US2910865A - Method of visualizing flow patterns - Google Patents

Description

Nov. 3, 1959 R. E. OPDYKE 2,910,865

METHOD OF VISUALIZING FLOW PATTERNS Filed Aug. 30. 1956 United States Patent Ofiice 2,910,865 Patented Nov. 3, 1959 METHOD OF VISUALIZING FLOW PATTERNS Richard E. Opdyke, West Allis, Wis., assignor to Allis- Chalmers Manufacturing Company, Milwaukee, Wis.

Application August 30, 1956, Serial No. 607,164

8 Claims. (Cl. 73-147) The present invention relates to a method of analysis and more particularly to a method of visualizing the flow patterns of noncombustible combustion supporting gas streams.

In the selection of conduit for containing a desired flow of gaseous fluids, it is frequently vital that the characteristics of gaseous flow through conduit of various geometric configurations be determined to permit the utilization of conduit most properly suited to the desired flow. The characteristics can best be determined by creating flow through a prototype and analyzing its flow pattern provided that pattern is true.

A further area in which knowledge of the characteristics of gaseous flow is vital is in the design of articles, such as aircraft, which operate in gas streams under flow conditions assimilated by the stream induced in the prototype. Again, it is essential that the flow pattern be true.

The problem of creating true gas flow patterns in prototypes of conduit and other aerodynamic apparatus has perplexed men in that art for many years. The problem is particularly aggravated in regions of flow having Reynolds numbers in excess of about 3,000 because the flow become turbulent in character.

. Basically, the prior art techniques or methods of visualizing gas flow fall into three categories, namely: (1) the contamination of the gaseous fluid with foreign matter; (2) the utilization of optical efiects; and (3) especially prepared flow passage boundaries.

The present invention reates to the first of these categories, to wit, the contamination of the gaseous fluid with foreign matter. The prior are methods in this category include the introduction of balsa Wood dust, elongated ribbons and strings, cotton tufts, and smoke trails. Of these, the introduction of smoke is perhaps the most successful but even it is limited to streamline or laminar flow, i.e., flows having a Reynolds number of less than 3000 and most generally less than 2100. These methods are further limited in that they are not adaptable to flow through rotating machine elements, such as blower impellers.

The smoke method specifica ly comprises introducing smoke into a conduit through which a gas flow has been created and observing, through a transparent Wall in the conduit. the path followed by the smoke as it is carried by the gas. With streamline flow, the smoke provides a decent laminar flow pattern having discrete paths. With turbulent flow, the smoke, in response to the turbulence, diffuses into a single cloud and no discrete paths are observable. Consequently with respect to turbulent flow, the smoke technique is virtually useless.

The other foreign particles enumerated above are subiect to the same general limitations as the smoke in varying degrees, i.e., independent paths cannot be observed. Furthermore, use of all of these foreign particles to achieve results usually requires costly and complicated equipment.

In addition to teaching the introduction of the aforementioned foreign matter into the gaseous fluid flow as a usual means for visualizing subsonic flow having low Reynolds numbers, the prior art teaches using especially prepared boundary patterns as another means for. determining the characteristics of subsonic flow and optical effects as the usual means for visualizing transonic and supersonic flow. Inasmuch as the present invention does not relate to the concept of either especially prepared boundaries or optical eflects, these techniques will not be further discussed.

In all the know prior art, there is no teaching of a method for accurately representing for visualization and/or otherwise recording the flow pattern of gases in the subsonic range at Reynolds numbers in excess of about 3000 and through moving or rotating machine elements. A need for such a method is very real and ver much present.

The present invention proposes to satisfy that need by a method comprising the introduction of low mass selfilluminating tracer particles into a gas stream for observing and/or otherwise recording the paths of the particles as they are borne by the stream and by various compositions of matter of which the particles are made, each of said compositions consisting of carbon, admixed with an oxidizing agent and a'binder. A reducing agent may also be incorporated into the admixture when certain flow conditions exist as will be more fully explained.

Accordingly, one of the primary objects of the present invention is to provide an improved method for visualizing flow patterns of gaseous fluids which is not limited to any particular range of Reynolds numbers and which provides equally satisfactory results regardless of the velocity of the fluid flow.

Another object of the present invention is to provide a method of visualizing flow patterns of gaseous fluids in which the flow pattern is accurately reflected by selfilluminating tracer particles which are introduced into and borne by the fluid stream.

Another object of the present invention is to provide an improved method for visualizing gas flow patterns in curved conduit by introducing into the gas flow particles having a sufliciently low mass to be carried by the fluid stream without being detoured by centrifugal action as would be characteristic of particles of larger mass.

A still further object of the present invention is to provide an improved method for visualizing flow patterns which is easily and simply performed and which does not require costly and elaborate setups and equipment.

An even further object of the present invention is the provision of an improved method for visualizing flow patterns utilizing a self-illuminating tracer particle having sufficiently low mass to respond to the velocity component of the fluid flow in the direction of flow to reflect a true pattern of that flow and to resist forces which might otherwise distort the pattern of flow.

A still further object of the present invention is the provision of an improved method for visualizing flow patterns by which subsonic turbulent flow through moving or rotating machine elements may be easily and readily determined.

These and still further objects will become apparent from the following detailed description when read in conjunction with the accompanying drawing in which:

Fig. 1 is a view in elevation of apparatus by which the present invention may be utilized; and

Figs. 2 and 3 are elevations of various sparkler configurations.

In Fig. 1, a'typical'aerodynamic prototype 11 is supported by suitable supports 12. A transparent plate 13 is disposed in the outer wall of a longitudinal portion 14 of prototype 11 and a transparent plate 15 is disposed in the outer wall of 'elbow 16. Transparent plates 13, 15

3 may be disposed in the outer wall of ariy portion of the prototype to observe the flow pattern in that portion since the position of plates 13, 15 in Fig. 1 is merely exemplary. Or the entire prototype may be made of transparient :inat'erial when testconditions dictate that it be so made.

To analyze and observe the flow pattern through the longitudinal portion 14 f the protoype 11, a Sparkler 21 is inserted in the prototype as at 22 and is supported by any suitable manner, such as by hand 23; The gaseous stream is created through the prototype in any suitable manner such as running a blower 2 4 having its outlet in register with prototype 11. Sparkler 21 is here shown un'ignited.

The method or the present invention specifically com= prises the introduction into a gaseous stream of burning or glowing particles of 'su'fliciently small mass that they are carried by the fluid flow and are not adversely infiu= enced by inertia or centrifugal forces. By either visual or photographic analysis of the luminous particle traces or paths through a wholly or partly transparent prototype, the gas flow pattern may be studied precisely and may be the subject of photographic analysis.

In addition to the utilization of sparklers in an improved method of visualizing gas flow by burning the sparklers and introducing the resulting sparks into a flowing gaseous stream, the present invention further embraces certain compositions of pyrotechnic matter from which the sparklers are made.

Certain characteristics are desired for a sparkler comprising a composition conforming to the present invention They are that the Sparkler shall: burn and emit sparks; be self-propagating; not flame; not smoke excessively; not burn too rapidly; not emit ash or other residue; and have a physical configuration which is adaptable to prototypes of many geometric configurations. Further, the emitted sparkshall be characterized in that it shall: be self-illuminating; have a mass which is sufliciently low to create a balance between the drag, S'WpDv, (where r 114; #:Viscdsity of the gas; Ddi= ameter of particle; and v,=radial velocity of particle), and the centrifugal force, mvf/f (where m' in'ass of particle; v 'tangential velocity of article; and r radius or curved section), acting on the particle in curved sec= trons,- and between the drag and the forces acting on the particle in straight "sections; have a long life; and have a visible brilliance.

The sparklers utilized may be or any suitable confi oration such as will give a maximum dispersion of sparks ihto' the fluid stream and are preferably limited only b the geometry or the prototype to be analyzed. For exam- }fl, in tli afifilyzifiiclfl of fluid flow through the; Cylindrical tubeor Fig. 1, a straight Sparkler 21 (shown enlarged sparkles Z1 iil Fig. 2) gives l-il ifiOSt desirable fes'llltS since it ETEWGTQS ih HOW pfbfilt Othi prototypes may be better suited to a spa-rider hoop (shown as 21' in Figs 3)= The sparklers may be preps-red aii'y suitable method such as that by which commercial Fourth of July sparklers are made, to Wit; the dry it'lgidiflis, add Stifiiifitwater to form it viscous paste, deposit the paste on a wire and dry the coatin on the wire. The paste can be deposited-on the wire by molding, dipping or othersuitable means. It is ref rred that the wire be shaped before coating since the dry coating has a tendarray to chip when bent.

While the methods of preparation are similar, commercial sparklers do not particularly lend themselves to the present invention because the mass of the iron particles they use is generally too great to permit burning iron particles to freely follow the gas flow. Comparative tests were conducted utilizing as the source of sparks, first, the so-called Fourth of July or commercial sparkler and, then, the sparklers ofthe present invention. In both runs, the sparks were introduced into an air 4 stream passing through an elbow at 60-80 fps with a Reynolds number of about 45,000. It was readily observed that the commercial sparks, because of the inertia resulting from their larger mass, ricochet .off the inner walls of the elbow instead of following the air stream; whereas the carbon sparks of the present invention, because of their smaller mass, follow the air stream.

The importance of the sparks having a low mass is further apparent, both in the detection of vortices and in the location of leaks in the conduit.

According the present invention further includes various sparklei compositions which provide all of the characteristics desired for use with the present method. The particles of these compositions are characteriZed by being self-illuminating and having sufiiciently low mass to be carried by the fiuid stream.

Sparkler compositions which give most satisfactory results when employed in the method of the present invention contain carbon, sugar, deXtriile; potassium chlorate, barium nitrate and aluminum. "Of these ingredients, the carbon is the source of the sparks which are carried by the gas stream. Sugar (C H O and deir'trine (Gail- 6 act as binders and as a source of readily oxidizable carbon. Care should be exercised not to use "more dextrine than sugar because excessive dextrine causes the occurrence of a liquid has during burning which deters satisfactor combustion. On the other hand, excessive sugar, 'i.'e., in proportion to the total ingredients in the nurture, results in inadequate binding and cornbustion residue is introduced into the gas stream. As a secondary effect, it is noted that the rate of combustion can bevaried by altering the sugar-to-dextrine ratio since sugar increases the rate of Combustion and dextrine reduces it. v

I Both potassium chlorate (KClO and barium nitrate (Ba(NU act asoxidants and supply oxygen to support combustion. It is no ed that the rate of combustion may also be controlled by varying the potassium-tobarium ratio in the mixture since potassium chlorate increases the burning rate and barium nitrate reduces it. Aluminum is used to increase the temperature of combustion and, though only 'optional in sparklers to be used to visualize streams "of low velocity, is a highly desirable ingredient: forsparklers which will be used to visualiie streams of high velocity. The passage of high velocity flow over a Sparkler which contains no aluminum transfers heat from the burning Spa kler so rapidly that soon the s'parkler is unable to kindle the unburned portion or the s 'arlder as it attempts to self-propagate. Consequeiitliy, when flow conditions are to be analyzed which will eifect a rapid heat transfer, the aluminum offsets the effector the rapid flow by providing additional heat. Thus even though the heat transfer continues, there is suhicient residual heat at the s arkler to keep the burning particles ld dling the unburned particles to effect the desired self-propagation. v

Thus, the compositions used in the practice of the present invention may be altered by the skilled artisan to lit the particular How conditions desired for study. If an increased burning rate is desired, the su andextrine ratio may be increased to a point where dextrine is eliminated completely so long as the ratio of sugar to the total com osition reinains substantially in the range disclosed by the examples set forth below. And the burning rate may likewise be increased by increasing the potassiumzbarium ratio to a point where barium is eliminated. Conversely, the burningrate may be retarded by reducing the sugarzdextri-ne and potassiumzbarium ratios although it is preferable that the suga-rzdextrine ratio be not less than 1:1.

Further, if high heat is desired, aluminum may be included; In all of the compositions, however, it is essential that they include a binder, such as sugar, an oxidant, such potassium chlorate, and a quantity of ture to form a thick paste, coating a wire form with the thick paste, and drying the coated wire for approximately twenty-four'hours at room temperature.

Example 1 The following ingredients comprise Mix No. 1:

Grams KClO 6.5 83(N03): 7.5 Aluminum 0.84 C H O 2.33 CHI-133011 Carbon 2.46

Example 2 The following ingredients comprise Mix No. 2:

Grams KClO 0.5 Ba(NO Aluminum 1.0 12 22 11 Carbon 1.0

Example 3 The following ingredients comprise Mix No. 3:

Grams KClO 1.0 Ba(NO 1.0 Aluminum 1.0 C H O 0.5 C H O 0.5 Carbon 1.0

Example 4 The following ingredients comprise Mix No. 4:

Grams KClO 1.0 CmHnOn 1.0 Carbon 1.0

The carbon of all four mixes may be either finely powdered wood charcoal or graphite, and preferably less than forty microns in diameter. Bone charcoal is not satisfactory because of its low carbon and high phosphate content.

Although the sparkler may be of any desired shape or form so long as it does not disturb the flow pattern (see Figs. 2 and 3), a one-fourth inch diameter sparkler has been found satisfactory in practicing the method with respect to most conventional prototypes having diameters of two and one-half inches or larger.

When the sparkler has been prepared and after the gas stream is initiated through the desired prototype, the sparkler is strategically placed in the stream and ignited. The sparks which are emitted from the sparkler then provide a brilliantly accurate and dramatic trace pattern of the flow through the prototype and may be readily photographed, if desired, to provide a permanent record. Incidentally, excellent results are obtained using both motion picture and still picture cameras, and, if an immediate picture is needed, the Polaroid Land Camera (manufactured by the Polaroid Corporation, Cambridge, Massachusetts) provides pleasing results. Several photographic records have been made of the particle paths in ranges of turbulent flow and all provided discrete particle paths such as have not been obtainable heretofore. It is to be noted that, in the flow patterns analyzed by the practice of the present invention, there is'no diffused blending of the particles into a single cloud mass as was characteristic of the smoke technique.

The terms gas, gaseous fluid and fluid are used interchangeably herein to define a gas, such as air, which will support combustion but which is not itself combustible.

It is understood that the foregoing description of one embodiment of the method and several exemplary sparkler compositions is for illustrative purposes only and that the present invention is not intended to be limited thereto. Rather, it is intended that such obvious modifications and equivalents as may readily occur to one skilled in the art from knowledge of this disclosure are likewise embraced by the present invention which is to be limited only by the scope of the appended claims.

What is claimed is:

1. The improvement in the art of visualizing the flow patterns of a stream of combustion supporting noncombustible gas passing through an aerodynamic prototype comprising introducing a burning tracer particle into the stream, and releasing said particle into the stream to be carried by the stream, said particle having sufficiently low mass to follow the velocity component of the stream in the direction of flow and to accurately reflect by its physical movement the pattern assumed by the flow.

2. The improvement in the art of visualizing the flow pattern of a stream of combustion supporting noncombustible gas passing through an aerodynamic prototype comprising introducing discrete incandescent tracer particles to the stream, and releasing said particles into the stream to be carried by the stream, said particles being characterized by a mass sufficiently low and a size sufiiciently small to enable it to resist the influence of forces acting thereupon to deter it from reflecting the true flow pattern of the stream.

3. A method of visualizing the flow pattern of a gas combustion supporting noncombustible gas stream passing through an aerodynamic prototype comprising presenting to the gas stream a sparkler comprising a sparking composition of pyrotechnic matter; burning said sparkler to create sparks; and causing said sparks to be emitted from the sparkler into the stream to be carried by the stream.

4. The method of visualizing gas flow patterns in conduit comprising initiating gas flow through a conduit; introducing self-illuminating pyrotechnic tracer particles into said flow, and releasing said particles into the stream to be carried by the stream, each of said particles having sufficiently low mass to effect a balance between the drag of the particle and the inertia and centrifugal forces acting on the particle, to enable the particles to follow the velocity component of the gas flow in the direction of the flow thereby accurately reflecting by their physical movement the pattern assumed by said flow.

5. The method of visualizing gas flow patterns in conduit comprising: initiating gas flow through a conduit; introducing discrete incandescent tracer particles into said flow, and releasing said particles into the stream to be carried by the stream, said particles being characterized by a mass sufliciently low to resist the influence of inertia and centrifugal forces acting thereupon; and recording the paths of said particles in said flow.

6. The method of visualizing the flow pattern of an air stream passing through an aerodynamic prototype comprising creating an air stream through an aerodynamic prototype; and causing burning sparks consisting essentially of carbon to be introduced into and carried by the air stream to accurately reflect the flow pattern of the air stream.

7. The method of visualizing the flow pattern of an air stream passing through an aerodynamic prototype comprising creating an air stream through an aerodynamic prototype; and causing burning sparks consisting essentially of carbon to be introduced into and carried by the 7 air stream, said carbon sparks being characterized by a critical diameter of not more than '40 microns.

8. The improvement in the art of visualizing the flow pattern of a stream of combustion supporting noncombustible gas passing through an aerodynamic prototype comprising: preparing a sparkler comprising carbon particles having a diameter of 40'microns or less; initiating a stream of combustion supporting noncombustible gas through an aerodynamic prototype; presenting said sp'arkler to said stream; burning said sparkler to liberate said carbon particles in a burning state; and utilizing said stream to prolong the bur-nin'gof said particles which '0 0 have entered into and are carried by said stream and cause 'visible recognition of the flow patternof said stream.

References Cited in the file of this patent UNITED STATES PATENTS 1,676,984 Fales et a1. July 10, 1928 2,131,041 Hale Sept. 27, 1938 2,616,291 Benedum 'Nov. 4, 1952 2,628,897 Vinton ..Q Feb. 17, 1.953. 2,637,208 Mellen May 5, 1953 2.795.738 Holliday -r----r---.---- June 11, 19,57

Claims (1)

1. THE IMPRIVEMENT IN THE ART OF VISULATING THE FLOW PATTERNS OF A STREAM OF COMBUSTION SUPPORTING NONCOMBUSTIBLE GAS PASSING THROUGH AN AERODYNAMIC PROTOTYPE COMPRISING INTRODUCING A BURNING TRACER PARTICLE INTO THE STREAM, AND RELEASING SAID PARTICULES INTO THE STREAM TO BE CARRIED BY THE STREAM, SAID PARTICULE HAVING SUFFICENTLY LOW

Images