A constant-output atomizer includes a body which has a generally frustoconical expansion nozzle for producing an air jet when a supply of pressurized air is connected to the nozzle upstream of the throat of the nozzle. A liquid feed line supplies liquid to be atomized by the air jet, and the body includes a groove which opens into the diffuser section of the nozzle downstream of the throat for conducting liquid from the feed line to the nozzle. The groove which extends in a direction perpendicular to the axis of the nozzle, and radially with respect to it, has a depth approximately equal to half the axial length of the nozzle. Liquid, conducted by capillary action in the groove to the nozzle, is atomized into a fine mist by the air jet in the nozzle; and the groove eliminates fluctuations in spray order

Dea, J. Y.

English

NASA Technical Reports Server

States Patent [191 
Dea 
11 11 4,413,784 
[451 Nov. 8,1983 
FOREIGN PATENT DOCUMENTS [54] CONSTANT-OUTPUT ATOMIZER 
558890 7/1957 Belgium .............................. 239/426 
Rep. .................................... 239/434 
[75] Inventor: Jack Y. Dea, Reno, Nev. 
[73] Assignee: The United States of America as 
32417 10/1964 German Democratic 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
Primary Examiner-John J. Love 
Assistant Exam jner-Michael J. Forman 
Attorney, Agent, or Firm-Joseph H. Beumer; John R. 
Manning; Leon D. Wofford, Jr. 
ABSTRACT [571 
[21] Appl. No.: 308,203 
[22] Filed: Oct. 2, 1981 
[51] Int. Cl.3 ................................................ B05B 7/08 
[52] U.S. C1. .................................................... 239/426 
[58] Field of Search ............... 239/310, 318, 418, 426, 
239/434 
1561 References Cited 
U.S. PATENT DOCUMENTS 
535,000 3/1895 Goodman ......... 
909,190 1/1909 Keller 
1,524,990 2/1925 Macaulay 
1,636,353 7/1927 Bullum ................................ 239/434 
2,062,097 11/1936 Lingard ............................... 239/318 
2,149,526 3/1939 Johnson .............................. 239/418 
2,253,071 8/1941 Gordon et a]. ..................... 239/426 
2,582,805 1/1952 Trumbour et al. 
3,591,088 7/1971 Green .................................. 239/426 
An improved constant-output atomizer (30) includes a 
body (38) which has a generally frustoconical expansion 
nozzle (36) for producing an air jet when a supply of 
pressurized air is connected to the nozzle upstream of 
the throat of the nozzle. A liquid feed line (40) supplies 
liquid to be atomized by the air jet, and the body in- 
cludes a groove (42) which opens into the diffuser sec- 
tion of the nozzle downstream of the throat for con- 
ducting liquid from the feed line to the nozzle. The 
groove extends in a direction perpendicular to the axis 
of the nozzle, and radially with respect thereto; and it 
has a depth approximately equal to half the axial length 
of the nozzle. Liquid, conducted by capillary action in 
the groove to the nozzle, is atomized into a fine mist by 
the air jet in the nozzle; and the groove eliminates fluc- 
tuations in spray order. 
6 Claims, 3 Drawing Figures 
30 
J 
https://ntrs.nasa.gov/search.jsp?R=19840004338 2020-03-22T07:36:41+00:00Z
US. Patent Nov. 8, 1983 4,413,784 
1 
CONSTANT-OUTPUT ATOMIZER 
4,413,784 
ORIGIN OF T H E  INVENTION 
The invention described herein was made in perfor- 
mance of work under a NASA contract, and is subject 
to the provisions of Section 305 of the National Aero- 
nautics and Space Act of 1958, Public Law 85-568 (72 
SCAT.435; 42 U.S.C. 2457). 
TECHNICAL F I E L D  O F  T H E  INVENTION 
The present invention generally relates to an atom- 
izer which is adapted to produce a substantially con- 
stant output and minimize fluctuation in the concentra- 
tion of droplets produced. 
BACKGROUND ART 
Fine-mist atomizers are used to generate aerosols for 
scientific experiments, inhalation therapy, and aerosol 
research. Most of these applications, however, require a 
substantially constant output, Le.. a concentration that 
remains substantially time-invariant as to droplet size, 
mass flow, and concentration. Conventional atomizers 
usually have unstable outputs, and are thus unsatisfac- 
tory for the purposes and uses listed above. It is, there- 
fore, an object of the present invention to provide a new 
and improved atomizer capable of producing a substan- 
tially constant output. 
DISCLOSURE O F  T H E  INVENTION 
An improved constant-output atomizer according to 
the present invention includes a body having an expan- 
sion nozzle for producing an air jet when a supply of 
pressurized air is connected to the nozzle upstream of 
the nozzle throat, and a groove in the housing opening 
into the nozzle downstream of the throat for supplying 
liquid to be atomized by the air jet. 
The liquid flows smoothly to the air jet due to the 
capillary action that takes place in the groove and the 
suction present at the open end of the groove. Further- 
more, the open groove prevents localized solid residues 
which would interfere with the rate at which liquid is 
delivered to the atomizer; and the conical nature of the 
nozzle eliminates any liquid build-up which, if present, 
would be swept away periodically by the air jet, causing 
fluctuations in the output of the atomizer, even if the 
rate of liquid input to the air jet were constant. Thus, 
the combination of nozzle and groove serves to inhibit 
any factor that would perturb the output of the atom- 
izer. Moreover, the atomizer according to the present 
invention is attitude-insensitive, and is capable of oper- 
ating with any liquid whose viscosity is not excessive. A 
stable output can be expected after about 5 minutes of 
operation. 
In one preferred form of the invention, the groove is 
located radially with respect to the nozzle axis; and the 
5 
10 
15 
20 
25 
30 
35 
40 
45 
50 
55 
width of the groove is approximately twice the diame- 60 
ter of the throat of the nozzle. In addition, the depth of 
the groove is about equal to half of the axial length of 
the nozzle. These dimensions are not, however, critical. 
BRIEF DESCRIPTION OF THE DRAWINGS 
An embodiment of the invention is shown in the 
FIG. 1 is a sectional view of a prior art atomizer; 
65 
accomanying drawings, wherein: 
2 
FIG. 2 is a sectional view of an improved constant- 
output atomizer formed in accordance with the present 
invention; and 
FIG. 3 is a front elevation of the improved constant- 
output atomizer of FIG. 2. 
DETAILED DESCRIPTION OF THE 
PREFERRED EMBODIMENTS 
Referring now more specifically to FIG. 1, reference 
numeral 10 designates a prior art atomizer which in- 
cludes generally cylindrical conduit 12 for connection 
to source S of compressed air. The conduit terminates in 
air exit 14 which is covered by jet orifice plate 16; 
through which compressed air is directed outwardly 
into generally cylindrical aperture 18 that functions as a 
nozzle, and terminates in free end 20. Liquid from a 
supply (not shown) is supplied via feed line 22 that 
terminates in a relatively narrow exit orifice 24 located 
in the bottom surface of aperture 18. Air from supply S 
passing through aperture 18 mixes with liquid exiting 
from orifice 24, thereby atomizing the liquid into a 
spray 26 which is directed outwardly from the aperture. 
As discussed above, a prior art atomizer such as that 
shown in FIG. 1 suffers from several major disadvan- 
tages. One is that exit orifice 24 at the end of the liquid 
feed line, which terminates adjacent to the bottom of 
the aperture, must be so small that it frequently becomes 
blocked or partially obstructed by solid residue, such as 
salt. Over a period of time, residue build-up reduces 
liquid flow into the nozzle, and thus the output of the 
atomizer changes with time. Additionally, as seen from 
FIG. 1, liquid directed to the nozzle by the feed line 
tends to collect both along the bottom of the generally 
cylindrical aperture, as indicated at 25, and also at annu- 
lar region 27, surrounding aperture 18. The collected 
liquid eventually builds up to a level at which the jet of 
air passing through aperture 18 sweeps the collected 
liquid into spray 26, causing a momentary perturbation 
in the volumetric output of the atomizer. 
FIG. 2 illustrates in detail the present improved con- 
stant-output atomizer 30. Body 38 of the atomizer has a 
cylindrical air supply conduit 32, which terminates in 
expansion nozzle 36 having generally cylindrical exit 
orifice 34. defining the throat of the nozzle, and frusto- 
conical diffuser section 50 that terminates at end face 37 
of atomizer head 38. The nozzle throat can be, e.g., a 
No. 78 drill hole. The conical walls of this expansion 
nozzle prevent any build-up of liquid, which continu- 
ously drains. Liquid, pressurized by pump P, is fed via 
conduit 40 in the atomizer head to orifice 43 located at 
the closed end of groove 42 that opens at 51 into dif- 
fuser section 50 of nozzle 36. The groove thus fluidi- 
cally connects frustoconical expansion nozzle 36 to 
orifice 43 of the liquid feed line. 
As shown in FIG. 2, groove 42 has a depth about half 
the axial length of diffuser section 50; and the groove 
extends in a direction perpendicular to the axis of the 
nozzle and radially with respect thereto, as shown in 
FIG. 3. The width of the groove (FIG. 3) is approxi- 
mately twice the diameter of the nozzle throat. 
As one example, the diameter of the body is 4 inch, 
and its length is also Q inch. The width of the groove in 
this example is 0.025 inch, and its length is 0.05 inch. 
In operation, pressurized air supplied via conduit 32 
enters the throat of the nozzle, and, in expanding, atom- 
izes liquid in open end 51 of the groove. Liquid is pre- 
cisely channelled into the expanding air jet as a result of 
the structure of the nozzle, groove, and air jet exit ori- 
4,4 13,784 
3 4 
fices, due to  capillary action of the liquid in the groove diameter of approximately 1 micron. This provides a 
and the suction or pressure drop caused by the nozzle. fine mist, which is advantageous, as described above. 
T h e  amount of liquid delivered to the nozzle via the From the foregoing description, one skilled in the art 
feed line and the channel is closely controlled by a can easily ascertain the essential characteristics of this 
precise metering pump. The  suction created at open end 5 invention, and, without departing from the spirit and 
51  by the action of diffuser section 50 eliminates accu- 
mulation of liquid, and eliminates a major cause of spray 
instability. 
The  atomizer can operate equally well in any posi- 
tion, and will atomize any solution not excessively vis- 
cous. A generally uniform output is achieved using the 
atomizer after approximately five minutes of operation. 
The atomizer is preferably used in combination with 
a liquid pump and a suitable source of dry, clean air, 
e.g., tank air o r  filtered and compressed air. When used 
in aerosol research, the atomizer is preferably mounted 
within a housing that channels the atomized mist to a 
dryer in order to evaporate the atomized droplets to 
thereby provide dry particles. One preferred aerosol- 
scope thereof, can make various changes and modifica- 
tions of the invention to adapt it to various usages and 
conditions. 
What is claimed is: 
1. An improved constant-output atomizer compris- 0 
ing: 
5 
generating system also includes a neutralizer, an elec- 20 
trostatic classifier for classifying the size of the aerosol, 
and an electrostatic aerosol detector to count the num- 
ber of particles in the mist. Such equipment is commer- 
cially available from Thermosystems, Inc. of St. Paul, 
Minn. 25 
The improved constant-output atomizer has been 
used successfully between 10 p.s.i. and 100 p.s.i., with 
the use of higher pressures permitting the attainment of 
finer mists. The  preferred range for liquid input is 0.05 
cc/min to 2.0 cc/min; the larger the liquid flow, the 30 
greater the formation of relatively large drops in the 
atomized spray. 
Recommended operation of the atomizer includes 
initially supplying air through the exit orifice 34, and 
thereafter supplying liquid to  the groove. By proceed- 35 
ing in this fashion, liquid will be prevented from enter- 
ing orifice 34. To terminate operation, the liquid is first 
shut off, and thereafter the air supply cut off, in order to 
minimize or entirely prevent excess liquid from collect- 
ing and being retained within the nozzle. After use, it is 40 
preferable to  wash and clean the apparatus with fresh 
water. 
The improved constant-output atomizer can be used 
to generate aerosols in cloud-physics experiments, e.g., 
in experiments such as those which are being proposed 45 
for use in the space shuttle. The atomizer can also be 
used in inhalation therapy and in aerosol research, both 
of which require a stable output of droplets from an 
atomizer. Further, the uniform, steady mist produced 
by the atomizer can be used to deliver an even and thin 50 
coating to desired surfaces. 
By using the atomizer to produce a very fine atom- 
ized mist, any dried particles, e.g., NaCI, which are 
present will be quite small, e.g., of sub-micron size; such 
particles are quite useful in cloud-physics studies. Fur- 55 
ther advantages are attained by using the atomizer in 
inhalation therapy, where the efficiency of a drug being 
introduced into the lungs increases in proportion to the 
fineness of the mist inhaled by the lungs. 
the atomizer of FIG.  2, the output of the present atom- 
izer was determined to be relatively constant, whereas 
the output of the atomizer of FIG.  1 produced a droplet 
output which varied over a larger range within a similar 
time. Additionally, the test results determined that the 65 
peak concentration of droplet size occurs at a droplet 
In tests which compared the atomizer of FIG.  1 with 60 
a body containing an air supply conduit; 
an expansion nozzle formed in the wall of one end of 
said body, said expansion nozzle having a Iongitu- 
dinal axis, said nozzle comprising an exit orifice 
connected to  said air supply conduit and a frusto- 
conical diffuser section connecting said exit orifice 
to the outside surface of said end of said body, said 
frustoconical diffuser section widening from a nar- 
row upstream end to a widened downstream end, 
said upstream end being contiguous with said exit 
orifice and of the same size as said exit orifice to  
form a smooth, continuous transition from said exit 
orifice to said frustoconical diffuser section; 
a transverse groove cut in the surface of said end of 
said body, one end of said groove connecting with 
and extending into the side of said frustoconical 
diffuser section; 
a liquid conduit formed in the wall of said one end of 
said body; 
a metering pump connected to one end of said liquid 
conduit for moving liquid to said atomizer at a 
precise and constant rate; 
an orifice for liquid connected to  the opposite end of 
said liquid conduit, said liquid orifice connecting 
said liquid conduit to said transverse groove; 
whereby liquid expelled from said orifice for liquid 
travels in a stream down the length of said trans- 
verse groove into said diffuser section where it 
combines with air expelled from said exit orifice 
and is atomized to produce a constant output. 
2. An improved constant-output atomizer in accor- 
dance with claim 1, wherein said exit orifice is cylindri- 
cal and said exit orifice and said frustoconical diffuser 
section are symmetrical about said longitudinal axis of 
said nozzle, said axis extending longitudinally through 
said exit orifice and longitudinally through said diffuser 
section and being perpendicular to said outer surface of 
said end of said body. 
3. An improved constant-output atomizer in accor- 
dance with claim 2 wherein said transverse groove is 
directed perpendicular to  the longitudinal axis of said 
nozzle. 
4. An improved constant-output atomizer in accor- 
dance with claim 3 wherein said transverse groove is 
radially located with respect to said nozzle longitudinal 
axis. 
5.  An improved constant-output atomizer in accor- 
dance with claim 4 wherein the depth of said transverse 
groove is approximately half of the axial length of said 
nozzle. 
6. An improved constant-output atomizer in accor- 
dance with claim 5 wherein the width of said transverse 
groove is approximately equal to twice the diameter of 
said exit orifice. * * * * *  


Constant-output atomizer

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