US3692118A

US3692118A - Fixed fire extinguishing system utilizing recirculation of combustion products

Info

Publication number: US3692118A
Application number: US131988A
Authority: US
Inventors: Cheng Yao
Original assignee: Factory Mutual Research Corp
Current assignee: Factory Mutual Research Corp
Priority date: 1971-04-07
Filing date: 1971-04-07
Publication date: 1972-09-19
Anticipated expiration: 1989-09-19

Abstract

A fixed fire extinguishing system wherein one or more aspiration members are disposed in an elevated position relative to the structure to be protected by fire. A sensor is adapted to respond to information received from the fire to actuate the aspiration member, and the latter receives the combustion products from the fire and discharges same together with extinguishing agent back to the fire to smother the fire. A method of extinguishing a fire.

Description

OR 396929118 SR p uuucu Draws ratent Yao [451 Sept. 19, 1972 [54] FIXED FIRE EXTINGUISHING SYSTEM UTILIZING RECIRCULATION OF COMBUSTION PRODUCTS [72] Inventor: Cheng Yao, Weston, Mass.

[73] Assignee: Factory Mutual Research Corporation, Norwood, Mass.

[22] Filed: April 7, 1971 [21] App]. No.: 131,988

[52] U.S. Cl. ..l69/1 A, [69/12 [51] Int. Cl. ..A62c l/l4 [58] Field of Search ..169/12, 1 A

[56] References Cited I UNITED STATES PATENTS 2,498,512 2/1950 Thompson ..l69/l2 3,407,880 10/1968 Davis 169/ 1 2 3,403,733 10/1968 Terry ..l69/12 X 3,463,234 3/1969 Van Baak ..169/12 X Primary Examiner-M. Henson Wood, Jr. Assistant Examiner-Thomas C. Culp, Jr. Attorney-Lane, Aitken, Dunner & Ziems ABSTRACT A fixed fire extinguishing system wherein one or more aspiration members are disposed in an elevated position relative to the structure to be protected by fire. A sensor is adapted to respond to information received from the fire to actuate the aspiration member, and the latter receives the combustion products from the fire and discharges same together with extinguishing agent back to the fire to smother the fire. A method of extinguishing a fire.

28 Claims, 6 Drawing Figures PATENTED P 19 9 3. 692.1 18

sum 1 or 3 INVENTOR C H ENG YA 0 PATENTEDSEPI 9 m2 SHEET 2 BF 3 60G INVENTOR CHENG YAO @MMWW A RNEY5 BY W PATENTEDSEP 19 m2 3.692.118

sum 3 0r 3 F IG. 5.

DETECTOR 92 Z50 3 F 86 VALVEI VALVE TIMER s4 Z 88 52 I00 FIG. 6. n2 jg/ns v INVENTOR CHENG YAO RNEYS This invention relates to a fixed fire extinguishing system and, more particularly, to such a system which utilizes the products of combustion from a fire to aid in extinguishing the fire.

In the majority of cases the hot products of combustion from a fire occurring in an enclosure, such as initial stage of fire growth in a very large building, rise from the fire into a turbulent plume and then flare out to travel radially along the ceiling from the point of impingement on the ceiling. The rising fire plume entrains air from the surrounding, and the oxygen content of the air will, of course, aid in further development of the fire. However, as the radially spreading products of combustion encounter vertical walls or the like, they stratify underneath the ceiling in a layer growing in depth with time. The rate of descent of the interface between the products of combustion and the ambient air is related to the entrainment rate of the fire plume and the rate of escape of the products of combustion from the enclosure through openings such as windows, doors, or the like. In case the rate of generation of products of combustion is faster than the rate of escape from the enclosure openings, the Stratified layer of products of combustion will eventually reach the combustion zone. As a result, the combustion products which have not escaped will feed back to the fire with the ambient air that is available through the enclosure openings. Prior art fixed fire protection systems normally installed in buildings do not employ means to enhance the smothering and inerting effect of products of combustion at the early stage of fire growth, and, therefore, their fire fighting capability is often severely curtailed.

SUMMARY OF THE INVENTION It is therefore an object ofthe present invention to provide a fixed fire extinguishing system and method in which the fire induced convective movement in an enclosure can be altered so that the combustion products from the fire are recirculated back towards the fire at the early stage of the fire development to prevent the ingress of air to the fire and to aid in fighting the fire.

According to the system and method of the present invention, a signal is initiated in response to a fire situation and the combustion products from the fire are circulated from the fire away from their normal convective flow path and in a path including said fire in response to said signal.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic representation of the flow field of the products of combustion from a fire in a buildingutilizing a typical prior art fire extinguishing system;

FIG. 2 is a view similar to FIG. 1, but depicts the flow field according to the system of the present invention;

FIG. 3 is a schematic view of the fixed fire extinguishing system of the present invention installed in a building;

FIG. 4 is a cross-sectional view depicting a nozzle utilized in the system of the present invention;

FIG. 5 is diagrammatic view depicting the electrical circuit utilized in the system of the present invention; and

FIG. 6 is a view similar to FIG. 4, but depicting an alternate embodiment of the nozzle utilized in the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 of the drawings depicts a typical prior art fire extinguishing system located in a building 10 having a ceiling 12, a floor 14, and two pairs of

side walls

16 and 18. A plurality of

openings

20, 21, '22, and 23 are formed in the

side walls

16 and 18 and represent doors, windows, or other openings found in a typical building.

The reference numeral 24 refers to a supply of combustible material representing anything normally kept or stored in the building.

The typical prior art fixed fire extinguishing system used in such a building consists of a plurality of sprinkler heads 26 mounted on the ceiling l2 and responsive to a fire condition for discharging water, or other extinguishant, onto the material 24.

The burning material 24 creates products of combustion which flow by convection in a general pattern shown by the flow lines 28. As shown, the products of combustion flow generally upward from the material 24, radially along the ceiling l2 and descend downwardly as a stratified layer with a portion of the combustion products escaping through the

upper openings

21 and 23 as shown by the flow lines 28a. In this manner, air enters the building through the

lower openings

20 and 22, as shown by the flow lines 30, and mixes with the combustion products remaining in the building, with the resultant mixture passing horizontally back into the fire. Of course, the air supplies oxygen to the fire and thus severely limits the ability of the system to extinguish the fire.

The system of the present invention is designed to overcome the above disadvantages by establishing a flow field for the products of combustion as shown in FIG. 2. In particular, a plurality of aspiration type nozzles 32 are mounted on the ceiling 12 and each has one or more inlet openings in its upper. end for receiving the products of combustion form the fire, and a discharge opening in its lower end for discharging the products of combustion back towards the fire. When actuated, the nozzles 32 thus create an aspiration effectwhereby products of combustion flow in the general pattern indicated by the flow lines 34, i.e., upwardly from the combustible material 24, through the nozzles 32 and downwardly into the fire. In this manner, air entering the building through the

lower openings

20 and 22 and passing towards the fire in a pattern indicated by the flow lines 36 is blocked and thus prevented from entering the fire by the barrier created by the recirculating products of combustion. Thus, the fire will be smothered, rendering it relatively easy to extinguish. Also, since the nozzles 32 can be actuated by a fire extinguishant, a very effective fore fighting capability is achieved.

The complete system for accomplishing the above is shown installed in a building 10 in FIG. 3. The system includes a source of extinguishant 40 which is connected to a line 42 having a riser portion 42a. The line 42 connects with a sub main 44, and a plurality of branch lines 46 are disposed along the sub main 44 at spaced intervals. The sub main 44 and the branch lines 46 are all fastened relative to the ceiling at a slight distance therefrom. A plurality of the nozzles 32 are disposed at spaced intervals along each branch line 46 so that the nozzles extend throughout the entire structure to be protected.

A plurality of fire detectors, shown schematically by the reference number 50, are disposed throughout the system and, for the purposes of example, are shown disposed at intervals of every five branch lines in one direction and every five nozzles in the other direction. These detectors are fastened with respect to the ceiling and are responsive to information received from the fire to generate signals. A pair of

valves

52 and 54 are connected in the line 42 and are electrically connected to the fire detectors 50 for regulating the flow of extinguishant through the system. The nozzles 32, the detectors 50, and the

valves

52 and 54 will be described in detail later.

The details of a nozzle 32 are shown in FIG. 4. In particular, the nozzle may be of a multistage type having an enlarged nozzle portion 60 disposed in tandem with two

smaller nozzle portions

62 and 64. Each of these nozzle portions has an inlet opening at one end, an outlet opening at the other, and a constricted portion between the inlet and outlet openings to form a venturitype arrangement.

Each of the

nozzle portions

60, 62, and 64 has a plu' rality of arms spaced therearound for interconnecting the nozzle portions, with two spaced therearound for interconnecting the nozzle portion being shown by the

reference numerals

60a, 62a, and 640 respectively. The arms terminate in flanges which are bolted to cooperating flanges formed on the nozzle portions as shown.

A flanged tubular member 68 is fastened to the flange associated with the arms 64a, and defines a conduit 70 extending therethrough. One end of the conduit 70 defines an inlet opening 700 which is adapted for connection to a branch line 46 for receiving extinguishant, and a valve seat 70b is formed at'the other end of the conduit. A valve member 76 is adapted to cooperate with the valve seat 70b in a conventional manner to control the extinguishant flow through the conduit 70. A rod 78 has one end connected to the valve member 76 and extends for the entire combined length of the

nozzles

60, 62, and 64. The other end of the rod 78 is supported by a lever 80, one end of which is pivotally mounted to a crimped portion 600 of the housing of the nozzle portion 60. The other end of the lever 80 extends through a slot in the latter housing and is attached to one half portion of a fusible link 82 the other half portion of which is attached to the outer surface of the housing. The fusible link 82 is of a conventional design of the type normally associated with a fire responsive sprinkler head, it being sufficient for the purposes of this application to note that the half portions of the line are normally fused together by a material which melts at a predetermined elevated temperature, permitting release of the half portions. This releases the corresponding end of the lever 80 enabling it to pivot and fall downwardly under the action of gravity and allowing the rod 78 to fall downwardly and release the valve member 76 from its seat 70b. This permits extinguishant to pass through the conduit 70, through each of the

nozzle portions

60, 62, 64, and outwardly through the discharge opening in the nozzle portion 60.

According to the preferred design, the fusible links 82 are less sensitive than the detectors 50, i.e., the detectors will respond to an elevated temperature that is lower than the temperature at which the links will respond. This is for reasons that will be apparent from the following.

The electrical circuit for actuating the

valves

52 and 54 is shown in FIG. 5 in connection with one fire detector 50, for the purpose of example. The detector 50 is connected in parallel with a source 86 of DC current, with a solenoid relay 88 being connected in series with the detector 50. The relay 88 operates in a conventional manner to actuate a pair of

switches

90 and 92 to move same from their normal positions shown by the solid lines in FIG. 5 to their alternate positions shown by the dotted line.

A second solenoid relay 94 is connected in parallel with the relay 88 and is adapted to actuate a pair of

switches

96 and 98 to move same from their normal open positions shown by the solid line to their alternate closed positions shown by the dotted lines.

Switches

90 and 96 are connected in parallel, with each being connected in series with the relay 94, while

switches

92 and 98 are connected in series with a timer 100. The switch 98 operates to connect the valve 54 with the power source 86 in the closed position of the switch while the switch 92 operates to selectively connect the timer 100 or the valve 52 in a circuit including the power source 86 and the closed switch 98. The timer 100 may be of a conventional design of the type that operates to open a switch after a predetermined time lag following the energizing of the timer. In this regard a normally closed switch 102 is connected in series with the switch 96 and the relay 94 and is adapted to be opened by the timer 100.

The detector 50 is adapted to close in response to a predetermined elevated temperature in its vicinity and reopen in response to a predetermined temperature in its vicinity which is less than the above elevated temperature. This can be achieved in a conventional manner such as constructing the detector 50 of a bimetallic material so that it expands to open and contracts to close. The

valves

52 and 54 may be of a conventional solenoid operated type whereby they open in response to the presence of an energizing electrical current and close in response to the absence of the current.

In operation of the device of the present invention, a fire in the immediate vicinity of a detector 50 causes the detector to close and energize the relay 88, thereby closing the switch 90 and moving the switch 92 to its alternate position shown by the dotted lines in FIG. 5. The closing of the switch 90 energizes the relay 94, which in turn closes

switches

96 and 98, the latter connecting the

valves

52 and 54 to the power source 86 to open the valves. The opening of the

valves

52 and 54 permits the extinguishant to flow from the source 40 through the line 42, the sub main 44, and the corresponding branch lines 46 to the nozzles 32.

In the event the temperature is hot enough to melt the fusible link 82 of one or more nozzles 32, the particular nozzle will open, causing its valve 76 to discharge therefrom and the extinguishant to pass through the particular

venturi nozzle portions

60, 62, and 64 of each nozzle 32. This creates an aspiration effeet which induces a large portion of the combustion products from the fire which have reached the ceiling level to enter the nozzle 32 in the direction indicated by the arrows in FIG. 4 and mix with the extinguishant flowing through the nozzle. The mixture of extinguishant and combustion products will be discharged back towards the fire. The design is such that a suitable balance between the buoyant force of the rising combustion products and the rate and momentum of the above aspiration action is established to insure a continual recirculation.

A subsequent reduction'in the temperature of the fire causes the detector 50 to open, thus de-engergizing the relay 88 and permitting the switch 90 to open and the switch 92 to move to the position shown by the solid linein FIG. 5. This closes the valve 52 and energizes the timer 100. It is noted that the

switches

96 and 98 remain closed because the relay 94 is energized by the current from the power source 86 through the

closed switches

102 and 96. Thus current continues to flow through the switch 98 to the timer 100 and to the valve 54. After a predetermined interval the timer 100 opens the switch 102 thereby de-energizing the relay 94 and causing the

switches

96 and 98 to open. This deenergizes and closes the valve 54 and the timer 100 to prevent all flow of extinguishant. It can be appreciated that the valve 52 can be designed with a predetermined inherent leakage in order that, during the time cycle permitted by the timer 100, a predetermined extinguishant flow can still flow through the system, although at a lesser rate than when both valves are open.

Thus, the system of the present invention permits a reduction in the extinguishant after the temperature of the fire had been reduced to a predetermined level. This permits the combustibles to be soaked to further reduce their temperature, yet achieves a very efficient use of extinguishant.

It can be appreciated that several variation can be made in the above without departing from the scope of the present invention. For example, the multistage venturi nozzle 32 may be replaced by a standard single venturi nozzle such as shown in FIG. 6 by the reference numeral 1 10. In this embodiment the extinguishant can be ejected into the nozzle 110 through a tube 112 having a valve 114 operated by the temperature-sensitive release device 116 which may be identical to the fusible link 82 of the previous embodiment. Both ends of the nozzle 110 are open so that upon the opening of the detector 50 and the valve 114 and the resultant flow of extinguishant through the valve, an aspiration effect is created and the combustion products from the fire are sucked into the upper end of the nozzle 110 and discharged from its lower end, as viewed in FIG. 6.

Although one embodiment of the present invention would utilize water as the extinguishant with the source of extinguishant 40 being simply a main or auxiliary water supply, it is understood that any known type of fluid extinguishants can be utilized in the system and method of the present invention.

However, the system of the present invention also lends itself to the use of other extinguishants which have excellent fire fighting properties but, due to their relatively high cost when compared to water, are not compatible with the fire fighting extinguishing systems of the prior art, since in the latter systems once the extinguishant is discharged into the fire it is no longer usable. However, since the system and method of the present invention achieve a recirculation of a large portion of the extinguishant along with a reduction in extinguishant discharge after the temperature of the fire reduces to a predetermines level, it is apparent that far less extinguishant is necessary than in prior art systems, despite the fact that the above-mentioned advantages are achieved. Therefore, other embodiments of the present invention would feature the use of pressurized nitrogen, carbon dioxide, halogenated hydrocarbon agents such as freon, or other similar gases as an extinguishant.

Also, it is understood that the detector 50 and the links 82 may be responsive to information from the fire other than temperature, such as smoke, etc.

Of course, still other variations of the specific construction and arrangement of the system disclosed above can be made by those skilled in the art without departing from the invention as defined in the appended claims.

I. A fixed fire extinguishing system comprising control means responsive to information received from the fire for initiating a first signal and responsive to additional information received from the fire for initiating a second signal, discharge means fixed relative to the structure to be protected and responsive to said first signal for discharging extinguishant towards said fire, said discharge means being responsive to said second signal for changing the rate of discharge of said extinguishant, and means responsive to said discharge of extinguishant for circulating the combustion products from said fire in a path including said fire.

2. The system of claim 1 further comprising discharge means fixed relative to the structure to be protected and responsive to said signal for discharging extinguishant towards said fire.

3. The system of claim'l wherein said circulating means comprises at least one aspiration member fixed relative to the structure to be protected, and adapted to receive the combustion products from said fire and discharge same back to said fire.

4. The system of claim 3 further comprising means to introduce a fluid to said aspiration member to actuate same.

5. The system of claim 3 wherein said aspiration member is in the form of a venturi nozzle having an inlet for receiving said combustion products and an outlet for discharging same.

6. The system of claim 3 wherein a plurality of aspiration members are provided and further comprising means for selectively actuating said aspiration members in response to said signal in accordance with the particular location of the fire.

7. The system of claim 3 wherein said discharge means is adapted to discharge said extinguishant into said aspiration member to create an aspiration effect.

8. The system of claim 4 wherein said fluid is water, and wherein said aspiration member directs said water towards said fire.

9. The system of claim 4 wherein said fluid is a halogenated hydrocarbon and wherein said aspiration member directs said halogenated hydrocarbon towards said fire.

10. The system of claim 4 wherein said fluid is carbon dioxide, and wherein said aspiration member directs said carbon dioxide towards said fire.

11. The system of claim 4 wherein said fluid is nitrogen, and wherein said aspiration member directs said nitrogen towards said fire.

12. The system of claim 1 wherein said products of combustion are circulated in a path immediately adjacent said fire in a manner to prevent the ingress of air to said fire.

13. The system of claim 1 wherein said control means reduces the rate of discharge of said extinguishant.

14. A method of extinguishing a fire comprising the steps of initiating a first signal in response to information received from the fire and a second signal in response to additional information received from the fire, discharging extinguishant towards said fire in response to said first signal, changing the rate of discharge of said extinguishant in response to said second signal, and circulating the combustion products from said fire in a path including said fire in response to said discharge of extinguishant.

15. The method of claim 14 further comprising the step of discharging extinguishant towards said fire in response to said signal.

16. The method of claim 14 wherein said step of circulating comprises the step of positioning at least one aspiration member relative to the structure to be protected and introducing a fluid to said aspiration member to actuate same, said aspiration member being adapted to receive the combustion products from said fire and discharge same back to said fire.

17. The method of claim 16 wherein a plurality of aspiration members are provided and further comprising the step of selectively actuating said aspiration members in response to said first signal in accordance with the particular location of the fire.

18. The method of claim 16 further comprising the step of discharging extinguishant towards said fire in response to said first signal.

19. The method of claim 18 wherein said extinguishant is discharged into said aspiration member to create an aspiration effect.

20. The method of claim 16 wherein said fluid is a fire extinguishant, and is directed towards said fire.

21. The method of claim 16 wherein said fluid is a gaseous fire extinguishant which is circulated in the same path as said combustion products.

22. The method of claim 14 wherein said products of combustion are circulated in a path immediately adjacent said fire in a manner to prevent the ingress of air to said fire.

23. The method of claim 20 wherein said fire extinguishant is water.

24. The method of claim 20 wherein said fire extinguishant'is a halogenated hydrocarbon.

25. The method of claim 20 wherein said fire extinguishant is carbon dioxide.

26. The method of claim 20 wherein said fire extinguishant is nitrogen.

27. A device for use in fixed fire extinguishing system comprising a housing having an inlet for connection to a source of extinguishant and an outlet for discharging gaid exting ishant, control eans mounted 0 said ousmg an responsive to in ormation receive from the fire for initiating a first signal, said control means being responsive to additional information received from the fire for initiating a second signal, means responsive to said first signal for permitting the discharge of extinguishant from said outlet, means responsive to said second signal for changing the rate of

Claims

1. A fixed fire extinguishing system comprising control means responsive to information received from the fire for initiating a first signal and responsive to additional information received from the fire for initiating a second signal, discharge means fixed relative to the structure to be protected and responsive to said first signal for discharging extinguishant towards said fire, said discharge means being responsive to said second signal for changing the rate of discharge of said extinguishant, and means responsive to said discharge of extinguishant for circulating the combustion products from said fire in a path including said fire.

3. The system of claim 1 wherein said circulating means comprises at least one aspiration member fixed relative to the structure to be protected, and adapted to receive the combustion products from said fire and discharge same back to said fire.

23. The method of claim 20 wherein said fire extinguishant is water.

24. The method of claim 20 wherein said fire extinguishant is a halogenated hydrocarbon.

25. The method of claim 20 wherein said fire extinguishant is carbon dioxide.

26. The method of claim 20 wherein said fire extinguishant is nitrogen.

27. A device for use in fixed fire extinguishing system comprising a housing having an inlet for connection to a source of extinguishant and an outlet for discharging said extinguishant, control means mounted on said housing and responsive to information received from the fire for initiating a first signal, said control means being responsive to additional information received from the fire for initiating a second signAl, means responsive to said first signal for permitting the discharge of extinguishant from said outlet, means responsive to said second signal for changing the rate of discharge of said extinguishant, and means responsive to said discharge of extinguishant for circulating the combustion products from said fire through said housing and in a path including said fire.

28. The device of claim 27 wherein said means for circulating the combustion products comprises aspiration means connected to said housing and responsive to the discharge of extinguishant from said outlet for inducing combustion products into said housing.