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Publication numberUS3788543 A
Publication typeGrant
Publication dateJan 29, 1974
Filing dateSep 14, 1972
Priority dateSep 14, 1972
Publication numberUS 3788543 A, US 3788543A, US-A-3788543, US3788543 A, US3788543A
InventorsP Amand, I Koff
Original AssigneeUs Navy
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Uniform size particle generator
US 3788543 A
Abstract
A method and apparatus is disclosed for generation of fine particles, for example of silver iodide, from a nebulizer for cloud seeding. The nebulizer comprises a large container in which is maintained a constant level of a combustible or highly volatile solution such as an acetone solution of silver iodide. An ultra-sonic generator in the base of the container produces micron size droplets of the solution in the airspace above the solution. The droplets are forced out of the container by a stream of solvent laden air into a burner or vent which burns or evaporates the solvent. Fine particles of the solute silver iodide remain for the cloud seeding operation.
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United States Patent 1191 St. Amand et al.

[ UNIFORM SIZE PARTICLE GENERATOR [75] lnventors: Pierre St. Amand; Irwin Koff, both of China Lake, Calif.

[73] Assignee: The United States of Americans represented by the Secretary of the Navy, Washington, DC

221 Filed: Sept. 14,1972 21 Appl. No.: 289,202

[52] US. Cl 239/2'R, 239/14, 239/102, v 239/136 51 Int. Cl A0lg 15/00 [58] Field of Search....,..... 239/2, 14, 102, 136, 142

[56] References Cited UNITED STATES PATENTS 7 2,527,231 10/1950 Vonnegut 239/2 R x 3,387,607 6/1968 Gauthier 239 102x 3,545,677 12 1970 Power 239 2 R Jan. 29, 1974 Primary ExaminerRichard A. Schacher Attorney, Agent, or Firm-R. S. Sciascia; Roy Miller; Gerald F. Baker [5 7] ABSTRACT A method and apparatus is disclosed for generation of fine particles, for example of silver iodide, from a nebulizer for cloud seeding. The nebulizer comprises a large container in which is maintained a constant level of a combustible or highly volatile solution such as an acetone solution of silver iodide..An ultra-sonic generator in the base of the container produces micron size droplets of the solution in the airspace above the solution. The droplets are forced out of the container by a stream of solvent laden air into a burner or vent which burns or evaporates the solvent. Fine particles of the solute silver iodide remain for the cloud seeding operation.

10 Claims, 2 Drawing Figures ULTRASONIC GENERATOR PATENTED JAN 2 9 I974 3nT885d3 ULTRASONIC GENERATOR NUCLEI COUNT A SOLUTION L9 GM SOL/MIN AT DIAL SETTING No.6 5-MIL DIAPHRGM O l/ SOLUTlON L9 GM SOL/MIN AT DIAL SETTING N0. IO 0.5 MIL DIAPHRGM 9 l l l l 1 o -2 -4 -s -s -|0 -12 TEMPERATURE, c

Fig. 2

. 1 1 UNIFORM SIZE PARTICLE GENERATOR BACKGROUND O THE INVENTION This invention relates generally to weather modification and more particularly to the seeding of clouds using ice-nucleating particles, for example silver iodide. Cloud seeding using crystals of silver iodide for example, has been accomplished by a combustion process of vaporizing silver iodide at a high temperature and causing it to recrystallize or by spraying into the atmosphere a solution of silver iodide in ammonia or by burning a solution of silver iodide in acetone.

These procedures, with variation, have been tested and used over a period of years with varying degrees of success depending upon the cloud conditions. It has been found, however, that these prior attempts at weather modification were erratic and unpredictable.

On the theory that control of particle size would result in more efficient and predictable cloud seedings, an apparatus according to the present invention was developed to provide minute particles of uniform size. These particles of controlled size and specific material can be used as cloud seeding nuclei to freeze supercooled water droplets at desired freezing temperatures within a particle cloud with greater realiability and predictability.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWING FIG. 1 is a plan view of a uniform particle size generator according to the invention; and

FIG.'2 is a graphic illustration of test data obtained from two test of an apparatus according to FIG. 1.

DESCRIPTION AND OPERATION The particle sizing process according the invention involves the use of an ultrasonic nebulizer, one form of which is generally indicated by numeral in FIG. 1. The nebulizer 10 comprises a neublizing chamber 12 mounted on a base 14. A combustible or highly volatile solution 16 of desired solute concentration is shown within thechamber 12. A-piezoelectric crystal 18, for example is located at the bottom of the nebulizing chamber and separated therefrom by a plastic energy transfer diaphragm l9. Acutation of said crystal generates sufficient ultrasonic energy to cause relatively uniform droplets to form from the solution. The micron size droplets thus generated in the nebulizing chamber, form a continuousv cloud that is continually removed from the chamber by the movement of solvent saturated air indicated by arrows 20. For this purpose a blower 22 is provided having a discharge nozzle 23 below the surface of solution 26 in container 24. Container 24 connects with the chamber 12 through tube 28. During operation, this solvent saturated air moves the cloud of droplets out of chamber 12 through a vent 30 having a plurality of buffers 31 and terminating at its outer end in a burner 32, for example, where the cloud of solvent etc. may be ignited by a glow plug or other igniter 34.

Burner 32 is shown surrounded by a structure 36 which may be closed by a sized screen that would further refine the segregation of large and small drops. As

the solvent burns or evaporates, the solute residue remains in the form of dry particles of a predetermined uniform size. The size of the particles is controlled primarily by the concentration of the solute in the solvent and secondarily by nebulizing parameters including solution level, input energy to the ultrasonic generator, solution viscosity, etc.

PRELIMINARY ICE NUCLEI ACTIVITY TESTS Two initial nuclei activity tests were conducted in a 24 cubic meter cold chamber. The first was performed without a liquid leveler in the nebulizing chamber and a l-mil thick plastic (Mylar) energy transfer diaphram. A minimum power setting was used. The subsequent test utilized a constant liquid level system 40, 42, 44 and a 5-mil thick Mylar diaphram 19. A medium power setting was used. Data obtained from the two tests are presented in FIG. 2. The data of the latter test indicate that the size of the nuclei is an important factor with regard to nuclei freezing threshold.

Although the above methodand apparatus has been described in terms only with respect to cloud seeding with silver iodide, obviously many other solutions may be utilized in the nebulizer not only for weather modification and fog dispersal but also for medication and other commercial application.

We claim:

1. A process for the seeding of clouds using ice nucleating particles including the steps of:

dissolving a salt in a combustible solvent to form a solution;

ultrasonically agitating said solution to provide an airbom collection of irregular droplets;

forcibly moving a stream of solvent laden air to create an airbom stream of said irregular droplets away from said solution;

separating and returning the larger droplets from said stream to said solution such that the resulting droplet stream comprises a narrow size spectrum of fine droplets of said solution;

dissipating the solventfrom said resulting stream of fine droplets; and dispensing the resulting particles of solute into the atmosphere.

2. The process of claim 1 wherein the solvent is dissipated by evaporation.

3. The process of claim 2 wherein the salt used is silver iodide.

4. The process of claim 1 wherein the solvent is dissipated by burning.

5. The process of claim 4 wherein the salt used is silver iodide.

6. Means for producing uniform particles comprising:

a first enclosed container;

a salt solution in said container;

ultrasonic means agitating said solution in said container to produce a cloud of airbom droplets of solution;

a second container communicating with said first container and being partially filled with solvent; forced air circulating means causing movement of said cloud of droplets by means of a stream of air forced through said solvent;

a vent defining a passageway for said cloud of droplets out of said container;

a plurality of baffles in said vent causing removal and return of larger droplets from said cloud of droplets; and means external of said vent and in the path I of said cloud of droplets for dissipating said solvent.

3 4 7. The apparatus of claim 6 wherein said solution droplets. comprisesavolatile solvent and said means for dissipat- 9. The apparatus of claim 8 wherein said solution ing is a burner. consists of silver iodide and acetone.

8. The apparatus of claim 6 wherein said solution 10. The apparatus of claim 6 wherein said solution comprises a combustible solvent and said dissipating comprises silver iodide. means serves to ignite said solvent in said cloud of

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2527231 *Oct 1, 1948Oct 24, 1950Gen ElectricMethod of generating silver iodide smoke
US3387607 *Mar 27, 1967Jun 11, 1968Vilbiss CoApparatus for inhalation therapy
US3545677 *May 3, 1968Dec 8, 1970Power Bernard AMethod of cloud seeding
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3877642 *Aug 9, 1974Apr 15, 1975Us NavyFreezing nucleant
US3899129 *Apr 16, 1974Aug 12, 1975Us InteriorApparatus for generating ice nuclei smoke particles for weather modification
US3926369 *Nov 30, 1973Dec 16, 1975George W PearceControlled spraying
US4129252 *May 23, 1975Dec 12, 1978Pouring Andrew AMethod and apparatus for production of seeding materials
US4176790 *Sep 22, 1978Dec 4, 1979Osorio Manuel MComposition for and method of causing rainfall
US4776990 *Sep 14, 1987Oct 11, 1988Rhinotherm Netzer SereniMethod and apparatus for nebulizing a liquid
US5922247 *Aug 8, 1997Jul 13, 1999Green Clouds Ltd.Ultrasonic device for atomizing liquids
EP2277371A1Jul 20, 2010Jan 26, 2011Ekodenge Cevre Danismanlik Ve Muhendislik Hizmetleri Limited SirketiPrecipitation management method by desert soil
EP2604915A1 *Dec 10, 2012Jun 19, 2013Valeo VisionLighting and/or signalling device and motor vehicle including such a device
WO2003061370A1Dec 25, 2002Jul 31, 2003Arkhipov VladimirMethod and apparatus for controlling atmospheric conditions
WO2008149334A2 *Apr 29, 2008Dec 11, 2008Amiram KeshetNebulizer and driver circuity therefor particularly useful for converting liquids to fine sprays at extremely low rates
Classifications
U.S. Classification239/2.1, 261/DIG.480, 239/102.2, 239/136, 239/14.1
International ClassificationA01G15/00
Cooperative ClassificationA01G15/00, Y10S261/48
European ClassificationA01G15/00