Abstract:
A fire suppression system for an aircraft having a compartment, the fire suppression system including an inert gas source in selective fluid communication with the compartment and a fire suppression agent source in selective fluid communication with the compartment, wherein an inert gas from the inert gas source and a fire suppression agent from the fire suppression agent source are at least partially combined to form a fire suppression mixture.

Description:
FIELD 
       [0001]    This application relates to fire suppression and, more particularly, to the suppression of fires in aircraft compartments. 
       BACKGROUND 
       [0002]    Aircraft, particularly commercial passenger aircraft, are commonly equipped with a fire protection system in the cargo compartment. A typical fire protection system comprises two sub-systems: a fire detection system and a fire suppression system. The fire detection system includes one or more fire detectors (e.g., smoke detectors) and the fire suppression system includes a fire suppression agent. When a fire is detected in the cargo compartment, the fire suppression agent is released and floods the cargo compartment with an appropriate quantity of the fire suppression agent. The release of the fire suppression agent may occur automatically in response to a positive fire detection by a fire detector or, alternatively, may occur in response to manual pilot intervention (e.g., after the pilot receives a warning signal and actuates one or more switches). 
         [0003]    Halon 1301 (bromotrifluoromethane) has long been the fire suppression agent of choice on aircraft. Halon 1301 is a clean fire suppression agent; it does not damage cargo or leave behind a residue. Furthermore, unlike inert gas-based fire suppression agents, such as carbon dioxide, Halon 1301 is effective in suppressing fires at relatively low concentrations (e.g., 3 to 10 percent by volume). Therefore, a breathable level of oxygen may remain after discharge of Halon 1301. 
         [0004]    Halon 1301 has a relatively high ozone depletion potential (“ODP”) and alternatives are being sought out. Several alternatives to Halon 1301 have been proposed, such as 2-bromo-3,3,3-trifluoro-1-propene. However, the alternatives proposed to date have been unsuitable for aircraft use because they cannot pass the United States Federal Aviation Administration&#39;s Aerosol Can Explosion Simulation Test, which is outlined in the Federal Aviation Administration&#39;s Minimum Performance Standard for Aircraft Cargo Compartment Halon Replacement Fire Suppression Systems, 2012 Update (DOT/FAA/TC-TN12/11). 
         [0005]    Accordingly, those skilled in the art continue with research and development efforts in the field of aircraft fire suppression. 
       SUMMARY 
       [0006]    In one aspect, the disclosed aircraft may include a compartment (e.g., a cargo compartment) and a fire suppression system, wherein the fire suppression system includes an inert gas source in selective fluid communication with the compartment and a fire suppression agent source in selective fluid communication with the compartment, wherein an inert gas from the inert gas source and a fire suppression agent from the fire suppression agent source are at least partially combined to form a fire suppression mixture. 
         [0007]    In another aspect, the disclosed fire suppression system for an aircraft having a compartment (e.g., a cargo compartment) may include a nozzle positioned in the compartment, a conduit network including a main line fluidly coupled with the nozzle, a first supply line fluidly coupled with the main line and a second supply line fluidly coupled with the main line, an inert gas source in fluid communication with the main line by way of the first supply line, and a fire suppression agent source in fluid communication with the main line by way of the second supply line. 
         [0008]    In yet another aspect, the disclosed method for suppressing a fire in a compartment of an aircraft may include the steps of (1) monitoring the compartment for presence of a fire and (2) after the fire is detected, simultaneously introducing into the compartment a first volume of an inert gas and a second volume of a fire suppression agent. 
         [0009]    Other aspects of the disclosed aircraft fire suppression system and method will become apparent from the following detailed description, the accompanying drawings and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a side elevational view of an aircraft equipped with the disclosed aircraft fire suppression system; 
           [0011]      FIG. 2  is a schematic flow diagram depicting one aspect of the disclosed aircraft fire suppression system; and 
           [0012]      FIG. 3  is a flowchart depicting one aspect of the disclosed aircraft fire suppression method. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    Various aircraft may be equipped with the disclosed aircraft fire suppression system. While a fixed-wing aircraft  100  is shown in  FIG. 1 , non-fixed wing aircraft, such as rotary-wing aircraft (rotorcraft), may also benefit from the disclosed aircraft fire suppression system and method. 
         [0014]    Referring to  FIG. 1 , one aspect of the disclosed aircraft, generally designated  100 , may include a fuselage  102  that longitudinally extends along an axis A from proximate a front end  104  of the aircraft  100  to proximate a rear end  106  of the aircraft  100 . A support floor  108  may extend from proximate (at or near) the front end  104  of the aircraft  100  to proximate the rear end  106  of the aircraft  100 , thereby defining a passenger compartment  110  and a cargo compartment  112  within the fuselage  102 . 
         [0015]    The passenger compartment  110  may include a plurality of seats  114  affixed to the floor  108 . Various additional features, such as carryon baggage storage compartments and the like, are well known in the art and may be included in the passenger compartment  110  without departing from the scope of the present disclosure. 
         [0016]    The cargo compartment  112  may be divided into a forward compartment  116  and an aft compartment  118 . The forward compartment  116  and the aft compartment  118  may provide a generally open area for holding various containers, bulk cargo and the like. One or more cargo doors (not shown) may provide access to the forward and aft compartments  116 ,  118  of the cargo compartment  112 . 
         [0017]    In one variation, the cargo compartment  112  may be a single compartment (not a divided compartment). In another variation, the cargo compartment  112  may be divided into three of more compartments, such as a forward compartment, a middle compartment and an aft compartment. 
         [0018]    The cargo compartment  112 , specifically the forward and aft compartments  116 ,  118 , of the aircraft  100  may be equipped with an aircraft fire suppression system  200 . As is described in greater detail herein, in the event of a fire in the cargo compartment  112 , the aircraft fire suppression system  200  may supply to the cargo compartment  112  a fire suppression mixture that includes an inert gas and a fire suppression agent. 
         [0019]    Referring to  FIG. 2 , one aspect of the disclosed aircraft fire suppression system, generally designated  200 , may include an inert gas source  202 , a fire suppression agent source  204 , a conduit network  206  and a controller  208 . The controller  208  may effect simultaneous release (to the cargo compartment  112  of the aircraft  100 ) of inert gas from the inert gas source  202  and fire suppression agent from the fire suppression agent source  204 , thereby forming a fire suppression mixture effective against fire. 
         [0020]    The inert gas source  202  may be any source capable of supplying a quantity of inert gas sufficient to form the disclosed fire suppression mixture. While six separate inert gas sources  202  are shown in  FIG. 2 , fewer inert gas sources  202  (e.g., only one) or additional inert gas sources  202  (e.g., seven or more) may be used without departing from the scope of the present disclosure. For example, the number of inert gas sources  202  may depend of the number of compartments within the cargo compartment  112 . 
         [0021]    The inert gas supplied by the inert gas source  202  may be any inorganic gas that does not readily participate in combustion reactions. The inert gas may be elemental or a compound. As one specific, non-limiting example, the inert gas from inert gas source  202  may consist essentially of a noble gas, such as helium or argon. As another specific, non-limiting example, the inert gas from inert gas source  202  may consist essentially of nitrogen. Using mixtures of inert gases is also contemplated. 
         [0022]    In one variation, the inert gas source  202  may include a pressurized vessel housing an initial quantity of the inert gas. For example, the inert gas source  202  may be a gas cylinder (e.g., a metallic gas cylinder) filled with pressurized inert gas (e.g., nitrogen and/or argon). 
         [0023]    In another variation, the inert gas source  202  may include a solid propellant gas generator (SPGG). The solid propellant gas generator may store inert gas as a solid material, and may rapidly release inert gas when the solid material is combusted. As one specific, non-limiting example, the solid propellant gas generator may contain a quantity of sodium azide (NaN 3 ) that, when ignited, produces sodium metal and nitrogen gas. Use of a liquid propellant is also contemplated. 
         [0024]    In yet another variation, the inert gas source  202  may include an on-board inert gas generation system (OBIGGS). The aircraft  100  may include an on-board inert gas generation system in connection with its fuel system, as is commonly done on modern aircraft to inert the fuel tank during flight. For example, the on-board inert gas generation system may employ a membrane separation technique to separate nitrogen from ambient air. Therefore, the on-board inert gas generation system of the aircraft  100  may be tapped as the inert gas source  202  of the disclosed aircraft fire suppression system  200 . 
         [0025]    The fire suppression agent source  204  may be any source capable of supplying a quantity of fire suppression agent sufficient to form the disclosed fire suppression mixture. While three separate fire suppression agent sources  204  are shown in  FIG. 2 , fewer fire suppression agent sources  204  (e.g., only one) or additional fire suppression agent sources  204  (e.g., four or more) may be used without departing from the scope of the present disclosure. For example, the number of fire suppression agent sources  204  may depend of the number of compartments within the cargo compartment  112 . 
         [0026]    The fire suppression agent supplied by the fire suppression agent source  204  may be any chemically active (non-inert) agent effective in fire suppression. Without being limited to any particular theory, it is believed that chemically active fire suppression agents suppress combustion by sequestering free radicals that propagate the combustion reaction. However, selection of a fire suppression agent to be contained in the fire suppression agent source  204  is not limited to any particular chemical mechanism. The fire suppression agent may be a liquid (e.g., a volatile liquid) or a gas at standard temperature and pressure. 
         [0027]    In one particular implementation, the fire suppression agent supplied by the fire suppression agent source  204  may be (or may include) an organofluorine compound. Specific examples of organofluorine compounds suitable for use as the fire suppression agent supplied by the fire suppression agent source  204  include, but are not limited to, 2-bromo-3,3,3-trifluoro-1-propene (2-BTP), 1,1,1,2,2-pentafluoroethane (HFC-125), and perfluoro(2-methyl-3-pentanone) (NOVEC™ 1230, commercially available from 3M Company of St. Paul, Minn.). 
         [0028]    The fire suppression agent source  204  may include a pressurized vessel housing an initial quantity of the fire suppression agent. For example, the fire suppression agent source  204  may be a cylinder (e.g., a metallic cylinder) filled with fire suppression agent. When the fire suppression agent is a liquid at standard temperature and pressure, the fire suppression agent may be pressurized with a small quantity of inert gas (e.g., nitrogen). 
         [0029]    The conduit network  206  may fluidly couple the inert gas source  202  and the fire suppression agent source  204  with nozzles  210 ,  212  in the cargo compartment  112  of the aircraft  100 . The nozzles  210 ,  212  may be configured and arranged to quickly and effectively distribute the fire suppression mixture throughout the cargo compartment  112 . For example, one or more nozzles  210  may be positioned in the forward compartment  116  of the cargo compartment  112  and one or more nozzles  212  may be positioned in the aft compartment  118  of the cargo compartment  112 . Additional nozzles may be included when the cargo compartment  112  includes compartments in addition to the forward and aft compartments  116 ,  118 . Fewer nozzles may be included when the cargo compartment  112  includes only a single compartment. 
         [0030]    The conduit network  206  may include a main line  214 , a first supply line  216  and a second supply line  218 . The main line  214  of the conduit network  206  may fluidly couple the first supply line  216  and the second supply line  218  with the cargo compartment  112  (e.g., with the nozzles  210 ,  212 ). The first supply line  216  may fluidly couple the inert gas source  202  with the main line  214 . The second supply line  218  may fluidly couple the fire suppression agent source  204  with the main line  214 . Various additional conduits may be included in the conduit network  206  to facilitate the simultaneous release to the cargo compartment  112  of the inert gas and the fire suppression agent. 
         [0031]    One or more flow control devices  220 ,  222  may be positioned on the main line  214  to control the flow of fluid along the main line  214 . For example, flow control device  220  may control the flow of fluid to the forward compartment  116  of the cargo compartment  112  and flow control device  222  may control the flow of fluid to the aft compartment  118  of the cargo compartment  112 . Additional flow control devices may be included when the cargo compartment  112  includes compartments in addition to the forward and aft compartments  116 ,  118 . Fewer flow control devices (e.g., only one or none) may be included when the cargo compartment  112  includes only a single compartment. 
         [0032]    The flow control devices  220 ,  222  of the main line  214  may be in communication with, and actuateable by, the controller  208 . For example, the flow control devices  220 ,  222  may be electronically actuateable valves, such as normally-closed solenoid valves or normally-open solenoid valves. Therefore, the flow control devices  220 ,  222  may selectively provide (or, alternatively, may selectively prevent) fluid communication with the cargo compartment  112  when actuated by the controller  208 . 
         [0033]    A first flow control device  224  may be associated with each inert gas source  202  to control the flow of inert gas from the inert gas source  202  to the first supply line  216  and, ultimately, to the cargo compartment  112  by way of the main line  214 . The type of flow control device  224  used may depend on the type of inert gas source  202  being used. As one example, when the inert gas source  202  is a pressurized vessel, the first flow control device  224  may be an electronically actuateable valve, such as a normally-closed solenoid valve. As another example, when the inert gas source  202  includes a solid propellant gas generator, the first flow control device  224  may be (or may include) an electrical discharge cartridge (e.g., a squib) that, when electronically actuated, ignites the solid propellant gas generator and fluidly couples the solid propellant gas generator with the first supply line  216 . 
         [0034]    A second flow control device  226  may be associated with each fire suppression agent source  204  to control the flow of fire suppression agent from the fire suppression agent source  204  to the second supply line  218  and, ultimately, to the cargo compartment  112  by way of the main line  214 . As one example, the second flow control device  226  may be (or may include) an electronically actuateable valve, such as normally-closed solenoid valve. As another example, the second flow control device  226  may be (or may include) an electrical discharge cartridge (e.g., a squib) designed to rupture a seal when actuated. 
         [0035]    The first and second flow control devices  224 ,  226  may be in communication with, and actuateable by, the controller  208 . Therefore, the first flow control device  224  may selectively provide fluid communication between the inert gas source  202  and the first supply line  216  when actuated by the controller  208  and the second flow control device  226  may selectively provide fluid communication between the fire suppression agent source  204  and the second supply line  218 . 
         [0036]    Thus, when the controller  208  actuates the first and second flow control devices  224 ,  226 , inert gas from the inert gas source  202  may flow into the first supply line  216  and fire suppression agent from the fire suppression agent source  204  may flow into the second supply line  218 . In the conduit network  206  (e.g., within the main line  214 ), the inert gas may mix with the fire suppression agent to form the fire suppression mixture, which may then pass into the cargo compartment  112  by way of the nozzles  210 ,  212 . 
         [0037]    In an alternative aspect, when the controller  208  actuates the first and second flow control devices  224 ,  226 , mixing of the inert gas with the fire suppression agent to form the fire suppression mixture may occur in the cargo compartment  112  rather than within the conduit network  206 . For example, one nozzle  210 ,  212  may release the inert gas into the cargo compartment  112 , while another nozzle  210 ,  212  may release the fire suppression agent, thereby allowing the inert gas to mix with the fire suppression agent within the cargo compartment  112 . 
         [0038]    A fire detector  230  may be provided in the cargo compartment  112  of the aircraft  100 . While the fire detector  230  is shown in  FIG. 2  generally positioned in the cargo compartment  112 , each compartment (e.g., forward compartment  116  and aft compartment  118 ) of the cargo compartment  112  may have a dedicated fire detector  230  (or plural dedicated fire detectors). 
         [0039]    The fire detector  230  may be (or may include) any apparatus or system capable of detecting smoke and/or fire. For example, the fire detector may be (or may include) a smoke detector, such as an optical smoke detector and/or an ionization smoke detector. 
         [0040]    When the fire detector  230  detects a fire, the controller  208  may initiate a fire suppression sequence, which may include actuating the first and second flow control devices  224 ,  226 , as well as one or more of flow control devices  220 ,  222 , as appropriate. In one configuration, the controller  208  may automatically initiate the fire suppression sequence when the fire detector  230  detects a fire. In another configuration, the fire detector  230  may trigger a warning (e.g., a visual and/or audible indication) to the pilot when a fire is detected. However, the controller  208  may not initiate the fire suppression sequence until the controller  208  receives a command from the pilot, such as when the pilot manually engages one or more flight deck controls  232  (e.g., switches). 
         [0041]    The cargo compartment  112  of the aircraft  100  may have a known volume, and may be filled with air (e.g., ambient air). The inert gas source  202  may be charged to yield a first quantity of inert gas and the fire suppression agent source  204  may be charged to yield a second quantity of fire suppression agent. Therefore, when the first quantity of inert gas and the second quantity of fire suppression agent are introduced into the cargo compartment  112 , an inerting concentration of fire suppression agent may be present in the cargo compartment  112 . Additionally, the first quantity of inert gas may be sufficient to displace air (specifically, oxygen) and correspondingly, enrich the fire suppression agent-to-oxygen volumetric ratio within the cargo compartment  112 , thereby yielding a fire suppression mixture capable of passing the United States Federal Aviation Administration&#39;s Aerosol Can Explosion Simulation Test. 
         [0042]    The fire suppression mixture may deliver a quantity of fire suppression agent sufficient to achieve within the cargo compartment  112  at least an inerting concentration of fire suppression agent. The inerting concentration of fire suppression agent may depend on the composition of the fire suppression agent. The inerting concentration for a particular fire suppression agent may be experimentally determined using various techniques. For example, when 2-bromo-3,3,3-trifluoro-1-propene is used as the fire suppression agent, a concentration of at least about 8.5 percent by volume may be required to be inerting. 
         [0043]    Furthermore, the fire suppression mixture may synergistically deliver a quantity of inert gas sufficient to achieve within the cargo compartment  112  an added concentration of inert gas. As used herein, “added concentration” refers to the inert gas introduced to the cargo compartment  112  from the inert gas source  202 , and does not include any inert gas that may be initially present (e.g., in the ambient air) in the cargo compartment  112 . For example, when the inert gas is nitrogen, the added concentration of nitrogen only accounts for the nitrogen supplied from the inert gas source  202 , and does not take into account the nitrogen already present in the cargo compartment by virtue of the fact that ambient air comprises a significant quantity (about 78 percent by volume) of nitrogen. 
         [0044]    In one expression, the fire suppression mixture may deliver a quantity of inert gas sufficient to achieve within the cargo compartment  112  an added concentration of inert gas ranging from about 15 to about 19 percent by volume. In another expression, the fire suppression mixture may deliver a quantity of inert gas sufficient to achieve within the cargo compartment  112  an added concentration of inert gas ranging from about 16 to about 18 percent by volume. In yet another expression, the fire suppression mixture may deliver a quantity of inert gas sufficient to achieve within the cargo compartment  112  an added concentration of inert gas of about 17 percent by volume. 
         [0045]    Thus, the inert gas source  202  and the fire suppression agent source  204  may be charged with sufficient quantities of inert gas and fire suppression agent, respectfully, to achieve within the cargo compartment  112  an added concentration of inert gas and an inerting concentration of fire suppression agent, which may allow the fire suppression mixture to prevent an explosion in the Unites States Federal Aviation Administration&#39;s Aerosol Can Explosion Simulation Test. 
         [0046]    The entire payload of inert gas and fire suppression agent may be delivered simultaneously from the inert gas source  202  and the fire suppression agent source  204 . Alternatively, a sequential release of inert gas and/or fire suppression agent may be used. For example, the first two inert gas sources  202  may be actuated with the first fire suppression agent source  204 , then after expiration of a first predetermined time interval the next two inert gas sources  202  may be actuated with the next fire suppression agent source  204 , then after expiration of a second predetermined time interval the final two inert gas sources  202  may be actuated with the final fire suppression agent source  204 . 
         [0047]    Optionally, a regulator  234  may be positioned on the second supply line  218  to regulate the flow of fire suppression agent from the fire suppression agent source  204 . For example, the regulator  234  may be configured to regulate the flow rate of fire suppression agent based on the flow rate of the inert gas such that the resulting fire suppression mixture has the desired composition. 
         [0048]    Accordingly, by simultaneously charging the cargo compartment  112  of the aircraft  100  with inert gas and fire suppression agent to achieve an inerting concentration of fire suppression agent and an added concentration of inert gas, the resulting fire suppression mixture may be capable of substitution for Halon 1301-based systems. 
         [0049]    Also disclosed is an aircraft fire suppression method. As shown in  FIG. 3 , one aspect of the disclosed aircraft fire suppression method, generally designated  300 , may begin at Block  302  with the step of monitoring a compartment of an aircraft for the presence of fire. For example, the cargo compartment of the aircraft may be provided with one or more fire detectors (e.g., smoke detectors). 
         [0050]    At Block  304 , the method  300  may query whether a fire has been detected. If no fire is detected, the method  300  may return to Block  302  to continue to monitor for the presence of fire in the compartment. However, when a fire is detected, the method  300  may proceed to the next step. 
         [0051]    At Block  306 , an optional warning may be issued when a fire is detected (at Block  304 ). The warning may be issued to the pilot of the aircraft. For example, the warning may include a visual and/or audible indication that a fire has been detected. The warning may prompt pilot intervention. 
         [0052]    At Block  308 , an inert gas and a fire suppression agent may be simultaneously released into the compartment of the aircraft. The release may be automatic or in response to a command from the pilot. The simultaneous release of inert gas and fire suppression agent may yield within the compartment an added concentration of inert gas (e.g., about 15 to about 19 percent by volume) and an inerting concentration of fire suppression agent. 
         [0053]    Although various aspects of the disclosed aircraft fire suppression system and method have been shown and described, modifications may occur to those skilled in the art upon reading the specification. The present application includes such modifications and is limited only by the scope of the claims.