Patent Application
20070181715
This invention relates generally to fire extinguishing systems, and more particularly, to expansion nozzle assemblies used to dispense foam in a fire extinguishing system.
Enclosed areas such as cargo holds within an airplane, inside cargo containers held within the cargo hold of an airplane, computer rooms, equipment rooms, and the like all may contain combustible materials which need to be extinguished during a fire. The type of combustible material and the use of the enclosed area may determine how a thermal event is extinguished.
Different types of fire extinguishing systems exist. A cargo hold, for example, may use a high or medium foam expansion system while a commercial office building may use a sprinkler system. In a foam expansion system, an expansion nozzle expands a foam solution into a blanket of foam bubbles. The nozzle may extend within a discharge tube and accepts the foam solution from a container under pressure or from an atmospheric tank and pump assembly. The discharge tube may be open or have an opening to the atmosphere or ambient air proximate the end where the foam solution is introduced, or may have orifices open to the atmosphere along the discharge tube.
When the system is activated, the foam solution is discharged into the nozzle. The nozzle sprays the foam solution in a spray pattern onto a screen at an opposite end of the discharge tube. The pressure in the discharge tube results in a Venturi effect, pulling air into the discharge tube and causing bubbles to form on an opposite side of the screen. The bubbles are released into the atmosphere through an open end of the discharge tube. When the bubbles break, the atmosphere or room air within the bubbles is released. The foam solution provides a wetting and extinguishing effect, but does not create an inert atmosphere in which combustion cannot take place. Therefore, combustible materials may re-kindle as a result of deep-seated combustion.
Other fire extinguishing systems attempt to maintain an atmosphere in which combustion cannot take place by injecting inert gas into the enclosed area. The inert gas mixes with and displaces the ambient air, and thus escapes or leaks from the enclosed area with the ambient air, making it difficult to maintain a desired percentage of inert gas. Optionally, intermittent additional discharges of inert gas or a slow continuous discharge of inert gas after the initial discharge may be used to compensate for the leakage. This requires a more complicated discharge system and more inert gas is needed.
Thus, the bubbles enclosing ambient air and/or the injection of inert gas as discussed above may not maintain a desired inerting atmosphere within the enclosed area. The inert gas may easily escape the area and is diluted with air. Also, adding additional gas periodically or continuously to maintain the inerting atmosphere requires more product and is thus more expensive.
Therefore, a need exists for an apparatus to maintain an inerting atmosphere in an enclosed area. Certain embodiments of the present invention are intended to meet these needs and other objectives that will become apparent from the description and drawings set forth below.
In one embodiment, a nozzle assembly for encapsulating a gaseous solution in bubbles comprises a discharge tube with a diffuser and a foam solution nozzle held within. The discharge tube has upstream and downstream ends. The discharge tube has a front face at the upstream end with a first opening configured to be joined to a gas supply line that provides a gaseous solution and a second opening configured to receive a non-expanded foam solution. The downstream end of the discharge tube is open. A chamber is formed within the discharge tube. The chamber receives the gaseous solution at the upstream end and releases the gaseous solution through the diffuser into the discharge tube towards the downstream end.
In another embodiment, a nozzle assembly for expanding a foam solution comprises a discharge tube having a chamber with first and second ends. The first end has a front face with a first opening configured to be joined to a gas supply line that provides a gaseous solution and a second opening configured to receive non-expanded foam solution. The chamber receives the gaseous solution through the first opening. A diffuser is retained within the discharge tube and comprises a diffuser plate and a diffuser tube. The diffuser plate is located at the second end of the chamber and has at least one orifice for conveying the gaseous solution from the chamber to the discharge tube. The diffuser tube provides a conduit between the second opening in the front face and a nozzle acceptance hole in the diffuser plate. A foam solution spray nozzle is held within the nozzle acceptance hole of the diffuser. The foam solution spray nozzle receives the non-expanded foam solution through the conduit and discharges the non-expanded foam solution into the discharge tube through at least one nozzle orifice.
In another embodiment, a nozzle assembly for expanding a foam solution comprises a discharge tube having upstream and downstream ends. The discharge tube has a front face at the upstream end forming a barrier between ambient air outside the discharge tube and air within the discharge tube. The downstream end of the discharge tube is open. A chamber is formed within the discharge tube for receiving gaseous solution through a first opening proximate the upstream end. The first opening is configured to be joined to a gas supply line that provides a gaseous solution. The chamber has at least one orifice for releasing the gaseous solution from the chamber into the discharge tube towards the downstream end. A foam solution spray nozzle is held within the discharge tube for receiving non-expanded foam solution through a second opening proximate the upstream end. The foam solution spray nozzle discharges the foam solution with a velocity into the discharge tube towards the downstream end. A screen is retained proximate the downstream end of the discharge tube for receiving the non-expanded foam solution discharged from the foam solution spray nozzle. The gaseous solution and the velocity of the foam solution pushes the non-expanded foam solution through the screen to form bubbles encapsulating the gaseous solution.
The foregoing summary, as well as the following detailed description of certain embodiments of the present invention, will be better understood when read in conjunction with the appended drawings. It should be understood that the present invention is not limited to the arrangements and instrumentality shown in the attached drawings.
The size of the mesh used in the screen 140 may be determined by the volume of area needed to fill or a desired expansion ratio, defining the ability to fill a container and the packing of the bubbles therein. Larger bubbles have a high expansion ratio, but lower thermal stability. Also, larger interstitial spaces exist between larger bubbles compared to smaller bubbles. Smaller bubbles formed by a smaller hole size in the mesh are more thermally stable, but also require more solution to produce.
Foam solution container 162 holds the foam solution under pressure. Alternatively, the foam solution container 162 may be an atmospheric tank with pressurized foam solution being supplied by means of a pump (not shown) located between the foam solution container 162 and the upstream end portion 180. The expansion ratio of foam is classified by the National Fire Protection Association. For example, medium expansion foam has an expansion ratio from 20:1 to 200:1. Medium expansion foam may be appropriate when the assembly 160 is used to provide protection for a cargo container.
Gaseous solution container 164 holds the gaseous solution under pressure. The gaseous solution may be any single inert gas or combination of inert gases. For example, Nitrogen, Argon, Helium, other inert gas, or a blend of more than one inert gas may be used. The foam solution may be a water-based or a non-aqueous solution. Additional components, such as polymers, may be used to achieve desired characteristics, such as drainage rate, elasticity, and thermal stability, and elasticity. For example, within a cargo container transported in an airplane, pressure changes occur due to changes in altitude. The bubbles are desired to have an elastic property to allow swelling and shrinking without breakage.
Foam solution supply line 166 connects the foam solution container 162 to the nozzle assembly 100. The foam solution supply line 166 may be a hose, tubing or other conduit, and is securely fastened to the upstream end portion 180 of the diffuser tube 158 of the diffuser 114. The upstream end portion 180 may be threaded externally, allowing the foam solution supply line 166 and/or other connector to be threaded thereon. Alternatively, the foam solution supply line 166 and the upstream end portion 180 may be fastened together using a clamp or other fastener.
Gaseous solution supply line 168 connects the gaseous solution container 164 to the nozzle assembly 100. The gaseous solution supply line 168 may also be a hose, tubing or other conduit. As stated previously, the inner surface 188 (
A controller of a fire suppression system (not shown) may be used to control the nozzle assembly 100 or a plurality of nozzle assemblies 100. Each nozzle assembly 100 may be dedicated to protect an area, such as a hazardous material storage building or paint locker within a building, or a cargo container within the cargo hold of an airplane. When the controller detects a thermal event or other fire related event, the controller determines which of the nozzle assemblies 100 are located in a position proximate the thermal event. The controller then activates actuators 172 and 174 or other mechanism to open the foam and gaseous solution containers 162 and 164. For example, one or both of the foam and gaseous solution containers 162 and 164 may be sealed with foil or other material which may be punctured, or may be accessed by opening a valve. Alternatively, the actuator 172 may start a pump (not shown) to pump foam solution out of the foam solution container 162.
The foam solution discharges from the foam solution container 162, is conveyed by the foam solution supply line 166 and enters the conduit 120 within the foam solution input opening 108. The foam solution sprays out of the foam solution spray nozzle 116 into an inner portion 124 of the discharge tube 102 and onto the screen 140 of the screen assembly 118. At the same time, the gaseous solution discharges from the gaseous solution container 164, is conveyed through the gaseous solution supply line 168, through the pipe nipple 170 held within the gaseous solution input opening 110 and into the chamber 122. The gaseous solution under pressure pushes the gaseous solution through the orifices 136 in the diffuser face 134 into the discharge tube 102. Referring again to
The bubbles 176 form a foam blanket that displaces other air within the container by pushing the ambient air out through any openings in the container. Therefore, the inerting gaseous solution, and thus also the air in the container, is essentially “thickened” by the bubbles 176, which helps to retain the gaseous solution within the container rather than allowing the gaseous solution to mix with and be pushed out with the ambient air (oxygen supply).
The bubbles 176 or foam blanket will extinguish the fire with its smothering, cooling and wetting effect. When the bubbles 176 eventually burst, the inert gas, which does not support combustion, is liberated. This is especially important for Class A combustibles such as paper and wood that burn with both flaming combustion and deep seated combustion. The foam both cools and wets the deep seated ember and the inert atmosphere suppresses any continued combustion.
The chamber or sealed plenum may also be used in foam expansion assemblies when high expansion foam encasing a gaseous solution is desired, such as in an aircraft hanger, a warehouse, a tunnel, mine or other large enclosed area. High expansion foam may have, for example, expansion ratios greater than 200:1.
An inner surface of the foam solution input opening 214 may be threaded for receiving and securing a tube 218 which extends beyond the front face 208. The downstream end of the tube 218 may be threaded to receive a nozzle assembly 220. The nozzle assembly 220 may have one or more foam solution spray nozzles 222. Optionally, the nozzle assembly 220 may also have a blower fan 224, which may be driven by the flow of the foam solution or by electrical power (not shown). When the blower fan 224 rotates, the foam solution spray nozzles 222, which are canted at an angle, are also rotated.
Screen assembly 226 extends from open end 230 proximate the downstream end 206 of the discharge tube 202. The screen assembly 226 may have an inner diameter which is larger than an inner diameter of the discharge tube 202, allowing screen 228 to have a greater surface area. The screen assembly 226 may be formed integral with the discharge tube 202, or may be a separate piece which is welded, riveted, or otherwise securely attached thereto. The screen 228 has multiple cones formed therein, although it should be understood that the screen 228 may be formed in other shapes and contours. The screen assembly 226 may be square in shape proximate the downstream end 206 to allow easier construction of the screen 228.
Connecting foam and gas solution containers to the foam expansion assembly 200 may be accomplished similar to the assembly 160 of
The foam solution discharged from foam solution container 232 is conveyed by the foam solution supply line 236 and enters conduit 242 within the foam solution input opening 214. At the same time, the gaseous solution discharges from the gaseous solution container 234, is conveyed through the gaseous solution supply line 238, through the pipe nipple 240 held within the gaseous solution input opening 216 and into the chamber 210. The flow rate of the gaseous solution may be determined by the desired rate of foam production. For example, if 5000 cubic feet of foam per minute is desired, the flow rate of the gaseous solution would also be approximately 5000 cubic feet per minute
The foam solution spray nozzles 222 spray the foam solution into the discharge tube 202 and onto the screen 228. The foam solution may also drive the blower fan 224 which helps to pull the gaseous solution within the chamber 210 towards the downstream end 206 and push the foam solution through the screen 228. Alternatively, the nozzle assembly 220 may have one or more air aspirating high expansion nozzles without an accompanying blower fan. The high expansion nozzle uses the Venturi effect to draw the gaseous solution downstream with the velocity of the foam solution stream. The velocity of the gaseous solution pushes the foam solution through the screen 228. The foam solution encapsulates the gaseous solution within bubbles 244 which are discharged out of the downstream end 206 of the screen assembly 226.
While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.
