JPH01272922A - Vortex flowmeter - Google Patents

Abstract

PURPOSE:To allow a user to confirm the uncertainty of measurement without using the large-scale flowmeter calibration testing device by enabling a vortex generation body to easily be attached and detached to and from a flowmeter main body. CONSTITUTION:The user can attach and detach the vortex generation body 2 by a vortex generation body fitting device 3 which uses engagement structure at right angles to the center part of the conduit 1 of the flowmeter main body without any leak of fluid nor any step in the internal diameter of a tube. Pressure variation which is caused by a vortex discharged to the downstream side of the vortex generation body 2 is detected by a differential pressure transducer 5 through a lead hole 4 and the vortex frequency is further measured by a signal processing part 6. It is estimated that an error in the fitting angle of the vortex generation body 2 is about 5 deg. and an error of the flowmeter is about 0.5%, so any special precise fitting device nor operation is required.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to a vortex flowmeter that allows measurement uncertainty assurance and calibration to be performed without actually flowing fluid.

``Prior Art'' It is known that vortices in opposite directions are alternately emitted from the left and right sides of a non-streamlined object placed in a flow, and the following equation holds.

f=S-U/d ---(1) f: Number of vortices released per unit time (hereinafter referred to as vortex frequency) S: Strouhal number (constant of proportionality) Us tlL body flow velocity d: vortex generation The convergence or vortex frequency of the body is proportional to the flow velocity. Therefore, by placing a vortex generator in a pipe through which the fluid to be measured flows and detecting the frequency of the emitted vortex, the flow velocity of the fluid to be measured can be determined.
Flow rate can be measured.

Based on the above principle, various vortex flowmeters with different shapes of vortex generators and vortex detection methods are currently in use. Vortex flowmeters have become widely used in the field of industrial measurement because they have many features such as a wide measurement range, no moving parts, excellent reliability and maintainability, and frequency output that is suitable for signal processing. ing.

"Problem to be Solved by the Invention" Equation (1) above shows that the vortex frequency is proportional to the flow velocity and inversely proportional to the width of the vortex generator, and the vortex frequency, which is the output of the vortex flowmeter, and the flow rate The relationship can be predicted to some extent from this equation. However, manufacturing errors in the dimensions of the vortex generator, how the vortex generator is attached to the main body, how the vortex is detected, etc. affect the vortex frequency in a complex manner.

Therefore, since it is not possible to guarantee that the indicated value of a vortex flowmeter will be as accurate as it is manufactured, in reality, it is necessary to use a calibration Ha that can generate a flow that accurately indicates the flow rate. It is necessary to perform a calibration test on the meter. In particular, when using a vortex flowmeter for fluid transactions, the problem is that you must either rely on the flowmeter manufacturer's calibration data as is, or request a third-party organization to perform a calibration test for each flowmeter you use. There is.

This invention was made to solve these problems, and the purpose is to enable the user to check the measurement uncertainty of a vortex flowmeter without using a large-scale flowmeter calibration test device. ``Means for Solving the Problems'' In order to solve the above problems, in the vortex flowmeter of the present invention, the vortex generator can be easily removed from the flowmeter body and attached to its original state. At the same time, the vortex generator is installed and the vortex is detected in a manner that has little effect on the detected vortex frequency, and the relationship between the state of the vortex generator and the measurement error of the flowmeter is given in advance. using means.

"Effect" The phenomenon of vortex shedding from a vortex generator in a flow is a self-excited vibration phenomenon of the fluid itself, so if the flow in the pipe and the state of the vortex generator are the same, it will always occur. The relationship between flow rate and vortex frequency is accurately reproduced. Therefore, as mentioned above, the flow condition is always maintained such that vortex detection etc. do not affect the vortex frequency, and the necessary experimental data regarding the vortex generator and vortex frequency of the flowmeter are given in advance. If so, the degree of error in the flowmeter can be determined by examining the manufacturing error of the vortex generator and how it is attached to the main body.

What is noteworthy here is that the shape of the vortex generator is simple;
The user should be able to easily make the required amount of measurement within an acceptable error range.

Also, regarding how to attach the vortex generator, it is only necessary to make sure that the front surface of the vortex generator is perpendicular to the tube axis of the main body and that it is installed at the center of the tube. These tasks are much easier than actually generating a flow and examining the measurement errors of a vortex flowmeter.

"Example" Currently, vortex detection in vortex flowmeters is performed using displacement, pressure, flow velocity, etc. sensors attached to the vortex generator, which measure the periodic circulation flow around the vortex generator caused by the vortices emitted from the vortex generator. A method of detecting the periodic pressure and flow velocity fluctuation caused downstream by the vortex emitted from the vortex generator using an ultrasonic sensor, pressure sensor, etc. installed downstream of the vortex generator has been put into practical use. The present invention utilizes these existing technologies.

The vortex flowmeter according to the present invention has a vortex generating body that can be easily removed from the flowmeter body so that the user can measure its dimensions, surface roughness, etc., and can be accurately attached to its original state. We are prepared. The detection of the vortex frequency is carried out in such a way that the frequency of the vortex emitted from the vortex generator is almost the same with and without the detection device. The vortex generator is attached to the main body with a structure that has no difference in the inner diameter of the pipe, or is attached to the main body with a support rod that has a structure that has little effect on the vortex frequency. For vortex flowmeters of various diameters with vortex generators of specific shapes and dimensions, how the relationship between vortex frequency and flow rate changes as the dimensions of the vortex generator change, or the vortex generator dimensions. It has data on the range of manufacturing errors within which changes in the relationship can be ignored in practical terms. In addition, the above-mentioned "doesn't change much", "has almost no effect", and "can be ignored" means that there is no problem if the change is within the allowable range for practical use. Therefore, the range varies depending on the amount of measurement error allowed. Regarding vortex detection, it is possible to confirm whether vortex detection is being performed correctly by attaching an output terminal to the vortex detection sensor and recording and observing the waveform.

FIG. 1 shows an overview of an embodiment of the present invention. Vortex generator 2
is installed perpendicular to the pipe axis at the center of the pipe line 1 of the vortex flowmeter main body so that there is no fluid leakage and there is no difference in the inner diameter of the pipe by the vortex generator mounting device 3 using a fitting structure. It can be easily installed and removed by the user.

Pressure fluctuations caused by the vortex emitted downstream of the vortex generating body are detected by the differential pressure converter 5 through the pressure guiding hole 4, and the vortex frequency is further measured by the signal processing section 6. Note that the error in the mounting angle of the vortex generator is about 5° and the error in the flowmeter is 0. 5
%, so no particularly precise installation equipment or work is required here.

FIG. 2 shows an example in which an ultrasonic sensor 8 is used instead of the pressure transducer in the vortex detection method of the example shown in FIG. In this case as well, there are no obstacles other than the vortex generator inside the tube of the main body.

FIG. 3 shows an embodiment of a system in which the force periodically applied to the vortex generator 2 is detected by a displacement sensor. Note that the vortex generator 2 and the vortex detector 10 have a structure that allows the user to remove them and reinstall them in their original state.

In the three embodiments illustrated above, the dimensions and roughness of the vortex generator, the mounting position and angle of the flowmeter main body to the pipe line,
Necessary data regarding the roundness, roughness, etc. of the main body pipe and the measurement error of the flow meter is provided. In addition to the above three embodiments, it is possible to remove the vortex generator, and it is also possible to measure the vortex frequency without affecting the vortex frequency by using other sensors such as flow velocity and pressure. It is.

[Effects] Although the vortex detection technology described in the above embodiment is an existing technology, it has a structure that allows the user to check the state of the vortex generator. A structure that does not have any adverse effects. Data on the state of the vortex generator and the error of the flowmeter are given.By combining the following three conditions, the flowmeter can be calibrated without using a flowmeter calibration facility. The user can obtain assurance of the degree of error of the flowmeter necessary for transactions, etc., in an unprecedented manner.

Although it takes a lot of effort to accumulate the data necessary for this purpose, once the data is obtained, it can be used by many people forever, so it can be said that it is well worth it if the ripple effect is taken into consideration.

[Brief explanation of the drawing]

1, 2, and 3 are configuration diagrams showing an embodiment of this patent. 1... Pipe line of the vortex flow meter body 2... Vortex generator 3... Vortex generator attachment device 4... Pressure guiding hole 5... Differential pressure converter 6... Signal processor 7 ... Emitted vortex 8 ... Ultrasonic sensor 9 ... Ultrasonic preamplifier 10 ... Vortex detector 11 ... Preamplifier designated representative

Claims (1)

[Claims] 1. The vortex generator can be easily removed from the flowmeter body and installed in its original state, and the installation of the vortex generator and the detection of the vortex are performed in a manner that has little effect on the detected vortex frequency. A vortex flowmeter further characterized in that the relationship between the state of the vortex generating body and the measurement error of the flowmeter is given in advance.