Abstract:
The present invention provides a system and method for generation of nitrogen enriched air for inerting aircraft fuels tanks. One embodiment of the present invention includes a duct assembly; a primary heat exchanger; a gas generating system heat exchanger; a first temperature sensor; a second temperature sensor; a controller monitor; a valve; an air separation module assembly having a primary module and a secondary module; at least one flow control orifice; and a pressure sensor. The present invention utilizes a minimal complement of components and streamlined processes, thus minimizing structural and operational costs while optimizing performance and safety features.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention generally relates to gas generation systems and particularly to systems and methods for nitrogen generation and for inerting aircraft fuel tanks.  
         [0002]     Aircraft fuel tanks contain potentially combustible combinations of oxygen, fuel vapors, and ignition sources. The flash point for explosion varies according to temperature, pressure and fuel type. Industry literature suggests that a “limiting oxygen content” (LOC) immunizes a fuel tank from explosion, regardless of flash point factors. Industry standards suggest various limits for the LOC. For example, current standards suggest that the minimum amount of oxygen needed to sustain combustion at sea level is slightly less than 12%. That amount increases to 14.5% at 30,000 feet above sea level, Croft, John, “FAA ‘Breakthrough’: Onboard Inerting”,  Aviation Week  &amp;  Space Technology , Jan. 6, 2003.  
         [0003]     Attempts have been made to reduce the oxygen level in aircraft fuel tanks by providing fuel tank foam systems to arrest explosions. Drawbacks exist, however, in foam inerting systems, including displacement of approximately 3.5% of the volume of the tank and inefficiencies associated with mandatory removal of the foam for maintenance purposes. Other inerting systems include a nitrogen-generating system (NGS), which introduces nitrogen enriched air into the fuel tanks. Typically, an NGS passes compressed air from the engines through filters to separate out the nitrogen content, which is then piped into aircraft fuel tanks.  
         [0004]     For example, U.S. Pat. No. 6,360,730 B1 to Koethe claims a method for inert loading of jet fuel by directly injecting an inerting agent into jet fuel while it is being loaded onboard an aircraft. U.S. patent application 20020162915 A1 to Mitani claims an environmental unit for an airplane wherein air of high-temperature and high-pressure is extracted from an engine or an auxiliary power portion of an airplane. The extracted air is regulated in temperature and pressure by an air conditioning portion and then the regulated air is supplied to a pressurized chamber, where the air exhausted from the pressurized chamber or air drawn out the pressurized chamber is separated into air enriched with nitrogen and air enriched with oxygen. The air enriched with oxygen is supplied to the pressurized chamber again. The air enriched with nitrogen is supplied to the fuel tanks. The air enriched with oxygen is once again supplied to the pressurized chamber by making use of the circulation line of the auxiliary air conditioning portion.  
         [0005]     The prior art inerting systems, however, have drawbacks, including a requirement for costly operational components. The components monopolize a predominance of the space and weight allowances for an aircraft, impeding overall system design. Further, redundant processes such as repetitive airflows into and from air conditioner components result in operational inefficiencies, again increasing the overall costs of such systems.  
         [0006]     As can be seen, there is a need for an improved method and system for gas generating systems and methods. There is also a need for such a system to and method to minimize component requirements; to minimize process complexity; to optimize safety features; and to minimize structural and operational costs.  
       SUMMARY OF THE INVENTION  
       [0007]     An aspect of the present invention includes a duct assembly; an air stream; a primary heat exchanger; a gas generating system heat exchanger; a first temperature sensor and a second temperature sensor; a controller monitor; a valve assembly; an air separation module (ASM) assembly having a primary module and at least one secondary module; at least one flow orifice; and a pressure sensor.  
         [0008]     Another aspect of the present invention includes a duct assembly with a bleed air inlet and a ram air inlet for ducting an air stream; an air stream exit; a control loop system having at least one control loop, which may include a conduit for nitrogen transfer from the ASM assembly and a pressure sensor for determining pressure in the conduit and generating at least one pressure value corresponding to the pressure; and a conduit exit for transferring nitrogen enriched air (NEA) from the ASM assembly; a controller monitor for receiving a pressure value and selectively preventing nitrogen flow; a primary heat exchanger for receiving the air stream from the ducting assembly and cooling the air stream, the primary heat exchanger located downstream from the at least one bleed air inlet and located downstream from the at least one ram air inlet; a gas generating system heat exchanger for receiving the air stream from the duct assembly, cooling the air stream, and providing the air stream to the duct assembly; an ejector for drawing in air over the gas generating heater exchanger and for ejecting a portion of the air stream, the ejector mechanically associated with duct assembly; a filter for filtering contaminates from the air stream, the filter mechanically associated with the duct assembly; a first temperature sensor and a second temperature sensor, each for determining temperature in the duct assembly and generating a temperature value corresponding to the temperature, each temperature sensor mechanically associated with the duct assembly; a controller monitor for receiving a temperature value and a pressure value, and generating a corresponding command signal; a panel indicator for visual confirmation of component status, the panel indicator electronically associated with the controller monitor; an altitude rate switch for monitoring changes in altitude and sending a signal corresponding to the change to the controller; a valve assembly for receiving and responding to the command signal, the valve assembly including at least one valve selected from a group essentially comprising a pressure regulating and shutoff valve, check valve, a flow shutoff valve, an ejector shutoff valve, a thermal shutoff valve, an ASM shutoff valve, and an isolation valve); an air separation module (ASM) assembly having a primary module and at least one secondary module, each module for receiving the air stream from the duct assembly; separating nitrogen enriched air (NEA) from the air stream; and providing nitrogen to the duct assembly, the ASM assembly located downstream from the at least one temperature sensor; at least one flow control orifice for controlling receiving and regulating nitrogen flow from the ASM assembly via the duct assembly, the at least one flow control orifice associated with a portion of the duct assembly located downstream from the ASM assembly; and at least one NEA check valve associated with the duct assembly, the check valve for preventing entry of contaminants into the duct assembly.  
         [0009]     Still another aspect of the present invention includes a duct assembly for ducting an air stream, with at least one bleed air inlet, at least one ram air inlet, and at least one air stream exit, a control loop system with a primary control loop and a secondary control loop; at least one pressure sensor for determining pressure in the conduit and generating at least one pressure value corresponding to the pressure; at least one conduit exit for transferring nitrogen enriched air (NEA); a controller monitor for selectively preventing NEA flow; a primary heat exchanger for receiving the air stream from the ducting assembly and cooling the air stream, the primary heat exchanger located downstream from the at least one bleed air inlet and located downstream from the at least one ram air inlet; a gas generating system heat exchanger for receiving the air stream from the duct assembly, cooling the air stream, and providing the air stream to the duct assembly; a first temperature sensor and a second temperature sensor, each temperature sensor for determining temperature in the duct assembly and generating a temperature value corresponding to the temperature, the temperature sensors mechanically associated with the duct assembly; a controller monitor for receiving a temperature value and a pressure value, and generating a corresponding command signal; a valve assembly for receiving and responding to the command signal, the valve assembly including at least one of the following: a pressure regulating and shutoff valve, a check valve, a flow shutoff valve, an ejector shutoff valve, a thermal shutoff valve, an ASM shutoff valve, and an isolation valve; an air separation module (ASM) assembly having a primary module and at least one secondary module, each module for receiving the air stream from the duct assembly; separating nitrogen enriched air (NEA) from the air stream; and providing the NEA to the duct assembly, the ASM assembly located downstream from the at least one temperature sensor; a primary flow shutoff valve for controlling NEA flow, the primary flow shutoff valve located downstream from the primary ASM and a secondary flow shutoff valve for controlling NEA flow, the secondary flow shutoff valve located downstream from the at least one secondary ASM; a primary flow control orifice and a secondary control orifice for controlling receiving and regulating NEA flow from the primary ASM and the at least one ASM, respectively, via the duct assembly, the primary flow control orifice and the secondary control orifice associated with a portion of the duct assembly located downstream from the ASM assembly; and a primary NEA check valve and a secondary NEA check valve for preventing entry of contaminants into the duct assembly, the primary NEA check valve and the secondary NEA check valve associated with the duct assembly.  
         [0010]     Yet another aspect of the invention includes steps of ducting the air stream via a duct assembly with at least one bleed air inlet, at least one ram air inlet, and at least one air stream exit; receiving the air stream from the ducting assembly and cooling the air stream with a primary heat exchanger, the primary heat exchanger located downstream from the at least one bleed air inlet and located downstream from the at least one ram air inlet; receiving the air stream from the duct assembly with a gas generating system heat exchanger, cooling the air stream, and providing the air stream to the duct assembly; determining temperature in the duct assembly and generating a temperature value corresponding to the temperature via a first temperature sensor and a second temperature, each temperature sensor mechanically associated with the duct assembly; receiving a temperature value and a pressure value, and generating a corresponding command signal via a controller monitor; receiving and responding to the command signal via at least one valve, the at least one valve selected from a group essentially comprising a pressure regulating and shutoff valve, a check valve, a flow shutoff valve, an ejector shutoff valve, a thermal shutoff valve, an ASM shutoff valve, and an isolation valve; receiving the air stream from the duct assembly, separating nitrogen enriched air (NEA) from the air stream, and providing the NEA to the duct assembly via an air separation module (ASM) assembly having a primary module and at least one secondary module, the ASM assembly located downstream from both temperature sensors; controlling NEA flow through the duct assembly from the ASM assembly to the conduit exit via the at least one flow control orifice, the at least one flow control orifice associated with a portion of the duct assembly located downstream from the ASM assembly; and preventing the entry of contaminants into the duct assembly from the conduit exit.  
         [0011]     A further aspect of the present invention includes steps of ducting an air stream through a duct assembly with at least one bleed air inlet, at least one ram air inlet, at least one air stream exit, and a conduit exit; receiving the air stream from the duct assembly and cooling the air stream with a primary heat exchanger located downstream from the at least one bleed air inlet and located downstream from the at least one ram air inlet; receiving the air stream from the duct assembly, cooling the air stream, and providing the air stream to the duct assembly with a gas generating system heat exchanger; drawing air into a duct assembly and over the gas generating system heat exchanger via an ejector mechanically associated with duct assembly; filtering contaminates from the air stream via a filter, the filter mechanically associated with the duct assembly; determining temperature in the duct assembly and generating a temperature value corresponding to each determined temperature via a first temperature sensor and a second temperature sensor, the temperature sensors mechanically associated with the duct assembly; receiving a temperature value and a pressure value, and generating a corresponding command signal via a controller monitor; visually confirming component status via a panel indicator, the panel indicator electronically associated with the controller monitor; monitoring changes in altitude and sending a signal corresponding to the change to the controller via an altitude monitor; receiving and responding to the command signal via at least one valve, the at least one valve selected from a group essentially comprising a pressure regulating and shutoff valve, a check valve, at least one flow shutoff valve, an ejector shutoff valve, a thermal shutoff valve, an ASM shutoff valve, and an isolation valve; receiving the air stream from the duct assembly; separating nitrogen enriched air (NEA) from the air stream; and providing the NEA to the duct assembly via an air separation module (ASM) assembly having a primary module and at least one secondary ASM module, the ASM assembly located downstream from the at least one temperature sensor; controlling, receiving, and regulating NEA flow from the ASM assembly via the duct assembly and via at least one flow control orifice, the at least one flow control orifice associated with a portion of the duct assembly located downstream from the ASM assembly; and preventing entry of contaminants into the duct assembly via at least one NEA check valve associated with the duct assembly.  
         [0012]     A still further aspect of the present invention includes steps of receiving in and venting the air stream via at least one orifice of a duct assembly, (the at least one orifice may include at least one bleed air inlet; at least one ram air inlet; at least one ram exit; and at least one ram air overboard exit); determining pressure in the duct assembly and generating a pressure value corresponding to the pressure via at least one pressure sensor; determining temperature in two points in the duct assembly and generating a temperature value corresponding to the determined temperature via a first temperature sensor and a second temperature sensor; receiving the pressure value and the temperature values, and generating at least one command based on the received values via a controller monitor, the at least one command generated to selectively control flow to portions of the duct assembly via a controller monitor; receiving the air stream from the ducting assembly and cooling the air stream via a primary heat exchanger, the primary heat exchanger located downstream from the at least one bleed air inlet and located downstream from the at least one ram air inlet; receiving the air stream from the duct assembly, cooling the air stream, and providing the air stream to the duct assembly via a gas generating system heat exchanger; receiving and responding to the command signal via at least one valve, the at least one valve selected from a group essentially comprising a pressure regulating and shutoff valve, a check valve, a flow shutoff valve, an ejector shutoff valve, a thermal shutoff valve, an ASM shutoff valve, and an isolation valve; receiving the air stream from the duct assembly; separating nitrogen enriched air (NEA) from the air stream; and providing the NEA to the duct assembly via an air separation module (ASM) assembly having a primary module and at least one secondary module, the ASM assembly located downstream from the temperature sensors; controlling NEA flow from the ASM assembly via a primary flow shutoff valve located downstream from the primary ASM and a secondary flow shutoff valve, the secondary flow shutoff valve located downstream from the at least one secondary ASM; receiving and regulating NEA flow from the primary module via a primary flow control orifice and receiving and regulating NEA flow from the at least one secondary module, the primary flow control orifice and the secondary control orifice associated with a portion of the duct assembly located downstream from the ASM assembly; and preventing entry of contaminants into the duct assembly via a primary NEA check valve located downstream from the primary flow control orifice and a secondary NEA check valve located downstream from the secondary flow control orifice; and transferring the NEA from the duct assembly via at least one conduit exit.  
         [0013]     In a gas inerting system having a duct assembly with a conduit exit; a primary heat exchanger; a gas generating system heat exchanger; the gas generating system heat exchanger; a controller monitor; a valve assembly including a pressure regulating and shutoff valve mechanically associated with a portion of the duct assembly upstream from the primary heat exchanger and a thermal shutoff valve mechanically associated with a portion of the duct assembly downstream from the gas generating system heat exchanger; an air separation module (ASM) assembly having a primary module and a secondary module, the ASM assembly mechanically associated with a portion of the duct assembly upstream from the thermal shutoff valve; a flow control orifice; an NEA check valve and a control loop system, a further aspect of the present invention includes a redundant temperature control system with a first temperature sensor for determining temperature in the duct assembly and generating a first temperature value for the controller monitor; and a second temperature sensor for determining temperature in a portion of the duct assembly located upstream from the first temperature sensor and downstream from the ASM assembly and for generating a second temperature value. The controller monitor receives the first temperature value and the second temperature value, selectively closes the pressure regulating and shutoff valve based on the received first temperature value, and selectively closes the thermal shutoff valve based on the received second temperature value.  
         [0014]     In a gas inerting system having a duct assembly with a conduit exit; a primary heat exchanger; a gas generating system heat exchanger; a first temperature sensor and a second temperature sensor; a controller monitor; a valve assembly including a pressure regulating and shutoff valve and a thermal shutoff valve; an air separation module (ASM) assembly having a primary module and a secondary module; a flow control orifice; and an NEA check, still another aspect of the present invention includes a cooling system with an ejector for drawing air into the duct assembly and over the gas generating system heat exchanger for cooling purposes.  
         [0015]     These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]      FIG. 1  is a schematic of an embodiment of a gas generating system, according to the present invention;  
         [0017]      FIG. 2  is a schematic of an alternate embodiment of an air separation module assembly of the gas generating system of  FIG. 1 , according to the present invention; and  
         [0018]      FIG. 3  is an alternate embodiment of a control loop system of the air separation module assembly system of  FIG. 2 , according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]     The following detailed description is of the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims.  
         [0020]     Broadly, the present invention provides a system and method for generating a gas from an air stream; for example, isolating nitrogen from an air mixture and providing the isolated nitrogen for use as an inerting agent. Unlike inventions of the prior art, which require a host of specific components and costly, redundant subprocesses, the present invention may utilize a minimal and flexible set of components as well as streamlined subprocesses, resulting in a cost-effective system and method.  
         [0021]     More specifically, the present invention recovers nitrogen from an air stream, using the recovered nitrogen for inerting systems or other applications. For example, the present invention may utilize jet engine air that is otherwise vented overboard to produce nitrogen enriched air (NEA) for introduction into an ullage of a center wing fuel tank.  
         [0022]     Referring now to the drawings, wherein similar reference characters designate corresponding parts throughout the drawings, and with reference to  FIG. 1 , there is shown an embodiment of gas generating system (GGS), shown generally at  10 , according to an embodiment of the present invention. The GGS  10  may comprise, for example, a duct assembly  12  having bleed air inlets  12   a  and conduits  12   b - 12   t ; a pressure regulating and shutoff valve (PRSOV)  14 ; an ozone/hydrocarbon converter  16 ; a gas generating system (GGS) heat exchanger  18 ; a heat exchanger bypass valve  20 ; an ejector  22 ; an ejector shutoff valve  24 ; a first temperature sensor  26 , such as a sensor or thermometer; a filter  28 ; a second temperature sensor  30 , such as a sensor or thermometer; a thermal shutoff valve  32 ; an air separation module assembly (ASM assembly)  34  having air separation modules (ASM)  36   a - d ; an ASM shutoff valve  38 ; a third temperature sensor  40 , such as sensor or thermometer; an OEA check valve  42 , a flow control shut-off valve actuator  44 , a flow control shutoff valve  46 ; a primary flow control orifice  48 ; a secondary flow control orifice  50 ; a primary NEA check valve  52 ; a secondary NEA check valve  54 ; a primary pressure sensor  56 ; a secondary pressure sensor  58 ; a controller monitor  60 ; an altitude rate switch  62 ; and a panel indicator  64 .  
         [0023]     Components operationally associated with the GGS  12  may include, for example, a ram air conduit  66  having passages  66   a ,  66   b ; ram inlet  66   c ; and ram exit  66   d ; a ventilation flap valve  68 ; a primary heat exchanger  70 ; an air conditioning system having a fan, such as a right-hand pack  72  or a left-hand pack  74 ; ram air overboard exit  76 ; and an isolation valve  78 .  
         [0024]     In various embodiments, control and monitoring functions of the GGS  10  may ensure temperature regulation of bleed air  13   b  entering the GGS  10  and selective shutoff of the bleed air supplies  13   c ,  13   e  and the air stream  13   i  to the ASM assembly  34  in the event of overtemperature and/or overpressure conditions. Typically, a cooling air such as ram air  67   c  may be used to cool bleed air  13   a  and  13   b  to temperatures acceptable for entry into the ASM assembly  34 . Ram cooling flow  67   c  to the GGS  10  may flow in any mode of airplane operation.  
         [0025]     Air stream sources (not shown) may enter at least one orifice of the GGS  10 , including the bleed air inlets  12   a  as  13   a , the ram air inlet  66   c  as  67   c , and the ram air overboard exit  76  as  77 . Portions of the duct assembly such as  66   a  and  66   b  may accommodate bi-directional flow of the air streams  77  and  67   a , and venting of the air streams may be accomplished via various orifices, including the ram exit  66   d  as  67   d  and the ram air overboard exit  76  as  13   q.    
         [0026]     For example, during in-flight operations, ram air  67   c  naturally feeds the GGS  10 . The ejector  22  may remain off in flight, and ram air  67   c  may be used to cool the bleed air  13   a  and  13   b  entering the GGS system  10 . For example, ram air may feed the GGS system  10  by entering a ram air inlet as  66   c , travel through the ram air conduit  66  as  67 , travel across the primary heat exchanger  70  as  67 , and exit overboard via ram exit  66   d  as  67   d.    
         [0027]     For ground operations, however, ram air is not available for cooling bleed air  13   a  and  13   b  entering the GGS system  10 , and heat sinking (cooling of the bleed air or other air stream) may be achieved by inducing a cooling airflow  13   g  through the GGS heat exchanger  18  using the ejector  22 . The ejector  22  may utilize bleed air (not shown) to induce ambient cooling air  67   a  through the GGS heat exchanger  18  for ground and low-speed flight operation because the ram air differential is insufficient to provide adequate cooling air to the GGS heat exchanger  18 . The ejector  22  may be located downstream of the GGS heat exchanger  18 . An array of uniformly-spaced converging nozzles  22   a  may be located at an inlet of the ejector  22 . The nozzles  22   a  may provide a high-momentum (increasing) primary flow  13   g  to induce secondary, low-pressure flow  66   a  from the GGS heat exchanger  18  cold side. Each nozzle  22   a  may be supplied with bleed air from a feed tube (not shown) connecting each nozzle  22   a  with a bleed air manifold; i.e., a conduit for receiving the bleed air and conducting it to each nozzle  22   a . Generally, the feed tubes (not shown) ensure an equal flow of bleed air (not shown) into each nozzle  22   a  with minimum pressure loss and ensure minimized drag and attendant pressure loss in the cold-flow side. For example, upon receiving a weight-on-wheels signal from the aircraft, the controller monitor  60  turns on the ejector shutoff valve  24  to energize the ejector  22  for heat sinking purposes, whereafter the ejector  22  may be fed high-pressure air (not shown) from a bleed air crossover duct (not shown) to a series of nozzles  22   a , which then draw cooling air  13   g  into the conduit  12   g , through the conduit  12   d  as airflow  13   d  and through the conduit  12   e  as airflow  13   e , then into the GGS heat exchanger  18 .  
         [0028]     During maintenance checkout intervals, the GGS  10  may also be enabled by sending a signaling from the controller monitor  60  to the PRSOV  14 , which opens the PRSOV  14 . Cooling airflows  13   g  and  67  may be provided by the ejector  22  or by an ECS fan (not shown) respectively, the ECS fan located downstream from the heat exchanger  70  and directly upstream from the ram exit  66   d . If, for example, simultaneous pack operation were desired, either the right-hand pack  72  or the left-hand pack  74  is turned on so as to induce airflow  77  via the ECS fan (not shown), backward through the GGS heat exchanger  18 . Thus, once the ECS fan (not shown) is activated, the airflow  77  is drawn in via the ram air overboard exit  76  and drawn backwards through the GGS heat exchanger  18 , and drawn as airflow  67   a  toward ram air conduit  66 . Meanwhile, the ECS fan also draws in the airflow  67   c  via the ram inlet  66   c . Both airstreams  67   c  and  77  are drawn together into airflow  67 , and drawn through the heat exchanger  70  to flow as airflow  67   d  through the ram exit  66   d . Although the airflow  77  may flow through the GGS heat exchanger  18  in the reverse direction from normal, this operation will have no effect on the performance characteristics of the GGS  10 .  
         [0029]     Regardless of the source of the air supply, once an air supply  13   c  reaches the conjunction of conduits  12   c  and  12   g , the air stream  13   c  is passed to the PRSOV  14 . The PRSOV  14  may provide a primary on/off functionality for the GGS  10 . In addition, the PRSOV  28  may regulate air pressure to minimize the probability of providing excessive pressure (and resulting flow) to the GGS  10 . The PRSOV  14 , may include for example, an on/off solenoid (not shown). The PRSOV  14  may be actuated and may receive pressurized air from a source (not shown) connected to the bleed air inlets  12   a . The solenoid (not shown) may then vent the PRSOV  14  upon receipt of a discrete signal given, for example, during ground operation or a cargo fire event. The PRSOV  14  may also be closed in case of an overtemperature detection or a shutdown signal from a controller source (not shown). For example, if the airflow  13   j  into the ASM assembly  34  is temperature-controlled at approximately 190□F, within an approximately 10° F. variance, airflow  13   j  is not expected to exceed 200° F. during steady state operation. If, however, airflow temperature exceeds the preselected setpoint, the controller monitor  60  may immediately close the PRSOV  14  to cut off the airflow  13   c  into the ASM assembly  34  and protect the GGS  10 .  
         [0030]     The PRSOV  14  may also provide downstream pressure regulation in the event of an overpressure condition. If the PRSOV  14  downstream pressure exceeds the desired pressure value, the PRSOV  14  may begin to regulate airflow  13   c . The overtemperature functionality may be also accomplished via the thermal shutoff valve  32 . The thermal shutoff valve may be located downstream of the GGS heat exchanger  18  and upstream of the ASM assembly  34 . For example, a second temperature sensor  30 , located immediately upstream of the thermal shutoff valve  32 , may monitor temperature of an airflow  13   i  in the conduit at  12   i . In the event of loss of temperature control, the second temperature sensor may provide a signal to the controller monitor  60  to shut down the PRSOV  14 , may provide a signal to the controller monitor  60  to shutdown the thermal shutoff valve  32 , or may provide signals to the controller monitor  60  to shutdown both.  
         [0031]     After the air supply  13   c  passes through the PRSOV  28 , it may pass via conduit  12   d  as airflow  13   d  to the ozone/hydrocarbon converter  16 , which may comprise a catalyst formulation effective for hydrocarbon oxidation as well as ozone decomposition, preventing the harmful effects of ozone on component materials such as those found in the ASM assembly  34 . The hydrocarbon oxidation may form carbon dioxide and water in quantities that do not affect the cabin environment.  
         [0032]     The airflow  13   e  may then be routed via conduit  12   e  to the GGS heat exchanger  18 . The GGS heat exchanger  18  may condition the hot, compressed bleed air  19  to a predetermined temperature prior to delivery to the ASM assembly  34 . The GGS heat exchanger  18  may also prevent hot bleed air  19  from entering the aircraft fuel tank (not shown) in case of system failures of various types.  
         [0033]     As the hot compressed bleed air  19  is present in the GGS heat exchanger  18 , ram air (not shown), also present in the GGS heat exchanger  18 , may function as a heat sink. Once the cooled air  13   f  has been drawn across the GGS heat exchanger  18 , and into the conduit  12   f , the first temperature sensor  26  may sense the air temperature and compare it against a preselected temperature setting, for example, a temperature control setpoint of 190° F., with a control band of approximately 10° F. If the first temperature sensor  26  determines that the sensed temperature falls outside a predetermined range, the first temperature sensor  26  may send a signal to the controller monitor  60 . Upon receiving said signal, the controller monitor  60  may generate a command signal to control the heat exchanger bypass valve  20 , closing the valve and stopping the flow of air from the GGS heat exchanger  18  to conduit  12   f . It is contemplated that the first temperature sensor  26  may comprise various designs and constructs; for example, a mixing thermostat (not shown). The first temperature sensor  26  may work in conjunction with the heat exchanger bypass valve  20 , which may pass a part of the airflow  13   h  around the GGS heat exchanger  18  via conduit  12   h  to control the air input into the air separation module assembly  34 , resulting in improved control, system stability, and improved response time.  
         [0034]     Once the air  13   f  passes the first temperature sensor  26 , it may enter the filter  28 , which may coalesce particulate and aerosol matter that may be present. For example, the filter  28  may capture dust, sand particles, oil, hydraulic fluid, and water, thus preventing excessive contamination buildup within the ASM assembly  34 , which would otherwise result in lower flow and undesirable oxygen levels in the NEA.  
         [0035]     After filtering, the air  13   i  may travel down the conduit  12   i  to devices such as the second temperature sensor  30  and the thermal shutoff valve  32 , which may be used to shut down the GGS  10  operation in the event of, for example, loss of temperature control. Such a shutdown may prevent catastrophic events. For example, the second temperature sensor  30  may provide a signal for the controller monitor  60  to shut down the PRSOV  14  in the event of loss of temperature control.  
         [0036]     In the event that the PRSOV  14  is unable to shutdown, the thermal shutoff valve  32  may automatically shut off flow to the ASM assembly  34 . Once the temperature of the air  13   i  exceeds a predetermined trigger point, the thermal shutoff valve  32  may automatically close and may be reset during, for example, ground maintenance. After passing through the thermal shutoff valve  32 , the air  13   j  reaches the ASM assembly  34  via the conduit  12   j.    
         [0037]     The ASM assembly  34  may include one or more ASMs, shown in  FIG. 1  as ASMs  36   a - d , each of which may comprise various designs, components, and constructs, as noted by one skilled in the art. In one example, the ASM assembly  34  may comprise a minimal complement of components that increases reliability; requires minimal electrical power; and may run continuously and autonomously. Each ASM may separate from the air one or more streams of predefined gases; for example, nitrogen enriched air (NEA).  
         [0038]     In various embodiments, the ASMs may include a primary ASM  36   a  and one or more (a series of) secondary ASMs  36   b - d . The secondary ASMs, such as ASMs  36   b - 36   d , may operate in parallel, depending on airflow requirements and overall aircraft design requirements and constraints. For example, as the airflow  13   j  may enter into the primary ASM  36   a  for full-time operation and portions of the airflow  13   j  may be diverted to airflow  13   r  via conduits  12   r  during high-flow (descent) operations. The airflow  13   r  may be separated into airstreams  13   r   1 ,  13   r   2 , and  13   r   3  for entry into respective secondary ASMs  36   b - d  via respective conduits  12   r   1 - 3 . Entry of the airstreams  13   r   1 - 13   r   3  into respective secondary ASMs  36   b - 36   d  is generally accomplished in close temporal proximity, thus providing approximately parallel nitrogen-separation operations in each secondary ASM  36   b - 36   d.    
         [0039]     Upon exiting the primary ASM  36   a , the NEA flow  131  may flow through the flow shutoff valve  46 , then via conduit  12   m  and NEA flow  13   m  to the flow control orifice  48 , which may regulate flow of the NEA  13   m , completely or partially restricting the flow of NEA during climb and cruise operations of the aircraft (conservation mode) or increasing the NEA flow  13   m  during descent operations of the aircraft. The NEA flow  13   m  may then enter check valve  52 , which may prevent backflow of contaminants into the ASM assembly  34 , then flowing as  13   p  to exit the GGS  10  via conduit exit  12   p . Upon exit, the NEA may be provided to, for example, a center wing fuel tank (not shown) for inerting purposes.  
         [0040]     All or a portion of the NEA flow  131  may also be ducted circuitously through a control loop system  80  having the primary control loop  81  comprising, for example, conduit  12   o  and the primary pressure sensor  56 . The NEA flow  13   o  passes through conduit  12   o , wherein the pressure may be sensed by the primary pressure sensor  56 . The primary pressure sensor  56  may send a signal to the controller monitor  60 , which, in turn, may actuate the flow control shutoff valve  46 , the flow primary flow control orifice  48 , or both, thus determining the direct or circuitous routing of the NEA to the conduit  12   n  as NEA flow  13   n , for onward transfer via conduit exit  12   p  as NEA flow  13   p.    
         [0041]     As NEA flow  13   p  passes to the center wing fuel tank (not shown) via conduit  12   p , the altitude rate switch  62  may determine that a descent has been initiated and may signal the controller monitor  60 , which may actuate the primary NEA check valve  52 , allowing a high flow rate of NEA to the ullage space of the center wing fuel tank (not shown). The primary NEA check valve  52  may prevent fuel vapors or splash back from entering equipment upstream thereof. The primary NEA check valve  52  may also prevent a back flow of air through the primary ASM  36   a  during conservation mode, protecting it and guarding against contamination of other standard or optional equipment.  
         [0042]     The altitude rate switch  62  may function in conjunction with the controller monitor  60  by determining altitude of the aircraft and signaling the controller monitor  60  accordingly. During conservation mode, only a small amount of extremely pure NEA  13   p  (low oxygen content) may be provided to an ullage space, thereby reducing the ullage oxygen concentration during cruise operations, which ultimately reduces the NEA requirements during descent.  
         [0043]     The remaining airflow  13   t  (absent the NEA) may be vented from the primary ASM module  36   a  through conduit  12   t , through the OEA check valve  42  and via conduit  12   q  (airflow  13   q ) to the ram air overboard exit  76 . The OEA check valve  42  may prevent back flow or back splash of contaminants into the ASM assembly  34 .  
         [0044]     A portion or all of the airflow  13   j  entering the ASM assembly  34  may also be directed to the secondary ASMs  36   b - 36   d  via conduit  12   j  and the ASM shutoff valve  38 , which may conserve the air by shutting off any and all ASMs not required during, for example, climb and cruise phases of a flight profile. During such phases only the primary ASM  36   a  may be operational. A trickle flow  13   r  to the secondary ASMs  36   b - 36   d  may be permitted to maintain a near operating temperature in the secondary ASMs  36   b - 36   d  when closed.  
         [0045]     The altitude switch  62  may control the ASM shutoff valve  38  by sensing descent, and, in response, energizing it. After exiting the ASM shutoff valve  38 , the airflow  13   r  may enter into the secondary ASMs  36   b - 36   d  via conduits  12   r   1 - 12   r   3  as airflows  13   r   1 - 13   r   3 , respectively. Optionally, the third temperature sensor  40  may operate in conjunction with the ASM controller monitor  60  to sense over-temperature conditions in the airflow  13   r  and effect closure of the ASM shutoff valve  38 .  
         [0046]     After air separation in the secondary ASMs  36   b - 36   d , the NEA  13   s  may flow via  12   s  to the secondary flow control orifice  50 , the secondary check valve  54 , and to the center wing fuel tank (not shown) via conduit  12   p  as NEA flow  13   p . It is contemplated that the secondary flow control orifice  50  and the secondary NEA check valve  54  will provide functionality similar to that described for the primary flow control orifice  48  and the primary NEA check valve  52 , respectively. Airflow  13   t  other than the separated NEA may exit the secondary ASMs  36   b - d  via conduit(s)  12   t  and the pass through the OEA check valve  42  for venting as airflow  13   q  via conduit  12   q  and the ram air overboard exit  76 .  
         [0047]     Turning now to  FIG. 2 , there is shown an alternate embodiment of the ASM assembly  34  of  FIG. 1  having in addition to the primary control loop  81 , a secondary control loop  82  and an additional ASM module  36   e . The addition of the ASM module  36   e  merely illustrates one of the possible designs for the ASM assembly  34  and may be utilized, for example, in relatively large aircraft requiring relatively high NEA output. The addition of the second control loop  82  provides a redundancy in pressure regulation and control of the NEA flow  13   s  by inclusion of a control loop dedicated specifically to the NEA output  13   s  of the secondary ASMs  36   b - 36   e.    
         [0048]     In the alternate embodiment of  FIG. 2 , the airflows  13   r   1 - 4  may enter the secondary ASMs  36   b - 36   e  via the conduits  12   j  and  12   r   1 - 4 . After gas separation in the secondary ASMs  36   b - 36   e , the NEA flow  13   s  may be ducted directly to the center wing fuel tank (not shown) via conduits  12   s , a secondary flow control valve  86 , the secondary flow control orifice  50 , and the secondary NEA check valve  54 . Alternatively, the NEA flow  13   s  may be ducted via  12   s  to the secondary control loop  82  that may provide redundant functionality to that of the first control loop  80 .  
         [0049]     The three-way solenoid  84  may function in conjunction with one or more sensors, such as the third temperature sensor  40 , the flow control sensor  46 , and the secondary flow control sensor  88  to actuate one or more valves such as the ASM shutoff valve  38 , the primary flow control valve  46 , and the secondary flow control valve  86 .  
         [0050]     Air  13   t  other than the NEA may exit the primary ASM  36   a  and the secondary ASMs  36   b - e  via conduits  12   t , and vented as  13   w  overboard via conduit  12   w.    
         [0051]     Turning now to  FIG. 3 , there is shown an alternative embodiment of a control loop system  80  of  FIG. 2 , wherein each control loop  81 ,  82  has an independent pressure conduit and an independent conduit exit; namely, primary conduit exit  12   p , secondary conduit exit  12   y , primary pressure conduit  90  and secondary pressure conduit  92 . The inclusion of the primary pressure conduit  90  and the secondary pressure conduit  92  may provide additional pressure regulation and control functionality for the ASM assembly  34 . The inclusion of the primary conduit exit  12   p  and the secondary conduit exit  12   y  may provide redundant inerting capabilities via redundant NEA flow  13   p  and  13   y , thus ensuring an NEA flow to the center wing fuel tank (not shown) in case of a control loop failure.  
         [0052]     After exiting the primary ASM  36   a , the NEA flow  131 ,  13   n ,  13   p  may be ducted directly to the center wing fuel tank (not shown) via conduit  121 , a flow control orifice  48   a  (functionally the same or similar to the flow control orifice  48  of  FIGS. 1 and 2 ), the conduit  12   n , the check valve  52 , and finally the primary conduit exit  12   p.    
         [0053]     Alternatively, all or a portion of the NEA flow  131  may be ducted through the primary control loop  81  via  12   o  as NEA flow  13   o  through a flow control orifice  48   b  (functionally the same or similar to the flow control orifice  48  of  FIGS. 1 and 2 ), through  12   n  as NEA flow  13   n , through the NEA check valve  52 , and to the center wing fuel tank via the primary conduit exit  12   p  as NEA flow  13   p . As previously described, the flow control shut-off valve actuator may operate in conjunction with the controller monitor (shown as  60  in  FIG. 1 ) to sense or measure flow and signal the controller monitor  60  which, in turn, may actuate closure or opening of the flow control shutoff valve  46 .  
         [0054]     The NEA may also be ducted via primary pressure conduit  90  as NEA flow  91  and the primary pressure sensor  56 , which may operate in conjunction with the controller monitor (shown as  60  in  FIG. 1 ) to gauge pressure and regulate flow. The NEA flow  91  may then be ducted via conduit  12   n  as NEA flow  13   n , exiting to the center wing fuel tank (not shown) via the NEA check valve  52  and the primary conduit exit  12   p  as NEA flow  13   p.    
         [0055]     The secondary control loop  81  may be functionally similar to the primary control loop  82 . For example, the secondary control loop  82  may receive NEA flow  13   s  via conduit  12   z  (NEA flow  13   z ) and duct the NEA directly to the center wing fuel tank (not shown) via a flow control orifice  50   a , which may regulate flow of the NEA, and the check valve  52 , and finally, as NEA flow  13   y , may be ducted to the center wing fuel tank (not shown) via the second conduit exit  12   y.    
         [0056]     NEA flow  13   s  may also be ducted through a flow control orifice  50   b  for flow regulation, and the NEA check valve  54 , then exit to the center wing fuel tank (not shown) as  13   y  via the secondary conduit exit  12   y . As previously described, the flow control sensor  88  may operate in conjunction with the controller monitor (shown as  60  in  FIG. 1 ) to sense or measure flow and signal the controller monitor (shown as  60  in  FIG. 1 ) which, in turn, may actuate closure or opening of the flow control shutoff valve  86 .  
         [0057]     The NEA flow  13   s  may also be ducted via secondary pressure conduit  92  as NEA flow  93  and the secondary pressure sensor  58 , which may operate in conjunction with the controller monitor (shown as  60  in  FIG. 1 ) to gauge pressure and regulate flow. The NEA flow  93  may then be ducted via conduit  12   z  as NEA flow  13   z , exiting to the center wing fuel tank (not shown) via the NEA check valve  54  and the secondary conduit exit  12   y  as NEA flow  13   y.    
         [0058]     It should be understood, of course, that the foregoing relates to preferred embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.