Abstract:
A vehicle has a body and a source of a propellant. An engine is carried by the body. The engine reacts the propellant to produce thrust. The engine has a heat exchanger transferring heat from the reaction to at least a component of the propellant and generating electricity thermoelectrically.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to heat exchangers. More particularly, the invention relates to exchangers using pre-combustion propellant to cool structures heated by the combustion. 
     A wide variety of heat exchanger technologies exist and are used in a wide variety of applications. Exemplary applications involving high differences in temperature are scramjet and rocket engines. In many such heat exchangers, heat is drawn from combusting propellant and received by incoming pre-combustion propellant or a component thereof. The heat exchangers may be positioned along combustion chambers and/or nozzles to cool such chambers or nozzles to maintain required engine life. An exemplary such use of a heat exchanger is discussed in Faulkner, R. and Weber, J., “Hydrocarbon Scramjet Propulsion System Development, Demonstration and Application”, AIAA Paper 99-4922, American Institute of Aeronautics and Astronautics, 1999. 
     Additionally, ceramic matrix composites have been developed for use in the aerospace industry. Various composites are discussed in U.S. Pat. No. 6,627,019 of Jarmon et al. for use in cooled engine components. U.S. Pat. No. 6,907,920 of Warburton et al. discloses use of a layer of a composite in a heat exchanger panel assembly. The composite panel serves as a so-called “hot face” or hot panel. The cooling channels may be formed between the hot panel and by one or more additional panels and may be bounded by tubular inserts. 
     SUMMARY OF THE INVENTION 
     One aspect of the invention involves a vehicle having a body and a source of a propellant. An engine is carried by the body. The engine reacts the propellant to produce thrust. The engine has a heat exchanger transferring heat from the reaction to at least a component of the propellant and generating electricity thermoelectrically. 
     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view of an aircraft. 
         FIG. 2  is a partially schematic longitudinal sectional view of a propulsion system of the aircraft of  FIG. 1 . 
         FIG. 3  is a partially schematic view of a scramjet portion of the system of  FIG. 2 . 
         FIG. 4  is a partially schematic view of a heat exchanger of the system of  FIG. 3 . 
         FIG. 5  is a partially schematic transverse sectional view of the heat exchanger of  FIG. 4 . 
         FIG. 6  is an end view of a precursor of a thermoelectric component of the heat exchanger of  FIG. 5 . 
         FIG. 7  is a schematic view of series-interconnected components of  FIG. 6 . 
         FIG. 8  is a schematic view of parallel-interconnected components of  FIG. 6 . 
         FIG. 9  is a partially schematic transverse sectional view of a first alternate heat exchanger. 
         FIG. 10  is a partially schematic transverse sectional view of a second alternate heat exchanger. 
     
    
    
     Like reference numbers and designations in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
       FIG. 1  shows a vehicle  20 . An exemplary vehicle is a manned aircraft. Alternative vehicles may be unmanned and may be reusable or may be one-way vehicles (e.g., warhead-carrying missiles or disposable launch vehicles). The exemplary aircraft is a hybrid turbine and ramjet aircraft. An exemplary ramjet is a dual mode (subsonic and supersonic combustion) ramjet engine (dual mode scramjet-DMSJ). 
     The exemplary aircraft  20  has a fuselage  22 , a wing  24 , and a tail assembly  26 . A dual mode scramjet engine  28  is formed in a cowl  29  on an underside of the fuselage  22 . A scramjet air flowpath  500  ( FIG. 2 ) carries a flow  501  between a forward inlet/intake  30  and an aft outlet  32  (e.g., an exhaust nozzle). Along the flowpath, the engine may include a forebody  34 , an isolator  36  (often integrated therewith), and a combustor  38 . A control system  40  (optionally a portion of the aircraft&#39;s avionics) may control operation of the combustor  38  in response to one or more of sensor input, operator input, and the like. 
     A turbine engine  48  ( FIG. 2 ) is located along a turbine engine air flowpath  502  carrying a flow  503  between a forward inlet/intake  50  and an aft outlet  52  and inboard of the scramjet flowpath (e.g., partially recessed into the fuselage above the cowl). Scramjet and turbine inlet flaps  60  and  62  selectively block the scramjet and turbine inlets and flowpaths when the scramjet or turbine, respectively, is not in operation. Similarly a turbine outlet flap  64  selectively blocks the turbine flowpath when the turbine is not in use so as to provide an efficient nozzle for the scramjet. This configuration is merely exemplary. 
       FIG. 3  shows further details of the scramjet engine  28  and flowpath  500 . The flowpath  500  is largely encircled by a heat exchanger  70  for transferring heat from the air and combustion gases to pre-combustion scramjet fuel. For an exemplary hydrocarbon-based liquid fuel (e.g., JP-8) the heat exchanger  70  is a liquid-gas heat exchanger. An alternate exemplary fuel is hydrogen gas. The exemplary heat exchanger  70  may have an upstream liquid fuel inlet  72  and a downstream liquid fuel outlet  74 . In the exemplary embodiment, the inlet  72  may be upstream of the combustor  38  along the flowpath  500  because pre-combustion aerodynamic heating may be relevant. A fuel flowpath  510  for the scramjet fuel may extend from a storage tank  80  to a fuel pump  82  and then to the inlet  72 . After exiting the outlet  74 , heated fuel may pass along the flowpath  510  to a fuel distribution valve network  84  and then to the combustor. The valves of the network  84  distribute the fuel to various combustor locations for various purposes (e.g., piloting v. main combustion) and to achieve desired staging. 
     The exemplary heat exchanger  70  thermoelectrically generates the electricity. Accordingly, the exchanger  70  may be coupled to an electrical power conditioning, storage, and distribution system  90 . The system  90  may receive raw electrical input from the heat exchanger  70  and output appropriate electricity (e.g., of a constant and proper voltage) to drive the control system  40 , fuel pump  82 , distribution valves of the network  84 , similar components associated with the turbine engine, and additional loads schematically shown as  92 . 
       FIG. 4  semi-schematically shows the heat exchanger  70 . The inlet  72  may be formed in an inlet manifold  100 . The outlet  74  may be formed in an outlet manifold  102 . Extending between the manifolds, an array of channels or passageways  104  may extend in a main body  105  from an upstream end  106  to a downstream end  108 . Fluidically, the exemplary passageways  104  may be in parallel. However, other configurations (e.g., serpentine) are possible. Similarly, although the exemplary passageways are shown having parallel flow relative to the flowpath  500 , other configurations are possible (e.g., counterflow, crossflow, or combinations, a well as multi-inlet/outlet exchangers, exchanger assemblies, and the like). First and second electrical leads  110  and  112  may extend to the system  90 . As with the fluid coupling, there are many options for the electrical coupling and several are discussed in further detail below. 
       FIG. 5  shows further details of one non-limiting exemplary heat exchanger body  105 . An interior/inboard surface  120  faces/bounds the flowpath  500 . An exterior/outboard surface  122  is opposite the surface  120  and typically at a lower temperature. The exemplary body is a composite (e.g., as ceramic composite) structure including structural fibers  124  and channel-forming assemblies  126  in a matrix  128 . In the exemplary implementation, the assemblies  126  are relatively close to the surface  120  for receipt of heat. The fibers  124  in an outboard portion  130  thus provide a principal structural portion of the body  105 . Exemplary structural fibers  124  are silicon carbide fiber (SiC) tows. An exemplary matrix material is melt-infiltrated silicon carbide (e.g., silicon carbide deposited by chemical vapor infiltration followed by a silicon metal melt to fill/seal porosity). Exemplary manufacturing techniques for such composites are discussed in U.S. Pat. No. 6,627,019 of Jarmon et al. 
     The exemplary assemblies  126  include a liner  132  surrounding and defining the associated channel  104 . While numerous transverse section geometries are possible, the exemplary liners  132  are polygonal in transverse section. The exemplary shape is a flattened hexagon of essentially equal-length sides. Flattening to increase a channel width W parallel to the surface  120  increases potential heat transfer. The flat exterior facets  134  facilitate the mounting of thermoelectric device assemblies  136  thereon. As is discussed further below, the assemblies  126  may comprise arrays of P-type and N-type material elements. Conductors within each array couple the elements. Additionally, the arrays may be coupled to each other in a variety of ways and, ultimately, to the conductors  110  and  112  to deliver power to the system  90 . Exemplary thermoelectric devices are shown in U.S. Pat. No. 6,300,150 of Venkatasubramanian. 
     One exemplary non-limiting method of manufacture utilizes sacrificial rods  140  to form the assemblies  126  ( FIG. 6 ). The exemplary rods  140  may be carbon based (e.g., graphite-epoxy composites). Exemplary rods may have a polygonal transverse section (e.g., as described above). The exemplary rods  140  may be manufactured with pre-formed central channels  142  (e.g., by extrusion) bounded by interior surfaces  144 . As is discussed in further detail below, the channels  142  (if present) may provide access for chemicals or high temperature gas to at least partially decompose the rods  140  after further assembly steps. The rods  140  may be coated with a sacrificial or non-sacrificial coating that may serve a variety of purposes. Exemplary non-sacrificial coating is a ceramic coating atop the rod exterior surfaces  146  to ultimately form the liner layer  132 . If present, the device arrays  136  may be applied atop each of the resulting faces  134 . The exemplary arrays  136  may include interspersed arrays of P-type elements  150  and N-type elements  152  electrically interconnected by conductors  154 . The arrays  136  of a given assembly  126  may be connected (e.g., in series or parallel). Alternatively, the elements of each array  136  may be fully interconnected with the other arrays so as to form a continuous array. The assemblies  126  may, in turn, be connected in series ( FIG. 7 ) or parallel ( FIG. 8 ). 
     Either before or after the interconnection of the assemblies  126 , the assemblies  126  may be mechanically assembled in the composite structure. The rods  140  may then be fully or partially removed by chemical, thermal, and/or mechanical means so as to expand the channels  142  to form the channels  104 . For example, the Jarmon et al. patent discloses an oxidative removal (e.g., by heating in air to 650° C. for forty-eight hours) of channel-forming elements. 
       FIG. 9  shows an alternate heat exchanger  200  having a body  202  that may be similar to the heat exchanger body  105 . Distinguished from the thermoelectric devices of the body  105 , the thermoelectric devices  204  are more remote from the individual channels  104  rather than surrounding them. In the exemplary body  202 , the devices  204  are arrayed as a layer along or near the near the exterior/outboard surface  122 . The devices  204  may be applied after formation of the composite material of the body  202 . Alternatively, to embed the devices, the devices  204  may be applied during the laying up of fiber tows  124 . 
       FIG. 10  shows an alternate heat exchanger formed as a panel assembly  300 . The exemplary assembly  300  may have a hot panel  302  having a first surface  304  along the scramjet air flowpath  500 . The hot panel  302  may be formed as a SiC/SiC composite as disclosed in the Jarmon et al. and Warburton et al. patents. The hot panel  302  may be mounted to a structural substructure or back structure  306  (e.g., as disclosed in the Warburton et al. patent). The exemplary substructure  306  may be a metallic panel. The panels  302  and  306  may be secured by fasteners  308  (e.g., as disclosed in the Warburton et al. patent). 
     In the exemplary non-limiting panel assembly  300 , the cooling channels  310  are defined within metal tubular conduits  312 . The exemplary conduits  312  are partially recessed in open channels  314  in the second surface  316  of the hot panel  302 . For improved heat transfer, the exemplary conduits  312  are elongate (e.g., obround) in transverse cross-section and oriented parallel to the surface  304 . Thermoelectric device arrays  320  are mounted to the conduits  312 . In the exemplary configuration, the device arrays  320  are on the hot side of the conduits  312 . An electrical insulator layer  322  may be included with the device arrays to electrically insulate them from the conduits (if the conduits are conductive). The insulator layer  322  may be included in the as-applied arrays  320  or may be pre-applied to the conduits (e.g., as a strip or a coating). In the exemplary assembly, a thermal insulation layer  330  is positioned between the panels  302  and  306 . 
     In addition to the generation of power for powering various on-board aircraft systems, the various aforementioned thermoelectric devices may be utilized to monitor (e.g., by the control system  40 ) operational and conditional parameters of the engine. For example, a local power increase might indicate a local thinning, cracking, or other wear or damage condition. This information could be used for several further purposes. The information can be used to provide a warning to a pilot or other operator. The information can be used to change operational conditions to avoid or defer failure (e.g., throttling back, altering fuel staging, and the like). For a reusable craft, the information can be used to determine a need for maintenance. Such maintenance might involve heat exchanger or panel replacement. For example, in the panel assembly  300  of  FIG. 10 , an indicated degradation of the hot panel  302  could signal that the panel be inspected and replaced, if appropriate. In such a replacement, the substructure  306  as well as the conduits  312  and their associated thermoelectric device arrays  320  could be retained. 
     One or more embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, when applied in a reengineering of an existing heat exchanger or for an existing application, details of the existing heat exchanger or application may influence details of any particular implementation. Accordingly, other embodiments are within the scope of the following claims.