U.S. patent application number 11/139067 was filed with the patent office on 2005-10-06 for method for measuring the flow of fluids.
This patent application is currently assigned to Osaka Gas Company Limited. Invention is credited to Hirano, Akira, Ikeda, Yuji, Ipponmatsu, Masamichi, Nakajima, Tsuyoshi, Nishigaki, Masashi, Suzuki, Minoru, Tsurutani, Tsuyoshi.
Application Number | 20050219507 11/139067 |
Document ID | / |
Family ID | 27460232 |
Filed Date | 2005-10-06 |
United States Patent
Application |
20050219507 |
Kind Code |
A1 |
Ipponmatsu, Masamichi ; et
al. |
October 6, 2005 |
Method for measuring the flow of fluids
Abstract
The disclosed method of measuring the flow of a fluid with a
porous particulate ceramic tracer and an optical instrument is
characterized in that spherical particles having diameters in the
range of 0.5 to 150 .mu.m are used as the tracer. Inasmuch as the
tracer particles for flow measurement are spherical, the sectional
area of scattered light to be detected by an optical sensor means
is constant regardless of the orientation of particles.
Furthermore, spherical particles have no surface irregularities
that might cause concatenation so that individual particles are not
agglomerated in tracking a fluid flow, thus contributing to
improved measurement accuracy.
Inventors: |
Ipponmatsu, Masamichi;
(Nishinomiya-shi, JP) ; Nishigaki, Masashi;
(Osaka-shi, JP) ; Hirano, Akira; (Nishinomiya-shi,
JP) ; Nakajima, Tsuyoshi; (Takarazuka-shi, JP)
; Ikeda, Yuji; (Kobe-shi, JP) ; Suzuki,
Minoru; (Osaka-shi, JP) ; Tsurutani, Tsuyoshi;
(Kobe-shi, JP) |
Correspondence
Address: |
JORDAN AND HAMBURG LLP
122 EAST 42ND STREET
SUITE 4000
NEW YORK
NY
10168
US
|
Assignee: |
Osaka Gas Company Limited
Osaka-shi
JP
|
Family ID: |
27460232 |
Appl. No.: |
11/139067 |
Filed: |
May 26, 2005 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11139067 |
May 26, 2005 |
|
|
|
10151839 |
May 20, 2002 |
|
|
|
6903812 |
|
|
|
|
10151839 |
May 20, 2002 |
|
|
|
09568866 |
May 9, 2000 |
|
|
|
6414748 |
|
|
|
|
09568866 |
May 9, 2000 |
|
|
|
08708906 |
Sep 5, 1996 |
|
|
|
6118519 |
|
|
|
|
08708906 |
Sep 5, 1996 |
|
|
|
08283476 |
Jul 22, 1994 |
|
|
|
08283476 |
Jul 22, 1994 |
|
|
|
07841913 |
Feb 25, 1992 |
|
|
|
Current U.S.
Class: |
356/28 |
Current CPC
Class: |
G01F 1/661 20130101;
G01P 5/005 20130101; G01F 1/7086 20130101; G01P 5/20 20130101; G01P
5/26 20130101; G01F 1/704 20130101; G01P 5/001 20130101 |
Class at
Publication: |
356/028 |
International
Class: |
G01P 003/36 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 1, 1991 |
JP |
3-036235 |
Aug 5, 1991 |
JP |
3-195472 |
Aug 28, 1991 |
JP |
3-217327 |
Aug 28, 1991 |
JP |
3-217335 |
Claims
What is claimed is:
1. A method of measuring the flow of a fluid using an optical
instrument and a porous particulate ceramic tracer which comprises
employing a spherical particulate ceramic tracer having a particle
diameter within the range of 0.5 to 150 .mu.m as said tracer.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method for measuring the
flow of fluids, herein after referred to as "flow measurement". It
should, however, be understood that the term "flow measurement" as
used throughout this specification means not only a measurement of
the flow velocity of a gas, such as air, fuel gas, etc., or a
liquid, such as water, liquefied gas, etc., but also a topological
visualization of the distribution of such gas or liquid.
BACKGROUND OF THE INVENTION
[0002] Prior Art
[0003] The particles heretofore used as tracer particles in optical
flow measurements are porous particles made of SiO.sub.2,
TiO.sub.2, SiC or the like which are obtainable by a
coprecipitation process or from a natural material such as the
mineral ore. These particles generally have a mean particle
diameter of about 0.5 to 150 .mu.m.
[0004] In a measurement of the flow velocity using a laser device
such as a laser Doppler velocimeter, a phase Doppler velocimeter or
the like, tracer particles somewhere between 0.5 and 10 .mu.m in
mean diameter, in particular, have so far been employed.
[0005] In technologies involving a visualization of a flowing fluid
by photographing the distribution of tracer particles in the fluid
with the aid of an instantaneous, powerful light source, such as a
flashlight or a pulse laser, and a determination of the flow
pattern from the resulting picture, particles somewhere between
about 5 .mu.m and about 150 .mu.m in mean diameter are generally
employed.
[0006] Electron microphotographs of the representative tracer
particles which are conventionally employed are presented in FIGS.
3 through 14; viz. white carbon in FIGS. 3 and 4, TiO.sub.2 in
FIGS. 5 and 6, talc in FIGS. 7 and 8, TiO.sub.2-talc in FIGS. 9 and
10, particles from kanto loam, and white alumina in FIGS. 13 and
14.
[0007] However, as apparent from these microphotographs, the
conventional tracer particles have the following drawbacks, 1)
through 5), which amplify the measurement error.
[0008] 1) Because the tracer particles are morphologically not
uniform, the sectional area of scattered light to be detected
varies according to the real-time orientation of each particle.
[0009] 2) Because the particle size distribution is broad and the
sectional area of light scattering varies with different individual
particles, the comparatively large particles scatter light in two
or more fringe at a time.
[0010] 3) Because the apparent specific gravity of the particulate
tracer differs markedly from that of the fluid to be measured, the
particles do not faithfully follow the on-going flow of the
fluid.
[0011] 4) Because the particle size distribution is broad and the
apparent specific gravity also has a distribution, the particles
follow the fluid flow with varying efficiencies to prevent accurate
quantitation of the flow measurement.
[0012] 5) Because the surface of the particle is irregular, the
individual particles tend to be concatenated with each other to
increase the effective particle size.
[0013] The technique used generally for launching tracer particles
into a fluid comprises either extruding tracer particles from a
screw feeder and driving them into the body of the fluid with the
aid of an air current or suspending tracer particles in a solvent
and ejecting the suspension in a mist form using an ultrasonic
humidifier. In any of the above methods, the rate of feed of the
tracer particles is not constant so that the accuracy of flow
measurement is inevitably sacrificed.
OBJECTS OF THE INVENTION
[0014] It is the object of the present invention to overcome the
above-mentioned drawbacks and provide a method of flow measurement
with improved accuracy.
SUMMARY OF THE INVENTION
[0015] The method of flow measurement according to the invention
comprises measuring the flow of a fluid using an optical instrument
and a porous particulate ceramic tracer, the diameter of which is
0.5 to 150 .mu.m.
[0016] In another aspect, the method of flow measurement according
to the invention comprises feeding a non-agglomerating particulate
tracer to an optical instrument, such as a laser device, from a
measuring wheel particle feeder.
[0017] The method of flow measurement according to the invention
comprises measuring the flow of a fluid using an optical instrument
and a porous particulate ceramic tracer, said porous particulate
ceramic tracer consisting of spherical particles having a diameter
of 0.5 to 150 .mu.m. Particularly in the method of measuring the
flow velocity using a laser instrument such as a laser Doppler
velocimeter, spherical ceramic particles having a diameter of 0.5
to 10 .mu.m are preferred from the viewpoint of relation with
fringe. A more satisfactory spherical particle diameter range is
1.5 to 2.5 .mu.m. In flow measurement which involves photographing,
the use of spherical particles having a diameter of 5 to 150 .mu.m
is preferred from the viewpoint of detecting light and flowing the
fluid flow. A more satisfactory particle diameter range is 30 to
100 .mu.m.
[0018] When the tracer particles for use in flow measurement with
an optical instrument are spherical as in the invention, the
sectional area of scattered light to be detected by a photosensor
or the like is constant regardless of the orientation of particles
at the moment of detection. Moreover, because such particles have
no surface irregularities that may cause concatenation, it does not
happen that two or more tracer particles flow as concatenated
through the body of the fluid. Therefore, the accuracy of flow
measurement is improved.
[0019] Where the fluid to be measured is a gas, said tracer
particles are preferably of hollow structure.
[0020] When the tracer particles are hollow, the specific gravity
of the particles is so low that even if the particle size is not
critically uniform, they may readily follow the gas flow.
Therefore, the accuracy of gas flow measurement is improved. The
improved accuracy of measurement afforded by such hollow spherical
particles over that attainable with solid spherical particles is
more remarkable when the flow rate of the fluid is high.
[0021] The shell thickness of such hollow spherical particles is
not so critical but is preferably in the range of one-third to
one-tenth of the diameter of the particle. If the shell thickness
is less than one-tenth of the particle diameter, the particles tend
to be collapsed in use. Conversely when the shell is thicker than
one-third of the particle diameter, the advantage of the hollow
structure will not be fully realized.
[0022] Where the fluid to be measured is a liquid, said tracer is
preferably a porous particulate ceramic tracer having closed pores
with a porosity of not less than 0.1 cm.sup.3/g.
[0023] When the tracer particles have closed pores with a porosity
of not less than 0.1 cm.sup.3/g, the specific gravity of the tracer
particles can be changed so as to minimize the differential from
the specific gravity of the fluid to be measured, thereby making it
easier for the particles to follow the dynamics of the fluid. In
this manner, the accuracy of flow measurement can be further
improved.
[0024] Where the fluid to be measured is a liquid, tracer particles
coated with a metal are used with advantage.
[0025] When such metal-clad porous spherical particles are used for
the flow measurement of a liquid, the intensity of reflected light
is greater than it is the case when bare particles are employed so
that the accuracy of flow measurement is improved. However, since
such metal-clad particles are higher in specific gravity and
expensive, they are preferably used where the conditions of
measurement specifically call for the use of such particles.
[0026] Particularly preferred are metal-clad porous ceramic tracer
particles having closed pores with a porosity of not less than 0.1
cm.sup.3/g. Application of a metal cladding increases the specific
gravity of particles as mentioned above but the adverse effect of
increased specific gravity can be minimized by using porous ceramic
particles having closed pores with a porosity of not less than 0.1
cm.sup.3/g.
[0027] For application of a metal cladding, any of the electroless
plating, electrolytic plating, CVD, vapor deposition and other
techniques can be utilized but the electroless plating process is
preferred in that a uniform cladding can be easily obtained.
[0028] The cladding metal includes, among others, Ni, Pt, Co, Cr,
etc. but nickel is preferred in that a quality cladding can be
easily obtained by electroless plating and that the resultant
cladding is comparatively high in chemical resistance.
[0029] The thickness of the metal cladding is not critical but is
preferably within the range of 0.05 to 5 .mu.m. If the cladding
thickness is less than 0.05 .mu.m, the effect of increased
reflectance is hardly obtained. If the cladding is over 5 .mu.m in
thickness, the proportion of the metal in the whole particle is too
large so that the bulk specific gravity of the tracer is
increased.
[0030] The starting material for said particulate tracer or for the
ceramic part of said metal-clad particulate tracer is not limited
in variety only if it is chemically stable. Thus, the starting
material can be selected from among, for example, alkaline earth
metal carbonates such as calcium carbonate, barium carbonate, etc.,
alkaline earth metal silicates such as calcium silicate, magnesium
silicate, etc.; and metal oxides such as silica (SiO.sub.2), iron
oxide, alumina, copper oxide and so on. Among these materials,
SiO.sub.2 is particularly desirable in that it is commercially
available at a low price and resistant to heat. When the heat
resistance of the ceramic material is high, particles prepared
therefrom can be effectively used without the risk of breakdown
even in high-temperature fluids.
[0031] The size distribution of tracer particles is preferably as
narrow as possible but when not less than 70% of the particles have
diameters within the range of .+-.50% of the mean particle
diameter, there is obtained a substantially uniform sectional area
of scattered light. Moreover, the kinetics of tracer particles in
the fluid body, that is to say the pattern of following the fluid
flow, are then rendered substantially uniform.
[0032] The tracer particles of the invention can be applied to the
measurement of fluids flowing at high speeds. Thus, in the
conventional flow measurement using a laser Doppler device, an
attempt to increase the sample data rate (the number of data
generated per unit time) by increasing the flow rate of the fluid
and, hence, the number of tracer particles passing through the
fringe per unit time resulted in a decrease in the mean effective
data rate, which is a representative indicator of measurement
accuracy, thus making it difficult to achieve an accurate
measurement of a high-velocity fluid. In accordance with the
present invention, the mean effective data rate is high even at a
high sample data rate so that the method can be effectively applied
to the measurement of fluids flowing at high speeds.
[0033] Furthermore, in the conventional flow measurement, the
concentration of tracer particles cannot be increased over a
certain limit because an increased feed of tracer particles for
generating a larger number of data per unit time should adversely
affect the mean effective data rate. However, in the method of the
invention, increasing the rate of feed of tracer particles for
increasing the sample data rate does not sacrifice the mean
effective data rate, with the result that the desired measurement
can be performed with an increased tracer concentration.
[0034] The particulate tracer or the ceramic core of the metal-clad
particulate tracer can be easily manufactured at low cost by the
reversed micelle technology which provides spherical or hollow
spherical porous tracer particles.
[0035] In this connection, when an aqueous solution of the
precursor for the tracer material is extruded from a porous glass
or polymer membrane having substantially uniform pores in an
organic solvent, there can be obtained uniform particles with a
narrow size distribution, and such particles are well suited for
use as the tracer particles or the core of metal-clad tracer
particles.
[0036] The above-mentioned porous glass or polymer membrane may be
any of the known membranes such as the membrane obtainable by
subjecting borosilicate glass to phase separation and washing the
product with a pickling acid solution, the membrane obtainable by
mixing a silica sol with a water-soluble organic polymeric
material, subjecting the mixture to phase separation at
polymerization and rinsing the product, and the membrane obtainable
by a technology involving irradiation with laser light to give
perforations of substantially uniform diameter.
[0037] The tracer particles can be advantageously fed to the laser
instrument by means of a measuring wheel particle feeder.
[0038] When the tracer particles are fed from the measuring wheel
particle feeder, the particles can be delivered quantitatively so
that the accuracy of velocity measurement or photographic
distribution measurement is further improved. Moreover, in the
conventional method, for obtaining of the high measurement
accuracy, it is essential to recalibrate the instrument after each
measurement cycle for minimizing the measurement error. This
operation is eliminated by use of the measuring wheel particle
feeder so that as many more measurements can be performed within a
given time period.
[0039] The construction of the measuring wheel particle feeder and
the mechanism of feed are described below, referring to FIGS. 15
and 16. As illustrated, a feeder body 101 is internally provided
with a disk 102 which is driven by a motor not shown. The top
surface of this disk 102 is provided with a circumferential groove
103.
[0040] The reference numeral 104 indicates a hopper which is filled
with a particulate tracer F. The hopper 104' has a lower portion
104a which is tapered towards the discharge end of the hopper and
the lowest part 104b thereof is open in the form of an orifice 104c
immediately over the groove 103, so that the particulate tracer F
in the hopper 104 may flow through the orifice 104c into the
circumferential groove 103.
[0041] The reference numeral 107 indicates a blow nozzle made of
plate material. This blow nozzle 107 is configured as a sector in
plan view and has a recess 109 having a tapered lateral surface 108
in a substantial center thereof. This recess 109 is centrally
provided with an orifice extending in the direction of the
thickness for passage of tracer particles (FIG. 16).
[0042] The reference numeral 105 indicates a particle duct which
runs through a casing 106 of the feeder body 101 and through which
the inside of the feeder body 101 is made communicable with the
outside thereof. This particle duct 105 is attached to the top of
the blow nozzle 107 in such a manner that its inward end 105a
covers said recess 109 to establish communication with said
particle duct 110.
[0043] The atmospheric pressure within the feeder body 101 is
maintained at a level higher than the external atmospheric
pressure. Because of this pressure gradient, the air flows into the
circumferential groove 103 adjacent said blow nozzle 107 at point X
beneath the blow nozzle 107. The air then flows out through a
particle passageway 110, said recess 109 and said particle duct
105. The arrowmarks in FIG. 16 indicate the flow of air.
[0044] As the particles F are carried by such an air flow, they are
successfully metered out from the feeder body 101 into the body of
the fluid to be measured.
[0045] In a second aspect, the invention provides a method of flow
measurement using an optical instrument and a particulate tracer
material, wherein a non-agglomerating particulate tracer is fed to
the laser or other optical instrument with such a measuring wheel
particle feeder.
[0046] When a non-agglomerating particular tracer material is fed
with the measuring wheel particle feeder for optical instrument,
the feed rate can be critically controlled even when the tracer has
a large particle size distribution and is morphologically divergent
as it is the case with the conventional tracer particles. Thus, the
conventional non-agglomerating tracer particles are generally large
in particle size and high in bulk specific gravity so that they
cannot faithfully follow the fluid flow but when this measuring
wheel particle feeder is employed, a better tracking performance
can be obtained for enhanced measuring efficiency under conditions
of high flow rate and least turbulence.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] FIG. 1 is an electron microphotograph (.times.2,000) showing
the particles manufactured in accordance with Production Example
1;
[0048] FIG. 2 is an electron microphotograph (.times.10,000)
showing the particles manufactured in Production Example 1;
[0049] FIG. 3 is an electron microphotograph (.times.10,000)
showing the conventional particles (white carbon);
[0050] FIG. 4 is an electron microphotograph (.times.50,000)
showing the same conventional particles (white carbon);
[0051] FIG. 5 is an electron microphotograph (.times.10,000)
showing the conventional particles (TiO.sub.2);
[0052] FIG. 6 is an electron microphotograph (.times.50,000)
showing the same conventional particles (TiO.sub.2);
[0053] FIG. 7 is an electron microphotograph (.times.1,000) showing
the conventional particles (talc);
[0054] FIG. 8 is an electron microphotograph (.times.10,000)
showing the same conventional particles (talc);
[0055] FIG. 9 is an electron microphotograph (.times.10,000)
showing the conventional particles (TiO.sub.2-talc);
[0056] FIG. 10 is an electron microphotograph (.times.50,000)
showing the same conventional particles (TiO.sub.2-talc);
[0057] FIG. 11 is an electron microphotograph (.times.10,000)
showing the conventional particles (source: Kanto loam);
[0058] FIG. 12 is an electron microphotograph (.times.50,000)
showing the same conventional particles (source: Kanto loam);
[0059] FIG. 13 is an electron microphotograph (.times.2,000)
showing the conventional particles (fused white alumina);
[0060] FIG. 14 is an electron microphotograph (.times.10,000)
showing the same conventional particles (fused white alumina);
[0061] FIG. 15 is a perspective view showing a measuring wheel
particle feeder;
[0062] FIG. 16 is a partial longitudinal section view showing the
blow nozzle of the feeder illustrated in FIG. 15;
[0063] FIG. 17 is a schematic view illustrating the manufacturing
equipment for tracer particles;
[0064] FIG. 18 is a diagrammatic representation of the particle
diameter distribution of the spherical SiO.sub.2 tracer used in
Example 3;
[0065] FIG. 19 is a diagrammatic representation of the particle
diameter distribution of the TiO.sub.2 tracer used in Comparative
Example 2;
[0066] FIG. 20 is a diagrammatic representation of the particle
diameter distribution of the SiO.sub.2 tracer used in Comparative
Example 3; and
[0067] FIG. 21 is a diagram showing the data obtained in Example 3,
Comparative Example 2 and Comparative Example 3.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0068] The following examples are further illustrative but not
limitative of the invention.
EXAMPLE 1
[0069] Using a hollow spherical particulate SiO.sub.2 tracer with
70% of individual particles having diameters within the range of
mean particle diameter=1.5 .mu.m.+-.0.4 .mu.m, the shell thickness
of which is one-fifth of the diameter of the particle, the velocity
of air within a cylinder was measured using a laser velocimeter
under the following conditions and the relationship between the
sample data rate and the mean effective data rate was investigated.
Thus, for increasing the number of data per unit time (sample data
rate) stepwise, the flow rate was increased stepwise (with the
concentration of tracer particles kept constant) to increase the
quantity of particles passing through the inference figure at the
flowmeter. Of the resulting data, the percentage of data useful for
velocity assessment (effective data rate) was determined. (Mean
flow rate=ca. 20 m/min.)
[0070] 1. Instrument: Fiber type laser Doppler velocimeter
(FLDV)
[0071] (cf. Ikeda, Y., Hikosaka, M., Ohira, T., and Nakajima, T.,
Scavenging Flow Measurements in a Fired Two-Stroke Engine by FLDV.,
1991. SAE Paper No. 910, p. 670)
[0072] (Specification)
[0073] Laser: He--Ne laser
[0074] Laser power: 8 mW.times.2
[0075] Lens diameter: 55 mm
[0076] 2. Measuring Conditions:
[0077] Center frequency: 20 MHz
[0078] Band width: .+-.16 MHz
[0079] Effective sample number: 5,000
[0080] Signal gain: 24 dB
[0081] Photomultiplier voltage: 760 V
[0082] The results are shown in Table 1.
[0083] [The mean effective data rate was determined with Dantec's
burst signal analyzer. When the symmetry of scatter signals is
disturbed, the peak frequency value after Fourier transformation is
depressed. Therefore, only the signals with a frequency
peak/reference frequency peak ratio over a given value were
regarded as valid data. In other words, the data lacking in signal
symmetry were invalidated.]
1 TABLE 1 Sample data Mean effective rate (Hz) data rate (%) 300 82
600 80 900 75 1,200 70 1,500 73 1,800 75
[0084] It will be apparent from Table 1 that increasing the sample
data rate does not result in any appreciable decreases in the mean
effective data rate which is a representative indicator of
measurement accuracy, indicating that the tracer particles of the
invention are fully effective for the measurement of high-velocity
fluids.
EXAMPLE 2
[0085] The same measurement as Example 1 was performed using a
hollow spherical particulate SiO.sub.2 tracer with 90% of
individual particles having diameters within the range of 1 to 5
.mu.m (the shell thickness was one-fifth of the diameter of the
particle). The results are shown in Table 2.
2 TABLE 2 Sample data Mean effective rate (Hz) data rate (%) 300 80
600 79 900 55 1,200 60 1,500 65 1,800 57
[0086] It will be seen from Table 2 that although the mean
effective data rates are not as high as those obtained in Example 1
because of the broader tracer particle size distribution, there are
obtained stable effective data rates even at high sample data
rates.
COMPARATIVE EXAMPLE 1
[0087] The same experiment as Example 1 was performed using a
wet-process white carbon, shown in FIGS. 3 and 4, which is a
representative prior art tracer (mean primary particle diameter 0.2
.mu.m, mean agglomerated particle diameter (effective particle
diameter) 6 .mu.m; NIPSIL SS-50F, manufactured by Nippon Silica
Industry Co., Ltd.). The results are shown in Table 3.
3 TABLE 3 Sample data Mean effective rate (Hz) data rate (%) 300 53
600 63 900 20 1,200 15 1,500 12 1,800 5
[0088] It will be apparent from Table 3 that the mean effective
data rates are invariably lower than the rates obtained in Examples
1 and 2, with extremely low rates found at high sample data
rates.
[0089] It is predictable that the use of the prior art tracer
particles shown in FIGS. 5 through 14 will also yield results
similar to those described above for white carbon.
EXAMPLE 3 AND COMPARATIVE EXAMPLES 2 AND 3
[0090] The velocity of a fluid flowing through an acrylic resin
pipe with an internal diameter of 100 mm was determined using: a
spherical particulate SiO.sub.2 tracer having the particle diameter
distribution of FIG. 18 (Example 3; FIGS. 1 and 2), a particulate
TiO.sub.2 tracer having the particle diameter distribution of FIG.
19 (Comparative Example 2; FIGS. 5 and 6) and a particulate
SiO.sub.2 tracer having the particle diameter distribution of FIG.
20 (Comparative Example 3; FIGS. 3 and 4). For determinations, the
same fiber type laser Doppler velocimeter (FLDV) as used in Example
1 was employed. A measuring wheel particle feeder (MSF-F, Liquid
Gas Co., Ltd.) was used to supply said spherical particulate
SiO.sub.2 particle and a fluidize bed feeder (Durst et al., 1976)
was used to supply said conventional TiO.sub.2 and SiO.sub.2
particles.
[0091] In each determination, the sample data rate was varied by
changing the concentration of tracer particles. The same average
measuring speed and root mean square velocity (r.m.s.v.), 122 m/s
and 3.5 m/s, respectively, were used for the three tracers.
[0092] The relationship between sample data rate and effective data
rate is diagrammatically shown in FIG. 21.
[0093] It will be apparent from FIG. 21 that, in accordance with
the present invention, the effective data rate is not decreased
even if the number of data per unit time is increased by increasing
the feed rate of particles.
PRODUCTION EXAMPLE 1
[0094] The following example is intended to illustrate the
production of tracer particles by the reversed micelle method.
[0095] A 10 .mu.m-thick polyimide film was irradiated with a KrF
excimer laser (wavelength 251 nm) to provide perforations sized 2.0
.mu.m. This perforated polymer film was mounted in an
emulsification device illustrated in FIG. 17 and an aqueous
solution of the tracer precursor substance was fed under pressure
into an organic solution with a syringe pump. The feeding rate was
1 g/cm.sup.2 and the temperature was 25.degree. C.
[0096] The construction of the device shown in FIG. 17 is
summarized below. The reference numeral 10 indicates a volumetric
syringe pump 10. The polymer membrane, indicated by 12, is mounted
in the forward portion of the volumetric syringe pump. The
reference numeral 14 indicates a screen for supporting said polymer
membrane. Indicated by the numeral 16 is a cylindrical reactor
which is communicating with said syringe pump 10. The reference
numeral 20 indicates a feed pipe for feeding an organic solvent 25
from a solvent beaker 24 to said reactor 16 through a metering pump
22. Now, an aqueous solution 11 of the tracer particle precusor
substance is quantitatively injected into the organic solvent 25
within the reactor 16 by said syringe pump 10. After formation of a
large number of emulsion particles, the organic solvent is returned
from the reactor 16 to the solvent beaker 24 via a withdrawal pipe
26.
[0097] In the example, a hexane solution of polyoxyethylene
(20)-sorbitan trioleate (20 g/l) was used as the organic
solvent.
[0098] As to the aqueous solution, a solution prepared by adding
1.0 mol of tetraethoxysilane, 2.2 mol of methanol, 1.0 mol of
N,N-dimethylformamide and 4.times.10.sup.-4 mols of ammonia to 10
mols of water was employed.
[0099] After emulsification at 5.degree. C., the slurry was
refluxed for 30 hours and the resulting emulsion particles (sol) in
the organic acid were precipitated by gelation. The precipitate was
dried and heated at 800.degree. C. to give a silica (SiO.sub.2)
tracer uniform in particle diameter. The silica tracer particles
thus obtained were spherical particles, 70% of which had diameters
in the range of mean diameter=2.5.+-.0.7 .mu.m (FIGS. 1 and 2).
EXAMPLE 4
[0100] For comparing the measuring accuracy obtainable with
spherical tracer particles with that obtainable with hollow
spherical tracer particles, the same experiment as Example 1 was
performed using the solid spherical particles prepared in
Production Example 1, that is the particles with 70% having
diameters within the range of mean=2.5.+-.0.7 .mu.m. The results
are shown in Table 4.
4 TABLE 4 Sample data Mean effective rate (Hz) data rate (%) 300 81
600 80 900 74 1,200 73 1,500 63 1,800 65
[0101] Comparison of Table 4 with Table 1 indicates that both at
low velocity (low sample data rate) and high velocity (high sample
data rate), high measurement accuracy values are obtained and that
particularly at high velocity, the hollow spherical tracer
particles yield a higher measurement accuracy than the solid
spherical tracer particles, even when the minor difference in
particle size is taken into consideration.
EXAMPLE 5 AND COMPARATIVE EXAMPLE 4
[0102] Using the conventional particulate TiO.sub.2 tracer for
fluid visualization having a mean particle diameter of 5 .mu.m and
a particle specific gravity of 6 g/cm.sup.3 (Comparative Example 4)
and a porous spherical particulate SiO.sub.2 tracer having a mean
particle diameter of 30 .mu.m and a particle specific gravity of
about 1 g/cm.sup.3 which is substantially comparable to the
first-mentioned tracer in average fluid tracking performance
(Example 5, 72% within the range of mean particle diameter.+-.50%),
a fluid visualization test was performed by the photographing
method using a flash lamp as the light source.
[0103] As a result, the mean reflection light quantity per particle
was about 20 times the value of the conventional tracer.
[0104] In terms of the width of spread of particles in the laminar
flow region, the porous spherical particles showed values about 0.8
to 0.5 times the values of the conventional particles.
[0105] It is easy to see that, with the average fluid-tracking
performance being fixed, the larger the reflection light quantity,
i.e. the signal quantity, and the narrower the spread of tracer
particles in the laminar flow region, the higher is the measurement
accuracy.
[0106] It is easily predictable that similar results will be
obtained when the conventional tracer particles illustrated in
FIGS. 5 through 14 are used in lieu of the above tracer particles
of Comparative Example 4.
EXAMPLE 6 AND COMPARATIVE EXAMPLE 5
[0107] The same visualization test as above was performed using,
instead of the porous spherical particulate SiO.sub.2 tracer with a
mean particle diameter of 30 .mu.m, a porous spherical particulate
SiO.sub.2 tracer with a mean particle diameter of 100 .mu.m
(Example 6; 72% of particles within the range of mean.+-.50%) and a
conventional particulate TiO.sub.2 tracer for fluid visualization
which is comparable to the first-mentioned tracer in fluid tracking
performance (Comparative Example 5).
[0108] Like the tracer of Example 5, the porous spherical SiO.sub.2
tracer having a mean particle diameter of 100 .mu.m was superior to
the conventional tracer in average reflection light quantity and in
terms of the width of spread of particles in the laminar flow
region.
EXAMPLE 7
[0109] Using the spherical particles manufactured in Production
Example 1, namely a spherical particulate SiO.sub.2 tracer with 70%
of particles having diameters within the range of 2.5.+-.0.7 .mu.m
(FIGS. 1 and 2) and the same laser Doppler velocimeter as used in
Example 1, the velocity of water flowing in a turbulent flow within
a pipe of circular section was determined and the relationship
between sample data rate and mean effective data rate was
investigated. Thus, the flow rate was increased stepwise to
increase the number of data per unit time (sample data rate) and,
hence, the quantity of particles passing through the fringe in the
velocimeter, with the concentration of particles being kept
constant. Of the data thus generated, the percentage of the data
useful for velocity assessment (effective data rate) was
determined.
[0110] 1. Instrument: A fiber type laser Doppler velocimeter
(FLDV)
[0111] (Ikeda, Y., Hikosaka, M., Ohira, T., and Nakajima, T.,
Scavenging Flow Measurements in a Fired Two-Stroke Engine by FLDV.
1991, SAE Paper No. 910670.)
[0112] (Specification)
[0113] Laser: He--Ne laser
[0114] Laser power: 8 mW.times.2
[0115] Lens diameter: 55 mm
[0116] 2. Measuring Conditions:
[0117] Center frequency: 20 MHz
[0118] Band width: .+-.16 MHz
[0119] Effective sample number: 5,000
[0120] Signal gain: 24 dB
[0121] Photomultiplier voltage: 760 V
[0122] The results are shown in Table 5.
5 TABLE 5 Sample data Mean effective rate (Hz) data rate (%) 1,000
72 2,000 69 3,000 70
COMPARATIVE EXAMPLE 6
[0123] Using the conventional particulate TiO.sub.2 tracer with a
mean particle diameter of 2 .mu.m (FIGS. 5 and 6), the velocimetric
test was performed under the same conditions as used in Example 7.
The results are shown in Table 6.
6 TABLE 6 Sample data Mean effective rate (Hz) data rate (%) 1,000
35 2,000 20 3,000 10
COMPARATIVE EXAMPLE 7
[0124] Using the conventional particulate SiC tracer with a mean
particle diameter of 3 .mu.m, the velocimetric test was performed
under the same conditions as in Example 7. The results are shown in
Table 7.
7 TABLE 7 Sample data Mean effective rate (Hz) data rate (%) 1,000
50 2,000 42 3,000 37
[0125] It will be apparent from Tables 5 through 7 that, compared
with the tracers of Comparative Examples 6 and 7, the tracer of
Example 7 yields high effective data rates which are substantially
constant up to a very high data rate.
EXAMPLES 8, 9 AND 10 AND COMPARATIVE EXAMPLES 8 AND 9
[0126] The five particulate tracers shown below in Table 8 were
respectively immersed in water for a predetermined time and the
bulk specific gravity of each wet tracer was determined. The
results are also shown in Table 8.
8 TABLE 8 Particulate tracer Bulk specific gravity [Example 8] 1.45
g/cm.sup.3 Porous spherical SiO.sub.2 particles, closed pore 0.05
cm.sup.3/g, mean particle diameter 2.7 .mu.m [Example 9] 1.20
g/cm.sup.3 Porous spherical SiO.sub.2 particles, closed pore 0.21
cm.sup.3/g, mean particle diameter 2.8 .mu.m [Example 10] 1.26
g/cm.sup.3 Porous spherical SiO.sub.2 particles, closed pore 0.15
cm.sup.3/g, mean particle diameter 15 .mu.m [Comparative Example 8]
2.3 g/cm.sup.3 Conventional SiC particles, mean particle diameter 3
.mu.m [Comparative Example 9] 3.1 g/cm.sup.3 Conventional TiO.sub.2
particles, mean particle diameter 2 .mu.m
[0127] It is apparent from Table 8 that compared with the tracers
of Comparative Examples 8 and 9, the tracers of Exmaples 8, 9 and
10 are smaller in the bulk specific gravity differential from
water, suggesting the greater ease with which they may follow a
water flow and that the tracer of Example 9 is particularly
excellent.
[0128] Since the fluid-tracking performance is inversely
proportional to the specific gravity differential from the fluid,
the tracer of Example 10 is considered to be substantially
equivalent to the tracer of Comparative Example 8 in tracking
efficiency. However, because the sectional area of the tracer
particle of Example 10 is approximately 25-fold greater, it is easy
to anticipate that, in the photographing method, it produces a
greater intensity of scattered light. The greater the intensity of
scattered light, the higher is the measurement accuracy. In other
words, the smaller the specific gravity differential from the fluid
to be measured, the larger is the tracer particle that can be
employed. Therefore, the fact that the tracer particle has closed
pores and the specific gravity of the particle can be controlled by
taking advantage of such closed pores has a great significance in a
measuring system where the distribution of tracer particles is
photographed using an instantaneous powerful light source such as a
flashlight or a pulse laser.
EXAMPLE 11
[0129] A velocimetric test was performed using a metal-clad
spherical particulate tracer prepared by depositing a nickel plate
about 0.05 .mu.m thick on the particles manufactured in Production
Example 1 by the electroless plating technique. The test conditions
were otherwise identical to those used in Example 7. The results
are shown in Table 9.
9 TABLE 9 Sample data Mean effective rate (Hz) data rate(%) 1,000
80 2,000 75 3,000 74
[0130] Comparison with Tables 5 through 7 and 9 indicates that the
effective data rates in Example 11 are higher than those obtained
in Example 7 and Comparative Examples 6 and 7.
EXAMPLE 12
[0131] Using a porous hollow spherical particulate SiO.sub.2 tracer
with a mean particle diameter of 1.5 .mu.m.+-.S.D. 0.3 .mu.m, the
shell thickness of which was one-fifth of the diameter of the
particle, a comparative feeding test was performed with the
measuring wheel particle feeder (MSF-F, Liquid Gas Co., Ltd.) and
the screw feeder. In both cases, the feed rate was set at 0.3 g per
minute.
[0132] The feeding accuracy was high for both the measuring wheel
feeder and the screw feeder but with the measuring wheel feeder the
tracer could be introduced with an accuracy of 0.3.+-.0.01 g/min.
This accuracy is about 5 times as high as the accuracy with the
screw feeder.
[0133] In the measurement of fluid velocity with a laser
instrument, it is easy to see that the higher the accuracy with
which the tracer can be fed to the instrument and, hence, to the
fluid to be measured, the higher is the accuracy of flow
measurement by the instrument.
COMPARATIVE EXAMPLE 10
[0134] Using the conventional non-agglomerating particulate
SiO.sub.2 tracer with a mean particle diameter of 1.5 .mu.m, a
feeding test was performed with the measuring wheel particle feeder
and the screw feeder. In both cases, the feed cate was controlled
at 0.3 g per minute.
[0135] With the measuring wheel feeder, the tracer particles could
not be successfully delivered due to agglomeration.
[0136] The feed accuracy with the screw feeder was 0.3.+-.0.14
g/min and it was found that, compared with Example 12, the use of
spherical tracer particles insures a comparatively higher accuracy
of feeding to the laser instrument.
[0137] In the measurement of fluid flow with a laser instrument, it
is easy to see that the higher the accuracy of feed to the fluid,
the higher is the accuracy of measurement by the instrument.
EXAMPLE 13 AND COMPARATIVE EXAMPLE 11
[0138] Using the conventional non-agglomerating particulate
TiO.sub.2 tracer with a mean particle diameter of 5 .mu.m, a
feeding test was performed with the same measuring wheel particle
feeder as used in Example 12 (Example 13) and the screw feeder
(Comparative Example 11). In both cases, the feed rate was set at
0.3 g per minute.
[0139] The feeding accuracies were 0.3.+-.0.02 g/min and
0.3.+-.0.08 g/min, respectively, indicating that the measuring
wheel particle feeder is conductive to a higher measurement
accuracy.
* * * * *