JPH06138136A - Method and apparatus for measurement of flow velocity - Google Patents

Abstract

PURPOSE:To accurately measure the flow velocity of a fluid by a simple constitution by a method wherein the image of a beam of scattered light by a tracer flowing in the intermediate layer having a structure of three layers in which the intensity of adjacent layers of light is different from each other and which have been brought into close contact is sensed and the flow velocity is found on the basis of the length of the track of the tracer. CONSTITUTION:In order to supply a gas to a sucking tube 24 and to measure the flow velocity of the gas inside a combustion chamber 36, a tracer is mixed with the compressed air from a compressed-air supply source 44 and supplied to the combustion chamber 36. On the other hand, a laser beam 29 from an argon ion laser source 28 is changed to a flat laser beam 33 by an optical system 32, it is passed through a filter 34, and it is changed to a laser beam 33 having a structure of three layers whose intensity is different from each other and which have been brought into close contact in the thickness direction. A cylinder 21 is irradiated perpendicularly with the laser beam 35, the image of a beam of scattered light by the tracer is sensed by a TV 42 via a reflecting mirror 38, a shutter 40 and an image intensifier 41, and the image is processed by a processing circuit 52. At this time, since the tracer which has been moved only inside the intermediate layer of the laser beam 35 can be discriminated, the flow velocity can be measured accurately on the basis of its track length and its exposure time.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to methods and apparatus for measuring the flow velocity of fluids such as gases or liquids.

[0002]

2. Description of the Related Art A typical prior art is shown in FIG. A flat laser beam 2 called a laser sheet is radiated into the gas mixed with the tracer, and the laser beam is emitted for a predetermined time.
The image is taken by the TV camera 3. As a result, scattered light is generated from the tracer irradiated with the laser light 2, and the scattered light is captured by the television camera 3.

In the prior art shown in FIG. 11 as described above, a tracer 4 passes the light 2 during a period in which the light 2 is imaged by the television camera 3 as shown in FIG. 12 (1). The tracer 5 moves to the position indicated by the reference numeral 4a, and the tracer 5 moves to the position indicated by the reference numeral 5a within the area irradiated with the light 2. When the tracer 4 moves to the position 4a, the state indicated by the thick solid line 4b is
An image is taken as indicated by reference numeral 4c in FIG. 12 (2). When the tracer 5 moves in the light 2 to the position 5a as indicated by the reference numeral 5b, its movement path is as shown in FIG.
An image is taken by the television camera 3 as indicated by reference numeral 5c in (2). FIG. 12C shows loci 4d and 5d that the tracers 4 and 5 actually move, respectively.
Image 5c of the tracer 5 taken by the TV camera 3
Is equal to the actual trajectory 5d, but the imaged image 4c of the tracer 4 that has passed the light 2 is less than the actual trajectory 4d. In this way, when the tracer 4 moves through the light 2 above or below during the image pickup of the television camera 3, even if the length of the imaged image 4c is measured, the actual moving distance, and hence the flow velocity. It is impossible to measure accurately.

Another prior art is "Analysis of vertical vortex breakdown process by laser color sheet method" on pages 5 to 6 of the 69th National Congress of the Japan Society of Mechanical Engineers (October 1991). 13 and is shown in FIG. The emission of the laser source 7 is separated into blue and green beams, and two acousto-optic elements 8,
After pulsing at different timing in 9 and then gathering,
A flat laser beam 11 is produced by using the lens 10 and is emitted into a fluid mixed with a tracer. The blue light from the laser source 7 is represented by reference numeral 7B and the green light is represented by reference numeral 7G. Such blue and green lights 7B and 7G are pulsed and emitted by the acousto-optic elements 8 and 9 with the timing shifted as described above, as shown in FIG. 14 (1). Therefore, when the tracer 12 of FIG. 14 (2) passing through the light 11 moves along the movement locus 13, a blue image is first captured as indicated by reference numeral 14, and then indicated by reference numeral 15. An image of a combined color of blue and green is obtained, and a green image is obtained as indicated by reference numeral 16. FIG. 14 (2) is a side view showing the upper and lower thicknesses of the light 11, and a plan view thereof is shown in FIG. 14 (3).

[0005]

According to the prior art shown in FIGS. 13 and 14, the blue and green lights need to be pulsed at different timings, which complicates the configuration. There's a problem.

It is an object of the present invention to provide a flow velocity measuring method and device having a simple structure and capable of accurately measuring the velocity of a fluid.

[0007]

SUMMARY OF THE INVENTION The present invention is a flow velocity measuring method for measuring a flow velocity by emitting flat light into a fluid mixed with a tracer and imaging the trajectory of scattered light by the tracer for a predetermined time. In the above-mentioned light, the trace of the scattered light imaged by the tracer that passes through the intermediate layer sandwiched between the two layers in which the three layers in which the intensities or colors of the adjacent light layers differ from each other The flow velocity measuring method is characterized in that the flow velocity of the fluid is measured based on the length.

The present invention also provides a tracer supply means for supplying a tracer into a fluid and mixing the tracer, and a light source for emitting flat light into the fluid mixed with the tracer, wherein the light is
At least 3 different temperatures or colors of adjacent layers
Such a light source in which the layers are in close contact with each other, an imaging means for imaging an area where the light of the fluid mixed with the tracer is emitted, and an imaging means for a predetermined time by the scattered light by the tracer in the fluid in the area Of the fluid based on the length of the imaged trajectory of the scattered light by the tracer that passes through the middle layer sandwiched between the two layers in response to the output of the imaging means And a means for measuring a flow velocity, which is a flow velocity measuring device.

Further, the invention is characterized in that the control means is interposed between the area and the image pickup means and guides light from the area to the image pickup means for a predetermined time.

Further, the present invention is characterized in that the control means emits the flat light into a fluid in which a tracer is mixed for a predetermined time.

[0011]

According to the present invention, light such as a flat laser beam is emitted into a fluid mixed with a tracer, and the trajectory of scattered light by the tracer is imaged for a predetermined time by the image pickup means, and the obtained light is obtained. Based on the image of the trajectory and the time, the flow velocity of the fluid can be measured, the light being at least 3 different in intensity or color of adjacent light layers.
It is possible to know whether the layers are closely arranged and thus the tracer has moved in the middle layer sandwiched between the two layers within said time or from said middle layer to the other layers, Based on the image of scattered light obtained by the tracer moving only in the middle layer, the flow velocity of the fluid is obtained,
In this way, accurate flow velocity measurement is possible.

In order to image the trajectory of the scattered light of the tracer by the imaging means for a predetermined time, the flat light emitted into the fluid mixed with the tracer may be emitted for a predetermined time. For that purpose, for example, an acousto-optic element for passing / blocking light may be used, or a light shielding plate having a light passing hole may be rotationally driven to allow light to pass through the light passing hole for the time. .

According to the invention, as described above, in order to enable the imaging means to perform imaging for a predetermined time, the area where light is emitted in the fluid mixed with the tracer and the imaging means. In between, a structure such as a camera shutter that allows light to pass therethrough for a predetermined time may be adopted.

Further, the image pickup means may be constituted so that, for example, the charge-coupled device on which an image is formed by a lens is activated for the predetermined time described above and is disabled for the remaining time.

[0015]

1 is a perspective view of a part of an embodiment of the present invention. In order to measure the flow velocity of the gas supplied from the intake pipe 24 in the combustion chamber of the internal combustion engine, a cylinder 21 similar to an actual internal combustion engine and a movable piston 22 inserted into the cylinder 21 are provided. Cylinder 21
The head 23 is provided with an intake pipe 24 and an exhaust pipe 25, and is further provided with an intake valve 26 and an exhaust valve 27. The cylinder 21 and the piston 22 are made of quartz or acrylic resin and are transparent. Laser light 29 having a circular cross section perpendicular to the axis from the Angon ion laser source 28
Is converted into a flat laser beam 33 by an optical system 32 including lenses 30 and 31 and passes through a filter 34. The flat laser beam 35 passing through the filter 34 is emitted perpendicularly to the axis of the cylinder 21. . This laser light 35
Are radiated into the virtual combustion chamber 36 between the top of the piston 22 and the cylinder head 23 in the cylinder 21.
The light obtained by emitting the laser light 35 into the combustion chamber 36 is supplied to the cylinder 22 as indicated by the reference numeral 37.
Is guided along its axis and the light scattered by the tracer is
From the reflector 38, it is guided as indicated by reference numeral 39,
Image intensifier 4 via shutter means 40
The intensity is increased by 1 and is imaged by the television camera 42 to obtain a plan view of the tracer as it moves. The television camera 42 may be realized by charge-coupled devices arranged in a matrix in which an image is formed by a lens. The shutter means 40 and the image intensifier 41 described above.
May be configured individually, but in one embodiment, a photomultiplier member for enhancing and outputting photons, which is one of the components of the image intensifier 41, is provided.
The intensity of the scattered light is enhanced by being activated by a voltage so that the shutter means is equivalently opened, and the shutter is equivalently disabled by immobilizing the photomultiplier without applying a voltage. It may be possible to achieve the closed state of the means.

In the photomultiplier member, for example, numerous thin channel holes are formed on a thin glass plate, and the inner wall surface of the channel hole emits secondary electrons upon collision of electrons.
When electrons enter each channel hole, the electrons are emitted from the other side while colliding with the inner wall of the channel hole several tens of times due to the potential gradient between the one surface and the other surface of the glass plate. The output electrons can be multiplied by, for example, several thousand times or more with respect to the incident electrons. At this time, the shutter means is equivalently opened, and the potential gradient in the thickness direction of the glass plate is set to zero. Equivalently, the shutter means described above can be closed. Such a glass plate can be called a microchannel plate.

FIG. 2 is an overall system diagram of an embodiment of the present invention including the configuration shown in FIG. In order to supply gas to the intake pipe 24 and measure the gas flow velocity in the combustion chamber 36, compressed air is supplied from the compressed air supply source 44, dust is removed by the filter 45, and a surge tank for pulsation prevention is provided. Four
6 through the flow control valve 47, and is supplied to the pipe line 48.
A tracer supply source 49 is connected to the conduit 48.
The tracer supply source 49 supplies the tracer at a predetermined constant flow rate. The compressed air mixed with the tracer is
It is supplied to the combustion chamber 36 from the intake pipe 24 through the intake valve 26 through the carburetor 50 similar to that provided in an actual internal combustion engine. Instead of using compressed air from compressed air source 44, other compressed gases and gases at atmospheric pressure may be used. The carburetor 50 may be omitted.

The tracer supplied from the tracer supply source 49 has, for example, a true specific gravity of 0.04 g / cm ³ and an average particle size of 4
It is a 0 μm microballoon and is made of synthetic resin.
The tracer may be made of silica or the like, has a hollow spherical shape, or may be, for example, starch powder or the like, and preferably has a uniform particle size. Since such a tracer has a small specific gravity, it moves along with air, which is a gas, and its responsiveness is good.

The output signal of the image picked up by the television camera 42 is given to a processing circuit 52 realized by a microcomputer or the like and arithmetically processed, and the result is displayed by a display means 53 such as a cathode ray tube or liquid crystal, Further, the printer 54 prints on recording paper.

FIG. 3 is a perspective view showing the structure of the filter 34. When the flat laser light 33 passes through the filter 34, the laser light 35 having a three-layer structure of light is obtained. The filter 34 has an opening 56 in a light blocking plate 55 made of a light blocking material such as synthetic resin, metal, or wood.
Is formed in the opening 56, and the light transmitting members 57, 5 are formed in the opening 56.
8,59 are fixed. These light transmitting members 57, 5
8 and 59 are made of a material such as glass or synthetic resin, and have a light transmittance, and therefore their members 57, 58 and 5
The intensity of the transmitted light after passing through 9 is as shown in FIG. The light transmittances I1 of the light transmitting members 57 and 59 are equal, and the light transmittance I2 of the intermediate light transmitting member 58 is set to be larger than that of the two light transmitting members 57 and 59. Therefore, the light transmitting members 57, 58, 59 of the filter 34 are
The light 35 transmitted through is composed of three layers 61, 62, 63, and the intensities of the adjacent light layers 61, 62; 62, 63 are different from each other. The light transmitting members 57, 58, 59 are arranged in close contact with each other in the vertical direction of FIG. 3, and thus the layers 61, 62, 63 of the light 35 are in close contact with each other in the thickness direction. Light 3
The upper and lower thicknesses of FIG.
It may be up to several mm.

In measuring the flow velocity of the gas in the combustion chamber 36, the intake valve 26 is closed, the exhaust valve 27 is opened, the piston 22 is raised to discharge the gas in the combustion chamber 36 to the outside, and then the intake air is taken. The valve 26 is opened, the piston 22 is displaced downward, and the light 35 is emitted into the combustion chamber 36.
At this time, the shutter means 40 is opened for a predetermined time Δt, for example, several 100 μsec to several msec, whereby the television camera 42 can take an image for that time. When the gas mixed with the tracer flows into the combustion chamber 36 and flows, the light 35 is emitted,
The light 35 causes Mie scattering by the tracer in the combustion chamber 36 to generate scattered light. This scattered light is transmitted to the TV camera 42.
Is imaged as described above.

The image taken by the television camera 42 is shown in FIG. During the said time when the shutter 40 is open, when the tracer is in the layer 62 in the middle of the light 35, the television camera 42 causes the FIG.
The image shown in is obtained. This image is an image having a large gradation corresponding to the intensity of the intermediate layer 62 as shown by hatching, and since the tracer has not moved into the low intensity layers 61 and 63, it is a large floor. Only the tonal image is obtained. In the processing circuit 52, the image of the television camera 42 is stored in the memory 64, and the image length L shown in FIG.
1, that is, based on the length L1 of the trajectory of the scattered light imaged by the tracer passing through the layer 62, and the time Δt during which the shutter 40 is open, the tracer in the combustion chamber 36 is calculated based on the equation 1. Is calculated, and thus the flow velocity V of the gas is calculated. Such a figure 5 (1)
The time Δt is determined so that the image 65 of

V = L1 / Δt (1) When the television camera 42 obtains the images shown in FIGS. 5 (2) to 5 (4), the flow velocity V is not calculated. In FIG. 5 (2), the image of the tracer has an image 66 passing through the layer 63 with low light intensity and an image 67 passing through the layer 62 with high light intensity, and in FIG. 5 (3), the light intensity is high. An image 68 that has passed through the layer 62 and an image 69 that has passed through the layer 61 with low light intensity are obtained. Furthermore, in FIG. 5 (4), the image 70 that has passed through the layer 63 with low light intensity and the layer 62 with high light intensity are obtained. An image 71 that has passed through and a image 72 that has passed through the layer 61 with low light intensity are obtained. When such images of FIGS. 5 (2) to 5 (4) are obtained, the virtual lines 73 to 76 are displayed.
, The tracer may have moved further at said time Δt, and therefore each image 66 ...
Even if only the difference of 71 is measured, it is impossible to obtain an accurate flow velocity. Therefore, when the images shown in FIGS. 5 (2) to 5 (4) are obtained, the flow velocity is not calculated. Not when the tracer moves from bottom to top in Figure 3,
When moving from top to bottom, the same operation as described above is performed.

A processing circuit 5 for calculating such a flow velocity V
Operation 2 is shown in FIG. From step n1 to step n2, it is judged whether or not there are low-intensity images 66, 69, 70, 72 in the image captured for the time Δt, and such low-intensity images 66, 69, 7 are detected.
Only when 0 and 72 do not exist, that is, in FIG.
Only when an image 65 having a large intensity is obtained as shown in, the process proceeds to step n3, the length L1 is measured,
In step n4, the flow velocity V is calculated according to Equation 1,
Thus, in step n5, a series of operations ends.

In the above-described embodiment, in the filter 34, the light transmittances I1 of the light transmitting members 57 and 59 are equal, and the light transmittance I2 of the intermediate light transmitting member 58 is large.
As shown in FIG. 7A as another embodiment of the present invention, the light transmittance of the intermediate light transmitting member 58a may be smaller than that of the light transmitting members 57a and 59a on both sides, or As shown in FIG. 7 (2), the light transmittances of these three light transmitting members 57b to 59b may be different from each other. Light transmitting members 57a, 57b; 58
a, 58b; 59a, 59b are the light transmitting members 5 described above.
It corresponds to 7, 58 and 59, respectively.

FIG. 7 shows another embodiment of the present invention.
As shown in (3), the light transmittance of the light transmitting member provided in the opening 56 of the filter 34 is shown by reference numeral 77, and as shown by reference numeral 78 in FIG. 7 (4). It may be changed continuously.

In the processing circuit 52, the discrimination level of the gradation image of the television camera 42 is determined by the discrimination levels 79 to 82 in FIGS. 7 (1) to 7 (4), and the flat light 35 having different light intensity in the thickness direction. The flow velocity V may be calculated as described above based on the length of the image of the tracer within the range discriminated by the discrimination levels 79 to 82.

Although three transmitting members 57, 58 and 59 are provided in the above-described embodiment, four or more transmitting members may be provided.

In the above embodiment, the shutter means 40 was used to capture the trace of the scattered light by the tracer for a predetermined time by the television camera 42. However, as another embodiment of the present invention, the laser of FIG. Such a shutter means may be interposed at a position 83 between the source 28 and the lens 32.

Instead of the shutter means 40 having a mechanical structure, a combination of the acousto-optic element 84 and the light shielding plate 85 shown in FIG. 8 may be used. The acousto-optic element 84 is
An ultrasonic wave generation source 87 is provided in the ultrasonic cell 86, and the incident light 88 is first-order diffracted at the time of ultrasonic wave generation to generate the light 89.
Is transmitted through the light transmission hole 90 of the light shielding plate 85, and when no ultrasonic wave is generated, the light 88 is guided as light 91 without being diffracted and is shielded by the light shielding plate 85.

FIG. 9 is a simplified perspective view of shutter means 165 according to another embodiment of the present invention. A disc-shaped light-shielding plate 166 made of metal or the like is driven to rotate by a motor 168 around an axis line 167 parallel to the optical axis of the light 39. A light passage hole 170 extending in the circumferential direction is formed in the light shielding plate 166. An image similar to the image shown in FIG. 5 can be obtained by capturing an image of the light 39 passing through the light passage hole 170 with the image intensifier 41 and the television camera 42. The light transmission hole 170 enables the television camera 42 to capture an image for the time Δt.

In order to image the trace of the scattered light by the tracer for the above-mentioned predetermined time Δt, as yet another embodiment of the present invention, the charge coupled device of the television camera 42 is activated for the predetermined time. , The remaining time may be configured to be disabled.

As another embodiment of the present invention, the television camera 42 may be used to image the scattered light of the tracer in the lateral direction of the light 35 (perpendicular to the paper surface of FIG. 2),
By doing so, it is possible to obtain velocities having different vector directions. In the above-described embodiment, the light 35 radiated to the combustion chamber 36 is configured such that the light intensity is changed in the thickness direction thereof, but as another embodiment of the present invention, FIG.
The filter 92 shown in FIG. 3 may be used to change the color in the thickness direction of the light 35. In the filter 92,
Light transmitting members 95, 96, and 97 that transmit the laser light 33 are provided in the opening 94 of the light shielding plate 93. These light transmitting members 95, 96, 97 transmit only the respective colors of red, green and blue, for example. If the television camera 42 is a color television camera, the length of the trace image of the tracer of only green which is the color transmitted by the light transmitting member 96 is detected, and the flow velocity V is calculated in the same manner as in the above-described embodiment. Good. Such a color change may be changed stepwise or continuously as in the above-described embodiment.

The invention is not only implemented in connection with the internal combustion period, but can also be implemented extensively in the field of combustion, in the field of air conditioning and in other fields for measuring flow velocity. it can.

[0035]

As described above, according to the present invention, flat light emitted in a fluid mixed with a tracer has at least three layers in which the intensities or colors of adjacent light layers differ from each other. The flow velocity of the fluid is based on the length of the trajectory of the scattered light imaged by the tracer, which is formed by the tracer passing through the intermediate layer sandwiched between the two layers, and the predetermined time imaged by the imager. The flow velocity of the fluid is not measured depending on the trace of the scattered light of the tracer that passes through the intermediate layer and the other layer closely adjacent to it, and thus the flow velocity can be accurately measured with a simple configuration. It becomes possible to measure.

[Brief description of drawings]

FIG. 1 is a perspective view showing a partial configuration of an embodiment of the present invention.

FIG. 2 is an overall system diagram of one embodiment of the present invention including the configuration shown in FIG.

FIG. 3 is a cross-sectional view showing the structure of a filter 34.

FIG. 4 is a diagram showing light transmittances of light transmitting members 57, 58 and 59 of the filter 34.

FIG. 5 is a diagram showing an image of a trajectory of scattered light by a tracer during a predetermined time, which is imaged by a television camera.

FIG. 6 is a flowchart for explaining the operation of the processing circuit 52.

FIG. 7 is a diagram for explaining the configuration of a filter 34 according to another embodiment of the present invention.

FIG. 8 is a cross-sectional view showing a configuration for transmitting / blocking light using an acousto-optic device 84 according to another embodiment of the present invention.

FIG. 9 is a perspective view showing a configuration of shutter means 65 according to another embodiment of the present invention.

FIG. 10 is a front view showing the configuration of a filter 92 according to another embodiment of the present invention.

FIG. 11 is a diagram showing a laser beam 2 of the prior art.

12 is a diagram for explaining the trajectory of scattered light by the tracer in the prior art shown in FIG.

FIG. 13 is a system diagram showing the configuration of another prior art.

FIG. 14 is a diagram for explaining the operation of the prior art shown in FIG.

[Explanation of symbols]

 21 Cylinder 22 Piston 28 Argon Ion Laser Source 32 Lens 33, 35 Flat Light 34 Filter 40, 65 Shutter Means 41 Image Intensifier 42 Television Camera 49 Tracer Supply Source 57, 58, 59 Light Transmission Member 61, 62, 63 Light Layer 84 Acousto-optic element 85 Light shield 92 Filter 95, 96, 97 Light transmitting member

Claims (4)

[Claims] 1. A flow velocity measuring method for measuring a flow velocity by radiating flat light into a fluid mixed with a tracer and imaging a trajectory of scattered light by the tracer for a predetermined time. Based on the length of an imaged trajectory of scattered light by a tracer that passes through an intermediate layer sandwiched between two layers, the three layers in which the intensity or color of the light layer are close to each other A flow velocity measuring method, characterized by measuring the flow velocity of the. 2. A tracer supply means for supplying and mixing a tracer in a fluid, and a light source for emitting flat light in the fluid in which the tracer is mixed, wherein the light is the temperature or color of an adjacent layer. Such light sources, in which at least three layers different from each other are in close contact with each other, imaging means for imaging a region where the light of the fluid mixed with the tracer is emitted, and scattered light by the tracer in the fluid in the region. A means for controlling the image pickup means to capture an image for a predetermined time and a length of a traced image of scattered light by a tracer which passes through an intermediate layer sandwiched between two layers in response to the output of the image pickup means. And a means for measuring the flow velocity of the fluid based on the height. 3. The flow velocity measuring device according to claim 2, wherein the control means is interposed between the area and the image pickup means, and guides light from the area to the image pickup means for a predetermined time. . 4. The flow velocity measuring device according to claim 2, wherein the control means emits the flat light into a fluid in which a tracer is mixed for a predetermined time.