be measured.

On the other hand, Karman vortex current meters are also frequently used to measure fluid flow velocity. C-cure is a method in which a Karman vortex generator is placed in a fluid flow, and the flow velocity is determined from the frequency of the Karman vortex generated. Since this current meter does not have a so-called pressure measuring hole, there is no problem of clogging of the hole, but powder or liquid may adhere to the Karman vortex generating body, which also causes problems.

In other words, if powder or the like adheres to the vicinity of the Karman vortex generator, the gas separation conditions become unstable, and the Karman vortex is not stably generated, resulting in measurement errors.

The present invention eliminates these drawbacks, and includes a columnar Karman vortex generator disposed in a fluid flow that generates a Karman vortex, and a means for measuring the frequency of the Karman vortex generated by the same generator. In the Karman vortex current meter consisting of
It is characterized by being equipped with a means for vibrating the Karman vortex generator in a direction perpendicular to its axis, and its purpose is to stabilize the generation of Karman vortices and create a Karman vortex current meter that does not cause errors in flow velocity measurement. This is what we provide.

The present invention will be described below with respect to an embodiment of a current meter shown in FIGS. 3 and 4.

Reference numeral 1 denotes a Karman vortex generator, which has a columnar shape with a pentagonal cross section as shown in FIG. 4, and is made of a magnetic member. This Karman vortex generator 1 is attached to the tip of a support rod 4 with a metal fitting 2.

It is arranged so that the flow and the axis are perpendicular to each other. In addition, one through hole is formed in the axial direction +5 of the Karman vortex generator l,
On the other hand, an opening IB is provided toward the downstream side so as to communicate with the through hole IA.

3 is an electromagnet buried in the metal fitting 2, and 7 lead wires 5
It is connected to the controller 6 via.

The Karman vortex generator 1 is made to vibrate at an arbitrary frequency in a direction perpendicular to its axis.

8 is a hot wire type sensor, which is disposed within the through hole IA of the Karman vortex generator 1 and close to the opening IB;
The frequency of the Karman vortex can be measured using known means.

Note that 10 is a streamline of gas in the flow, and 11 is a streamline of particles.

Now, when the fluid hits the Karman vortex generator l.

A Karman vortex is generated in its wake. The frequency is detected by the sensor 8 and the flow velocity is determined by a linear equation.

V = ar,'st Kokoso, ■: Gas flow velocity [m/s] d: Width of Karman vortex generator (m) Stnis-Drawhal number [constant] f second side wave number (1/,) The amount of powder increases When the ratio of the powder flow rate to the gas flow rate becomes large, the powder adheres to the vicinity of the corner 1C of the Karman vortex generator 1, and the separation of the gas streamline 1o becomes unstable.

At this time, the controller 6 is activated to alternately excite the electromagnet 3 at an appropriate frequency, and the Karman vortex generator 1 is aligned with its axis.
In other words, it vibrates in a direction perpendicular to the flow. Since a space is created between the surface of the corner 10 of the Karman vortex generator 1 and the powder, the separation conditions of the gas streamline 10 at the corner IC are stabilized.

Karman vortex will be generated stably.

Furthermore, when the strength of the Karman vortex is weak, if the excitation frequency of the electromagnet 3 is controlled to resonate with the frequency of the Karman vortex, the strength of the Karman vortex will increase, and the measurement accuracy of the frequency of the Karman vortex will improve. As described above, according to the current velocity meters of the two embodiments.

(1) By vibrating the Karman vortex generator 1 with the electromagnet 3, powder or droplets do not adhere to the vicinity of the corner IC of the Karman vortex generator 1, and therefore in the high concentration region of multiphase flow. Also, Karman vortices are more likely to occur, and the gas flow velocity can be measured continuously without gas purge. Therefore, the measurement time can be significantly reduced compared to the conventional method.

(2) Control the excitation frequency of the Karman vortex generator l.

By making it resonate with the Karman vortex frequency, pressure fluctuations due to the Karman vortex become larger, and the vortex frequency becomes easier to detect, thereby improving the measurement accuracy of the gas flow velocity.

You can obtain effects such as

[Brief explanation of the drawing]

Figures 1 and 2 are illustrations of a pitot tube, Figure 3 is a diagram of a current meter showing an embodiment of the present invention, and Figure 4 is an IV of Figure 3.
-IV sectional view. 1: Karman vortex generator, 3: electromagnet, 8: sensor

Claims (1)

[Claims] In a Karman vortex velocimeter, which consists of a columnar Karman vortex generator that is placed in a fluid flow and generates a Karman vortex, and a means for measuring the frequency of the Karman vortex generated by the generator, the Karman vortex generator is connected to the axis of the Karman vortex generator. A Karman vortex current meter characterized by comprising a means for vibrating in a direction perpendicular to the core.