JPH01118721A - Flow rate measuring instrument - Google Patents

Abstract

PURPOSE:To eliminate the need for air bleeding between a measurement tip part and a sensing part by fitting a thin pipe penetrating a cylindrical main body clamped between piping flanges at right angles and fitting >=1 pressure sensor on its surface. CONSTITUTION:The cylindrical main body 12 is clamped 11b between the piping flanges 11a of a conduit 11 and fluid is made to flow, so that the fluid flows around the thin pipe 13 perpendicular to the flow (a) along its surface. Then pressure sensors 14 and 15 (consisting of a semiconductor and a small strain gauge) which are arranged in parallel and at right angles to the flow (a) detect the static pressure and total pressure (dynamic pressure plus static pressure) of the fluid respectively. Their pressure values are connected to a computing element 16 such as an operational amplifier which is provided externally. Then the dynamic pressure, flow velocity, and flow rate are calculated. When plural pressure sensors are used, the mean value of those detected values is calculated. The fitting of this device to the piping 11 is facilitated and measuring operation is speeded up.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flow rate measuring device that calculates a flow rate by detecting the static pressure and total pressure of a fluid flowing in a pipe.

(Prior art) - Conventionally, there are various methods for measuring flow rate, one of which is flow rate measurement using a Pitot tube, which measures differential pressure based on Bernoulli's theorem regarding fluids. As shown in the principle diagram, there is a hole 2 at the tip of the tube 1, and a hole 3 on the circumference.
A passage 2a that penetrates the inside of the liquid pipe j
and 3a, and are connected to pressure gauges 4 and 5, respectively.

When the pitot tube 1 is positioned parallel to the flow a in the direction of the arrow, the fluid is blocked at the tip of the liquid tube 1, so the pressure P acting on the opening 2 is equal to the static pressure Ps of the fluid and It represents the total pressure (Ps + Pd) which is the sum of the dynamic pressure Pd, and the pressure acting on the aperture 3 represents the static pressure Ps. It is now displayed by.

Then, by measuring the differential pressure between the two pressures P and P3, that is, the dynamic pressure Pd, the speed is calculated as follows: V= iτ〒
--Ps completion curve-(ρ: density of fluid) = r (γ: unit volume weight of fluid it), and the flow is 1! tQ is obtained from Q=A, v (A: cross-sectional area of the tube).

[Problem that the invention seeks to solve]

The above-mentioned flow rate measurement using a Pitot tube requires the air to be removed from the pipe from the tip 2 of the Pitot tube 1 to the pressure detection part using the pressure gauge 4.5 each time a measurement is made, so it is not suitable for use in experiments. However, the problem was that it was useless as an industrial measuring instrument.

Furthermore, when there was turbulence in the flow, the average value was obtained by manually raising and lowering the pitot tube 1, but there was a problem in that such an operation was only possible for experimental purposes.

The present invention is a flow meter that measures the difference between total pressure and static pressure, that is, dynamic pressure, to determine the flow rate, and in order to be usable for industry, (i) air venting between the measuring tip and the sensing part is required. (ii) The technical challenge is to create a structure that allows an average value to be obtained when there is turbulence in the flow.

[Means for solving problems]

In order to solve the problems and technical problems of the prior art described above, the present invention has been developed by attaching a thin pipe to a cylindrical body sandwiched between piping flanges by penetrating the pipe in a perpendicular direction. A pressure sensor for measuring static pressure placed parallel to the flow and a pressure sensor for measuring total pressure placed perpendicular to the flow are respectively attached to the pipe, and the wiring for both pressure sensors is passed through the pipe and connected to the outside. The feature is that the flow rate is calculated from the pressure values detected by both pressure sensors by taking it out and connecting it to a calculator.

In practice, the arithmetic unit inputs the sensor output to an operational amplifier when performing analog calculations, and is connected to a microcomputer when performing digital calculations.

[For production]

Since the present invention is configured as described above, when the cylindrical main body is sandwiched between the piping flanges of the pipeline whose flow rate is to be measured and the fluid is caused to flow, the fluid flows through the thin pipe that is perpendicular to the flow. flows around the surface. Therefore, a pressure sensor placed parallel to the flow on the surface of the pipe detects the static pressure of the fluid, and a pressure sensor placed perpendicular to the flow senses the total fluid pressure (dynamic pressure + static pressure) is detected.

Each pressure value detected by the pressure sensor as described above is connected to a calculation H such as an operational amplifier or a microcomputer installed externally through the wiring inside the pipe, where the static pressure detected from both of the above sensors is Dynamic pressure Pd is determined from the difference between Ps and total pressure P, flow velocity y=iac is calculated from the dynamic pressure Pd, and then flow ff1Q=A·g is calculated.

When performing the above calculation in an analog manner, the output of the pressure sensor is inputted into an operational amplifier, and when performed in a digital manner, the output is manually input to a microcomputer.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

Fig. 1 is a sectional view of the main part of a flow rate measuring device showing one embodiment of the present invention, Fig. 2 is a side view taken along the line ■-■ in Fig. 1, and Fig. 3
The figure is a sectional view taken along the line ■-■ in FIG. 2.

In the figure, both flanges lla of two pipes 11.11
, lla, a cylindrical main body 12 is held between the ports zb, and a thin pipe 13 is attached to the main body 12 so as to pass through the main body 12 in a perpendicular direction.

On the surface of the pipe 13, there are one or more pressure sensors 14 (one in the figure) parallel to the flow a for measuring static pressure, and one or more pressure sensors 14 (three in the figure) perpendicular to the flow for measuring the total pressure. A total of 15 sensors 15 are installed respectively. These pressure sensors may be well-known ones made of semiconductors or small strain gauges, such as pressure transducers with a small and thin structure that use a foil strain gauge as a transducer element and form a bridge inside the transducer. There is.

Each of the two types of pressure sensors 14 and 15 is connected within the pipe 13 to wirings 14a and 15a led to the outside, respectively, and these wirings 14a and 15a are connected to a computing unit 16. The arithmetic unit 16 is configured such that the sensor output is input to an operational amplifier when analog processing is performed, and the output is input to a microcomputer when digital processing is performed.

With the above configuration, the static pressure Ps is detected by the pressure sensor 14, and the total pressure P is detected by the pressure sensor 15, and these detected values are transmitted to the wiring 14a,
15a to the calculator 16, where first the dynamic pressure Pd is calculated from Pd=P-Ps, then the flow velocity V is calculated from =fiiA〒, and the flow rate Q is calculated from Q=A-Ps.
Calculated from V. At this time, since three pressure sensors 15 are used, the total pressure of the fluid is the average value of the values detected by these three pressure sensors.

In the above-described embodiments, a structure is described in which a single pipe 13 is provided to penetrate through the cylindrical main body 12, but the pipe can also be formed into a cross shape or a lattice shape. By increasing the number of pressure detection points in this way, it is possible to bring the measured flow rate closer to the flow rate that actually flows inside the pipe.

Further, the mounting position and number of pressure sensors to be mounted are also appropriately selected depending on the flow state in the pipe.

〔Effect of the invention〕

As explained above, according to the present invention, a thin pipe is attached to the cylindrical body held between piping flanges by penetrating it in a perpendicular direction, and a thin pipe is installed on the surface of the pipe parallel to the flow. A pressure sensor for measuring static pressure and a pressure sensor for measuring total pressure placed perpendicular to the flow are installed, and the wiring for both pressure sensors is connected to an external calculator through the above pipe to calculate the flow rate. By doing so, the following effects can be achieved.

(i) The flow rate of the fluid flowing inside the pipe can be determined by sandwiching the cylindrical body between the piping flanges, making it easy to attach the measuring device to the pipe.

(ii) Pressure sensors are made of semiconductors and small strain gauges, so they are thin and small, and even when installed on the surface of a pipe, they have little effect on the flow, and the pressure introduction part and detection part are completely destroyed. Therefore, unlike conventional beat tubes, air does not accumulate between these two parts. Therefore, the measurement operation can be carried out quickly.

(ij) Since the static pressure of the fluid flowing in the pipe is also measured by the pressure sensor, the pressure value can be obtained at the same time as the flow rate.

(iv) Long lifespan as there are no moving parts.

(v) Since multi-point measurement is easy, measurements can be made even if the flow is considerably turbulent.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of the main part of a flow rate measuring device showing one embodiment of the present invention, Fig. 2 is a side view of Fig. 1 I[-IN cotton, and Fig. 3 is drawn from Fig. 2 The sectional view and FIG. 4 are explanatory diagrams showing a conventional example. 11... Piping, lla... Flange,
12... Cylindrical body, 13... Pipe, 14
...Pressure sensor for measuring static pressure, 15...Pressure sensor for measuring total pressure, 14a, 15a... Wiring, 16... Arithmetic unit. Figure 2

Claims (1)

[Claims] 1. A thin pipe is attached to a cylindrical body held between piping flanges by penetrating it in a right angle direction, and a static pressure measuring device is placed on the surface of the pipe parallel to the flow. A pressure sensor and a pressure sensor for measuring the total pressure placed perpendicular to the flow are installed, and the wiring for both pressure sensors is taken out through the above pipe and connected to a computing unit, and the wiring from both pressure sensors is connected to the computer. A flow rate measuring device characterized in that a flow rate is calculated from a detected pressure value. 2. The flow rate measuring device according to claim 1, wherein the arithmetic unit comprises an operational amplifier or a microcomputer. 3. The flow rate measuring device according to claim 1, wherein a plurality of both pressure sensors can be installed at different locations.