JP2001194193A - Flow meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flow meter having an extensive range of measurement from a small value to a large value by expanding the range of the flow rate for measurement. SOLUTION: A straightening appliance 21 comprising a honeycomb or the like is disposed in an upstream side of a measurement pipe 1, the pressure at an inlet and an outlet of the straightening appliance 21 is led to a differential pressure sensor 24 by an upstream side conduction pipe 22 and a downstream conduction pipe 23 to detect the differential pressure between the two. A vortex generator 31 comprising a triangular prism or the like is mounted across the flow in the downstream adjacent to a laminar flow meter 2, and a vortex detection sensor 32 is mounted across the flow on the downstream side thereof. The low from the laminar flowmeter 2 is straightened, and thus, the vortex generator 31 can generate regular and stable Karman vortexes even when any straight portion or any straightening appliance for the vortex flow meter 3 is not provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow meter, and more particularly, to a flow meter in which a vortex flow meter is arranged in series downstream of a laminar flow meter to provide a wide flow range from a minute flow region to a large flow region. It relates to a flow meter capable of measuring.

[0002]

2. Description of the Related Art A differential pressure flow meter and a vortex flow meter are conventionally used as typical flow meters for measuring the flow rate of a liquid or gas. The differential pressure flow meter can be applied to any of liquid, gas, and steam, has no moving parts, has a simple structure, and is easy to maintain. Therefore, it has been used in a wide range of fields as an industrial flow meter for a long time. In a differential pressure flow meter, a flow meter in which a fluid to be measured is measured in a laminar flow state is particularly called a laminar flow meter.
Since the flow region in a laminar flow state is generally narrow, a laminar flow meter is used in a small flow region where the flow is small, and the measurement range is usually narrow. The vortex flow meter is a flow meter that utilizes the vibrational phenomena of fluid caused by Karman vortices and has a simple structure and does not require mechanically movable parts.It is hardly affected by the composition, density, temperature, and pressure of the measured fluid. It can be applied to any of liquid, gas and vapor. The vortex flowmeter has a relatively wide range of measurable flow rates and good measurement accuracy. However, it is necessary to discharge a regular and stable vortex. Therefore, in order to remove the influence of the turbulence of the flow, the swirling flow, the distortion of the flow velocity distribution, and the like, a straight pipe portion having a certain length or more is required on the upstream side and the downstream side.

[0003]

The laminar flow meter and the vortex flow meter have the above-mentioned features, respectively. The laminar flow meter is suitable for measuring a small flow rate region, and the vortex flow meter has a vortex flow meter. It is suitable for measuring a flow rate region above a small flow rate range that can be generated regularly and stably. There are various types of flow meters with regard to measurement range and measurement accuracy.When measuring the flow rate of a fluid, select and measure an appropriate flow meter according to the expected flow rate of the fluid to be measured and the required accuracy. At present, there is no flow meter suitable for flow measurement in which the flow rate fluctuates greatly from a small flow rate to a large flow rate. Accordingly, an object of the present invention is to provide a flow meter having a wide measurement range from a minute flow rate to a large flow rate by expanding the range of the measured flow rate. Another object of the present invention is to provide a compact and low-cost flowmeter.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above object, and a first technical means of the present invention is to use a laminar flow using an upstream side of a measuring pipe through which a fluid to be measured flows. A flow meter is configured, and a vortex flow meter is configured in series using a downstream side adjacent to the laminar flow meter. A second technical means is the flow meter according to the first technical means, wherein the laminar flow meter constitutes a rectifier by the measurement tube, and detects a pressure difference near an inlet and an outlet of the rectifier. There is a feature. A third technical means is the flow meter according to the first technical means, wherein the vortex flow meter is provided with a vortex generator in the measuring tube and detects a vortex generated by the vortex generator. It is characterized by.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides a flow meter having a wide measuring range covering a measuring range of a laminar flow meter and a vortex flow meter, and a rectifier of a laminar flow meter is used as a rectifier of a vortex flow meter. Thus, a compact and low-cost flowmeter can be obtained.

Hereinafter, embodiments of the present invention will be described with reference to examples shown in the drawings. (Embodiment) FIG. 1 is a schematic view showing an embodiment of a flow meter according to the present invention. In the flow meter according to the present invention, a laminar flow meter 2 is provided upstream of a measurement pipe 1 through which a fluid to be measured flows.
And a vortex flow meter 3 is provided in series on the downstream side adjacent to. FIG. 2 is a schematic diagram showing the laminar flow meter 2,
A rectifier 21 is mounted inside the measurement tube 1. The rectifier 21 rectifies the flow in the measuring tube 1 into a laminar flow, and is a combination of a plurality of honeycomb pipes, a collection of various pipes such as a circular pipe, a square pipe, a deformed pipe, and a plate body. Can be used in the form of a grid,
The length, thickness, density when assembled, and the like of the pipes can be appropriately determined theoretically or by experiment.

An upstream pressure outlet is opened near the inlet of the rectifier 21 and a downstream pressure outlet is opened near the outlet, and the respective pressures are sensed by an upstream pressure pipe 22 and a downstream pressure pipe 23. 24, and a pressure difference between the two is detected. Since the pressure difference is proportional to the flow rate within a certain range, the pressure difference is converted into another appropriate electric quantity by the converter 25 to obtain the flow rate.

FIG. 3 is a schematic diagram showing the vortex flowmeter 3. As shown in FIG.
A vortex generator 31 is attached to the inside of the measurement tube 1, and a vortex detection sensor is provided downstream thereof. As the vortex generator 31, in addition to the triangular prism shown in FIG. 3, a cylinder, a ring, or the like is used. As the vortex detection sensor 32, a heat wire, a thermistor, or a vortex, which detects the vibration of the fluid due to the generation of the vortex as a change in electric resistance. A diaphragm, a strain gauge, or the like that converts a pressure change of the fluid generated by the generation into a displacement of the elastic body is used. In the vortex flowmeter, if the flow velocity distribution in the measurement tube becomes non-uniform in principle, it may affect the generation of Karman vortices and may cause an error. Therefore, it is necessary to discharge a regular and stable vortex.However, in order to remove the effects of turbulence, swirling flow, and distortion of the flow velocity distribution, straight pipes of a certain length or more are installed upstream and downstream. Need. If a sufficient straight pipe section cannot be obtained due to the installation space, or if more accurate measurement is required, a rectifier should be installed.

The present invention has a measuring range that covers the measuring range of the laminar flow meter 2 and the measuring range of the vortex flow meter 3, and both the laminar flow meter 2 and the vortex flow meter 3 have a measuring range. It is made by paying attention to having a rectifier. In FIG. 1, a rectifier 21 composed of a honeycomb pipe or the like is installed in an upstream pipe of the measurement pipe 1, an upstream pressure outlet is opened near an inlet of the rectifier 21, and a downstream pressure outlet is opened near an outlet of the rectifier 21. The pressure in each opening is guided to the differential pressure sensor 24 by the upstream pressure guiding tube 22 and the downstream pressure guiding tube 23, and the pressure difference between the two is detected. A vortex generator 31 composed of a triangular prism or the like is attached downstream of the laminar flow meter 2 so as to intersect the flow, and a vortex detection sensor 32 is further inserted downstream from the opening of the measurement tube 1. Installed. Laminar flow meter 2
Of the rectifier 21 is in a rectified state without a rotational flow or the like, so that the vortex generator 31 is regular and stable without providing a straight pipe section or a rectifier for the vortex flowmeter 3. Karman vortices can be generated.

The differential pressure output obtained by the differential pressure sensor 24 and the output obtained by the vortex detection sensor 32 are input to the converter 4,
In the converter 4, the same processing as that of the converter of the conventional laminar flow meter and vortex flow meter is performed, and the flow rate is obtained. During the flow rate measurement, whether to adopt the flow rate obtained by the laminar flow meter 2 or the flow rate obtained by the vortex flow meter 3 is to preferentially adopt the value measured by one of the flow meters. Alternatively, when the flow rate exceeds the measurement range of the flow meter, the flow rate can be automatically switched to the measurement value of the other flow meter.

[0011]

As is apparent from the above configuration, the present invention has the following effects. (1) A flow meter with a wide measurement range covering the measurement range of the laminar flow meter and the vortex flow meter can be obtained. (2) Since the rectifier of the laminar flow meter and the rectifier on the upstream side of the vortex flow meter can be used in common, a compact and low-cost flow meter can be obtained. (3) Since the conventionally used laminar flow meter and vortex flow meter can be used as they are, a period required for development is short and a low-cost flow meter can be obtained.

[Brief description of the drawings]

FIG. 1 is a view schematically showing an embodiment of a flow meter according to the present invention.

FIG. 2 is a diagram schematically showing a laminar flow meter.

FIG. 3 is a diagram schematically showing a vortex flowmeter.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Measurement pipe, 2 ... Laminar flow meter, 21 ... Rectifier, 22 ... Upstream pressure impulse pipe, 23 ... Downstream pressure impulse pipe, 24 ... Differential pressure sensor
3 vortex flow meter, 31 vortex generator, 32 vortex detection sensor
4 ... Converter.

Claims (3)

[Claims] 1. A laminar flow meter is constructed using an upstream side of a measuring pipe through which a fluid to be measured flows, and a vortex flow meter is constructed in series using a downstream side adjacent to the laminar flow meter. And flow meter. 2. The flow rate according to claim 1, wherein the laminar flow meter forms a rectifier with the measurement tube, and detects a pressure difference near an inlet and an outlet of the rectifier. Total. 3. The flow meter according to claim 1, wherein the vortex flow meter is provided with a vortex generator in the measurement tube and detects a vortex generated by the vortex generator.