JPH049717A - Flow rate measuring apparatus - Google Patents

Abstract

PURPOSE:To measure the flow rate with good accuracy and stability even in an area of low Reynolds number by applying vibrations of a high frequency to a fluid flowing in a fluid device from outside of the liquid device with use of a vibrator such as a piezoelectric element. CONSTITUTION:A turbulent flow device 11 is provided which generates a turbulent flow by applying vibrations of a high frequency to a fluid running in a fluid logic element F of a fluid logic element flowmeter as a liquid device with use of a vibrator 11a, e.g., a piezoelectric element from outside of the flowmeter. In other words, the turbulent flow device 11 is attached to an upper lid 13 at the side downstream of an inlet 1 to a space 12. Since vibrations of a high frequency generated by force through excitation of the piezoelectric element 11a are added to the fluid from a main nozzle 2, the uniformity of the fluid velocity in the main nozzle 2 is improved, and the viscosity of the fluid is restricted. Therefore, the flow becomes a sufficiently developed turbulence even in an area of low Reynolds number. In this manner, it becomes possible to measure the flow rate with good accuracy and stability over an area of low Reynolds number.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention provides a flow rate measuring device, particularly a flow rate measuring device that makes the flow inside a fluid device turbulent and uses this turbulence to make it possible to measure particles with good particle size. It is related to.

(Prior art) The flow state in the flow path of a fluid device is particularly affected by the flow velocity distribution. In this case, the pressure loss as energy lost due to the flow in the flow path is expressed as Δρ, When the average speed of is v and k is a constant, it is expressed by the following formula.

△ρ=kv'・・・・・・・・・・・・・・・・・・
・・・・・・・・・-(1) On the other hand, in a fluid device, the cross section of the part where the fluid flows is A, the circumference of the inner wall in contact with the fluid is S, the dynamic viscosity coefficient of the fluid is C, and the average depth of the fluid is m-A
/s, the above-mentioned laminar flow or turbulent flow is determined based on the value of the Reynolds number (hereinafter referred to as the Re number) shown by the following equation (2).

When the ν Re number is approximately 2320, this is called the critical Reynolds number (hereinafter referred to as Rec), and the flow in the region above Rec is called turbulent flow, and the flow in the region below Rec is called laminar flow. It is known that the value of n in equation (1) is different between a turbulent region where the Re number is greater than Rec and a laminar region where the Re number is less than Rec.

Further, when the fluid flows inside the fluid device, there is no slippage on the inner wall surface, and the flow velocity is zero. In a thin layer close to the inner wall surface, the fluid is affected by friction with the inner wall surface and the viscous force of the fluid, so the flow velocity is low. That is, within the thin layer of fluid in contact with the inner wall surface, the flow velocity on the inner wall surface gradually increases from zero toward the outside, and eventually becomes equal to the flow velocity of the main flow outside the thin layer. This thin layer is called the boundary layer. In this boundary layer as well, a laminar boundary layer and a turbulent boundary layer exist depending on the Re number.

Furthermore, when the cross-sectional shape of the flow path of a fluid device is rectangular, localized flow occurs in the flow path, and the constant velocity line becomes distorted. This phenomenon is significantly different from the case where the cross section is circular.

When a fluid flows in a fluid device, the flow velocity distribution in the fluid device is composed of the above-mentioned mainstream and boundary layer flow, but this is a configuration in a turbulent region, and in a laminar region, the viscosity of the fluid The effect of force is total destruction.

In this way, the state of the flow velocity distribution greatly influences the flow characteristics within the fluidic device.

In order to measure the flow rate of fluid flowing in fluid equipment, various types of flowmeters have been used, including analog flowmeters such as orifice and turbine meters, as well as fluid vibratory flowmeters such as vortex flowmeters and fluid logic element flowmeters.

(Problem to be solved by the invention) However, the shape of the flow velocity distribution has a great influence on the characteristics of fluid equipment such as flowmeters, and especially in flowmeters that require good measurement particle size, Since the state of distribution is the most important consideration, the range in which a flowmeter can be used with good accuracy is approximately Re Even if the number is 104 or more and there is a turbine meter, it is assumed to be used in a completely turbulent region.

Among these, vortex flowmeters, which belong to fluid vibration type flowmeters, have an Re number of 104 or more in practice, and fluid logic element flowmeters, which belong to the same fluid vibration type flowmeters, have a Re number of about 104 and the pressure loss is at the practical upper limit. There was a problem that there were restrictions on the usage area, such as when getting close to .

This invention was made in order to solve these problems, and does not satisfy the constraints given to these various flow rate measuring devices, that is, the use condition that the device must be in a high Re number region. It is an object of the present invention to provide a flow rate measuring device that can measure with good accumulation and stability even in a low Re number region.

[Means to solve the problem]

Therefore, the flow rate measuring device of the present invention uses a piezoelectric element as a vibrator to force the fluid flowing inside the fluid device to vibrate at a high frequency from outside the fluid device. A turbulence device configured to make a sufficiently developed turbulent flow with an oscillating frequency even when the flow is turbulent, and a means for making the flow rate of the fluid turbulent by the turbulence device. It is equipped with the following.

[For production]

A turbulence device that uses a piezoelectric element vibrator or the like to forcibly apply high-frequency vibrations to the flow inside a fluid device from outside the fluid device can generate sufficiently developed turbulence even in a flow with a low Reynolds number. Lagoon to be able to state.

Furthermore, by means of determining the flow turbulent by the turbulence device, even flows with low Reynolds numbers can be detected with high accuracy.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS A fluid measuring device according to an embodiment of the present invention will be described below with reference to the drawings.

Fig. 1 is a perspective view showing a fluid measuring device according to an embodiment of the present invention, Fig. 2 is a sectional view of the same, Fig. 3 is a space where forced vibration is applied from the outside, and Fig. 4 is an example of a graph showing characteristics. , FIG. 5 is a plan view showing a fluid logic element flowmeter.

In FIG. 4, F is a fluid logic element which is an oscillator that oscillates with the energy of the fluid, M is a fluid logic element flowmeter using this fluid logic element F, and 1 is a fluid logic element flow meter that uses this fluid logic element F. 2 is a main nozzle provided on the downstream side of the inlet 1, 3.3a is a wall in contact with the fluid ejected from the main nozzle 2, and 4.4a is a part of the jet from the main nozzle 2. Feedback loops 5, 5a through which the fluid passes through the feedback loops 4, 4a form a feedback nozzle through which the fluid flows as a jet, and the feedback loop 4.4' and feedback nozzle 5.5a form a feedback mechanism. .

6 is a fluid outlet, 7 is an outlet provided on the downstream side of this outlet 6, 8 is a semiconductor pressure sensor which is a detector for detecting a naturally generated oscillation frequency, and 9 is the wall 3.38.
It is a space surrounded by

The fluid logic element flowmeter M is a fluid logic element that is an oscillator that naturally oscillates due to the energy of the fluid, by combining the wall adhesion phenomenon of a jet due to the Coanda effect described later with the feedback action of a feedback mechanism. F, and a detector 8 that detects this naturally oscillated oscillation frequency.

In the above configuration, the fluid flowing in from the inlet 1 is ejected from the main nozzle 2, or the fluid is unstable because it cannot maintain a straight state due to the space 9 surrounded by the wall 3.3a. It depends on either 3 or 3a.

Due to the Coanda effect, this lopsided flow strongly adheres to the wall 3 or 3a on the side of the flow and becomes stable, but a part of the flow passes through the feedback loop 4 or 4a and is fed back to the wall 3 or 3a. This becomes a jet stream from the nozzle 5 or 5a.

Due to the action of this jet flow, the deviated mainstream is switched to the opposite side. The same phenomenon occurs on the opposite side, resulting in a natural oscillation state. Then, the fluid flows through the outflow path 6
After passing through, it flows from the outflow lower to the outside.

The frequency f of this oscillation is proportional to the flow NQ of the fluid flowing within the fluid logic element flowmeter M, and is expressed as the following equation.

f=C+Q=cAv……+Conflict・……(3) Here,
(2) is the average flow velocity of the fluid flowing through the main nozzle 2 whose cross-sectional area is A, and C is a constant.

The oscillation frequency f naturally oscillated by the fluid flow is detected by the semiconductor pressure sensor 8 or the thermistor thermometer (not shown) installed in the feedback loop 14.4a, but at a small flow rate, the average flow velocity is naturally becomes smaller. Therefore, the Re number also becomes a small value. In a low Reynolds number region, for example, oscillation occurs even when the Re number is 102, but equation (3) no longer holds true and the oscillation frequency becomes significantly small.

Although it varies depending on the various elements of the fluid logic element flow meter, such as the asbet ratio, offset, splitter, and attached wall angle, the accuracy of the flow meter difference is approximately within ±0.5% when the Re number is 103 or more. However, Re number 104
Since the pressure loss is approximately the upper limit of the practical value in terms of degree, there is a tendency that the flow rate range that can be accurately measured becomes narrow in the micro flow rate region.

In particular, those for small flow rates have a small main nozzle width and a rectangular cross section of the main nozzle 2, so they produce localized flow.
The flow velocity distribution is also easily disturbed, which has the disadvantage of adversely affecting instrumental particle size.

FIG. 3 is an example of a graph showing the instrumental error characteristics and pressure loss characteristics of a fluid logic element flowmeter, and it can be seen from the graph that the above-mentioned instrumental error granularity becomes worse.

Five points of two points Regarding fluid logic element flowmeters with such characteristics, the first
As shown in Fig. 2 and Fig. 2, when high-frequency vibrations are applied from the outside to the front and back of the main nozzle 2, or to either of them, the main flow that is flowing is changed to -like, and the action of the boundary layer is changed. As a result, the influence on the flow becomes weaker, resulting in a turbulent flow even in the low Reynolds number region.

An embodiment of the present invention will be described in detail below with reference to FIGS. 1 and 2. In the explanation of the background technology, the same or equivalent parts are denoted by the same reference numerals,
Avoid duplication of explanations.

10 is the fluid measuring device of this embodiment, 11 is a turbulence device using a vibrator 11a such as a piezoelectric element for oscillating forced vibration attached to this fluid measuring device 10, and 12 is a turbulence device that uses a vibrator 11a such as a piezoelectric element for oscillating forced vibration. A space 13 given by 13 is the upper lid of the flowmeter outside of this space 12, and the turbulence device 11 is attached by mounting the vibrator 11a at an appropriate location such as 1i13 on top of this. In this embodiment, a case will be explained in which the vibrator 11a is attached to the upper cover 13 on the downstream side of the main nozzle 2.

14 is an optical fiber, 15 is a ball, and 16 is the optical fiber 14. This is a shuttle-type frequency detector which is a device that detects the frequency oscillated by forced vibration by applying high frequency vibration from the vibrator 11a of the turbulence device 11 to the fluid using the ball 15.

Reference numeral 17 denotes a flow rate measuring means, and a shuttle-shaped detector 16 causes the ball 15 in the pipe to move to the left due to the pressure difference between the feedback loops 4 and 4a.
is used to detect the oscillation frequency fa of the vibration of the fluid brought into an oscillation state by the forced vibration, and measure the flow rate.

Since the principle of the fluid logic element is a two-dimensional phenomenon, the cross section of the main nozzle 2 is rectangular, so localized flow may also occur due to the declination angle.
Attached to the upper lid 13 of the part extending from the downstream side to the space 12,
Since the fluid from the main nozzle 2 is subjected to high-frequency vibrations that are forcibly oscillated by exciting the piezoelectric element 11a, the uniformity of the flow velocity within the main nozzle 2 is improved, and the viscous force of the flow is suppressed. Even a flow in a low Reynolds number region can be made to have sufficiently developed turbulence.

As a result, the flow that has become turbulent can be explained as described above (
3) Equation is applicable even in the low Re number range,
As shown by the broken line in FIG. 3, a region with good measurement accuracy extends toward the small stream side. Therefore, an ultra-micro flow meter with a flow rate of 10117 hours or less can be put into practical use, and the measurable flow rate range is also significantly expanded.

Note that the frequency of the vibrator 11a is several tens of kilohertz, which is an order of magnitude higher than the oscillation frequency f1 of the flowmeter, which ranges from one to several hundred kilohertz, so there is no effect on the oscillation frequency f. For this reason, the method according to this embodiment is
We decided to call it turbulence and to refer to the device that makes this happen.

Fluid vibratory flowmeters, which have been represented only by vortex flowmeters, have a frequency output proportional to the flow rate, have no mechanical moving parts, and have good measurement accuracy. It has many advantages over other flowmeters, such as being able to perform all measurements and having a wide flow range, but it has a rather large pressure loss and is not suitable for measuring low Re numbers. The Re number is 103 or more, and in practice the Re number is 104 or more, which is inappropriate for measuring small flow rates.

Fluid logic element flowmeters belonging to the same fluid vibration type flowmeter are:
It has a complementary relationship with the vortex flowmeter and has a low Re number of less than 104.
However, since the flow path has a rectangular cross section, the uniformity of the flow velocity tends to be lost compared to a flow path with a circular cross section, and it is limited to the low Re number range.

If this restriction is removed by using a turbulence device,
The flow range of the fluid logic element flow meter is significantly expanded to the low Re number side, and at the same time, it becomes possible to measure ultra-small flow rates of 10 IL/h or less.

Together with the vortex flowmeter, the fluid logic element flowmeter has extremely excellent characteristics and can be applied to an extremely wide range from ultra-micro flow rates to large flow rates.

As described above, in one embodiment of the present invention, a piezoelectric element or the like is used as the vibrator 11a for the fluid flowing in the fluid logic element F of the fluid logic element flowmeter M, which is a liquid device, and A turbulence device 11 for creating turbulent flow by applying high frequency vibration from the outside of the element flowmeter M
By providing this, even flows in the low Reynolds number range can be made into fully developed turbulence with a forced oscillation frequency f, and a means for measuring the flow rate of this turbulent fluid can be obtained. 17, it is possible to measure the flow rate with good accuracy and stability over the low Reynolds number region.

Note that the turbulence device can be used not only for fluid vibrating flowmeters, but also for various flowmeters that assume turbulent flow.
Characteristics in the low Re number range are improved.

Furthermore, it can also be applied to fluid equipment other than flowmeters, so
Wide range for floors.

[Effects of the Invention] As described above, according to the flow rate measuring device of the present invention, a piezoelectric element or the like is used as a vibrator to generate high-frequency vibrations from the outside of the liquid device. By providing a turbulence device to create turbulence by giving Since the measuring means is provided, it is possible to provide a flow rate measuring device that can measure the flow rate with good accuracy and stability over a wide Reynolds number range including a low Reynolds number range.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing a flow rate measuring device according to an embodiment of the present invention, Fig. 2 is a sectional view of the same, Fig. 3 is a space where forced vibration is applied, Fig. 4 is an example of a graph showing characteristics, FIG. 5 is a plan view showing a fluid logic element flowmeter. 1...Inlet 2...Main nozzle 7...Outlet 10...Fluid measuring device 11... . . . Turbulent flow device 11a = . . . Vibrator 17 - . . . Flow rate measuring means In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] By using a piezoelectric element as a vibrator to force a high-frequency vibration from outside the fluid equipment to the fluid flowing inside the fluid equipment, it is possible to create sufficiently developed turbulence even in a flow in a low Reynolds number range. 1. A flow rate measurement device comprising: a turbulence device configured to perform turbulence; and means for measuring the flow rate of a flow made turbulent by the turbulence device.