JPH0338537B2 - - Google Patents

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a method for visualizing a flow.

(Prior art) Up until now, flow visualization has often focused on relatively slow, steady flow, but recently, it has become possible to visualize not only periodic flows due to the creation and disappearance of eddies, but also In addition to visualizing unsteady flows around moving objects, it is becoming possible to measure flow velocity distributions from these records. moreover,
With visualization methods, it is not only possible to intuitively understand the overall pattern of the flow area, but also to simultaneously measure the flow velocity distribution over the entire area, and if continuous imaging is used, it is also possible to see temporal changes in the velocity distribution. As a result, interest in flow visualization, particularly in the tracer method, which allows easy observation of trends over the entire flow area at a glance, has increased significantly.

(Problem to be solved by the invention) However, in the conventional tracer method, air bubbles, dye liquid such as ink, or powder such as plastics are injected into the flow as a tracer, and the flow is visualized using the movement. Therefore, qualitative information can only be obtained within the range in which the movement of the tracer can be observed. For example, the dye liquid tracer method is limited to a laminar flow with a flow rate of 1 m/s or less because it tends to stain the observation window and the dye liquid tends to diffuse, and the powder tracer method requires a large amount of tracer to be stably supplied over a long period of time. Each method has the disadvantage of high costs because it requires equipment for preparation and separation and collection of tracers, and in each case, complex flows cannot be visually recognized. In addition, in the tracer method using air bubbles, there was no means to stably supply a large amount of fine and homogeneous air bubbles in a dense manner, so even if you tried to obtain a large amount of air bubbles, you could only obtain heterogeneous air bubbles. However, it cannot be used for quantitative analysis due to large errors due to differences in specific gravity, and bubbles have a centripetal property that gathers at the center when the flow swirls, so it is not possible to accurately track flow fields that involve swirling. There is.

In this way, in the conventional tracer method, the flow is visualized only by the movement of the tracer, which is a foreign object, so it is not possible to realize the visualization of complex flows or flows in arbitrary cross sections, and it is difficult to visualize the flow qualitatively or partially. It only provides quantitative information.

The present invention aims to improve the above-described tracer method and provide a flow visualization method that can detect not only qualitative information but also quantitative information such as concentration fields and velocity fields.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention forms a flow field in a transparent model aquarium with a colloid solution containing colloid particles and having a uniform concentration. The flow in an arbitrary cross section is visualized by scattering the slit light irradiated onto the flow field by the colloid particles, and the intensity of the scattered light is quantitatively measured by a light detection means that detects the intensity of the light. This is a flow visualization method characterized by the following.

(Function) A flow field is formed in the model water tank by a colloid solution containing colloid particles and a uniform concentration. When this flow field is irradiated with slit light, the slit light is scattered by the colloid particles, so the scattered light is The flow state in any cross section can be visually observed depending on the strength and weakness.

Furthermore, by quantitatively measuring the intensity of the scattered light using a light detection means that detects the intensity of light, the concentration field, velocity field, and their fluctuations can be quantified from outside the flow without contact. Can be measured accurately.

(Example) The configuration of the present invention will be described in detail below based on an example shown in the drawings.

FIG. 1 schematically shows a visualization device that implements the flow visualization method of the present invention. The visualization device includes a model water tank (hereinafter referred to as water tank) 1 that reproduces a flow field to be visualized, and a fluid supply unit that supplies a liquid/colloid solution mixed with colloid particles 4 to this water tank 1, for example, from the bottom. 2 and a slit light source 3 that irradiates a localized light 5 onto the flow field within the water tank 1. In this visualization device, the colloidal solution that flows in from the bottom of the water tank 1 reproduces a flow field within the water tank 1 and is then drained from the drain port 6 above the water tank 1 through a water pipe (not shown). The colloidal solution is normally drained as is or after being subjected to necessary treatment, but it is also possible to circulate it to the fluid supply unit 2 and use it again. The colloidal solution can be introduced from above the water tank 1 and drained from the bottom, or it can be introduced from the side.

In the case of this embodiment, as shown in FIG. 2, the water tank 1 is made of a translucent material such as acrylic resin or glass and is formed into a rectangular cylinder shape with a square cross section, and has a drain port 6 at the top. It has an injection port 7 on the bottom surface. This water tank 1 is only a container for forming a flow field in the case of a water flow model such as a nozzle or a burner, but it is used as a model in itself when visualizing the flow of fluid in a pipe. Therefore, aquarium 1
The shape is not limited to that shown in the drawings, and can take various shapes depending on needs, such as a cylinder or an elbow shape. Further, a model, such as a nozzle model or a burner model 8, which reproduces the flow field to be observed is generally attached to the injection port 7 on the bottom of the water tank. However, there are cases in which the model is placed in the aquarium 1 away from the injection port 7 and no change is made to the flow at the injection port 7. In the case of this embodiment, a burner nozzle model 8 and a burner tile model 9 are installed,
In order to measure the mixing state and ratio of fuel and air, a fluid containing colloidal particles 4 (corresponding to fuel) is injected from the burner nozzle model 8, and a fluid containing no colloidal particles (corresponding to fuel) is injected from the burner nozzle model 8. The burner tile model 9 is provided so as to mix the two in the burner tile model 9 by injecting secondary air (corresponding to secondary air). Of course, the number and position of the injection ports 7 are not limited to those shown. For example, when a water flow model is used when a plurality of burners are installed in a furnace, the effect of burner arrangement on heat distribution may be observed using the water flow model. In addition, since the entire peripheral wall of the water tank 1 of this embodiment is formed of a transparent material, the surface facing the observer or observation equipment corresponds to the observation window 10, and the surface facing the slit light source 3 corresponds to the incident light source. This corresponds to the optical window 11. However, the entire circumferential wall of the aquarium 1 does not need to be made of a translucent material, and it is sufficient that at least the observation window 10 and the incident light window 11 are made of a transparent material. This observation window 1
0 and the incident light window 11 are in the same direction as the incident direction of the slit light 5.
The optimal diffused reflection can be obtained at an angle θ between 90 and 145 degrees, so it is best to position it within that range.
If the water tank 1 is formed into a cylindrical shape, the circumferential wall should be
The range of 145 degrees can be changed by forming it with a perforated material. Note that the observation window 10 and the incident light window 1
If the peripheral wall surfaces other than 1 (including the bottom surface) are formed of light absorbers, observation can be facilitated because only the colloidal particles 4 stand out due to scattered light without turning off the illumination in the observation chamber. Here, the light absorber may be one in which only the inner surface of the aquarium 1 is colored black. Further, when observing the state of the flow field in a plane orthogonal to the flow direction, that is, in slices, the range of 90 to 145 degrees with respect to the slit light 5 crossing the flow field corresponds to the ceiling and upper side of the aquarium 1. Therefore, in this case, an observer or observation equipment is placed above the aquarium 1.

The colloidal solution supply unit 2 that supplies the colloidal solution to the water tank 1 described above is provided with a colloid particle injection part 13 in the middle of the pipe line 12 that connects the fluid supply source (not shown) and the water tank 1, and injects colloid into the fluid that is being pumped. By forcefully injecting particles 4 quantitatively, a colloidal solution of a constant concentration is supplied. Of course, the supply unit 2 is not limited to the one described above. For example, a colloidal solution adjusted to a low concentration in advance may be stored in a tank and taken out using a metering pump and pumped into the water tank 1.

Generally, colloids have a diameter of approximately 0.1 μm to 1 μm.
However, in this specification, it refers to a material system containing fine particles that float in a liquid and do not easily settle. This colloidal solution consists of a liquid (dispersion medium) that forms a flow field and colloidal particles (dispersed phase) 4 that function as tracers, and the colloidal particles 4 are used as much as possible without affecting the formation of the flowfield. It is maintained at a dense concentration. Although water is most commonly used as the liquid, it is not limited to this, and other liquids may be used as necessary. For example, to prevent refraction of incident light, water may be used that has been adjusted to have the same refractive index as water tank 1 by dissolving sugar or the like.

The colloid particles 4 include spherical particles (solid phase) of so-called fine ceramics such as MgO, SiO, Al ₂ O ₃ , etc., for which fine particles with a diameter of about 1 μm are easily available;
It is preferable to use milk or the like (liquid phase) containing extremely fine milk fat globules. In particular, milk is one of the most preferred colloid particles because it is easily available, inexpensive, easy to handle, and provides high-intensity scattered light. In processed milk, milk fat globules are generally less than 2 μm in diameter (41.8% less than 1 μm, 1-2 μm).
47.7%), making it suitable for forming colloids in liquids. Therefore, in the case of this example, 0.2% by weight of processed milk is included in water to form a hydrophilic colloid.

Note that when fine ceramic particles are used, unlike milk, they cannot immediately form a colloidal state just by pouring them directly into a flow. Therefore, we prepared what can be called a highly concentrated colloidal solution by soaking fine ceramics in a small amount of water in advance. This highly concentrated colloid solution is, for example,
It is produced by stirring and mixing a certain ratio of water and fine ceramic particles in a tank under reduced pressure, and completely defoaming the air bubbles attached to the surface of the particles. This highly concentrated colloid solution is
It is quantitatively supplied to the fluid supply unit 2 using a metering slurry pump and mixed with water supplied from the fluid supply to form a colloidal solution of constant concentration.

The flow field in the water tank 1 is provided so that an arbitrary position of the flow can be sectioned and visualized in one plane by local illumination represented by a slit light 5. The slit light 5 can be easily obtained by a known slit light source 3 or by expanding it using a two-dimensional optical system. Furthermore, by oscillating the laser beam as it is at high speed, it is also possible to obtain a substantial slit beam.

Furthermore, three-dimensional visualization may be performed by emitting the slit light continuously and instantaneously at different positions. The slit light 5 is normally incident on the water tank 1 at right angles to prevent refraction. However, if the refractive index of the water that forms the flow field is made to be the same as that of the material of the water tank 1 by adding a medium that increases the refractive index such as sugar or increasing the temperature, the slit light 5 The angle of incidence is not limited. In this specification, the slit light 5 includes the substantial slit light generated by the above-mentioned laser beam.

The flow visualization method of the present invention will be described with respect to a burner model using the visualization device configured as described above.

First, a necessary amount of a fluid/colloid solution densely containing homogeneous colloidal particles 4 is stably supplied to the water tank 1 and blown out from the injection port 7 at the bottom of the tank to create a flow field in the water tank 1. The colloidal solution used is one that forms a flow field and whose total amount is adjusted in advance to a concentration suitable for visualization, or one that is mixed and adjusted during pumping in the fluid supply unit 2.
Next, this flow field is irradiated with slit light 5 and the colloidal particles 4 diffusely reflect the flow, thereby extracting and visualizing the flow in an arbitrary cross section. Scattered light can best be detected in the range of 90 to 145 degrees from the direction in which the slit light 5 is incident, so it is observed or measured within that range. Visualization using this scattered light is
Unlike conventional visualization methods in which only the outer ring of the flow field can be observed, since the movement of colloidal particles 4 in one cross section is tracked, flow phenomena, flow direction, etc. can be accurately known. Moreover, the intensity of light diffused by sufficiently fine and homogeneous colloidal particles 4 is considered to be proportional to the number of colloidal particles in a unit volume, that is, the colloid density, which means that the intensity of the diffused light corresponds to the concentration. Therefore, the concentration of the flow and its fluctuations can be visually observed at the same time depending on the intensity of the scattered light due to the density of the colloidal particles 4.

In addition, since the intensity of the scattered light and its fluctuations contain various quantitative information such as the concentration of the liquid and its fluctuations, it is possible to perform various quantitative measurements by detecting this scattered light using an ITV camera. It is also possible to use For example, the flow field in an arbitrary section visualized by diffusely reflecting the slit light 5 due to the presence of the colloidal particles 4.
A photo is taken by a TV camera 20, zoomed in as necessary, and projected onto a cathode ray tube of a monitor television 21. is converted into an electrical signal, which is passed through a filter 23 to remove screen scan signals, and then output from a transient recorder 24 to an oscilloscope 25 or an XY recorder 26 for measurement or recording (Fig. 4). reference). In this measurement, it is necessary to adjust the monitor so that even the darkest part of the measurement area shows a minute output, for example, about 3 mV, and so that the brightest part is close to the maximum value of the measurement range. The measurement position is changed by moving the photo sensor 22 on the cathode ray tube or by slightly moving the camera 20 during traverse (not shown).

Here, the concentration is based on the knowledge that there is a proportional relationship between the brightness intensity of scattered light and the concentration level, that is, in two fluids in a mixed state, as the proportion of fluid that does not contain colloid particles 4 increases, Based on the knowledge that the amount of colloidal particles decreases and the brightness is lost, the voltage obtained by electrically converting the brightness at the outlet of burner model 8 is set as the reference voltage (equivalent to 100% concentration), and at this reference voltage It is determined by dividing the measurement voltage obtained from the brightness of scattered light at the measurement point where the two fluids are mixed.

Furthermore, by measuring the concentration at predetermined measurement points using a computer, we can calculate combustion temperature, CO amount, and O ₂
It is also possible to simulate the distribution state of the amount, etc.

Furthermore, although it is virtually impossible to specify one colloidal particle 4 and measure the time it takes for that colloidal particle 4 to move a predetermined distance L, the time it takes for a group of colloidal particles at a certain concentration to move is close to each other. Based on the knowledge that it is possible to grasp the time lag in the concentration change measured by the point photo sensor, another photo sensor 27 is installed on the cathode ray tube of the concentration measuring device described above, as shown in FIG. The velocity can be determined by detecting the travel time of the colloidal particles moving between the two photo sensors 22 and 27. Furthermore, the fifth
In the figure, numeral 28 is a computer, 29 is a display, and 30 is a printer.

[Effects of the Invention] As is clear from the above description, the flow visualization method of the present invention involves forming a flow field in a transparent model water tank with a colloid solution containing colloid particles and having a uniform concentration; By scattering the irradiated slit light by the colloidal particles, the flow in any cross section can be visualized, so it is possible to not only qualitatively observe the flow state and flow direction in a certain cross section, but also to observe the scattered light. The concentration distribution and fluctuations throughout the flow can be observed at a glance from the strength and weakness of the flow. In addition, colloidal particles have excellent ability to follow the liquid that forms a flow field, and do not exhibit centripetal behavior when the flow swirls, making it possible to accurately visualize flows that involve rotation or vortices.

Further, the present invention quantitatively measures the intensity of scattered light generated by colloidal particles densely present in a liquid using a light detection means that detects the intensity of light,
Since the flow is visualized, the states of dispersion, aggregation, and movement of colloidal particles in the flow field, that is, the liquid concentration, velocity, and their fluctuations can be quantitatively understood as the intensity and fluctuations of scattered light. Moreover, the intensity of the scattered light is considered to be proportional to the number of colloidal particles in a unit volume, which means that the intensity of the brightness of the scattered light is proportional to the concentration level. Therefore, since the intensity and fluctuations of scattered light are detected using an optical system from outside the flow, it is possible to quantitatively measure the concentration field, velocity field, fluctuations thereof, etc. without contact.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a visualization device that implements the flow visualization method of the present invention, Fig. 2 is a cross-sectional plan view of a model aquarium, Fig. 3 is an explanatory diagram showing a visualized flow field, and Fig. 4 is a diagram of the present invention. FIG. 5 is a schematic diagram of a concentration measuring device using the flow visualization method of the invention, and FIG. 5 is a schematic diagram of a velocity measuring device using the same visualization method. 1...Model aquarium, 4...Colloid particles, 5...
... Local illumination light (slit light), 10 ... Observation window, 11 ... Incident light window, 20 ... TV camera, 2
1... Monitor TV, 22... Photo sensor (light detection means).

Claims (1)

[Claims] 1. A flow field is formed in a transparent model water tank with a colloid solution containing colloid particles and a uniform concentration, and the flow in an arbitrary cross section is visualized by scattering the slit light irradiated onto this flow field by the colloid particles. 1. A flow visualization method comprising quantitatively measuring the intensity of the scattered light using a light detection means that detects the intensity of the light.