Patent Application
20160245181
The present disclosure relates generally to jet engines and, more particularly, to the fuel systems of jet engines. Specifically, the present disclosure relates to cooling fuel within the fuel systems.
A gas turbine engine typically includes a high-pressure spool, a combustion system, and a low-pressure spool disposed within an engine casing. These components form a generally axial, serial flow path about an engine centerline. The high-pressure spool includes a high-pressure turbine, a high-pressure shaft extending axially forward from the high-pressure turbine, and a high-pressure compressor connected to a forward end of the high-pressure shaft. The low-pressure spool includes a low-pressure turbine disposed downstream of the high-pressure turbine. The low-pressure spool also includes a low-pressure shaft typically extending coaxially through the high-pressure shaft, and a low-pressure compressor connected to a forward end of the low-pressure shaft forward of the high-pressure compressor. The combustion system is disposed between the high-pressure compressor and the high-pressure turbine. The combustion system receives compressed air from the compressors as well as fuel provided by a fuel injection system. A combustion process is carried out within the combustion system to produce high-energy gases. These high-energy gases produce thrust and turn the high- and low-pressure turbines. In turn, the high- and low-pressure turbines drive the compressors to sustain the combustion process.
In jet engines, fuel is commonly used prior to combustion as a heat sink for cooling heat-producing aircraft components. For example, in a gas turbine engine, fuel can be used to cool bleed air from an engine compressor in a cabin air cycle control system, heat-producing components in a thermal management system, and/or an engine turbine in a turbine cooling system. Using the fuel itself as a coolant is more efficient than adding a cooling fluid flow to cool aircraft components. However, the cooling capacity of fuel is limited because oxygen initiates the formation of soot deposits, or coke, at temperatures between about 350° F. (177° C.) and about 850° F. (454° C.). Accordingly, efforts have been made to increase the cooling capacity of fuel.
Methods of increasing the cooling capacity of fuel in gas turbine engines include deoxygenating the fuel. Deoxygenating the fuel reduces the likelihood of coke formation, or coking. However, some propulsion devices such as supersonic combustion ramjet (SCRAM) jet engines operate at temperatures near 850° F. (454° C.) and up to 1700° F. (927° C.). At such temperatures, deoxygenating the fuel may not provide enough cooling capacity to cool aircraft components to a desired temperature without coking.
One method of increasing the cooling capacity of fuel for cooling components in SCRAM jet engines is endothermic cracking. Endothermic cracking absorbs a significant amount of heat by breaking long chain fuel molecules into lower molecular weight hydrocarbons through the use of a nanoparticle catalyst. The hydrocarbons can then be burned in the combustor more easily, reducing the probability of coking. Endothermic cracking of fuel is a common cooling strategy for combustor walls in SCRAM jet engines.
In order to disperse the nanoparticle catalyst within the fuel, a component of a fuel system, such as the walls of a heat exchanger, can be coated with a layer of the catalyst. When fuel passes over the catalyst coating, endothermic cracking occurs, creating a heat sink and transforming the fuel into an advanced coolant. However, the catalyst coating becomes less effective over time as the anchored nanoparticles react with the fuel.
Current methods of endothermic cracking utilize a nanoparticle catalyst suspension added to liquid fuel to improve the efficiency of the endothermic reaction. The catalyst can be tailored to break apart specific molecular components to maximize the heat required for the reaction while reducing the amount of coking. In this manner, lighter hydrocarbons are burned in the combustor, increasing combustor efficiency while reducing the tendency for coke formation, resulting in a concurrent emissions benefit. However, nanoparticles settle out of the suspension over time due to gravity. Without homogenous dispersion in the fuel, the advantages of the nanoparticle catalyst are reduced. Thus, nanoparticle precipitation makes long-term storage of fuel treated with a catalyst suspension impractical.
A system for dispersing a catalyst in a fuel includes a first reservoir containing the fuel, and a second reservoir including an agitator and containing a quantity of the catalyst suspended in the fuel. The system also includes a first conduit extending from the first reservoir, a second conduit extending from the second reservoir, and a mixing nozzle connected to the first conduit and the second conduit. The mixing nozzle includes a first meter positioned within the first conduit, a second meter positioned within the second conduit, a valve positioned upstream from the second meter within the second conduit, a junction in flow communication with the first conduit and the second conduit, a mixer downstream from the junction, a sensor positioned between the mixer and an outlet; and a controller connected to the valve and the first and second meters, the controller receiving feedback from the sensor.
A method for dispersing a catalyst in a fuel includes storing the fuel in a first reservoir, suspending the catalyst in the fuel in a second reservoir, and delivering a first flow from the first reservoir and a second flow from the second reservoir to a mixing nozzle. The method also includes mixing the first flow and the second flow within the mixing nozzle, sensing a quantity of the catalyst in the mixing nozzle after the first flow and the second flow have been mixed, and regulating the first flow and the second flow within the mixing nozzle based on the quantity of catalyst sensed.
An on-board system for dispersing a catalyst includes a reservoir containing an untreated fuel and a conduit extending from the reservoir to an outlet. The system also includes a flow regulator positioned within the conduit; a catalyst device positioned within the conduit downstream from the flow regulator, wherein the catalyst device is replaceable; a mixer positioned within the conduit downstream from the catalyst device; a sensor positioned within the conduit downstream from the mixer and upstream from the outlet; and a controller connected to the flow regulator, the controller receiving feedback from the sensor.
In the embodiment shown in
Treated fuel reservoir 24 stores fuel for an aircraft or other vehicle treated with a nanoparticle catalyst. Nanoparticle catalyst treated fuel is referred to as “treated fuel” herein. The nanoparticle catalyst can be any number of catalysts to provide the desired fuel properties, namely augmenting the cooling capacity of a given type of fuel. The catalyst can include any transition metal catalyst, including a tungsten-based catalyst, platinum-based catalyst, and combinations thereof. For example, the catalyst could be finely dispersed tungsten, molybdenum, or niobium oxides with or without noble metal additions, such as platinum and rhenium. The nanoparticles can be functionalized with organic solvent molecules to help with dispersion in the hydrocarbon fuel. Additional chemical molecules can be used in treating the fuel to impart additional characteristics as desired, such as increasing reaction activity and inhibiting sintering.
The nanoparticle catalyst endothermically cracks the fuel to increase the cooling capacity of the fuel for absorbing heat from aircraft components. As used in this disclosure, the term “crack” or “cracking” refers to decomposing a molecule or molecules into lighter molecules. The decomposition reaction absorbs heat and thereby increases the amount of heat the aircraft fuel can absorb. The cracking reaction can be any number of reactions that create a heat sink, such as cleaving of carbon-to-carbon bonds or dehydrogenation. The ratio of nanoparticle catalyst to fuel can be selected based on the type of fuel to be used. A typical ratio of nanoparticle catalyst to fuel may range from about 0.5 wt. % to about 5 wt. %. The ratio of catalytic sites on the nanoparticle catalyst can also be selected based on the type fuel to be used. Thus, for a given fuel having a known composition, the cooling capacity of the fuel can be adjusted.
The nanoparticle catalyst can range in size from about 50 nm to about 1,000 nm. Over time, nanoparticles in suspension with the fuel can settle to the bottom of treated fuel reservoir 24. Agitator 26 mixes nanoparticles that have precipitated out of the mixture back into suspension with the fuel. In the embodiment of
Valve 30 and treated fuel meter 32 are located within treated fuel conduit 28. Valve 30 controls the flow of treated fuel within treated fuel conduit 28. The concentration of nanoparticle catalyst in treated fuel reservoir 24 (not shown in
Untreated fuel from untreated fuel conduit 14 mixes with treated fuel at flow junction 36. Untreated fuel meter 34 is positioned within untreated fuel conduit 14. Untreated fuel meter 34 monitors the flow of untreated fuel within untreated fuel conduit 14. Mixer 38 is located downstream of flow junction 36 to mix the treated and untreated fuels and make the resulting fuel as homogenous as possible. Mixer 38 can be a swirl mixer as shown in
Catalyst device 52 is a replaceable or refillable device (described in further detail below and in
Access door 62 is located in on-board conduit 56 to allow for nanoparticle bed 58 or three-dimensional matrix 60 to be replenished or replaced. Nanoparticle bed 58 can be any number of structures configured to gradually release nanoparticle catalyst or catalysts into untreated fuel. Nanoparticle bed 58 can be made from a variety of materials and have any variety of nanoparticle catalyst or catalysts bound to its surface. For example, nanoparticle bed 58 can be a cartridge, package, or any other assembly removable and replaceable through access door 62. Alternatively, nanoparticle bed 58 can be a fixed assembly refillable through access door 62. In other embodiments, a fluid rich in nanoparticles can be run across nanoparticle bed 58, the nanoparticles being captured by a powder bed segment of the system and released slowly into untreated fuel during engine operation. In other embodiments, nanoparticle bed 58 can include a semi-permeable membrane that controls dispersion of nanoparticles into untreated fuel. In other embodiments, nanoparticle bed 58 can include fin structures on its inner walls to partially trap nanoparticles to control release.
Three-dimensional matrix 60 can be made from a variety of materials and have any variety of nanoparticle catalyst or catalysts bound to its surface. For example, three-dimensional matrix 60 can be machined from a variety of metals or polymers, or produced by additive manufacturing. In one embodiment of this disclosure, three-dimensional matrix 60 is a matrix including a rectangular, repeating ligament structure. The structure of three-dimensional matrix 60 provides greater surface area for holding the nanoparticle catalyst. In this manner, a uniform volume of catalyst can be gradually released as fuel runs through three-dimensional matrix 60. In other embodiments, three-dimensional matrix 60 can be any three-dimensional structure providing increased surface area for gradual nanoparticle release, including but not limited to a mesh structure or screen. In other embodiments, three-dimensional matrix 60 can vary in density throughout the structure. For example, the thickness, size, and/or spacing of the ligaments or other repeating units can be varied. Three-dimensional matrix 60 can be placed within on-board conduit 56 such that all untreated fuel will pick up the nanoparticle catalyst from the surface of three-dimensional matrix 60.
The nanoparticle catalyst can be partially trapped against the flow direction within on-board conduit 56 for gradual catalyst release. In one embodiment of this disclosure, the nanoparticle catalyst can be coated onto three-dimensional matrix 60 using binders in slurry form. The binders can then be removed by a thermal process that leaves a layer of the nanoparticle catalyst bound to the surface of three-dimensional matrix 60. If a thicker nanoparticle coating is desired, this process can be repeated multiple times. In other embodiments, a slurry of nanoparticle catalyst can be sprayed onto the surface of three-dimensional matrix 60, which can then be thermally treated.
On-board conduit mixer 64 is located downstream from nanoparticle bed 58 or three-dimensional matrix 60 and mixes the fuel after the fuel has picked up nanoparticles from the surface of nanoparticle bed 58 or three-dimensional matrix 60. Downstream sensor 66 is located between on-board conduit mixer 64 and distribution system 54. In one embodiment of this disclosure, downstream sensor 66 is a light-scattering sensor. In other embodiments, downstream sensor 66 can be any sensor for detecting the concentration of nanoparticles after the fuel has passed nanoparticle bed 58 or three-dimensional matrix 60 and before the fuel reaches distribution system 54. Downstream sensor 66 communicates with on-board conduit controller 68 and upstream sensor 70 to regulate the flow of the fuel through on-board conduit 56. In this manner, the concentration of nanoparticle catalyst in the fuel can be closely monitored and controlled while an aircraft is in flight.
The following are non-exclusive descriptions of possible embodiments of the present disclosure.
A system for dispersing a catalyst in a fuel, according to an exemplary embodiment of this disclosure, among other possible things, includes a first reservoir containing the fuel, and a second reservoir including an agitator and containing a quantity of the catalyst suspended in the fuel. The system also includes a first conduit extending from the first reservoir, a second conduit extending from the second reservoir, and a mixing nozzle connected to the first conduit and the second conduit. The mixing nozzle includes a first meter positioned within the first conduit, a second meter positioned within the second conduit, a valve positioned upstream from the second meter within the second conduit, a junction in flow communication with the first conduit and the second conduit, a mixer downstream from the junction, a sensor positioned between the mixer and an outlet; and a controller connected to the valve and the first and second flow regulators, the controller receiving feedback from the sensor.
The system of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:
A further embodiment of the foregoing system, wherein the fuel comprises fuel for an aircraft.
A further embodiment of any of the foregoing systems, wherein the catalyst comprises a nanoparticle between about 50 and about 1,000 nm in size.
A further embodiment of any of the foregoing systems, wherein the catalyst comprises a transition metal compound.
A further embodiment of any of the foregoing systems, wherein the mixing nozzle comprises a handle and a lever for manually releasing fluid from the mixing nozzle.
A further embodiment of any of the foregoing systems, wherein the mixer is a swirl mixer.
A further embodiment of any of the foregoing systems, wherein the sensor is a light-scattering sensor.
A method for dispersing a catalyst in a fuel, according to an exemplary embodiment of this disclosure, among other possible things, includes storing the fuel in a first reservoir, suspending the catalyst in the fuel in a second reservoir, and delivering a first flow from the first reservoir and a second flow from the second reservoir to a mixing nozzle. The method also includes mixing the first flow and the second flow within the mixing nozzle, sensing a quantity of the catalyst in the mixing nozzle after the first flow and the second flow have been mixed, and regulating the first flow and the second flow within the mixing nozzle based on the quantity of catalyst sensed.
The method of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:
A further embodiment of the foregoing method, wherein suspending the catalyst in the fuel comprises agitating the liquid.
A further embodiment of any of the foregoing methods, wherein sensing the quantity of the catalyst comprises detecting light scatter after the first flow and the second flow have been mixed.
A further embodiment of any of the foregoing methods, wherein regulating the first flow and the second flow comprises monitoring the first flow with a first meter positioned in the first conduit and monitoring the second flow with a second meter positioned in the second conduit.
An on-board system for dispersing a catalyst according to an exemplary embodiment of this disclosure, among other possible things, includes a reservoir containing an untreated fuel and a conduit extending from the reservoir to an outlet. The system also includes a flow regulator positioned within the conduit; a catalyst device positioned within the conduit downstream from the flow regulator, wherein the catalyst device is replaceable; a mixer positioned within the conduit downstream from the catalyst device; a sensor positioned within the conduit downstream from the mixer and upstream from the outlet; and a controller connected to the flow regulator, the controller receiving feedback from the sensor.
The system of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:
A further embodiment of the foregoing system, wherein the untreated fuel comprises fuel for an aircraft.
A further embodiment of any of the foregoing systems, wherein the on-board catalyst device comprises a nanoparticle bed.
A further embodiment of any of the foregoing systems, wherein the nanoparticle bed is replaceable or refillable via an access door in the conduit.
A further embodiment of any of the foregoing systems, wherein the on-board catalyst device comprises a nanoparticle catalyst on a surface of a three-dimensional matrix.
A further embodiment of any of the foregoing systems, wherein the three-dimensional matrix is additively manufactured.
A further embodiment of any of the foregoing systems, wherein the three-dimensional matrix is replaceable.
While the disclosure has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiment(s) disclosed, but that the disclosure will include all embodiments falling within the scope of the appended claims.
