Note: Descriptions are shown in the official language in which they were submitted.
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Vibrating Element for Ultrasonic Atomization
Technical Field
This invention relates generally to an ultrasonic
atomizing apparatus such as an ultrasonic injection nozzle,
and particularly to a vibrating e:Lement suitable for use on
an ultrasonic atomizing apparatus for atomizing liquid
intermittently or continuously, such atomizing apparatus
including (1) automobile fuel injection apparatus such as
electronically controlled gasoline injection valves or
electronically controlled diesel injection valves, (2) fuel
nozzles for use with a gas turbine, (3) burners for use with
industrial, commercial and domestic boilers, heating furnaces
and stoves, (4) industrial liquid atomizers, drying atomizers
for drying liquid materials such as foods, medicines,
agricultural chemicals, fertilizers and the like, and spray
heads for controlling temperature and humidity, atomizers
for calcining powders (pelletizing ceramics), spray coaters,
and reaction promoting devices, and (5~ liquid atomizers for
uses other than industrial use, such as spreaders for
agricultural chemicals and antiseptic solution.
Background Art
Pressure atomizing burners or liquid atomizers have
been used to spray or atomize liquid in the various fields
as mentioned above. (The term "liquid" herein used is
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intended to mean not only liquid but also liquid materials
such as solutions, suspensions and the like.) Injection
nozzles used with such spray burners or liquid atomizers
are adapted to atomize the liquid by the shearing action
between the liquid as discharged through the nozzles and
the ambient air ~atmospheric air). Thus, atomization of
supply liquid required increased pressure to supply liquid,
resulting in requiring complicated and large sized liquid
supplying means such as pumps and piping.
~ urthermore, the regulation of the flow rate of the
injection was effected either by varying the pressure of
the supply liquid or by varying the area of the nozzle
opening. However, the former method provided poor atomization
at a low flow rate (low pressure), as a remedy for which air
or steam was additionally used on medium or large-sized
boilers to enhance the atomization of liquid fuel, requiring
more and more complicated and enlarged apparatus. On the
other hand, the latter method required an extremely intricate
construction of nozzle which was difficult to control and
maintain.
In order to overcome the drawbacks to such conventional
injection nozzles, attempts have been made to impart ultrasonic
waves to liquid material while injecting it out through the
jet of the injection nozzle under pressure.
However, the conventional ultrasonic liquid injecting
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nozzle had so small capacity for spraying -that it was unsuitable
for use as such injection nozzle as described above which
required a large amount of atomized liquid.
As a result of extensive researches and experiments on the
ultrasonic liq~id atomizing mechanism and the configuration of
the ultrasonic vibrating element in an attempt to achieve
atomization of a large amount of liquid, the present inventors
have discovered that a large quantity of liquid may be atomized
by forming an edged portion at the end of an ultrasonic vibrating
element and delivering liquid to an along said edged portion in a
film form, and have proposed an ultrasonic in~ection method and
in~ection nozzle (see applicants European Patent Application No.
O 159 189 published October 23, 1985).
As a result of further researchers and experiments on the
configuration of the vibrating elements of the various ultrasonic
atomizing devices such as the ultrasonic in;ection nozzle of the
type described above, the present inventors have found put that
the geometry of the vibrating element has a great effect on the
amount of liquid being atomized (sprayed) and the angle of spray
spread.
Based on such novel knowledge, the present invention relates to
the ultrasonic injection nozzle of the type according to the
invention of the aforesaid prior patent application and other
various ultrasonic atomizing apparatus, particularly to an
improvement over the vibrating element for use with such
ultrasonic atomizing apparatus and is characterized by the shape
and dimensions of the vibrating element.
The invention provides an ultrasonic vibrating element for
atomization capable of delivering liquid intermittently or
continuously.
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The invention also provides a vlbrating element for ultrasonic
atomization which is capable of spray spreading liquid over a
wider angle, and delivering and spraying or in~ecting a larger
quantity of liquid, as compared to the conventional atomizing
apparatus and ultrasonic atomi~ing apparatus.
The invention again provides a vibrating element for ultrasonic
atomization which is capable of accomplishing consistent
atomization in that there is no change in the conditions of
atomization (flow rate and particle size) depending upon the
properties, particularly viscosity of the supply liquid.
The present invention thus provides a vibrating element for
ultrasonic atomiza-tion which is formed around its outer periphery
with a multi-stepped edged portion having one
or more steps, said edged portion being supplied with liquid
to atomize said liquid, characterized by the height (h) and
width (w) of each step being such that
0.2 mm s h ~ ~/4 and
0.2 mm ~ h ~ ~/4
wherein A is the wave length of the ultrasonic wave.
According to a preferred embodiment of this invention, the
height (h) and width (w) of the edged portion of each step
are such that 1 ~ h/w ~ 10.
Specific embodiments of the present invention will now
be described by way of example and not by way of limitation
with reference to the accompanying drawings.
Brief Description of the Drawings
Fig. 1 is a fragmentary front view of one embodiment of
the vibrating element for ultrasonic atomization according
to the present invention;
Fig. 2 is a cross-sectional view of an ultrasonic
atomizing apparatus incorporating the vibrating element for
ultrasonic atomization according to this invention;
Figs. 3 to 5 are fragmentary front views of alternate
embodiments of the vibrating element for ultrasonic atomization
according to this invention.
Description of the Embodiments
First, one form of ultrasonic injection nozzle with
which the vibrating element according to the present invention
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may be employed will be described with reference to Fig. 2.
While the present invention is suitably applicable to
atomizing apparatus for various uses, it will herein be
described with reference to a fuel noæzle for a gas turbine.
Referring to Fig. 2, an in~ection nozzle which is a
fuel nozzle 10 for a gas turbine in the illustrated embodiment
includes a generally cylindrical elongated valve housing 8
having a central bore 6 extending centrally therethrough.
A vibrating element 1 according to this invention is disposed
extending through the central bore 6 of the valve housing 8.
The vibrating element 1 includes an upper body portion la,
an elongated cylindrical vibrator shank lb having a diameter
smaller than that of the body portion la, and a transition
portion lc connecting the body portion la and shank lb. The
body portion la has an enlarged diameter flange ld which is
attached to the valve housing 8 by a shoulder 12 formed in
the upper end of the valve housing 8 and an annular vibrator
retainer 14 fastend to the upper end face of the valve housing
by bolts ~not shown).
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The forward end of the vibrating element 1, that is,
the forward end of the shank lb is formed with an edged
portion 2, the geometry of which will be described in details
hereinafter. The valve housing 8 is formed through its
lower end portion with one or more supply passages 4 for
feeding fuel to said edged portion 2. The fuel supply port
16 of the supply passage ~ is supplied with liquid fuel
through an external supply line (not shown) from a source
of fuel (not shown). The flow and flow rate of fuel are
controlled by a supply valve (not shown) disposed in the
external supply line.
With the construction described above, the vibrating
element 1 is continuously vibrated by an ultrasonic generator
100 operatively connected to the body portion la. Thus,
liquid fuel is ~ed through the line, the supply valve and
the supply passage 4 to the edged portion 2 where it is
atomized and jetted outwardly.
The edged portion 2 of the vibrating element 1 is in
the form of an annular staircase including five steps having
progressively reduced diameters as shown in Fig. 5, but may
be in the form of a staircase having two, three or four or
six steps.
More specifically, with the construction as described
above, as liquid which is fuel in the illustrated embodiment
is delivered to the edged portion 2, the stream of fuel is
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severed and atomized at each edge. The fuel is first partially
atomized at the edge (A) of the first step, and the excess
portion of the fuel which has not been handled at the edge
~A) of the first step is fed successivel~ through the second
step edge (B), the third step edge (C) and so forth to be
handled thereby. At a higher flow rate of fuel requiring
larger effective areas for atomization, more stepped edges
are required~ At a lower flow rate, however, a smaller
number of steps are required before the atomization is
completed. With the vibrating-element 1 according to this
invention, the number of steps required for atomization will
vary with changes in the flow rate so as to insure generally
uniform conditions such as the thickness of liquid film at
the location of each step where the atomization takes place,
resulting in uniform particle shape and size of the droplets
being atomized. The vibrating element according to this
invention provides for a full range of flow rates usually
reguired for atomization so that atomi~ation of various
types of liquid materials may be accomplished, whether it
may be on an intermittent basis or on a continuous basis.
It will be appreciated from the foregoing that the
height (h) and width (w) of the edged portion shown in Fig.
1 is such that it may act to render the liquid filmy and to
dam the li~uid flow. Researches and experiments conducted
by the present inventors have shown that the height (h) and
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width (w) of the edged portion must be kept ~n a predetermined
range as follows in order to effect atomization of supplied
liquid in a large quantity:
0.2 mm S h S A/4 (1)
O.2 mm ~ w S ~/4 t23
wherein ~ is the wavelength of the ultrasonic wave.
In a preferred embodiment of this invention the height
(h) and width (w) of the edged portion of each step are such
that 1 5 h/w 5 10. Particularly for the vibrating element
of the configuration as illustrated in Fig. l the height
(h) is preferably less than 4 mm. The wavelength of the
ultrasonic wave is typically 5 cm to 50 cm depending upon
the material (such as inconnel, titanium or the like) of
which the vibrating element is made.
The output of the ultrasonic generator for exciting
the vibrating element is on the order of 10 W, and the
amplitude and frequency of vibration of the vibrating element
are in the ranges of 30 to 70 ~m and 20 to 50 KHz, respectively.
The diameter (D) of the vibrating element is suitably in the
range of ~/10 to ~/4. The greater the amplitude of ~ibration
and the diameter (D), the greater the capacity for handling
the liquid.
The vibrating element of the present invention is not
limited to the configuration as shown in Fig. 1, but may take
various forms as shown in Fig. 3 to 5.
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The forward end of the vibrating element shown in Fig. 3
is formed with an annular edged portion 2 having one or more
steps of equal diameter, three steps (A), (B), (C) in the
illustrated embodiment. The shape of the edged portion 2
as viewed in the direction of the arrow (X) is not limited
to a circular shape, but may be triangular, square or other
polygonal shapes. According to the present invention, the
height (h) and width (w) of the edged portion 2 are sized
as defined by the equations (1) and (2) as indicated herein-
above. The angle (~) may be suitably selected. The angle
of injection (angle of injection spread) may be adjusted by
selecting the height (h), width (w) and engle (~) as desired.
While the edged portion 2 has been described as
comprising protrusions (A), (B) and (C) which are all of the
same angular shape, those protrusions need not be of angular
shape but may be of any other shape, provided that they are
formed around their outer periphery with edges.
Figs. 4 and 5 illustrate alternate embodiments of this
invention in which the multi-stepped edged portion having
one or more steps 2 is formed around the inner periphery of
the forward end of the vibrating element 1. Again in these
embodiments, satisfactory atomization may be achieved if the
aforesaid conditions are satisfied. Of course, in these
embodiments, liquid is fed to the edged portion through a
liquid supply passage 4 formed through the vibrating element.
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An example of various parameters and dimensions of the
ultrasonic atomizing apparatus according to this invention
is as follows: It has been found that such construction
provides for atomization in a ve:ry large amount.
Output of ultrasonic vibration
generating means: 10 watts
Amplitude of vibration of
vibrating element: 30 ~m
Frequency of vibration of
vibrating element: 38 KHz
Geometry of edged portion (embodiment of Fig. 1
Width (w) of edged portion: 0.5 mm
(diameter D of vibrating element edged portion)
First step: 7 mm in diameter (Do)
Second step: 6 mm in diameter
Third step: 5 mm in diameter
Fourth step: 4 mm in-diameter
Fifth step: 3 mm in diameter (d)
Height of each step: 2 mm
Fuel Type of oil: Gas oil
Flow rate: ~ 0.06 cm3 per injection
Injection pressure: 1~ 70 kg/cm2
Temperature~ normal temperature
Material of which the vibrating
element is made: Titanium
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Effects of the Invention
As is described hereinabove, the vibrating element
having a geometry defined according to the present invention
is capable of providing a wider angle of spray spread and
achieving atomization in a large amount, and thereby enables
the provision of an ultrasonic atomizing apparatus capable
of accomplishing consistent atomization in that there is no
change in the conditions of atomization (flow rate and
particle size) depending upon the properties, particularly
viscosity of the supply liquid.
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