1. Field of the Invention
This invention relates to a method and apparatus for improving aircraft safety. More specifically, this invention pertains to inert gas generating systems used on aircraft for preventing combustion in aircraft fuel tanks and cargo spaces. In particular, this invention relates to a super charger used to increase the air supply pressure to the air supply module of an inert gas generating system. The super charger transforms hydraulic power into pneumatic power, and provides an alternate air source for the inert gas generating system.
2. Description of Related Art
Military aircraft have used On-board Inert Gas Generating Systems (OBIGGS) for some years to protect against fuel tank explosions due to undesired phenomena, such as penetration from small arms fire. However, military aircraft are not the only aircraft that would benefit from OBIGGS. For example, investigations into the cause of recent air disasters have concluded that unknown sources may be responsible for fuel tank ignition and explosion. Subsequently, OBIGGS has been evaluated as a way to protect commercial aircraft against such fuel tank explosions started by unknown ignition sources.
OBIGGS protects against fuel tank explosions by replacing the potentially explosive fuel/air mixture above the fuel in the tanks (the ullage) with an inert gas, usually nitrogen. This nitrogen airflow, otherwise known as nitrogen enriched air (NEA), is generated by separating oxygen, otherwise know as oxygen enriched air (OEA), from local ambient air. The NEA is then pumped into the ullage. The device which separates the NEA from OEA is usually termed an Air Separation Module (ASM).
The performance of such OBIGGS systems, and their efficiencies are largely dependant on how well the ASM performs. For optimum performance, the ASM requires a compressed air supply to achieve efficient separation of NEA from OEA. In conventional OBIGGS systems, air supply for the ASM is obtained from engine bleed-air or from a rotary compressor. However, in extreme flight profiles, engine bleed-air may not be available to provide a supply of compressed air. Furthermore, during such extreme flight profiles, electrical power may not be available to drive a rotary compressor. In addition, a rotary compressor is inherently inefficient at transforming electrical energy into compressed air energy, thereby increasing fuel costs and diminishing performance of the OBIGGS.
Accordingly, an improved OBIGGS system that addresses the drawbacks of the prior art would be highly desirable. In particular, it would be advantageous to provide a compressed air supply that is not reliant on engine-bleed air or a rotary compressor. It would also be beneficial to provide such improvements with an efficient system that does not increase fuel costs or have other detrimental effects on the operation of the OBIGGS.
According to the invention there is provided an inert gas generating system. The inert gas generating system includes an air separation module (ASM) and a super charger. The ASM includes an ASM inlet configured for receiving an air flow, and having an ASM outlet configured for expelling nitrogen enriched air (NEA). The super charger has a hydraulic system configured to be coupled to a hydraulic pressure differential, and a pneumatic system coupled to the hydraulic system. The pneumatic system is configured to supply the air flow to the air separation module.
The hydraulic system and the pneumatic system are isolated from each other to prevent contamination of the output air sent to the air separation module. The hydraulic system includes a cylinder, a hydraulic piston housed within the cylinder, and a switching valve. The switching valve has a hydraulic fluid inlet, a hydraulic fluid outlet, and hydraulic passages fluidly coupling the switching valve to the cylinder near opposing ends of the cylinder. The switching valve is configured to alternate hydraulic fluid received at the fluid inlet between the hydraulic passages.
The pneumatic system preferably comprises identical pneumatic pistons coupled to opposing sides of the hydraulic piston, where the pneumatic pistons are coupled to separate pneumatic chambers each having an air inlet and an air outlet coupled to the ASM inlet. Each pneumatic chamber may be a bellows or a pneumatic cylinder. The super charger also includes check valves at the air inlet and air outlet to prevent retrograde air flow.
Accordingly, the super charger improves the performance of the OBIGGS by providing a continuous supply of compressed air to the ASM, even under extreme flight conditions. In other words, the super charger is not reliant upon engine bleed air or an electrically powered rotary compressor. The supercharger can also provide an alternate air source for the OBIGGS system in the event that conventional systems fail. Furthermore, the super charger is easily adapted to operate with conventional OBIGGS systems.
In addition, the supercharger may be used as a source of compressed air wherever a source of hydraulic power is available.
For a better understanding of the nature and objects of the invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawing, in which:
Like reference numerals refer to the same components throughout the figures.
The hydraulic input system includes a switching valve 200 and a hydraulic piston 202 housed within a hydraulic cylinder or bore 204. The switching valve 200 includes two hydraulic passages 206A and 206B for supply and return of hydraulic fluid to and from the hydraulic cylinder 204. The switching valve 200 also includes a hydraulic fluid inlet 208A and a hydraulic fluid outlet 208B for receiving and expelling hydraulic fluid into and out of the switching valve 200, respectively.
The switching valve 200 is preferably configured to alternate hydraulic fluid received at the hydraulic fluid inlet 208A between the two hydraulic passages 206A and 206B and into the cylinder 204. Similarly, the switching valve 200 is preferably configured to alternate hydraulic fluid expelled from the cylinder 204 through one of the two hydraulic passages 206A and 206B and out of the hydraulic fluid outlet 208B. In a preferred embodiment, the hydraulic passage 206A is connected to a first side 210A of the cylinder 204 and the hydraulic passage 206B is connected to a second side 210B of the cylinder 204, i.e., separated by the piston 202.
The hydraulic piston 202 is directly coupled on each side to a pair of pneumatic pistons 214A and 214B, such as by pushrods 212A and 212B, respectively. In a preferred embodiment, the ratio between the surface area of the hydraulic piston 202 and the surface area of the pneumatic pistons 214A and 214B is sized to provide optimum pneumatic pressure. For example, if the aircraft hydraulic pressure is on the order of 3,000 psi and the pneumatic pressure desired is ideally on the order of 100 psi, then the ratio of the pneumatic to hydraulic piston surface area is approximately 30:1.
The pneumatic pistons 214A and 214B are attached to pneumatic chambers 216A and 216B, respectively. In some embodiments, the pneumatic chambers 216A and 216B comprise bellows 218A or 218B which compress and contract in phase with the movement of the pneumatic pistons 214A and 214B, respectively. In an alternative embodiment, the pneumatic pistons 214A and 214B are housed within their own pneumatic cylinders or bores. The pneumatic chambers 216A and 216B are provided with air supply inlets 222A and 222B, respectively. In a preferred embodiment, the air supply inlets 222A and 222B provide air to the pneumatic chambers 216A and 216B from the surrounding environment, such as ambient air collected by an air scoop or the like. The air supply inlets 222A and 222B also preferably have check valves 220A and 220B, respectively, to prevent backwards air flow during the compression cycle of the pneumatic chambers 216A and 216B.
The pneumatic chambers 216A and 216B also preferably have air supply outlets 226A and 226B, respectively. These air supply outlets 226A and 226B direct the pressurized air to the inlet 104 (
n use, pressurized hydraulic fluid from an aircraft hydraulic system (not shown) enters the hydraulic inlet 208A. The switching valve 200 directs the hydraulic fluid to a respective side, say 210A, of the cylinder 204. This creates a pressure differential on the opposing sides of the hydraulic piston 202 causing the hydraulic piston 202 to move in a first direction (upward in
Movement of the piston 202 causes movement of the pneumatic pistons 214A and 214B, thereby either compressing or expanding the pneumatic chambers 216A and 216B. When compressed, the air inside the pneumatic chambers 216A or 216B is forced out through the check valves 224A or 224B and though the air supply outlets 226A and 226B to the ASM 102 (
Accordingly, the super charger improves the performance of the OBIGGS by providing a continuous supply of compressed air to the ASM, even under extreme flight conditions. In other words, the super charger is not reliant upon engine bleed air or an electrically powered rotary compressor. The supercharger can also provide an alternate air source for the OBIGGS system in the event that conventional systems fail. Furthermore, the super charger is easily adapted to operate with conventional OBIGGS systems.
The foregoing descriptions of specific embodiments of the present invention are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously many modifications and variations are possible in view of the above teachings. For example, hydraulic pressure may be obtained from any one of multiple systems on board the aircraft, or a separate system could be provided for the operation of the super charger. In another example, the compressed air provided by the pneumatic chambers could be bled off to reduce the outlet pressure or provide pressure to other aircraft systems. Other embodiments may be advantageous for reasons of cost, fuel efficiency, safety, or the like.
The embodiments were chosen and described above in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.
This application claims the benefit of U.S. Provisional Application Ser. No. 60/586,842, filed Jul. 8, 2004, entitled “Hydraulic Powered Pneumatic Super Charger for On-Board Inert Gas Generating System”, which is hereby incorporated by reference for all purposes. This application is also related to the following issued patents, each of which is hereby incorporated by reference: U.S. Pat. No. 6,729,359, “Modular On-Board Inert Gas Generating System,” issued on May 4, 2004; and U.S. Pat. No. 6,739,359, “On-Board Inert Gas Generating System Optimization by Pressure Scheduling,” issued on May 25, 2004.
Number | Date | Country | |
---|---|---|---|
60586842 | Jul 2004 | US |