Transpiration cooling system

A system for cooling a structure or mechanism through transpiration processes. Generally a porous structural material may be used to form a hot wall surface of a high temperature or high heat flux environment component, typically used in combustion type devices. Coolant pressurized on the “cold” or cooler side of the wall is bled, “sweated”, or otherwise transpired to the “hot” wall surface in an effort to control the hot wall surface temperature by shielding the surface with a coolant layer at the surface and by removing heat via coolant flow past the surface. This may be done to manage the hot wall temperature for structural purposes, more effectively manage high heat fluxes, or to hide thermal signatures. The porous material can be selectively made such that the coolant material flows substantially in one direction only through the porous material to transfer thermal energy only away from the structure rather than towards the structure.

FIELD OF THE INVENTION

The present invention relates generally to cooling systems for transpiration cooling, and particularly to systems and methods of forming selectively porous laminate materials for transpiration cooling.

BACKGROUND OF THE INVENTION

Many materials are known to be porous, generally being inherently porous. The naturally porous materials can be provided as filters or as transpiration coolers for various applications. Nevertheless, many natural materials include a porosity that is also substantially “natural”. Simply, the natural porosity of many materials is highly variable. Although porosity for various materials may be within a generally known range, the porosity can be unevenly distributed throughout the material. Moreover, the natural porosity of a selected material may be within a large range rather than within a narrow porosity range. Furthermore, a material having a selected porosity may not include other selected or desirable characteristics, such as strength.

Nevertheless, it is desirable to provide materials that include a selected porosity, and more specifically a porosity that is substantially consistent throughout the material such that natural variations do not occur within the material. Therefore, the porosity will include a selected porosity and pore size. The entire material should have a known physical characteristic and capable of being applied in a substantially consistent manner.

Moreover, most often porous materials include a substantially multi-directional porosity. That is, the porosity is distributed such that flowable materials may move through the pores in both directions, from a first side to a second side and from the second side to the first side of the material. If the porous material is provided as a filter or membrane, a pressure differential across the membrane must be relied upon to move the material in a selected direction. Generally, this requires including additional manufacturing steps or structural elements in the final structure or device.

Therefore, it is also desirable to provide a material that is substantially directionally porous. Simply, a material that includes a porosity that allows material to flow in only one direction relative to the porous material. With a pressure differential supplied across the membrane, the pores of the membrane would allow a flow of material in only one direction. The flow may be dependent upon the material in which the pores are made or the material being flowed across the membrane; nevertheless, the membrane may be substantially uni-directional in its porosity for selected flowable materials.

It is also desired to provide many materials including selected porosities. That is, materials of various types including a selected porosity that include both a selected pore density, selected pore size, and selected directional porosity. Therefore, rather than providing only a single material including a selected porosity with a general technique, the materials could be varied and used in many different applications including different strengths and weight requirements that may be provided by various materials.

Also, it is known to cool various components, such as components of a rocket engine including turbine parts, combustion chambers, and nozzles. Cooling these systems in particularly harsh environments can be difficult due to the high heat flux, strength, and heat resistance needed of the various cooling components. Therefore, providing a cooling system in such an environment is often difficult, heavy, complex, or expensive. In addition, the cooling systems are generally large and bulky due to the requirements for heat transfer and strength in the environment. Therefore, it is also desirable to provide a cooling system that can easily cool a component in a harsh environment without great size or complexity.

SUMMARY OF THE INVENTION

The invention provides a system for providing pores in a structure according to selected properties. Generally a structure, such as a laminate, may be formed with a selected pore according to a selected porosity or other physical attributes. The porosity may be formed by positioning pins or pore forming members through a laminate preform before the preform is processed to form the laminate structure. After forming the laminate structure the pins can be removed according to various processes which do not harm the physical characteristics of the laminate structure. Therefore, the porosity of the final laminate material is provided according to a selected size, direction, distribution, and porosity rather than being generally random according to a natural process.

The invention further provides a system for cooling a component through substantially transpiration processes. A laminate material including required physical characteristics, such as strength or toughness, and including selected pores, is provided adjacent or around the apparatus to be cooled. The selected pores allow for transpiration of a coolant which can be flowed between the porous material and the apparatus to be cooled or the source of the heat flux. The coolant, which is transpirated through the porous member or structure, absorbs thermal energy from the apparatus to be cooled or heat source. This removes thermal energy from the apparatus and allows a selected temperature of the apparatus to be maintained during operation of the apparatus. Therefore, only the coolant material and an area for the coolant material to flow is required between the apparatus and the porous membrane. Thus, a small system is provided for cooling the selected apparatus.

The invention further provides, according to an embodiment a way to cool a structure by transpirating a material through the structure wall. For example, a structural component that is subject to high heat fluxes may include or be formed of a porous material. A coolant may then be provided to flow through the porous material from a coolant source and be evaporated on the hot side of the porous material to cool the porous material, thereby keeping the porous material, which is the structural component, at a selected temperature. This transpiration or “sweat” cooling allows the coolant material to be flowed through the structural component being cooled without requiring additional or bulky components that must be provided to pump or transport a coolant adjacent a structural component to be cooled. Rather, the coolant flows through the structural member to cool it on contact. Also, various cooling conduits, evaporators, and compressors would not be necessary.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of various embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

With reference toFIG. 1, a laminated structure10includes at least two layers, a first layer12and a second layer14formed generally adjacent one another. In addition, an intermediate layer16may be formed or positioned between the first and second layers12,14. The intermediate layer16may be used for adhering the first and second layers12,14to one another during a formation or laminating process. Nevertheless, it will be understood that laminated layers may include a pre-impregnated material which can be used to affix the first and second layers12,14together during the formation process. Alternatively, the first and second layers12,14may be fixed to one another, during the formation process, without any additional adhesive material. Also, it will be understood that the laminate structure10may include any number of appropriate layers. Simply, only illustrating the first layer12affixed to the second layer14is for clarity and is merely exemplary and not intended to limit the scope of the present disclosure. Therefore, the laminate structure10including any appropriate number greater than the two structural layers12,14and a single intermediate layer16may be used.

Formed through the laminate10are a plurality of bores or pores20. The pores20can be formed through the laminate10in any appropriate or selected manner. Generally, however the pores20are formed such that a uniform density or porosity is formed in a selected area such as a first set of pores22. Moreover, the pores may be formed such that a non-porous area24is also formed. Furthermore, the pores20may be formed to include desired physical characteristics such as being uni-directional. For example, a plurality of uni-directional pores26allow the flow of a flowable material from a first side12ato a second side14a. It will be understood that the uni-directional pores26may also be formed such that material flows substantially only from the second side14ato the first side12a. In addition, due to the formation of the uni-directional pores26, it may be that the uni-directional pores26are positioned in any selected area of the laminate10D. The pores20may also include an angled pore or pores28. The angled pores28may be formed an any selected angle θ relative to a side12aor14aof the laminated structure10. This allows for a cooling or a flow of material from one selected position to another selected position through the laminate structure10.

The first laminate layer12and the second laminate layer14may generally be formed of any appropriate material, for example non-oxide or oxide ceramic matrix composite materials. Alternatively, both the first layer12and the second layer14may be formed of a silicon carbide material reinforced with carbon fibers and formed in an appropriate manner. As a further example, oxide layers may include alumina or alumina silicates with or without reinforcement fibers such as alumina, sapphire, or quartz. Therefore, it will be understood any appropriate material may be used.

Generally, the first and second layers12,14are formed to include selected physical characteristics, such as strength or durability. In addition, the first and second layers12,14may be formed of a material that includes other physical characteristics such as thermal or electrical conductivity. It will be understood that the layers12,14may be substantially non-porous. Moreover, after the laminate10is formed, it may include generally no pores except for the manufactured pores20. The materials may also be reinforced with various fibers or materials, such as carbon or metal fibers. When the first and second layers12,14are laminated together in the laminate structure10, the laminate structure10includes the selected physical characteristics. The pores20formed in the laminate structure10are formed without destroying the selected physical characteristics of the laminate structure10. Physical characteristics may also include inherent strength or toughness of the laminate structure10in addition to characteristics of the various layers. Thus the laminate structure10may include both selected physical properties and porosity.

Forming the pores20through the laminate10as the laminate10is formed substantially ensures that the porosity or the pores20formed in laminate10are formed in a selected manner and according to selected requirements. Selectively forming the pores20also helps ensure a selected and complete porosity. Also, forming the pores20during the manufacturing of the laminate10ensures that the formation of the pores20or the presence of the pores20does not substantially destroy the selected physical or chemical characteristics of the laminate10. It will be understood a limited amount of degradation may occur but not so much as to significantly affect selected properties of the material overall or the laminate10.

With reference toFIG. 2, the pores20(illustrated inFIG. 1) may be formed using a pore forming apparatus30. The pore forming apparatus30generally includes a base32and a plurality of pins or pore forming members34extending from the base32. Generally, the pins34include a relatively sharpened top or engaging end36that is used to pierce a portion of a laminate preform40. The laminate preform40includes each of the layers which will form the laminate structure10, but which have not been laminated that is the process to make each of the layers12,14substantially coherent has not occurred. The pins34pierce the laminate preform40to form desired pores in the laminate preform40which become the pores20once the pins34are removed. As the pins34pierce the laminate preform40, they can push aside any reinforcement fibers without substantially breaking or weakening the fibers. The pins34allow for the formation of the pores20in the laminate structure10without substantially weakening any structural properties of the laminate structure10. In part, this is done by not destroying any reinforcement fibers that are positioned in the laminate perform40.

With continued reference toFIG. 2and additional reference toFIG. 3, the laminate preform40is pressed onto the pins34a selected distance. Generally, the pins34include a height to provide a pore depth of a selected depth through the laminate structure10. Generally, providing pores through laminate structure10is selected such that a flowable material is able to pass from the first side12ato the second side14a. The pore forming apparatus30can be pressed through the laminate preform40or the laminate preform40pressed onto the pore forming apparatus30. Nevertheless, the pins34generally engage and pass through selected layers of the laminate preform40to form regions that become the pores20in the laminate structure10.

The pins34may be formed or placed on the base32of the pore forming apparatus30in any appropriate shape or pattern. Moreover, the pin forming apparatus30may be shaped to any appropriate geometry. In this way as the laminate preform40is placed over the pore forming apparatus30it conforms to the shape of the pore forming apparatus30such that a complimentary shape or a similar shape is formed in the laminate preform40as the pores20are formed in the laminate preform40.

Because the pins34may be positioned on the base32in any appropriate design or pattern, selected porosities or designs of porosities can be formed in the laminate10. In addition, each of the pins34positioned on the base32may be of a selected size or geometry. Therefore, a first set of the pins34may be a first size, while a second set is a different size. Moreover, the pins34may include a selected geometry to create a uni-directional pore, such that the flowable material passes only in one direction, and again only some of the pins placed on the base32may include this attribute while others do not.

With reference toFIG. 4A to 4C, exemplary pore forming geometries are illustrated. With particular reference toFIG. 4A, the pore forming apparatus30aincludes a plurality of the pins34formed into a plurality of rows421to42n. An opening44is left in the pattern such that pores will not be formed in a selected area of the laminate10. The open area44may be any appropriate shape or size and may used for forming an opening or hole in the laminate10. Particularly, if there is an opening for a rod or tube, no pores would be formed therein.

With particular reference toFIG. 4B, the pore forming apparatus30bincludes a first set of pins46having a first diameter X and a second set of pins48having a second diameter Y. The first diameter X may be any diameter different, yet appropriate, than the diameter Y. Therefore, the laminate10will have pores formed therein that include pores of various sizes. This may be desirable especially if the laminate10is to be used cover to adjacent sections requiring a different size pore in each section. This technique may also be used to vary the transportation of material across the laminate10.

With particular reference toFIG. 4C, a pore forming apparatus30cincludes a first section of pins50and a second section of pins52. The first section pins50may be formed in a particular pattern, such as a triangle for forming pores in the laminate10in the selected pattern. Moreover, the pins in the first section50include a first density which is different than the density of the pins in the second section52. Furthermore, the shape or general pattern of the second set of pins52may differ from to the first set of pins50. Further, the pins52may be set at any angle for the intended creation of pores which traverse the laminate at the angle relative to the laminate surface12aor14a(SeeFIG. 1). Therefore, several different pore forming apparatus can be produced to provide various different porosities, pore sizes, pore shapes or pore patterns. In this way the laminate10may include a porosity of any selected manner.

The laminate structure10can be formed according to any appropriate method. Depending upon the material from which the laminate structure10is formed, the method for selectively forming the pores20in the laminate structure10may vary. Moreover, the layers12,14of the laminated structure10, which are first placed adjacent one another in the preform40, may be substantially non-porous. Thus, substantially all pores formed in the laminated structure10would be through the removal of the pore forming members32from the laminated structure10after the laminate preform40had been laminated.

Various methods include, forming selected pores in a non-oxide material may require specific etching or non-oxide melting methods. For example, forming selected pores in the laminate structure10when the laminate structure10is formed of a non-oxide material is disclosed in U.S. patent application Ser. No. 10/624,905 entitled “Method and Apparatus For Processing Non-Oxide Selectively Porous Materials”, to Miklos Paul Petervary and Min Zhou Berbon, and commonly assigned. It will be understood, however, that any appropriate method may be used for forming the laminate structure10that includes the selected pores20for use according to various embodiments of the invention.

With reference toFIG. 5, a transpiration cooling system56, for use in various applications, is illustrated. The transpiration cooling system56is intended for use with an apparatus or component60which is required to be cooled, although it will be appreciated that the apparatus60does not form a part of the system56. The apparatus60may include any appropriate item such as a turbo pump or turbine for various applications, such as a rocket engine or turbine engine. It will also be understood that the apparatus60may include items such as the exterior of a turbine engine, for example an engine for an aircraft, and other appropriate apparatus which may produce or transport heat containing or producing items.

For example, the apparatus60may transport a heated fluid62. As the heated fluid62is transported through the apparatus60, a wall or exterior64of the apparatus may become heated due to a heat transfer or thermal energy transfer from the heated material62to the wall64The apparatus60, however, is generally maintained at a selected temperature.

Positioned around the wall64of the apparatus60may be the laminate structure10. The laminate structure10includes the plurality of pores20formed therein. The pores20are formed in the laminate structure10to have a selected physical property relative to the laminate structure10or another material. For example, a cooling or radiating material70may be provided in an area or cooling space72between the laminated structure10and the wall64of the structure60. The cooling material70is provided from a cooling supply73. The cooling material70may flow in the cooling area72and through the pores20. Generally, the cooling material70would move from the first side12a, or inside in this instance, to the second side14a, or outside, of the laminate structure10.

As the cooling material70moves from the first side12ato the second side14a, thermal energy is also moved from the cooling area72to the second side14aof the laminate structure10. As the cooling material70moves within the cooling space72, it absorbs thermal energy from the wall64of the structure60. Therefore, as the cooling material70moves away from the wall64thermal energy is also moved away from the wall64. This cools the wall64and cools the apparatus60. Generally, the passing of the cooling material70through the pores20of the laminate structure10is by the process of transpiration. More specifically, the cooling of or removal of thermal energy from the apparatus60is by transpiration cooling of the apparatus60. Therefore, providing the laminate structure10with pores20and flowing the coolant material70such that it absorbs thermal energy and moves the thermal energy away from the apparatus60allows transpiration cooling. This allows the apparatus60to be maintained at a selected temperature.

Because the material70moves away from the structure60, the structure60is able to maintain the transference of the material62through the structure60. This allows the structure60to be formed of a material which is substantially less heat resistant than if the apparatus60were not cooled by the cooling material70. Moreover, the structure60may be cooled by only providing the laminate structure10and the supply73of the cooling material70.

The cooling material70flows through the cooling area72and through the pores20according to natural or inherent mechanisms. For example, the pores20may be formed in the laminate structure10to have a substantially uni-directional property. The pores20, particularly the uni-directional pores26, allow the coolant material70to move in only one direction relative to the laminate structure10. That is, the uni-directional pores26allow the cooling material70to move from the cooling space72to the exterior14aof the laminate structure10and not from the exterior of the laminate structure14ato the cooling space72. Thus, the transfer of thermal energy occurs in substantially only one direction. In addition, the pressure created within the cooling area72, due to the heating of the cooling material70, also assists in driving the cooling material70through the pores20of the laminate structure10.

Due to the selected formation of the pores20within the laminate structure10, selected amounts of cooling may occur around the structure60. This allows for varying cooling rather than providing a substantially uniform cooling. Because the pores20are selectively formed in the laminate structure10, the porosity, size, and direction of the pores20can be selected. Therefore, the single laminate structure10can include a plurality of regions to allow for varying degrees of cooling and transpiration. For example, a specific area of the apparatus60may need to be cooled more rapidly than another area of the apparatus60. Therefore, a greater porosity or size of pores can be provided in that area of the laminate structure10relative to the apparatus60. However, if less cooling is required in a different area a lesser porosity may be provided in favor of greater material density of the laminate structure10to allow for greater rigidity.

Uni-directional pores may also be used to transfer thermal energy from one area to another of the apparatus60. In a first area, the laminate structure10may provide for a removal of heat from the apparatus60by moving the coolant material70from the cooling area72to the exterior14aof the laminate structure10and further uni-directional pores allow for the coolant material70to move from the exterior14ato the coolant area72. Therefore, thermal energy may be transferred from one area to another thereby allowing cooling of one region and heating of another region of the apparatus60. Nevertheless, the plurality of pores20in a laminate structure10can be formed for any selected properties or structure.

In addition, because the pores20are formed within the laminate structure10during a processing step, the laminate structure10can include any selected physical property. For example, the laminate structure10may include a selected tensile strength such that the laminate structure10may be included as a structural component of the apparatus60. Therefore, rather than simply providing a cooling mechanism for cooling the structure60, the laminate structure10may also be provided as a structural component of the apparatus60.

Moreover, because the laminate structure10can be selected of various materials, the materials which form the laminate structure10can be selected to withstand any environment in which the apparatus60is placed. Therefore, if the cooling system56is positioned within a rocket engine, which may reach high temperatures, the material of the laminate structure10can be selected to withstand such high temperatures. For example, the laminate structure10can be formed of an oxide, substantially a ceramic, which includes various laminated oxide layers that may withstand extremely high temperatures. Also, because the laminate structure10is formed of a plurality of layers12,14that are laminated together, the laminated structure10includes inherent strengths. Moreover, the various layers can be chosen to provide even greater strengths or other physical properties. These strengths are maintained or enhanced in part because the pore-forming members34are positioned in the laminate preform40before the laminate structure10is formed. Therefore, the final laminate structure10includes selected properties that are uninhibited by the inclusion of the plurality of pores20.

It will be understood that the laminate structure10can be used in the cooling system56for cooling the selected apparatus60. It will be understood that the structure60may be any appropriate structure which is required to be cooled and can be cooled with transpiration cooling. Furthermore, it will be understood that the cooling material70may be any appropriate cooling material which can be provided in the cooling area72. It will also be understood that the laminate structure10can be provided in any appropriate shape to create the cooling area72around the apparatus60. For example, the apparatus60may be substantially cylindrical, therefore the laminate material may be provided in a substantially cylindrical shape to surround the apparatus60. Furthermore, the apparatus60may include irregularities in the wall64which can also be mirrored in the shape of the laminate structure10.

With reference toFIG. 6, an apparatus to be cooled may include a turbine fan or fin, or particularly a leading edge apparatus80of any appropriate system such as a turbine blade or a leading edge of a plane wing for a vehicle which may be heated due to frictional air forces. Therefore, the edge fin80, is exemplary of any of these systems which include the leading edge80that may become heated due to frictional forces. Generally, an internal or structural component82provides an internal support for the edge80. An external surface or skin84of the fin edge80is formed of a porous material. A plurality of the pores20are selectively positioned along the fin edge80. The pores20are formed in the skin84of the fin edge80using the above-described methods. During the formation process, the skin84may be formed into any appropriate shape, such as the leading edge of the fin edge80. Moreover, the skin84may be formed as a leading edge of a wing for an aircraft and may include the appropriate aerodynamic properties. Nevertheless, the skin84may be formed of the ceramic materials, including oxides and non-oxides, that include appropriate or selected strength, environmental compatibility, and heat resistant properties.

During use, especially when the skin84is heated due to frictional or other forces, the skin84may be cooled through transpiration. If the blade80is a blade of a turbine fan as it spins aerodynamic frictional forces increase the temperature of the leading edge80or the surface84aof the skin84. If the blade80is exemplary leading edge of a wing of an aircraft, it will increase in temperature during flight, such as re-entry of a spacecraft. Nevertheless, the skin84is spaced a distance from the internal structure82thus forming a coolant pathway86. In the coolant pathway86is flowed a coolant88. The coolant88flows through the pores20in the direction of arrow B. That is, the coolant88flows from the coolant pathway86to an exterior84aof the skin84. As the coolant88reaches the exterior of skin84a, heat is removed from the skin84through various means.

The coolant88, as it flows through the pores20, can remove thermal energy from the skin84according to various methods. For example, as the coolant88flows through the exterior of84a, of the skin84, the coolant88may change phase, such as vaporizing thus turning from a liquid to a gas. This phase change cools the skin84and using some of the thermal energy on the exterior84aof the skin84thereby cooling the skin84. In addition, sheer forces of the hot gases flowing around the exterior84aof the skin84removes a volume of the coolant88as it flows through the pores20. Moreover, the coolant88is substantially constantly flowing through the pores20producing a film or coating on the exterior84aof the skin84. The film of the coolant88also helps ensure that the skin84maintains a selected temperature

Therefore, the skin84including the pores20, formed as described allows for transpiration cooling of the blade80. The coolant88removes thermal energy from the skin84according to any appropriate or physically possible method. Nevertheless, this transpiration of the coolant88through the pores20allows the coolant88to cool the skin84. Thus, the skin84can be kept at a selected temperature that does not compromise various properties of the skin84, such as strength or toughness. Moreover, the pores20formed in the skin84provide a substantially efficient method of cooling the skin84without providing substantially complex circuitry and cooling systems.

With reference toFIG. 7, an apparatus100includes the pores20formed in a wall102as a structural component of a apparatus or device100subject to high heat fluxes. Generally, the heat fluxes may be formed by the flowing of hot gases or a flame, such as in a combustion chamber or in a nozzle of a rocket engine or the like. For example, hot gases may flow in the direction of arrow C within the wall102that includes a plurality of the pores20formed therein. Formed on an exterior of the walls102is an external or cooling plenum wall104. Space between the plenum wall104and the wall102of the apparatus is a cooling space or conduit106.

Through the cooling conduit106flows a coolant108that is able to flow through the pores20into the heated area or a flow chamber110. The gases flowing in the direction of arrow C flow through the flow chamber110and substantially heat the walls102. Nevertheless, the coolant108flows through the pores20in the direction of arrow D to substantially cool the wall102to a selected temperature. As the coolant108flows through the pores20, it can change phases or cause a film to form on the interior of the wall102. As discussed above, a change in phase of the coolant108removes thermal energy from the wall102and allows it to be maintained at the selected temperature. In addition, the sheer forces on the film, which forms on the interior of the wall102, helps cool the wall102as the hot gases flow past the direction of arrow C. Any cooling method using the coolant108may be used to cool the wall102. Nevertheless, the wall102can be cooled by flowing the coolant108through the pores20. The only structure that is provided is the cooling plenum wall104to hold the coolant108relative to the hot wall102.

Although the porous material has been illustrated to be a high heat flux hot wall of the turbine fan80or a rocket thruster nozzle102, it will be understood that the porous material may be used in any appropriate application. The porous material allows the coolant to flow from a supply area or conduit through the porous material to the hot wall side of the porous material. There the coolant may change phase or form a cooling film relative to the hot wall. This allows the hot wall to be maintained at a selected temperature while it surrounds an area of substantially high heat flux. For example, using the oxide and non-oxide ceramics, as discussed above, the porous materials may be used to cool areas and manage applications or designs having a heat flux beyond the capability of an actively cooled metal solution. Therefore, the porous ceramic matrix laminates can be used to contain substantially higher temperature higher heat flux reactions than presently available.

Moreover, forming the porous laminated structures with the pin method, as described above, allows of the laminate structures to substantially maintain the physical properties of the laminate structure. Therefore, the selected porous properties can be formed in the laminate materials without sacrificing the physical characteristics of the laminate material, such as strength or toughness.