US3169508A

US3169508A - Elastic wave generator

Info

Publication number: US3169508A
Application number: US251838A
Authority: US
Inventors: Stanley R Rich
Original assignee: Northern Industries Inc
Current assignee: Northern Industries Inc
Priority date: 1963-01-16
Filing date: 1963-01-16
Publication date: 1965-02-16
Anticipated expiration: 1982-02-16

Description

Feb. 16, 1965 s. R. RICH 3,169,508

ELASTIC WAVE GENERATOR Filed Jan. 16, 1963 2 Sheets-Sheet 1 FIG! INVENTOR STANLEY R. RICH ATTORNEY Feb. 16, 1965 s. R. RICH ELASTIC WAVE GENERATOR Filed Jan. 16, 1963 2 Sheets-Sheet 2 5| ST T SUPERHEA ER SO E 26 INVENTOR.

STANLEY R. RICH BWZW ATTORNEY 3,169,508 ELASTIC wAva oannrznron Stanley Ranch, west Hartford, Conn, assignonby 'm'esne assignments, to Northern Industries, *Iuc Dover, Del.,

a corporation-f Delaware Filed Jan. 16, 1963, Ser. No. 251,838 7 Claims. (Cl. 116-137) This invention relates in general to apparatus for gen erating high intensity elastic waves in a gaseous medium for industrial purposes, and more particularly to the class of such apparatus which depends for its operation upon fluid dynamics in a structure having parts fixed relative to one another, rather than upon relative motion between parts of a structure having relatively movable parts. i. J

Apparatus of the class to which the invention relates is generally characterized by jahollow acoustic resonator having an opening thereinto, and a gas nozzle confronting the opening for propelling a stream of gastoward the opening to generate elastic wave energy While such apparatus is now available for continuous use over long periods of time with dry'air or other gas, attempts to use a wet gas, such as saturated or wet steam, have not met with the same success because liquid collecting in the resonator interrupts the operation. The problem is not the same as is encountered'with steam Whistles which are intended only forintermittent operation, and can be mounted so that their resonators have their open sides or ends at the bottom, and which, moreover, are designed for audible sound generating only; and are consequently relatively large as compared with generators to which the present invention relates. The latter generators are preferably designed to operateiin the superaudible regions, or

in the upper audible regions (e.g., 8 lie/ sec. or'higher),

and consequently have resonators which a're'quite small as compared with audible whistles. Furthermore, gasborne elastic wave generators for industrial purposes should preferably be able to be mounted in any conceivable position or orientation, and in many cases must be mounted with their resonators open at the top. These considerations, taken together with the requirement for the ability to be operated continuously for longperiods of time, have heretofore substantiallyfprevented'the use of steam as the driving gas forthe'gas-driven fluid-dynamic class of generators of gas bor'ne elastic wave energy for industrial purposes.

It is theprincipal object of the present invention to provide new and improved apparatus of the fluid-dynamic class for generating elastic waves in a gaseous medium, which can be operated continuously for long periods of time with steam or other wet or liquid-bearing gas, as Well as with any of the dry gases heretofore useful. Another object is to provide such improved apparatus which can be made to operate in the ultrasonic frequency range.

Additional objects are to provide such improved apparatus which is self-cleaning, which does not have severe dimensional tolerances, which can be operated in any position or attitude, which will be economical to build and operate, and rugged in construction, which will'requii'e little or no maintenance, which will resist contamination during operation with foams, for example, which' will be easily cleaned, assembled and put into use, and which can be adapted to all types and kinds of gas-phase'applications of elastic wave power. v

According to thefinve'ntion in one of its more general aspects, there is provided a new and improved apparatus for generating elastic waves in a gaseous medium comprising a hollow acoustic resonator having an opening thereinto, means to propel a stream of gas at said opening for generating said waves, and means comprising a 3,169,508 Patented eh. '1 6, i965 of liquid at all times during operation of the apparatus.

According to 'the invention in one of its more particular aspects, there is provided, in one embodiment, "an apparatus for generating elastic waves in a gaseous medium comprising a hollow acoustic resonator having an opening thereinto, means to propel 'a stream of gas at said opening for generatingsaid'waves, means providing an 'annular'passa'ge the cross-sectional area of which progressively increases 'substanti'ally-withthe radius thereof cou- "pled at its smaller end to said opening for exhausting the "gas ot'said stream and guiding said waves .to am ambient region, wave director means in register with the larger end of said passage to direct'said exhaust gas and waves in a common direction, and means comprising a separate passage from said resonator to drain liquid from. said resonator substantially toward said common direction.

Thisapparatus may conveniently be realized in a circular 'or cylindrical form which ispa'rticularly easyjto manufacture and assemble.

According to another aspect of the invention, the r'es- 'onator may be realized'in a separate part, which can be exchanged in a particular apparatus, so that a desired operating frequency can be chosen without changing the entire apparatus, and this part can include the drain means for the particular resonator it'embo'dies.

According to still another aspect' of the'inventi'on, there 'is provideda "system for generating elastic Waves 'in a gaseous medium comprising in combination, a hollow acoustic resonator havingan opening thereinto, a source of steamunder'pressure, riieans'connected to said source to propel a stream of steam at said opening for generating "said 'Waves,"and means comprising'a separate passage from 'said resonator to drainliquid from said resonator.

The invention isparticularly useful for generating high intensity elasticwave energy in a gaseous medium, using either wet'ordry gas as the source of driving energy. By the term high intensity is meant ei'asti'c wave'energy inla gaseous medium '(e.g., sonic or ultrasonic energy) atan intensity level upto' about db (.1 watt/cm?) or more. By the term gas it is meant to include-steam, air, nitrogen, carbon dioxide, and the like, without limitation.

The invention will now be described with reference to the accompanying drawings, wherein: 1

FIG. 1 is an axial section through a generator according to the invention;

'FIG. 2 is'an end view, on a reducedscale, of PEG. 1 as seen from the right-hand end of FIG. 1;

FIG. 3 is a cross-section on line 3-3 of FIG. 1; and

FIG. 4 is a system incorporating a generatorv according to FIGS. 1-3, inclusive.

Referring to FIGS. 1-3, inclusive, a first cylindrical body 10, having a convex conical surface 11 and first axial bore lz passing through it, confronts a second cylindrical body 15 having a concave conicalsurface 16 and Y a second axial bore llpassing through'it. These'two bodies are mounted one tothe other by stand-off

posts

18, 19, which may be welded or otherwise fastened in place, so that the convex and concave surfaces 11 and A cylindrical elongated resonator part 20 is located in the bore 12 of the first body 10. The resonator part has at one end a resonator cavity 21,'of which one end 22 confronting the second body 15 is open; the other end 23 is closed except for a vent passage 24 of smaller diameter than the resonator cavity which extends from the closed end 23 through the remainder of the resonator part 20. The resonator part 20 is held in the bore 12 by a set screw 25. A somewhat hemispherical cover 26 is fitted over the right-hand ends of the first body and the resonator part 20, for streamlining purposes. This cover has a vent passage 27 through'it in axial register with the vent passage 24 from the resonator 21-, and is held in place by a second set screw 28.

The bore 17 in the second body is fitted with a gas nozzle 30 confronting the open end 22 of the resonator cavity 21. This nozzle comprises a hollow cylindrical part 31 which fits tightly into the bore 17, and has its inner cross-section tapered to a smaller diameter as it approaches the resonator cavity 21, and a solid cylindrical part 32 axially disposed within the'hollow part to provide an annular gas passage 33 confronting the resonator cavity. The outer diameter of the gas passage is approximately the same as, or slightly smaller than, the

diameter of the open end 22 of the resonator cavity. The

nozzle parts

31 and 32 are held together by a spanner bar 34 which is fitted into two diametrically-

opposite slots

36, 37 in the end of the hollow member 31 remote from the resonatorcavity 21, and in a slot 38 at the corresponding end of the solid part 32. The region at the end 3970f the bore 17 most remote from the first body 10 may be internally threaded, for attachment to a feed pipe 41 for gas or steam (as shown in FIG. 4).

A wave director 42, having a cylindrical collar part 43 and an integral bell part 44 holds the second body 15 in the collar part. The base 45 of the collar part is apertured for passage of a gas feed pipe (not shown in FIG. 1). The bell part 44 has its inner surface at the collar part 43 in register with the concave surface 16 of the second body 15, from which the bell part flares outward from the axis AA and projects forward to envelop the first body 10 and its contents.

The generator apparatus of the present invention may be operated in a system as illustrated in FIG.. 4. A source of steam 50 may be connected by a pipe 51 to a superheater 52 and thence via another pipe 41 to the generator. With -a generator according to the present invention the superheater 52 is optional, since the generator can be operated with wet steam. Practical embodiments of the generator shown in FIGS. 1-3, inclusive, use /2 to pound of steam per minute at 30 to 40 p.s.i. (gauge). a

In operation, the driving gas from the nozzle passage 33 cooperates with the resonator cavity 21 to produce gas-borne elastic wave energy in a known manner. Ex haust gas and the generated elastic wave energy pass through the annular passage defined by the conical walls 11 and 16 to the bell part 44 of the wave director, which directs both forward over the first body 10 and the cover 26.

Any liquid which enters the resonator cavity 21 can readily and without delay escape via the liquid

drain vent passages

24 and 27. The bottom 23 of the resonator cavity is desirably tapered toward the vent passage 24, to facilitate the escape of liquid. The diameter of the vent passage 24 is so small, relative to the wavelength of elastic wave energy in air at the operating frequency, typically about 0.060 inch at frequencies up to about 25 kc./sec., for example, that the elastic wave energy cani not propagate through the vent passage, while liquid and gas can escape through it. The vent passage may be regarded as a vent which is so small relative to the bore of the resonator cavity 21 that it functions as an acoustic inductance of which the reaotance, jwM, is large com- KLw7=2Trf; I M=rnass of air (or other gas) in the vent column; and =the operating frequency.

The length of the vent passage 24 does not'appear to be critical; however, it can readily be made to be t/4 relative to the wavelength of the elastic wave energy being generated, if desired.

It will be recognize that liquid will escape via the vent passage 24 regardless of the orientation or attitude of the generator. If its axis AA is vertical, liquid will obviously pour out of the resonator cavity 21. If the axis AA is horizontal, liquid will be blown out by gas from the nozzle 30. This will not interfere with or degrade the elastic-Wave generator function of the apparatus. Further, there is no need to mate the meeting surfaces of the resonator part 20 and the cover 26 (when the latter is used); since liquid in the space between them has no effect on the generation of elastic wave energy. Liquid in that space readily escapes in any. event, due either to gravity or to gas escaping through the

passages

24 and 27.

Apparatus according to the invention has been successfully used repeatedly on an industrial scale with steam, both wetand dry, air under pressure and contaminated with oil, and other liquid-bearing gases.

As is well-known, the frequency of operation is deter mined essentially by the depth of the resonator cavity 21. Typical depths for frequencies in the range 8,000 to 24,000 cycles per second, in a cavity inch in diameter,

(a) for frequencies of the order of 20 kc./sec.: inch (b)for frequencies of the order of 12 kc./sec.: inch These depths are measured to the beginning of the taper in the bottom 23. As has been indicated above, the diameter of the vent passage 24 may typically be about 0.60 inch.

The apparatus may be made of any suitable material. Stainless steel of the 300 series is preferred.

The embodiments of the invention which have been illustrated and described herein are but a few illustrations of the invention. Other embodiments and modifications will occur to those skilled in the art. No attempt has been made to illustrate all possible embodiments of the invention, but rather only to illustrate its principles and the best manner presently known to practice it. Therefore, while certain specific embodiments have been described as illustrative of the invention, such other forms as would occur to one skilled in this art on a reading of. the foregoing specification are also within the spirit and scope of the invention, and it is intended that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

What is claimed is:

1. Inapparatus for generating elastic waves in a gaseous medium with an acoustic resonator cavity, an opening at one end of said cavity and means to pnopel a stream of gas at said opening for generating said Waves, the improvement comprising, a comically shaped wall means in said cavity opposite said opening, said wall means providing a vent column of generally uniform cross-section smaller than the cross-section of said cavity and extending away from the wall means in said cavity opposite said opening for draining liquid from said resonator, said cross-section of said vent column being so small that said vent column functions as an acoustic inductance, with respect to said waves, of which the reactance jwM is large compared with the acoustic impedance of said resonator cavity, where uw 27rf; f the frequency of said waves; and M =mass of gas in said vent column.

from said opening, and means providing a vent column of generally uniform cross-section extending away'frorn said other end of said passage for draining liquid from said resonator, said cross-section of said vent column being so small that said vent column functions as an acoustic inductance, with respect to said waves, of Which't'ne reactance jwM is large compared with the acoustic impedance of said resonator cavity, where f=the frequency of said waves; and yi=rnass of gas in said vent column.

3. Apparatus according to claim 1 in w hich said cavity is cylindrical, said opening is at one end of the cylinder and said vent column is at the other end of said cylinder and extends straight on the cylinder axis away from said resonator. i

4. Apparatus according to claim 2 in which said cavity is cylindrical, said opening is at one end of the cylinder and said vent column is at the other end of said cylinder and extends straight on the cylinder axis away from said resonator. I V

5. Apparatus according to claim 3 in which said means to propel a stream of gas at said opening provides an annular stream of gas the outer diameter of which is not larger than the diameter of said resonator.

6. Apparatus according to claim 1 in combination with a source of steam under pressure connected to said means to propel a stream of gas at said opening.

7. Apparatus according to claim 1 in which said source of steam includes a steam sunerneater.

References Cited by the Exaer UNi'iLi) s'rArEs PATENTS 84,239 11/63 Wfiinmaiin 116-137 1,930,171 11/34 Amy Q 116-137 2,238,663 4/41 Wellenstein 116l37 2,788,656 4/51 Sander 73-24 2,944,029 7/59 Jones et a1 116-137 3,664,619 1 1/62 Fortman Q 116- 137 3,081,979 3/63 Lindsey 259-1 FOREIGN PATENTS 70,342 11/58 France. 1

' 749,021 11/44 Germany.

Louis I. CAPOZI, Primary Examiner.

Claims

1. IN APPARATUS FOR GENERATING ELASTIC WAVES IN A GASEOUS MEDIUM WITH AN ACOUSTIC RESONATOR CAVITY, AN OPENING AT ONE END OF SAID CAVITY AND MEANS TO PROPEL A STREAM OF GAS AT SAID OPENING FOR GENERATING SAID WAVES, THE IMPROVEMENT COMPRISING, A CONICALLY SHAPED WALL MEANS IN SAID CAVITY OPPOSITE SAID OPENING, SAID WALL MEANS PROVIDING A VENT COLUMN OF GENERALLY UNIFORM CROSS-SECTION SMALLER THAN THE CROSS-SECTION OF SAID CAVITY AND EXTENDING AWAY FROM THE WALL MEANS IN SAID CAVITY OPPOSIRE SAID OPENING FOR DRAINING LIQUID FROM SAID RESONATOR, SAID CROSS-SECTION OF SAID VENT COLUMN BEING SO SMALL THAT SAID VENT COLUMN FUNCTIONS AS AN ACOUSTIC INDUCTANCE, WITH RESPECT TO SAID WAVES, OF WHICH THE REACTANCE JWM IS LARGE COMPARED WITH THE ACOUSTIC IMPEDANCE OF SAID RESONATOR CAVITY, WHERE "W"=2$F; "F"=THE FREQUENCY OF SAID WAVES; AND "M"=MASS OF GAS IN SAID VENT COLUMN.