Patent Application
20140345700
The present invention relates to imposing an inert environment for a fuel tank with a gas, and more particularly to a pressure monitoring system for a fuel tank, as well as a method of monitoring over-pressurization of a fuel tank.
Conventional fuel tank systems require an inert gas to reduce unwanted chemical reactions of the fuel stored therein. Typically, a compressed air source is conditioned by separating various gases of the air source, with at least one of which used to replace air otherwise present in the fuel tank. The flow to the fuel tanks is controlled by a flow control valve at the outlet of a component that separates the various gases, thereby linking a high pressure air source and the fuel tanks. The high pressure air source introduces the capability to over-pressurize the fuel tanks in the event a fuel tank vent is blocked or submerged in fuel, leading to undesirable conditions, such as a loss of fuel or a fuel tank rupture which may cause a safety hazard.
According to one embodiment, a pressure monitoring system for a fuel tank includes a supply line fluidly coupling a fluid source with at least one fuel tank for supplying an inert gas to the at least one fuel tank. Also included is a pressure relief valve in communication with the supply line configured to detect a pressure differential between a supply line pressure and an ambient pressure. Further included is a pressure sensor configured to detect the supply line pressure. Yet further included is a controller in operable communication with the pressure sensor and the fluid source, wherein the controller is configured to modify a flow rate of the inert gas in the supply line upon detection of the supply line pressure exceeding a predetermined pressure limit.
According to another embodiment, a method of monitoring over-pressurization of a fuel tank is provided. The method includes detecting a supply line pressure within a supply line that fluidly couples a fluid source with at least one fuel tank, wherein a pressure sensor in operative communication with the supply line detects the supply line pressure. The method also includes communicating a signal from the pressure sensor to a controller if the supply line pressure exceeds a predetermined pressure limit. The method further includes modifying a flow rate of an inert gas flowing through the supply line with the controller upon receipt of the signal from the pressure sensor.
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
Referring to
Irrespective of the precise type of fuel stored within the fuel tank 12, it is desirable to provide an inert environment within the fuel tank 12 to reduce unwanted chemical reactions of the stored fuel. Such an environment is attained by supplying an inert gas 14 to the fuel tank 12 via a supply line 16. Various contemplated inert gases may be employed, with an exemplary embodiment of the inert gas 14 supplied comprising nitrogen. In an embodiment of the fuel tank supply system 10 disposed on an aircraft, an airflow 18 is provided from a fluid source 20. In one embodiment, the fluid source 20 comprises a compressed airflow generated from a standalone, onboard compressor. In yet another embodiment, the fluid source 20 comprises compressed air in the form of engine bleed airflow. Regardless of the particular source, the airflow 18 is routed to an air separation module 22 along an air separation module feed line 24. The air separation module 22 is configured to separate nitrogen and oxygen from the airflow 18, with the nitrogen enriched air employed to inert the fuel tank 12 upon routing along the supply line 16. Proximate an outlet of the air separation module 22 is a flow control valve 26 disposed within the supply line 16. The flow control valve 26 controls the flow rate of the inert gas 14 throughout the supply line 16. The flow control valve 26 may also be configured to vent the supply line 16. Alternatively, a separate vent may be present within the supply line 16.
Based on the need to avoid over-pressurization of the fuel tank 12, the fuel tank supply system 10 includes a primary vent structure 40 that comprises a vent 42 and a flame arrestor 44. The vent 42 is configured to vent the inert gas 14 to ambient and prevent over-pressurization. A redundant feature of the fuel tank supply system 10 is included in the form of a pressure monitoring system 28. The pressure monitoring system 28 comprises a pressure relief valve 30 disposed downstream of the flow control valve 26 within the supply line 16, with the pressure relief valve 30 configured to detect a pressure differential between a supply line pressure and an ambient pressure outside of the supply line 16. The pressure relief valve 30 opens to vent and relieve the inert gas 14 of the supply line 16 upon detection of a predetermined pressure differential. The predetermined pressure differential will vary depending upon the particular application and the overall system characteristics of the fuel tank supply system 10. In one embodiment, the predetermined pressure differential employed to trigger opening of the pressure relief valve 30 ranges from about 2 psi (about 14 kPa) to about 15 psi (about 103 kPa).
The pressure monitoring system 28 also includes a pressure sensor 32 located downstream of the flow control valve 26 and is in operative communication with the supply line 16 to detect a pressure within the supply line 16. This detection, or measurement, is conducted independently of the pressure differential detected by the pressure relieve valve 30 and operates as a second pressure detection mechanism, in the supply line. Additionally, a secondary corrective action is associated with the pressure sensor 32, which may be beneficial if the pressure relieve valve 30 fails to open. Specifically, the pressure sensor 32 is in operative communication with a controller 34 and sends a signal to the controller 34 to convey the detected pressure within the supply line 16. The pressure communicated to the controller 34 is compared to a predetermined pressure limit that is programmed into the controller 34. As is the case with the predetermined pressure differential associated with the pressure relief valve 30, the predetermined pressure limit will vary depending upon the particular application and the overall system characteristics of the fuel tank supply system 10. Regardless of the precise predetermined pressure differential, the controller 34 is configured to modify the flow rate of the inert gas 14 flowing through the supply line 16 upon detection of the supply line pressure exceeding the predetermined pressure differential. In one embodiment, the controller 34 is in operative communication with the flow control valve 26 located proximate the outlet of the air separation module 22. The controller 34 modifies the flow rate of the inert gas 14 by partially or fully closing the flow control valve 26 to reduce or shut off the flow of the inert gas 14 entering the supply line 16, thereby preventing additional over-pressurization of the supply line 16 and consequently the fuel tank 12.
The redundant aspects of the pressure monitoring system 28 described above account for the possibility that the primary vent structure 40 fails to operate properly. Specifically, failure of the vent 42 to vent to ambient and/or malfunction of the flame arrestor 44. A failure of the vent 42 to open may occur due to a number of reasons. In some embodiments, the vent 42 is disposed in the fuel tank 12 itself, or proximate an outlet of the fuel tank 12. In such an embodiment, the fuel stored within the fuel tank 12 may submerge the vent 42, thereby impeding desired venting. Such a situation may be imposed during maneuvers of the vehicle, such as an aircraft, in such an embodiment. The redundant aspect of the pressure monitoring system 28 advantageously provides secondary monitoring and corrective action capability. Specifically, the supply line 16 may be vented at a remote location, with respect to the fuel tank 12. In one embodiment, the flow control valve 26 and/or is the pressure relief valve 30 are located closer in proximity to the air separation module 22 than to the fuel tank 12.
In addition to the corrective action described in detail above, the controller 34 is in operative communication with an operator computer 36, such as a flight crew computer in the case of an aircraft embodiment, and is configured to generate a signal to a system operator that an over-pressurized condition is present, thereby prompting the operator to perform appropriate actions. Alternatively, the pressure sensor 32 may be in operative communication with the operator computer 36 to directly send a signal that alerts the operator, or flight crew, of the over-pressurized condition.
A method 100 of monitoring over-pressurization of the fuel tank 12 is also provided, as illustrated in
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
