US3447610A - Apparatus for producing a stream of dry chemical particles - Google Patents

Description

June 3, 1969' A. B. GUISE ETAL 3,447,610

APPARATUS FOR PRODUCING A STREAM OF DRY CHEMICAL PARTICLES Filed July 19, 1966 Sheet of 3 IN VEN TORS 4R THUR B. 60/55 CYZRRY O. HANSON June 3, 1969 A, B. GUISE ETAL 3,447,619

APPARATUS FOR PRODUCING A STREAM OF DRY CHEMICAL PARTICLES Filed July 19, 1966 Sheet 2 i l 1 v FIG.2

I? I Q g y INVEN'IORS v i ARTHUR B. 60185 N i Q1 ATTORNEYS June 3, 1969 GUISE ETAL 3,447,510 APPARATUS FOR PRODUCING A STREAM OF DRY CHEMICAL PARTICLES Filed July 19. 1966 Sheet 3 of 3 INVENIURS ARTHUR 8. 61/156 BY GARRY 0. HANSON A 7' TORNEYS United States Patent U.S. Cl. 169-31 4 Claims ABSTRACT OF THE DISCLOSURE A nozzle for use in a dry powder fire extinguisher of the convergent-divergent type.

This invention relates to a new and improved method of and apparatus for producing a stream of dry chemical particles for extinguishing a fire. More specifically, the present invention relates to a new and improved method of and a nozzle for directing a stream of dry chemical fire extinguishing agent.

Dry chemical compositions have long been recognized and used as superior fire extinguishing agents. Such compositions may comprise finely powdered solid particles of sodium bicarbonate such as disclosed in US. Patent 1,793,420. Alternatively compositions of monoammonium phosphate, potassium bicarbonate have been found useful for fire extinguishing purposes. These dry chemical materials typically have a particle size not exceeding about 125 microns.

Numerous types of fire extinguishing devices have been employed for discharging the dry chemical particles and for directing them to the site of the fire.

One form of such device is known as the cartridge type. In this form of device the dry chemical is maintained in a storage container and a suitable supply of gas such as compressed carbon dioxide, nitrogen, etc. is maintained in a cartridge connected to the container. Upon actuation of the device, the gas is fed into the dry chemical container to fluidize or aerate the dry chemical. Upon opening a valve the fluidized dry chemical is then fed from the dry chemical container to a hand manipulated nozzle which is aimed at the fire.

In another form of fire extinguisher device known as the stored pressure type the dry chemical is maintained in a container under pressure. To release the dry chemical a valve on the container is opened and the dry chemical is discharged through a nozzle.

In other types of fire extinguisher apparatus the dry chemical may be mounted on a vehicle which can be propelled to a position adjacent the conflagration and the nozzle is manually manipulated.

The present invention is directed to a method of and a nozzle for discharging dry chemical fire extinguisher agents and is useful in conjunction with the various types of fire extinguisher apparatus described above.

Nozzles which have been used in the past for discharging dry chemicals have generally been of the straight bore type, i.e. a tubular construction have a bore of uniform diameter throughout its length. Such nozzles and other similar types have long been used in the dry chemical fire extinguishment field. There has been, however, a continuing and long standing demand for a nozzle which would increase the range and effectiveness of the dry chemical stream.

One attempt to increase the effectiveness of dry chemical nozzles has been to simply lengthen the tube. This approach, however, is inadequate because the increased length of nozzle results in increased friction and therefore decreases velocity of the dry chemical being discharged. The decrease in velocity necessarily results in a decreased range of the fire extinguisher agent.

Another difiiculty with the conventional tube type of nozzle is that the fluidized chemical is under considerable pressure while in the nozzle and thus as soon as it leaves the nozzle it is at a pressure greater than atmospheric pressure and blossoms outwardly there-by considerably shortening the length of the stream. This phenomena is sometimes referred to as an under-expanded nozzle.

On the other hand, if the exit pressure of the nozzle is less than atmospheric pressure, then overexpansion occurs within the tube or nozzle and the range of the fire extinguishing agent is greatly reduced.

Studies of the streams discharged by dry chemical fire extinguishers have shown that there is generally a weight ratio of dry chemical to gas between 50 to 25.0 to one. Thus it is not believed that the dry chemical streams behave as either a gas or a vapor. Accordingly, nozzles which are generally effective for gases are not necessarily effective for dry chemical streams.

Thus, while the gas molecules can expand freely, the particles of dry chemical agent have inertia and resist being carried by the expanding gas. Hence a dry chemical fire extinguishing system is a two component system, i.e., gas and dry chemical particles and the nozzle contours must take into account the characteristics of the combination of those components which individually have different characteristics.

In order for the emitted dry chemical stream to be effective to extinguish fires it is necessary that the dry chemical particles be relatively evenly spaced throughout the stream. This has not been effectively accomplished with prior art nozzles.

In the straight bore type nozzle there is a tendency for underexpansion to occur and full expansion occurs outside the nozzle. The resultant effect is that the dry chemical load tends to be torn apart by the expansion shock waves and there is a considerable loss of solid particles perpendicular to the axis of the nozzle that results in a condition sometimes referred to as blossoming. The turbulence and expansion at the exit face of the nozzle will cause an unequal concentration of particles in the cross sectional area of the stream. The major concentration of particles will tend to be in the center of the stream but voids in the pattern will allow the fire to creep back towards the user of the fire extinguishing device.

An overexpanded nozzle is the result of too large an exit area resulting in increased back pressure in the dry chemical gas mixture. The high back pressure cause oblique shock waves at the nozzle exit and a great loss of energy. In an overexpanded nozzle the major concentration of particles is in the center of the stream with considerable voids in the stream pattern.

The present invention relates to a method and nozzles for dry chemical fire extinguisher agents which results in increased range and effectiveness. The expression range and effectiveness consists of essentially two factors. These factors are the distance from the nozzle and area for which the dry chemical is effective for fire fighting purposes. The present invention results in a stream of dry chemical particles which is effective over a greater distance and a greater area than has heretofore been possible.

It is therefore an object of this invention to provide a stream of dry chemical fire extinguisher agent with an increased range and effectiveness.

[mother object of this invention is to provide a method of controlling the discharge of a dry chemical stream from a fire extinguisher apparatus which results in a 3 stream of dry particles having an increased range and effectiveness.

A further object of this invention is to provide a nozzle for use in combination with a dry chemical apparatus which results in a stream of dry chemical particles having an increased range and effectiveness.

Still another object of this invention is to provide a method of a device for discharging dry chemical fire extinguishing agents which utilizes the full potential of the energy imported to the dry chemical particles by a gas propellant.

Other objects and advantages of the invention are set forth in part herein and in part will be obvious herefrom, or may be learned by practice of the invention, the same being realized and attained by means of the steps and instrumentalities and combinations pointed out in the appended claims.

Briefly described, the present invention controls a stream of dry chemical which has been aerated or fluidized by gas under pressure and includes the steps of directing the stream of fluidized dry chemical into a confined converging zone and gradually compressing the fluidized material towards a longitudinal axis in such a manner as to increase the linear velocity of the stream, passing the stream through a throat portion wherein the linear velocity of the stream is further increased and the stream is given a predetermined shape, expanding under controlled conditions the fluidized material in a diverging zone so that the particles have a resultant movement in a direction parallel to the longitudinal axis of the stream and dry chemical particles are relatively evenly spaced through said stream.

The process of the invention may be accomplished with the new and improved dry chemical nozzle disclosed herein. Briefly, the nozzle comprises three sections which are functionally and structurally related to provide new and unexpected results. As embodied, the nozzle includes a first converging section having an entrance which converges gradually toward a throat portion to compress the stream towards the longitudinal axis of the nozzle and increase the linear velocity of the stream. The throat portion of the nozzle of the present invention further increases the linear velocity of the dry chemical stream and forms the stream into a predetermined shape. The throat portion of the nozzle leads to a diverging portion wherein the stream expands in a controlled manner so that the dry chemical particles are substantially evenly spaced throughout the stream.

In accordance with this invention the cross sectional area of the opening of the converging zone is related to the cross sectional area of the throat portion. Also it has been found that the included angle of the converging zone and the included angle of the diverging zone if maintained within certain limits described hereinafter will lead to new and unexpected results.

Thus, it has been found that the cross sectional area of the throat portion should have an area in the range of to 65% the cross sectional area of the entrance to the converging zone and the included angle of the converging zone should be from about to 75 and preferably about 60".

Furthermore, the included angle of the divergent zone should be from 8 to 12 in order to obtain increased range and effectiveness of the dry chemical stream. Within these limits the compressed gas is essentially fully expanded by the time the stream reaches the exit of the diverging zone and the dry chemical particles given a resultant movement in a direction parallel to the longitudinal axis of the stream with the result that the stream has the dry chemical particles evenly distributed therein. It has also been found that superior results are obtained if the length of the nozzle is about five and one half times the square root of the area of the throat.

It has been found that with a nozzle constructed in accordance with this invention that the stream tends to follow the angle of divergence after passing through the exit with the dry particles relatively evenly distributed. In one embodiment of the invention there is provided a tube which extends from the outlet of the nozzle and re-directs the flow of the issuing stream parallel to the axis of the nozzle. It has been found that addition of the tube to the diverging nozzle of the present invention results in a starting increase in the range of the nozzle.

The invention consists in the novel parts, constructions, arrangements, combinations and improvements herein shown and described.

It will be understood that the foregoing general description and the following detailed description as well are exemplary and explanatory of the invention but are not restrictive thereof.

The accompanying drawings, referred to herein and constituting a part hereof, illustrate one embodiment of the invention, and together with the description, serve to explain the principles of the invention.

OF THE DRAWINGS FIGURE 1 is a front elev-ational view of a fire extinguisher including the nozzle of the present invention;

FIGURE 2 is an enlarged longitudinal view, partly in section, of the nozzle assembly for the fire extinguisher of FIGURE 1, including one embodiment of the nozzle of the present invention;

FIGURE 3 is a longitudinal sectional view of the nozzle shown in FIGURE 2; and

FIGURE 4 is longitudinal sectional view of another embodiment of the nozzle of the present invention, particularly adapted for use as a turret nozzle.

Referring now in detail to the illustrative embodiments of the present invention, there is shown in FIGURE 1 a portable fire extinguisher 10' having a storage container 12 for dry chemical particles as described, for example, in the Block Patent No. 1,793,248, Feb. 17, 1931. Suitably connected to the container 12 is a cartridge located inside cartridge guard 14 which cartridge contains inert gas under pressure and which may be fed into the container 12 as shown in the G uise Patent No. 2,719,590, Oct. 4, 1955. An outlet hose 1 6 is connected to the container 12 and is provided at its free end with a nozzle assembly 18 for controlling the flow of the dry chemical stream from the extinguisher 10.

As shown in FIGURE 2, the nozzle assembly 18 includes a handle 20 that is connected at one end 22 to the hose 16 having a passage 23 through for the fluidized dry chemical stream. The forward end 24 of the handle 20 is adapted to receive the nozzle 26 of the present invention.

Thus, as shown one end of nozzle 26 is externally threaded for engagement with internally threaded portion 30 in the handle 20'.

Reciprocally mounted in the holder 20 is a plunger type valve 34 which controls the flow of the dry chemical stream from the passage 26 and into the nozzle 26.

The valve 3-4 reciprocates through a seal 35. The valve 34 is engaged by a lever 36 pivotally mounted on the handle 20. Located between the lever 36 and handle 20 is a spring 37 that constantly urges the lever 3-6 away from the handle 20.

Extending through the nozzle 26 is an axial passage 38 N having a cylindrical wall 40. At the inlet end 28, the wall 40 is chamfered to form a valve seat 42 for the beveled end 44 of the plunger valve 34. The valve 34 is maintained on its seat 42 by spring 37, and is unseated or opened by depressing the lever 36.

The foregoing general descriptions illustrate a specific form of fire extinguisher device with which the present invention is useful. It will be understood, however, that the present invention can be used with other and different types of fire extinguisher apparatus.

Referring now to FIGURE 3 a specific embodiment of the invention is shown therein.

As can be seen therein the nozzle comprises three basic sections or portions. The first section is a converging section which includes a relatively large opening leading gradually to a throat portion 48. The converging section gradually compresses the fluidized material towards the longitudinal axis of the nozzle to increase the linear velocity of the stream. While FIGURE 3 shows the converging section in frustoconical form, this form is not absolutely necessary. However, it has been found that new and unexpected results are achieved if the included angle of the converging zone is from 25 to 75 and preferably about The next portion or section of the nozzle is the throat portion or section. At the throat portion 48 the linear velocity of the fluidized stream is further increased and reaches its maximum value. The throat portion also shapes the stream into .a predetermined desired form. Thus depending upon the anticipated use of the fire extinguisher device varying shapes for stream may be desirable.

It has been found that there is a preferred and desirable relationship between the area of the entrance to the converging zone and the area of the throat portion. Thus it has been found that the area of the throat portion should be from 20% to the area of the entrance to the converging section to obtain the maximum increase in linear velocity of the dry chemical particles.

After passing through the throat portion 48, the fluidized stream passes into the third portion or section the diverging section 50. While in the diverging section the fluidized stream expands in a controlled manner so that the dry chemical particles move radially outwardly and yet have a resultant movement in a direction generally parallel to the axis of the nozzle.

-It has been found that the angle of divergence is critical in obtaining new and unexpected results. Thus it has been found that new and unexpected results are obtained where the included angle of divergence is between 8 and 12 inclusive. With the included angle of divergence in this range it has been found that the extinguishing stream of dry chemical covers a wider effective area at a greater distance than has been heretofore possible with conventional nozzles because the dry chemical particles are relatively evenly spaced throughout the dry chemical stream while having a maximum linear velocity.

Thus it has been found that where the included angle of divergence is less than about 8 there may be an increase in the frictional resistance to the stream thus substantially reducing the effective range of the issuing stream. Furthermore, nozzles having a divergent included angle of less than 8 degrees are typical examples of underexpanded nozzles with the result of a substantially reduced range. Thus, the stream blossoms as it emerged from such a nozzle reducing the effective range of the issuing stream. In this case the potential energy of the dry chemical particles is spent almost immediately as they exit from the nozzle.

On the other hand, where the included angle of divergence is more than about 12 the effectiveness of the stream was substantially reduced because of overexpansion. In such an instance some of the potential energy of the dry chemical particles is spent within the nozzle.

In accordance with the present invention and with an included diverging angle of about 8 to 12 maximum utilization of the potential energy is obtained. The fluidized stream is expanded in a controlled manner within the confines of the diverging section so that the issuing stream has the dry chemical particles uniformly dispersed in the issuing stream and yet has a maximum linear velocity.

The length of the diverging zone has also been found to be a factor which effects the range of the nozzle. Where the nozzle is too short maximum utilization of the potential energy of the expanding gas is not obtained and the issuing stream expanded rapidly or blossomed as it issued from the nozzle. On the other hand, where the diverging section of the nozzle is too long, the frictional forces reduce the range of the issuing stream. The most desirable and new and unexpected results have been obtained where the length of diverging section is about 5 and one half times the square root of the area of the throat.

The superior and unexpected results obtained by the present invention can be seen in the following examples and tables. In the examples the expression range means the distance from the nozzle that the fire extinguisher agent is effective to extinguish the flame. The dimensions referred to in the examples are shown in the drawing and in particular FIGURES 3 and 4. In this connection it will be noted that the dimensions T and C refer to the diameter and that cylindrical nozzles were employed.

Example I A dry chemical having a composition essentially containing mono-ammonium phosphate and fluidized by nitrogen to form a stream having a pressure of 129 lbs. per square inch was fed through a nozzle as shown in FIG- URE-S l, 2 and 3. The included angle of convergence was 60 and the included angle of divergence for the diverging section was 10. The nozzle had the following dimensions:

Inch C 0.39 T 0.199 L 1.40

The fluidized stream was expelled at the rate of 0.57 lb. per second. The stream had dry chemical particles uniformly dispersed throughout and did not blossom. The effective extinguishing range of the stream was 31 feet.

The following comparison table shows the results obtained in a comparison test between nozzle N in accordance with the present invention and nozzles not in accordance with the present invention.

In each instance below nozzle A had an entrance diameter of 0.40 inch which converged with an included angle of 60 to a throat portion. The nozzle diverged at an angle of 12 degrees.

In each instance below nozzle B had an entrance diameter of 0.50 inch which converged with an included angle of 45. From the throat portion of the nozzle there was a tubular portion of uniform diameter.

In each instance the fire consisted of a square pan con taining two inches of gasoline over water leaving six inches of space above the gasoline to the top of the pan.

The other dimensions and the results are set forth in the following table.

In bracketed pairs the flow rates equal.

Extinguish- Type of Length Throat Fire area, ing time, dry

( .1) (T) it. sec. chemical A H} 1. 49 0.209 75 5. 8 N aHCOa 5. 0 0. 75 0. 228 75 Fail NaHCO; 1. 49 0. 201 75 3. 4

5. 6 MAP 0. 75 0.228 75 Fail MAP 1. 54 0. 266 5. 0 MAP 6.0 0. 75 0. 295 100 Fail MAP 1. 56 0. 290 7.0

6. 2 NaHCOa 0.75 0. 313 150 Fail NaHCOg 1. 49 0. 266 200 7. 2 KHCOa 8. 0 0. 75 0. 272 200 Fail KHCO:

It will be noted that in no instance was the straight bore type of extinguished capable of extinguishing the fire whereas nozzles in accordance with the present invention were quite effective.

In other tests with nozzles made in accordance with the present invention have provided a range from 40% to 70% more than can be obtained with conventional straight bore nozzles. Similarly, nozzles made in accordance with the present invention have consistently shown the capability of extinguishing fires having in excess of 25% more square feet than can be accomplished with nozzles not in accordance with the present invention.

In certain instances a nozzle capable of ranges even greater than that obtainable with the nozzles described above is desirable. For example nozzles mounted on turrets on moving vehicles such as fire trucks and boats are commonly called upon to deliver extremely long streams of dry chemicals.

A surprising addition to the range of the nozzle can be obtained where a straight tube is added to the end of the diverging nozzle. This embodiment of the invention is shown in FIGURE 4.

In this form of the invention a nozzle 52 such as shown and described in FIGURE 3 is utilized.

The range of the nozzle 52 can be increased by providing a hollow tube 68 that extends the outlet 69 of the nozzle 52 and which is slidably mounted thereon. To secure the tube 68 to the nozzle 52 the rear portion of the tube 68 is provided with a plurality of bores 70 about its periphery which are alignable with threaded recesses 72 in the outer wall 74 of the nozzle 52. A series of screws 76 may then be inserted in the bores 70 and threaded into the recesses 72.

After the stream of dry chemical leaves the convergingdiverging nozzle of the present invention, it is neither underexpanded nor overexpanded but the stream tends to follow the angle of divergence of the nozzle. By adding a tube which extends from the outlet end of the nozzle, such as the tube 68 shown in FIG. 4, the flow of the stream is redirected so that it flows forwardly parallel to the axis of the nozzle and without harmful constriction. This results in a greater proportion of dry chemical in a dry chemical stream that has been given its maximum attainable forward velocity.

The length of the portion of the tube that extends in front of the nozzle (LE) is desirably from about one to two and one-half times the length of the diverging section (LD). It has been that when the length of the tube was less than the length of the diverging section, the tube did not completely redirect the stream to flow parallel to the axis of the nozzle. Conversely, if such length was more than about two and one-half times the length of the diverging section, the frictional losses of the stream caused a reduction in its range that outweighed the advantages obtained in redirecting its flow.

An example of utilizing the form of the invention shown in FIG. 4 is set forth below.

Example H A dry chemical having a composition essentially consisting of sodium bicarbonate and fluidized by nitrogen to form a stream having a pressure of 100 lbs. per square inch was fed through the nozzle and tube shown in FIG. 4. The included angle of convergence was 60 and the included angle of divergence was 8, and nozzle and tube had the following dimensions:

Inches C 2.07 T 1.00 L E 2.25 L, 10

side to side. The nozzle was pointed down a strip of gasoline 10 feet wide and up to 200 feet long, and the range is the maximum distance from the nozzle at which no flame existed.

It is to be understood that the invention in its broader aspects is not limited to the specific elements and steps shown and described, but also includes within the scope of the accompanying claims any departures made from such elements or which do not sacrifice its chief advantages.

What is claimed is:

1. In a fire extinguishing device the combination of a supply of dry chemical particles and a supply of propellant gas for intimately mixing with and thereby fluidizing said dry chemical particles and propelling said fluidized dry chemical through a conduit to a nozzle, said nozzle comprising:

(a) a converging portion for compressing said fluidized material towards the longitudinal axis of the nozzle while directing said fluidized material in a direction generally parallel to said longitudinal axis, said converging portion having an included angle in the range of 25 degrees to degrees,

(b) a throat portion at the small end of said converging portion, said throat portion being in a plane substantially perpendicular to the longitudinal axis of the nozzle and having a cross sectional area in the range of 20-65 percent of the cross sectional area of the entrance to the converging portion,

(c) a diverging portion beginning at the end of said throat portion for causing uniform dispersion of the dry chemical particles, said diverging portion having an included angle of not less than 8 degrees and not more than 12 degrees,

((1) said fluidized dry chemical being propelled from the converging portion to the throat portion and then to the diverging portion and being expelled to the atmosphere from the exit of the diverging portion.

2. A device as defined in claim 1 wherein the length of the diverging portion is not less than 5 and one-half times the square root of the cross sectional area of said throat portion.

3. A device as defined in claim 2 where the included angle of said converging zone is about 60 degrees.

4. A device as defined in claim 1 having a tube of uniform diameter extending from the diverging portion, said tube having a length from one to two and one-half times the length of the diverging section.

References Cited UNITED STATES PATENTS 2,477,947 8/ 1949 Yadoff 169--31 2,533,685 12/ 1950 Nurkiewicz 16 9-31 3,092,183 6/1963 Guise et al. l6931 FOREIGN PATENTS 916,374 8/ 1946' France.

703,992 3/1941 Germany. 1,053,939 1/1953 Germany.

4,315 9/ 1910 Great Britain.

EVERETT W. KIRBY, Primary Examiner.

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