High performance ejector and pressure recovery method

Abstract: A high-efficiency, low weight ejector and ejector system is provided wherein the primary gas to the ejector is the reaction product of a hydrocarbon fuel and decomposed hydrogen peroxide. In a preferred embodiment, the ejector is made substantially from a carbon-carbon fiber composite material.

Description: FIELD OF THE INVENTION This invention relates generally to ejector systems and, in particular, to high performance pressure recovery systems capable of use with a high energy chemical laser. BACKGROUND Ejectors and ejector systems are commonly used for moving a gas from an area of low pressure to an area of high pressure, such as to an area at ambient pressure. Ejectors and ejector systems are commonly used in certain chemical lasers which operate under vacuum conditions. Such ejector systems draw reaction products from the chemical laser reaction chamber so as to reduce the pressure within the reaction chamber to below ambient. By use of the ejector system, reaction gases are drawn from the reaction chamber and exhausted to a suitable exhaust site, such as to the atmosphere. Large chemical lasers, such as those useful in producing very high energy laser beams for military weapons purposes, generally require very large ejectors, typically multi-stage ejectors. Such ejector systems are, therefore, generally very heavy and very lengthy. Where the chemical laser must be used as an anti-theater ballistic missile system, the laser is only effective if it is mounted in an airplane flying high above a theater ballistic missile launch site. This is because the effectiveness of chemical lasers as anti-theater ballistic missile weapons is largely limited to the ability of the chemical laser to intercept the theater ballistic missile with its high energy laser beam during the first few seconds after launch. After that, the effectiveness of the chemical laser to destroy theater ballistic missiles is greatly reduced. To install and operate a chemical laser within an airplane requires that the chemical laser be as efficient, as lightweight and as compact as possible. Accordingly, the large and lengthy ejectors and ejector systems previously used for high energy chemical lasers have been found to be impractical in an aircraft-mounted chemical laser system. There is, therefore, a need for a high efficiency (high performance ratio) ejector and ejector system which can effectively perform in conjunction with a high energy chemical laser without requiring undue weight or length. SUMMARY The invention satisfies this need. The invention is a method for moving a secondary gas from a low pressure zone to a high pressure zone comprising the step of educting the secondary gas to the high pressure zone with an ejector which uses as a primary gas the reactive products of a hydrocarbon fuel and decomposed hydrogen peroxide. Such ejectors have been found to be adaptable to very highly efficient, one-stage non-metallic ejectors having sufficiently reduced weight and length to be useable in a high energy airborne chemical laser system. The invention is also an ejector manufactured substantially from a carbon-carbon fiber composite. It has been found that such ejectors can be effectively used in high efficiency, one-stage ejector systems having very low weight and, therefore, being suitable for use in airborne chemical laser weapons systems. DRAWINGS These features, aspects and advantages of the present invention will become better understood with regard to the following description, appended claims and accompanying figures where: Figure 1 is a perspective view of an ejector having features of the invention; Figure 2 is a cross-sectional side view of another ejector having features of the invention; Figure 3 is a schematic diagram showing a COIL chemical laser usable with the invention; Figure 4 is a perspective view of a pressure recovery system of an airborne COIL chemical laser having features of the invention; Figure 5 is a perspective view of the gas generator portion of the pressure recovery system shown in Figure 4. DESCRIPTION OF THE INVENTION The invention is defined by claims 1 and 4. Various embodiments are defined by the dependent claims. The following discussion describes in detail one embodiment of the invention and several variations of that embodiment. This discussion should not be construed, however, as limiting the invention to those particular embodiments. Practitioners skilled in the art will recognize numerous other embodiments as well. The invention is a method of moving a secondary gas from a low pressure zone to a high pressure zone comprising the step of educting the secondary gas to the high pressure zone with an ejector which uses as a primary gas the reaction products of a hydrocarbon fuel and decomposed hydrogen peroxide. In most applications, the high pressure zone is substantially at ambient pressure. The decomposed hydrogen peroxide is mostly molecular oxygen and water. The decomposing of hydrogen peroxide can be accomplished by contacting the hydrogen peroxide at elevated temperatures (e.g., about 37.7°C-93.3°C (100°-200°F)) and elevated pressures (e.g., about 100-600 psig) with a silver-containing catalyst. To minimize the amount of weight incumbent in the hydrogen peroxide - especially when the ejector is to be used on an airborne platform - the purity of the hydrogen peroxide is preferably higher than about 70% (by weight), for example, 70% - 90% or, more preferably, 80%-90%. The hydrocarbon fuel is typically an aviation or jet fuel, such as the hydrocarbon fuel known in the industry as JP-8. Where the decomposed hydrogen peroxide is derived from a hydrogen peroxide having a purity of about 85% or greater, the reaction of the decomposed hydrogen peroxide with, for example, JP-8, is auto-igniting (without the assistance of a spark plug) at practical conditions of temperature and pressure. Use of such a reaction mixture, therefore, eliminates the need for separate ignition equipment. The reaction of JP-8 and decomposed 85% hydrogen peroxide is typically carried out at oxygen/fuel ratios of about 30.5 and produces reaction products having a temperature of about 1315°C (2400°F). The reaction of the hydrocarbon fuel and the decomposed hydrogen peroxide produces a high energy stream of reaction products composed largely of carbon dioxide and water. To maximize the efficiency and compactness of the ejector, the high pressure reaction product stream is passed through a set of multiple nozzles (e.g., 7 nozzles) and is thereby made supersonic before introduction into the inlet end of the ejector. The method has been found effective to move the secondary gas from a low pressure zone to a high pressure zone when the pressure differential between those zones is greater than about 0.2 atmospheres, even greater than about 0.3 atmospheres with only a single stage ejector. The ejector is made substantially from a carbon-carbon fiber composite. To minimize weight, the ejector can be greater than about 50% by weight carbon-carbon fiber composite material, preferably greater than about 80% by weight. As shown in Figure 1, the ejector 10 has an inlet section 12 , a throat section 14 and an outlet section 16 . In a preferred embodiment, the inlet section 12 and the outlet section 16 are both rectangular in cross-section to maximize operating pressure margins. However, the throat section 14 is generally circular or oval in cross-section. As shown in Figure 2, the inlet section 12 of the ejector 10 comprises an inlet zone 18 for the primary gas 19 and an inlet zone 20 for the secondary gas 21 . The inlet zone 18 for the primary gas 19 accepts high velocity primary gas 19 produced in the primary gas generator 24 and directs the primary gas 19 towards the throat section 14 . This draws secondary gas 21 from the low pressure zone 25 into the inlet zone 20 for the secondary gas 21 . The primary gas 19 and the secondary gas 21 are mixed in a convergent duct or constant pressure mixing zone 26 and flow as a combined gas mixture 28 at supersonic velocities through the throat section 14 of the ejector 10 . Near the outlet section 16 of the ejector 10 , the flow of gases 28 is reduced to subsonic velocity and the gases 28 are discharged via the outlet section 16 to the high pressure zone 30 . Where the combined secondary and primary gas streams 28 contain oxygen, it is preferable that any carbon-carbon fiber composite materials used on the interior walls of the ejector 10 be coated with a suitable anti-oxidant material, such as a silicon-based anti-oxidant material, so as to minimize oxidative degradation of the carbon-carbon fiber composite material. The invention has been found to provide an extremely useful high efficiency (high pressure ratio) eduction system having a fraction of the weight commonly inherent in prior art systems. Because of the high efficiency (high pressure ratio) of the ejector system, the system can frequently use single-stage ejectors, rather than multi-stage ejectors. This is extremely important when the ejectors are used on an airborne platform, where restrictions as to length (as well as weight) are a common problem. Figures 3 and 4 illustrate the use of the invention in a chemical oxygen iodine laser ("COIL"). Figure 3 illustrates a typical COIL 40 in which singlet-delta oxygen 42 is produced in a singlet-delta oxygen generator 44 and is then reacted with iodine 46 in a photon generator 48 to produce a high energy laser beam 50 . The photon generator 48 in a COIL 40 typically operates under reduced pressure conditions. Reaction products 52 produced in the photon generator 48 are exhausted to the atmosphere 54 using a pressure recovery system 56 comprising a diffuser 58 , a plenum 60 and one or more ejectors 10 . Figures 4 and 5 illustrate a pressure recovery system 56 using the invention in an airborne COIL 40 . Reaction products 52 from the photon generator 48 are drawn through the diffuser 58 by a plurality of (e. g., six) single-stage ejectors 10 of the invention disposed in parallel. A supersonic stream of primary gas 22 is generated in the primary gas generator 24 disposed within a plenum 60 by the reaction of a hydrocarbon fuel and decomposed hydrogen peroxide. The primary gas 22 is injected into the inlet section 12 of the ejectors 10 where it is mixed with the reaction products 52 from the photon generator 48 , and the combined gaseous mixture 28 is flowed through the throat section 14 . As the mixture 28 passes through the throat section 14 and into the outlet section 16 , its velocity is slowed to subsonic, and the mixture 28 is exhausted to the atmosphere 54 through suitable exhaust fairings in the airborne platform (not shown). Typically, the primary gas generator 24 shown in Figure 5 is jacketed with a jacket (not shown) so as to allow the primary gas generator 24 to be cooled by a coolant flowing through the jacket. The use of such a jacket effectively maintains the primary gas generator 24 sufficiently cool to prevent thermal degradation. In a preferred embodiment, the coolant is the hydrocarbon fuel to minimize the weight associated with the use of a separate coolant material and to allow the heat removed from the primary gas generator 24 to be efficiently used to pre-heat the hydrocarbon fuel prior to its being contacted with the decomposed hydrogen peroxide. Having thus described the invention, it should be apparent that numerous structural modifications and adaptations may be resorted to without departing from the scope and fair meaning of the instant invention as set forth hereinabove and as described hereinbelow by the claims.

Claims: A method of moving a secondary gas from a low pressure zone of a chemical laser to a high pressure zone (30) comprising the step of educting the secondary gas (21) to the high pressure zone (30) with an ejector (10) which uses as a primary gas (19) the reaction products of a hydrocarbon fuel and the decomposition products of hydrogen peroxide. The method of claim 1 wherein the secondary gas (21) comprises the reaction products of a chemical laser; and/or wherein the secondary gas (21) comprises the reaction products of an oxygen iodine COIL chemical laser; and/or wherein the high pressure zone (30) is substantially at ambient pressure; and/or wherein the pressure differential between the high pressure zone (30) and the low pressure zone is greater than about 0.2 atmospheres; and/or wherein the pressure differential between the high pressure zone (30) and the low pressure zone is between about 0.3 atmospheres; and/or wherein the ejector (10) is at least about 50 % carbon-carbon fiber by weight; and/or wherein the ejector (10) is at least about 80 % carbon-carbon fiber by weight; and/or wherein the primary gas generator (24) is jacketed and the primary gas generator (24) is cooled by a coolant flowing through a jacket-; and/or wherein the ejector (10) has an inlet section (12) which has a rectangular cross-section; and/or wherein the ejector (10) has an outlet section (16) which has a rectangular cross-section; and/or wherein the ejector (10) comprises inlet (12) and outlet (16) sections having rectangular cross-sections, an a throat section (14) having a round or oval cross-section; and/or wherein the decomposition products of hydrogen peroxide are obtained from hydrogen peroxide whose non-decomposed composition was between about 70 % and 95 % hydrogen peroxide by weight; and/or wherein the decomposition products of hydrogen peroxide are obtained from hydrogen peroxide whose non-decomposed composition was between about 80 % and 90 % hydrogen peroxide by weight; and/or wherein the decomposition products of hydrogen peroxide are obtained from hydrogen peroxide whose non-decomposed composition was about 85 % hydrogen peroxide by weight; and/or wherein the hydrocarbon fuel is an aviation or jet fuel; and/or wherein the hydrocarbon fuel is JP-8; and/or wherein the decomposition products of hydrogen peroxide are obtained by contacting hydrogen peroxide with a silver-containing catalyst at a pressure between about 100 psig and about 600 psig and at a temperature between about 100° and about 200°F; and/or wherein the ejector (10) has an inlet section (12) and the velocity of the primary gas (19) in the inlet section (12) is supersonic. The method of claim 2 wherein the ambient pressure is the ambient pressure at the altitude of an airborne platform; and/or wherein the coolant is the hydrocarbon fuel. An ejector (10) for educting a secondary gas from a low pressure zone of a chemical laser to a high pressure zone, made substantially of a carbon-carbon fiber composite material. The ejector (10) of claim 4 wherein the weight percent of the carbon-carbon fiber composite material in the ejector (10) is at least 50 % by weight; and/or wherein the weight percent of the carbon-carbon fiber composite material in the ejector (10) is at least 80 % by weight; and/or wherein the ejector (10) has an inlet section which has a rectangular cross-section; and/or wherein the ejector (10) has an outlet section (16) which has a rectangular cross-section; and/or wherein the ejector comprises inlet (12) and outlet (16) sections having a rectangular cross-sections, and a throat section (14) having a round or oval cross-section; and/or wherein the ejector (10) comprises an inlet section (12) and a throat (14) section constructed in part of carbon-carbon fiber composite material and wherein the inlet (12) and throat (14) sections have an anti-oxidant material covering a substantial portion of the carbon-carbon fiber composite material therein. The ejector of claim 5 wherein the anti-oxidant material is a silicon-based material.

Inventors: HAFLINGER DONALD E, KRUSE WILLIAM D, MAGIAWALA KIRAN R, HAFLINGER, DONALD E., KRUSE, WILLIAM D., MAGIAWALA, KIRAN R.
Applicants: TRW INC, TRW INC.
Application year: 1998
Main classification: H01S3
IPC codes: H01S3