JPS6114521A - Device and method of measuring flow rate of gas - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a transducer for measuring the discharge rate of a turbine wheel, and more particularly to a flow meter for measuring gas flow rate at low cost.

(Description of Prior Art) A conventional tube-type gas flow meter has a glass tube installed vertically, a chain tube containing a spherical ball float, and the float in the tube is adjusted in proportion to the flow rate of gas flowing through the glass tube. It moves up and down.

This type of tube-type flow meter has been used for a long time in various gas analyzers, gas measuring devices, gas chromatograph devices, and the like. It is conceivable that it would be advantageous to use an economically appropriate flow rate sensor as an alternative to the glass tube type flow meter and generate an electrical signal proportional to the flow rate, but to the best of the present inventor's knowledge, Such devices have not been adopted at present, probably because the market price of electronic flow sensors is too high.

Most devices for measuring gas flow require a very small amount of gas flow for measurement. The amount of gas required is often in the range of 100 to 1.000 milliliters, and almost all in the range of flow rates of 20 to 10,000 milliliters per minute. Therefore, it is desirable that the gas flow meter has the following characteristics. In other words, it can be manufactured at low cost. The design must be simple and reliable. 20～
Ability to measure flow rates within the range of 10,000-74 minutes. Very low pressure drop across the transducer.

Electrical output must be linearly proportional to flow rate.

be small in size.

Currently, there are two representative types of commercially available gas flow transducers that are widespread and used in a limited sense in the metering industry: thermal sensors and axial turbine sensors.

Due to the high cost of these sensors in low quantities, gas meter manufacturers continue to use traditional tube flow meters for most applications.

The method of using thermal sensors is quite old and was published in 1911 by U.S. Patent No. 172.411 by C. C. C. Thomas of the Journal of the Franklin Institute.
It is first mentioned in the issue. Subsequently, an improvement to the method of thermally detecting flow rate using a combination of thermistors was described by Earle, Niss, and Gutdeyer in "Electrical Manufacturing", October 1956, page 90. This pair of thermistors is still used by manufacturers of thermally sensitive flow transducers.

However, the thermistors must be assembled by hand to obtain the correct result, which is expensive.

Axial flow turbine type flow transducer (written by Twoton,
The Handbook of Transducers for Electronic Measuring Systems (first published in 1969) was originally developed for measuring atmospheric flow, but has since become popular in many other fields.

A typical turbine rotor has propeller blades suspended inside a tube, and when a gas flow passes through the tube, the turbine rotor rotates in proportion to the flow rate. Significant problems arise in terms of bearing friction whenever the measured gas flow rate is below 1000 rn1/min.

Therefore, the sensitivity of this type of turbine-type gas flow meter is high (as the rotor blades must be time-consuming to balance by hand, and the manufacturing costs associated with eliminating friction problems also increase). To increase.

In addition, conventional flowmeters are shaped like a Pelton turbine wheel with a large impact surface area.

Regarding turbine wheels with such a large impact area, U.S. Pat.
No. 3021170, No. 4011757, No. 3867
No. 840, No. 400331, No. 4172381, No. 37921310, No. 3949606, No. 4023
No. 410 and No. 3,701,277.

According to this prior art, it can be seen that much attention has been paid to the structure of the turbine wheel or paddle wheel whose liquid flow rate is to be measured. From the viewpoint of sensitivity, the typical construction of these water wheels is made of plastic whose density is approximately equal to the density of the liquid to be measured. This has the advantage that even though the sheet metal turbine wheel is quite heavy, the flowmeter floats on the liquid being measured, so the weight of the turbine wheel is removed from the bearings and friction problems can be largely reduced. Since all liquids have a fairly high viscosity compared to normal gases, Pelton water turbines either have to have a large number of webs, or have a high flow rate due to the high viscosity of the liquid being measured. The resistance of the turbine wheel then increases to an unacceptable degree and the sensor produces a non-linear electrical output.

Because conventional turbine wheels tended to float in the liquid being measured, at least some of the weight of the turbine wheel was taken off the bearings, which tended to reduce friction problems, as discussed above. However, especially in the case of low-velocity gas, the frictional resistance of the water wheel makes it unsuitable for measuring gas flow rates. Furthermore, since the specific gravity of gas is very small, a gas flowmeter cannot provide the same buoyancy effect as a liquid flowmeter.

US Pat. Nos. 3,788,285 and 3,217,539 disclose propeller-type rotors in flow sensors rather than paddle wheels. A photoelectric circuit is used to detect the flow rate based on the rotation of the rotor, which is detected by blocking the reflected light. However, due to their shape, the area of the light-reflecting surface of these rotors is limited, and furthermore, they are unsuitable for measuring gases with very low flow rates.

SUMMARY OF THE INVENTION The present invention encompasses an apparatus for measuring gases with low flow velocities. The gas to be measured is passed through.Small turbine blades are placed around the disk.
bine blades) or teeth are formed to receive the gas entering the chamber with a substantially constant impact. Gas entering the chamber by nozzle inlet means provided in the housing impinges on the teeth of the disc, causing the disc to rotate.

A photoelectric circuit shines light onto the sides of the disk and measures the relative movement of the disk in response to gas impulses applied to the disk's turbine blades. Since a reflective surface is formed on the side of the disk to reflect the light emitted from the photoelectric circuit, the reflected light can be detected photoelectronically and the gas flow rate can be measured electrically.

The present invention discloses a turbine wheel that can rotate with a gas flow rate of, for example, 20-7 minutes or less relative to air.

In the present invention, the impact torque simply applied to the turbine blades by the gas is equal to the friction created in the opposite direction by the weight of the turbine wheel supported on the shaft bearing support when the measured gas flow level is this low. It turned out that we had to exceed the torque.

When measuring gas with a low flow rate using a flow sensor,
We found that it is important to determine the maximum impact force applied to the turbine blades by the gas flow when the measured flow rate is the lowest among various factors, and we placed the turbine blades at a large outer radius of the impeller. This provides the maximum torque of the impact force generated by the gas flow to the turbine wheel, while at the same time minimizing the weight of the turbine wheel and minimizing the opposite torque due to bearing friction.Furthermore, It has been found desirable to rotate the turbine wheel horizontally about a vertical axis to minimize precision balancing of the turbine wheel.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the introductory drawings, the device of the invention is designated by the reference numeral A. The apparatus A of the invention is particularly used for measuring small gas flow rates, for example on the order of 20 d/min.

Apparatus A can also be used to measure the flow rate of gases where the gas flow rate is low and the pressure drop is as small as 10-20 inches of water column to 1 or 2 inches. One example of how device A can be used to monitor gas flow rates is for environmental purposes, such as in connection with pollutant measurement or emission control. The apparatus A comprises a housing H, through which a measuring gas passes through a chamber C. A disk D is rotatably disposed in a chamber C, a plurality of turbine blades or teeth are formed around the disk D, and the gas enters the chamber C through a nozzle N at an inlet I and receives an impact. Since the photoelectric circuit P1 illuminates the side of the disk D, the reflective surface of the disk D can reflect the light and form an electrical signal representing the gas flow rate.

Disks and Nozzles As previously mentioned, apparatus A is used to measure gas flow rates where the gas flow rate is low and the pressure drop across the flow transducer is low. The inventor has found that when the gas flow rate is low and the pressure drop is small, the structure of the disk D and the teeth T of the disk, the attachment of the disk D to the housing H, and the arrangement of the nozzle N with respect to the disk D are important. . Experimental results revealed that the shape of the gas outlet exiting the nozzle differs depending on whether the drop in gas pressure across the nozzle is above or below a critical value.

Flow transducers according to the present invention are naturally suited for applications where the pressure drop is very low (e.g., 10 to 20 inches of water column).
Since it is used in the following, only the shape of the spout when the back pressure is less than 20 inches of water column will be described. In this case, the outlet usually flows out in a cylindrical parallel flow,
Its surface is gradually slowed down by the surrounding gas,
A mixing zone is formed within which the velocity of the jet eventually decreases to the velocity of the surrounding gas. However, in the case of the present invention, the disk D and the nozzle N are constructed and arranged in such a way that such a problem does not occur. The velocity of the jet outlet exiting from the small, round nozzle is in the speed range of 5 to 20 feet/second in the present case, and FIG. This shows how the impact force decreases as the two move apart.

As is clear from FIG. 2, in order to not substantially lose the advantage of the impact force applied to the turbine wheel blades from the gas nozzle outlet, the turbine wheel blades of the disk D are used in the present invention. It has been found that the blades T must be spaced less than 0.10 inches apart. In the present invention, the blade T extends around the disk D by 10 degrees to 2 degrees.
Segments with an angle of 0 degrees are spaced apart from each other. In this way, when the representative disk D of the present invention is a relatively large disk with a diameter of 0.64 inches and the number of turbine blades T is 24, the disk D
The desired spacing between the two is 0.084 inch, at which time there is almost no loss in impact force from the nozzle N (approximately 4 cf
3). It should be understood, however, that the dimensions described above are merely exemplary and that other dimensions may be used as well. As shown in Figure 2, if the spacing between the teeth T provided around the disk D is too far apart, the rotational frictional resistance of the shaft bearing of the disk D will be reduced and the rotational state will be maintained.
The inventor has discovered that in order to achieve this, the nozzle velocity of the gas coming out of the nozzle N must necessarily be increased. However, increasing the gas nozzle velocity increases the gas flow rate, which is not desirable.

A plurality of teeth T (
FIG. 1) are arranged symmetrically, and each tooth is formed with an impact surface 0611, a top surface α□□□, and a hanging back surface 20+. The impact surface (16j is formed along a radial line extending from the central axis @ of the disk D.

The surface area of the impact surface Q6) is such that when the lowest expected pressure and flow rate of gas enters the chamber using the largest diameter nozzle, the disk D can move so that the next impact surface appears. Size. Furthermore, the impact surface O
D is assumed to have a relatively small portion of about 10% of the radius of the disk D protruding.

From nozzle N, along the long sleeve, as shown by the line (to),
It is noteworthy that the gas enters at an acute angle rather than perpendicularly to the impact plane fl[D. The present inventor has found that it is more advantageous to make the nozzle N and the impact surface (161) at an acute angle than to make them orthogonal to each other. When comparing the inventions, the part of the gas flow applied to the impact surface of the dole at ) flows downward along the impact surface, creating a Bernoulli effect, and an attractive force acts on the tsukdoru impeller to rotate it in a predetermined direction of rotation. However, as shown in Figure 1, the nozzle N of the present invention has a tendency to pull the paddle wheel in the opposite direction.
Since the angle is made at an acute angle of about 15 degrees with respect to l, almost no potential torque loss is observed.

Another feature of the teeth T of the disk D is that the back surface (to) is sloped from the tangent to the top surface (181).

This angle of inclination is usually on the order of 30 degrees, but may be smaller, for example 25 degrees. Since the inclination angle is formed in this way on the back side mark a, when the disk D rotates, a part of the surface 0e is exposed, and the read position (
1A) to the position where the entire surface 06) is exposed (the first
B), when moving to the retracted position where a part of the surface αe is exposed, the impact surface (16) can continuously receive the force of the gas sent from the nozzle N.

Furthermore, as shown in FIGS. 3 and 7, the side surface of the disk D (
16) and the yoke Y loaded with the nozzle N is extremely small, so that almost no gas entering the chamber C escapes to the side, and the incoming gas is Almost all the force acts on the rotation of disk D, entering (
The gas can apply a torque to the disk D almost continuously. In the case of the disk D and nozzle N of the present invention, which are formed taking these points into consideration, each successive pressure applied to the gas pressure from the nozzle N or the impact surface α6) of the tooth T is equal to The tooth T is maintained in a substantially constant state until the tooth T is in a position to receive the blast from the jet port of the nozzle N.

The disk D should be made as thin as possible to reduce the overall weight, since this is the main cause of frictional torque generation during the rotation of the disk D. for example,
The thickness of disk D is 003 inches (0,743+++m)
) is exemplified, but it goes without saying that other dimensions can be adopted. It is desirable that the disk D is made of a lightweight material such as synthetic resin that does not easily deteriorate due to the type of gas flowing through the chamber C. Glass is such a material.
% filled polyphenyline sulfide is exemplified. A suitable number of reflective surfaces or coatings are formed on at least one side of the disk D. The remaining sides of the disk D are typically rendered non-reflective by either forming the disk D from a non-reflective material or by applying a non-reflective paint or similar coating. While the disk D is rotating, a light beam is emitted from the photoelectric circuit P,
Each time the light beam passes through a reflective surface (support), the light beam is reflected and a pulse of the reflected light beam can be generated.

This light beam is used in a photoelectric circuit P to form an electrical signal representative of the gas flow rate through device A.

A shaft (22) (Fig. 7) is provided in the center of the disk D, and is rotatably equipped with a tip (30) made of a suitably hardened metal such as stainless steel. In response to the passage, the disk D is supported while being rotated. A yoke or support saddle Y is formed with an arm (32) on each side of the disk D to hold the disk D in place within the chamber C (FIG. 3) and is inserted as previously described. Prevent gas from flowing to the sides 17).

The arm @ has a sapphire support surface (17) of 7 characters and 4 sizes (Fig. 7) that receives the tip of the shaft (2). The combination 1 of the pivot tip (30) consisting of the sapphire bearing (33) and the stainless steel tip causes rotational movement of the disk D1, and the friction loss at that time is extremely small (G1° nozzle device Nozzle device N is It is removably attached to the yoke Y, and the nozzle diameter can be varied depending on the flow rate to be measured. and the recess formed (3
8) includes a cylindrical sleeve (34) mounted along the first longitudinal portion; Around this part of the snob (34) is a Q IJ marker (
or other suitable seal (42), which is fitted into an annular space (40) formed in the main body member (40) adjacent to the recess t38+t, and which is fitted with a channel/<-C. Seal inlet I.

Installation is done using the sleeve (remaining part of the circle, i.e. the front part (the recess (3)).
8) This is accommodated in a recess (46) formed in the yoke Y adjacent to the nozzle device N. Su IJ
- The tube forms a hollow part in the center that allows gas to pass through. As mentioned above, ejection pipes of different sizes +411
) in the sleeve (34), it is possible to provide nozzle devices N of different sizes and flow capacities.

Housing The housing H can be formed into any shape and is generally formed by connecting a body member (40) and a cap.
26). The gas entering the chamber C through the inlet (2) and the nozzle N exits through the outlet O formed in the main body member (40i).

The body member (40) and the cover (5 as shown) are connected by a port 60 or other suitable fastening means (thereby forming a cavity C).A seal (56) is connected to the body member (4)
0) and the cover (52) to seal the chamber/<-C.

The seal (56) is disposed in a groove (58) formed with the body member +40j i as shown, but the groove is
Even if t521+ is formed, the main body member and cut-
Both (this Jf9 can also be done.

The main body member (4o) has a pocket hole for receiving the yoke, and is adjacent to the recess (to), and a surface (FIB @ (64)) is formed. The width of the chamber C in this part of the main body member is approximately equal to the width of the yoke Y, as shown by the arrow -. The yoke Y and nozzle device N are held firmly in place in the chamber C.

In the preferred embodiment, disk D and apparatus A are arranged so that disk D is rotatable about a vertical axis, but they can also be arranged so that disk D is rotatable about a horizontal axis. . In the latter case, the gas velocity of the nozzle to start the rotation of disk D is greater, but this means that the accuracy of the balance of the disk when it is mounted rotatably around a horizontal axis is not as good as in the former case. This seems to be due to a reason. FIG. 8 is a plot of the nozzle gas velocity required to start rotation of the disk, showing this phenomenon as a function of the nozzle inner diameter.

photoelectric circuit The photoelectric circuit P is shown in FIGS. 4 and 5.

The photoelectric circuit P includes, for example, an infrared light emitting diode (LED).
) and, for example, an optical-Darlington transistor pair (70
1, which receives the reflected light,
It converts the sensed light into an electrical output signal.

The light emitting diode (8) and the transistor pair (7111) are arranged close to each other on the common side of the disk D (FIG. 4). Deployed in very close proximity,
The distance that light must travel through chamber C is minimized. In this way, the flow rate of a somewhat cloudy or translucent gas can be measured. This was unimaginable with conventional structures that require light to pass through the chamber. Light emitting diodes and phototransistors (+70) may be arranged on both sides of the disk D1 in the chamber C, if necessary.

The electrical signal formed by the transistor pair (7) can be measured or monitored in several ways. For example, by connecting it to a pulse counter (2), it responds to the sensed light and the transistor pair σ The number of electrical pulses formed by the counter (2) is provided as an input to a display, iff41, for observation and monitoring.
The output signal from 0) is as shown by the imaginary line in FIG.
It is also possible to connect to a pulse meter to measure and display the number of electrical pulses formed by the transistor pair T1. Furthermore, the data pulses from the transistor pair ('?O) can also be converted to DC level by a D-A converter (7) if required.

The number of electrical pulses formed on the photoelectric circuit P is
, which represents the gas flow rate passing through the chamber C. That is, light is applied to the side of the rotating disk D from the light emitting diode haze. When the reflective surface (a) passes through the light emitting diode (681), the light is reflected towards the transistor pair qα.The time for the reflective surface (a) to face the transistor pair 17Ql and reflect the light to the transistor pair is determined by It is proportional to the rotational speed of
Therefore, the gas flow rate can be measured. FIG. 6 shows that the present invention provides a linear relationship between air flow rate and light beam pulses per second delivered from the reflective surface, ie, the output signal from transistor pair q0.

To measure the flow rate of gas using the present invention, the gas to be measured is introduced through the inlet I, applied to the teeth T, and the disk D is rotated. When the disk D rotates, the reflective surface (■) formed on the side of the disk D passes through the light emitted from the light emitting diode (681), and the light reflected from the reflective surface (681) passes through the transistor pair ('?α). is received by the device A to form an electrical output signal representative of the gas flow rate through the device A.

The foregoing disclosure and description of the present invention is merely exemplary and illustrative, including details of circuit element connections and illustrated construction, as well as sizes, shapes and materials (which may depart from the spirit of the invention). Various changes can be made without doing so.

[Brief explanation of drawings]

FIGS. 1, 1A, 1B, and 1C are views showing the disk and nozzle used in the apparatus of the present invention in slightly different positions. FIG. 2 is a graph of impact force as a function of nozzle spacing for the structure of FIG. 1 in accordance with the present invention. FIG. 3 is a partially cutaway top view of the device according to the invention. FIG. 4 is a side view of the apparatus shown in FIG. 1. FIG. 5 is a schematic diagram of the electrical circuit of the device according to the invention. FIG. 6 is a graph showing the output voltage as a function of the flow rate for varying nozzle diameters of a device according to the invention. FIG. 7 is a side view showing the installation of the rotating disk of FIGS. 1 and 4 according to the present invention. FIG. 8 is a graph showing the gas velocity within the nozzle as a function of the nozzle diameter in an apparatus according to the present invention. A... Gas flow rate measuring device C... Chamber D... Disk H... Housing T... Teeth N... Nozzle P... Photoelectric circuit applicant
Robert Day, McMillan, Jr. FIG, IC

Claims (15)

[Claims] (1) A device for measuring a small gas flow rate, in which a chamber through which the gas to be measured passes is formed in the housing, a disk is rotatably arranged in the center of the chamber, and a chamber is provided around the disk. forming a turbine blade with an impact surface for impacting the incoming gas, and providing nozzle means in the housing to direct the gas entering the chamber onto the impact surface of the disk, providing light to the side of the disk and also gas flow measurement, comprising a photoelectric circuit for measuring the relative motion of a disk in response to a gas impact on an impact surface of the disk, said disk having a reflective surface on a side of the disk for reflecting light emitted from the photoelectric circuit means. Device. (2) While the impact surface moves away from the nozzle, the turbine blade is formed with a back surface that is at an acute angle with respect to the tangent to the disk so that it can continuously receive the gas sent from the nozzle. Equipment described in Section. (3) The nozzle means is attached at an acute angle to the impact surface so that the gas impinges on the impact surface.
Equipment described in Section. (4) The device according to claim 1, wherein the impact surface is formed along a radial line extending from the center of the disk. (5) The device according to claim 1, wherein the impact surface is formed along a portion of a radial line extending from the center of the disk. (6) The disk is provided with a shaft in the center and a removable carrying means for attaching the disk in the chamber, and the shaft is formed with a pivot chip that supports the disk in a freely rotatable manner;
2. Apparatus according to claim 1, wherein said conveying means comprises a bearing surface for rotatably engaging said shaft. (7) An apparatus according to claim 6, wherein the conveying means is provided with nozzle means for applying gas to the teeth of the disk. (8) The device according to claim 1, wherein the teeth that receive the gas sent from the nozzle during rotation of the disk are formed individually and in succession. (9) In a flowmeter that includes a housing having a chamber through which the gas to be measured passes and a photoelectric circuit that measures the relative motion of a rotating body due to the gas passing through the housing, the disk member is placed inside the chamber. The disk is rotatably arranged, and a plurality of turbine blades are formed around the disk to receive the impact of the gas entering the chamber, and a portion of the disk has a reflector that reflects light emitted from the photoelectric circuit. A rotating body device that measures a small amount of gas flow on a surface. (10) The apparatus according to claim 9, wherein the turbine blade is formed with a back surface at an acute angle with respect to the tangent to the disk so that the impact surface can continuously receive gas during rotation of the disk. (11) The device according to claim 10, wherein the impact surface is formed along a radial line extending from the center of the disk. (12) The device according to claim 10, wherein the impact surface is formed along a portion of a radial line extending from the center of the disk. (13) In a flowmeter that includes a housing provided with a chamber through which a gas to be measured passes and a photoelectric circuit that forms an output proportional to the gas flow rate, a disk member is used to freely support the member in rotation. A shaft with a pivot tip is placed in the center, a turbine blade is formed around the disk that receives the impact of the gas entering the chamber, and a part of the disk reflects the light emitted from the photoelectric circuit. A rotating disk device for measuring a small gas flow rate, wherein a reflecting surface is formed, a conveying means for attaching a disk is removably provided in the chamber, and the conveying means has a bearing surface for rotatably attaching a shaft. 14. The apparatus according to claim 13, wherein the conveying means comprises a nozzle device for bombarding the turbine blades with gas at controlled positions. (15) The gas to be measured is applied to an impact surface formed around a rotatable disk in a chamber through which the gas passes, and light from a photoelectric circuit is applied to a reflective surface formed on the side of the disk. Measuring a small gas flow rate characterized by comprising the steps of detecting the amount of light reflected from a reflective surface on the disk and measuring the relative movement of the disk in response to the detected amount of light. how to.