Abstract:
One embodiment of the present invention is a unique engine. Another embodiment of the present invention is a unique combustion system. Other embodiments include apparatuses, systems, devices, hardware, methods, and combinations for engines and combustion systems. Further embodiments, forms, features, aspects, benefits, and advantages of the present application will become apparent from the description and figures provided herewith.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims benefit of U.S. Provisional Patent Application No. 61/428,731, filed Dec. 30, 2010, entitled ENGINE AND COMBUSTION SYSTEM, which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to engines, including but not limited to gas turbine engines, pulse combustion engines and pressure gain combustors, and more particularly, to wave rotor combustors utilizing either detonative or deflagrative combustion employed in engines or as engines. 
       BACKGROUND 
       [0003]    Engines and combustion systems for engines remain an area of interest. Some existing systems have various shortcomings, drawbacks, and disadvantages relative to certain applications. Accordingly, there remains a need for further contributions in this area of technology. 
       SUMMARY 
       [0004]    One embodiment of the present invention is a unique engine. Another embodiment of the present invention is a unique combustion system. Other embodiments include apparatuses, systems, devices, hardware, methods, and combinations for engines and combustion systems. Further embodiments, forms, features, aspects, benefits, and advantages of the present application will become apparent from the description and figures provided herewith. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein: 
           [0006]      FIG. 1  schematically depicts some aspects of a non-limiting example of an engine in accordance with an embodiment of the present invention. 
           [0007]      FIGS. 2A and 2B  schematically depict some aspects of a non-limiting example of a combustion system in accordance with an embodiment of the present invention. 
           [0008]      FIGS. 3A and 3B  schematically depict some aspects of a non-limiting example of a combustion system in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    For purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It will nonetheless be understood that no limitation of the scope of the invention is intended by the illustration and description of certain embodiments of the invention. In addition, any alterations and/or modifications of the illustrated and/or described embodiment(s) are contemplated as being within the scope of the present invention. Further, any other applications of the principles of the invention, as illustrated and/or described herein, as would normally occur to one skilled in the art to which the invention pertains, are contemplated as being within the scope of the present invention. 
         [0010]    Referring to the drawings, and in particular  FIG. 1 , some aspects of a non-limiting example of an engine  10  in accordance with an embodiment of the present invention are schematically depicted. In one form, engine  10  is a gas turbine engine. Engine  10  includes a compressor system  12 , a combustion system  14  in fluid communication with compressor system  12 , and a turbine system  16  in fluid communication with combustion system  14 . In one form, compressor system  12 , combustion system  14  and turbine system  16  are disposed about an engine centerline  18 , e.g., the axis of rotation of compressor  12  and turbine  16 . In other embodiments, other arrangements may be employed. In various embodiments, engine  10  may or may not have a compressor system and/or a turbine system, or may have additional turbomachinery components in addition to a compressor system and/or a turbine system. In some embodiments, engine  10  may be a direct propulsion engine that produces thrust directly from combustion system  14 . In other embodiments, combustion system  14  may form a gas generator for a gas turbine propulsion system, or may be employed in a gas turbine engine topping cycle. In still other embodiments, engine  10  may be one or more of other types of engines that employ combustion systems, such as combustion system  14 . 
         [0011]    Referring to  FIGS. 2A and 2B , in one form, combustion system  14  is a wave rotor system having a wave rotor  30 , an end structure  50  and an end structure  60 . Wave rotor  30  includes a plurality of circumferentially spaced combustion channels  32 . In one form, combustion channels  32  are formed by a cylindrical inner wall  34 , a cylindrical outer wall  36 , and a plurality of partition walls  38 . Partition walls  38  partition the annulus formed by inner wall  34  and outer wall  36  into the plurality of combustion channels  32 . In other embodiments, combustion channels  32  may take other forms, may be formed by other features, and/or may have contiguous, spaced-apart and/or staggered relationships relative to each other. In one form, combustion channels  32  are approximately rectangular in cross-sectional shape, and are oriented longitudinally in an axial direction parallel to engine centerline  18 . In other embodiments, combustion channels  32  may be of any shape, oriented in any one or more directions, including radial, axial and circumferential directions, or combinations thereof, other two or three dimensionally curved channels or any other shape suited to the particular application. 
         [0012]    Each combustion channel  32  includes an open end  40  and an open end  42 , and extends therebetween. Combustion channels  32  are configured to contain a combustion process. The combustion process maybe deflagration combustion and/or detonation combustion. In various embodiments, combustion channels  32  may include flame accelerators (not shown) or other devices. The flame accelerators may be configured to accelerate a combustion flame front sufficient to yield a deflagration to detonation transition (DDT). Or, the flame accelerators may be configured to accelerate a deflagration combustion process without transitioning to a detonation combustion process. In some embodiments, the flame accelerators may be configured to accelerate a deflagration combustion flame front without achieving DDT at some operating conditions, while achieving DDT at other operating conditions. 
         [0013]    Although embodiments are described herein as with respect to a wave rotor combustion system, it will be understood that other embodiments may take other forms. For example, in some embodiments, combustion system  14  may be a rotary valve combustion system, wherein combustion channels  32  are part of stationary combustor, e.g., a combustor similar in configuration to wave rotor  30 , but non-rotating, wherein end structures  50  and  60  are rotary valves that rotate relative to the combustion channels  32 . In other embodiments, wave rotor  30  and end structures  50  and  60  may each rotate, e.g., at different speeds and/or in different directions. 
         [0014]    Referring to  FIGS. 3A and 3B  in conjunction with  FIGS. 2A and 2B , end structure  50  is disposed adjacent to open ends  40  of combustion channels  32 . In one form, end structure  50  is positioned in close proximity to open ends  40  to seal combustion products and pressure within wave rotor  30 . In various embodiments, one or more seal arrangements, e.g., spring loaded carbon seal rings, may be disposed between end structure  50  and wave rotor  30  to seal combustion products and pressure within wave rotor  30 , e.g., within combustion channels  32 . 
         [0015]    In one form, end structure  50  includes an inlet port  52 . Inlet port  52  is configured to expose open ends  40  to a fuel and oxidant to permit open ends  40  to receive the fuel and oxidant into combustion channels  32 . In one form, the fuel is a hydrocarbon fuel, such as JP-5. In one form, the oxidant is air. In other embodiments, other types of fuels and/or oxidants may be employed. 
         [0016]    In the illustrated example, end structure  50  is illustrated in the form of an end plate, which may be referred to as a seal plate. It will be understood that the illustrated geometry is schematic in nature and by way of example only, and that end structure  50  may take any form suitable for sealing disposition with respect to open ends  40  of wave rotor  30 . In addition, although only a single port (inlet port  52 ) that exposes open ends  40  is illustrated, it will be understood that embodiments may include additional ports in end structure  50 , e.g., as in a four-port wave rotor system or other wave rotor or rotary valve combustion systems. 
         [0017]    End structure  60  is disposed adjacent to open ends  42  of combustion channels  32 . In one form, end structure  60  is positioned in close proximity to open ends  42  to seal combustion products and pressure within wave rotor  30 . In various embodiments, one or more seal arrangements, e.g., spring loaded carbon seal rings, may be disposed between end structure  60  and wave rotor  30  to seal combustion products and pressure within wave rotor  30 , e.g., within combustion channels  32 . 
         [0018]    End structure  60  includes an exhaust port  62 . Exhaust port  62  is configured to discharge combustion products from combustion channels  32 . In one form, exhaust port  62  is centered about a different circumferential location than inlet port  52 . The phase relationship between inlet port  52  and exhaust port  62  may vary with the needs of the application. In the illustrated example, end structure  60  is illustrated in the form of an end plate, which may be referred to as a seal plate. It will be understood that the illustrated geometry is schematic in nature and by way of example only, and that end structure  60  may take any form suitable for sealing disposition with respect to open ends  42  of wave rotor  30 . In addition, although only a single port (exhaust port  62 ) that exposes open ends  42  is illustrated, it will be understood that embodiments may include additional ports in end structure  60 , e.g., as in a four-port wave rotor system or other wave rotor or rotary valve combustion systems. 
         [0019]    Disposed in end structure  60  is an ignition source  64 . Ignition source  64  is configured to ignite a fuel/oxidant mixture in an adjacent open end  42  of a combustion channel  32 . In one form, ignition source  64  is an igniter, such as a spark plug, disposed in an opening in end structure  60 . In one form, ignition source  64  is a high energy spark discharge device configured to initiate detonation or deflagration combustion of the fuel/oxidant mixture in the adjacent combustion channel  32 . In other embodiments, ignition source  64  may be an igniter configured to initiate deflagration combustion in the adjacent combustion channel  32 . In still other embodiments, ignition source  64  may take other forms, including, for example, an opening in end structure  60  for transferring a flame or other combustion process or hot products of combustion that was initiated at another location or transferred from a previous combustion channel  32 . 
         [0020]    In one form, during normal operation of combustion system  14 , end structure  50  and end structure  60  are stationary, whereas wave rotor  30  rotates in a direction  86 , sequentially exposing each combustion channel  32  to inlet port  52 , and to exhaust port  62 . Wave rotor  30  is supported by bearings (not shown). In other embodiments, either or both of end structures  50  and  60  may rotate at the same or different speeds to sequentially expose each combustion channel  32  to inlet port  52 , and to exhaust port  62 . 
         [0021]    In one form, a fuel  90  and an oxidant  92  are received into each combustion channel  32  as a fuel/oxidant mixture  94  when open end  40  of the respective combustion channel passes inlet port  52 . In one form, mixture  94  is supplied from an initial portion  521  of inlet port  52 , whereas only oxidant  92  is supplied from a final portion  52 F of inlet port  52 . In one form, oxidant  92  is received from the discharge of compressor system  12 . In other embodiments, oxidant  92  may be received from any convenient source, pressurized or not, depending upon the needs of the particular application. In one form, fuel  90  is supplied by one or more injectors  96  that inject fuel  90  into oxidant  92  upstream of inlet port  52 . In other embodiments, fuel  90  may be supplied via other arrangements, e.g., via direct injection into combustion channels  32  and/or injection at inlet port  52 . 
         [0022]    Combustion products  98  from the combustion of mixture  94 , e.g., in a previous combustion cycle, are discharged from combustion channels  32  through open ends  42  via exhaust port  62  when open ends  42  of the respective combustion channel passes exhaust port  62 . In one form, inlet port  52  and exhaust port  62  are staggered circumferentially such that any given combustion channel  32  will be exposed to exhaust port  62  at open end  42  prior to being exposed to inlet port  52  via open end  40  during rotation of wave rotor in direction  86 . 
         [0023]    In one form, the combustion process is a constant volume combustion process (or approximately so), resulting in a pressure rise in combustion channel  32 . For example, a detonation combustion process is an approximately constant volume combustion process, and hence embodiments employing detonative combustion are considered constant volume combustion systems. In other embodiments, deflagration combustion may also yield a constant volume combustion process, e.g., depending on the configuration of combustion channel  32 , the speed of the combustion flame front(s) and whether additional oxidant  92  (without fuel  90 ) is supplied to combustion channel  32 , e.g., subsequent to supplying mixture  94  to combustion channel  32 , and the amount of any additional oxidant  92 . 
         [0024]    Once a combustion channel  32  is exposed to exhaust port  62  via open end  42 , the combustion products expand and are ejected through exhaust port  62 . With continued rotation of wave rotor  30 , the combustion channel is also exposed to an incoming mixture  94  via inlet port  52 . In some embodiments, the gas dynamics of the exhausting combustion products  98  assist in pulling in a new charge of mixture  94  into combustion channel  32 . With continued rotation of wave rotor  30  in direction  86 , the open end  42  of each combustion channel  32  is sequentially closed off as it passes the final portion  62 F of exhaust port  62 . 
         [0025]    In one form, as rotation of wave rotor  30  rotates each combustion channel  32  past initial portion  52 I of inlet port  52  and into final portion  52 F of inlet port  52 , additional oxidant  92  is supplied into combustion channel  32  via open end  40 , being drawn into the combustion channel  32  by the continued movement of portions of mixture  94  toward end structure  60 . In one embodiment additional oxidant  92  is drawn into combustion channel  32  until the pressure disturbance (caused by the sequential closing off of channel  32  as it passes the final portion  62 F of exhaust port  62 ) arrives at the open end  40 . In another embodiment additional oxidant  92  is supplied into combustion channel  32  via open end  40 , dynamically pushing mixture  94  toward end structure  60 . Reference number  95  represents the interface between mixture  94  and the additional oxidant  92 . In various embodiments, the amount of additional oxidant  92  supplied to each combustion channel  32  may vary. In some embodiments, no additional oxidant  92  may be supplied. 
         [0026]    Continued rotation of wave rotor  30  rotates each combustion channel past ignition source  64 , which ignites mixture  94 , advancing a combustion flame front  100  along combustion channel  32  toward open end  40 , leaving combustion products  98  in its wake. In some embodiments, the combustion rate results in essentially constant volume combustion. In some embodiments, the expanding combustion products  98  resulting from the constant volume combustion process compress the oxidant  92 , wherein oxidant/mixture interface  95  progresses in a flow direction toward open end  40  of combustion channel  32 . The combustion process continues in the direction toward open end  40  until mixture  94  is consumed by the combustion process, leaving pressurized oxidant  92  and combustion products  98  remaining in combustion channel  32 . In some embodiments, the pressurized oxidant  92  may be extracted for various purposes. Continued rotation of wave rotor  30  eventually exposes each combustion channel  32  to exhaust port  62 , where combustion products  98  (and some or substantially all of the additional oxidant  92  in some embodiments) are discharged, e.g., toward turbine  16  in embodiments so equipped. In some embodiments, combustion products  98  may be employed to provide direct thrust. 
         [0027]    Under some operating conditions, some remaining additional oxidant  92  (and/or mixture  94  and/or combustion products  98 , e.g., depending on the embodiment and on operating parameters and/or other parameters) from a previous combustion cycle may remain in channel  32  in the vicinity of open end  42 , identified in  FIG. 3A  as a remainder R. Also, during the combustion channel  32  filling process, mixing may occur between mixture  94  and oxidizer  92  remaining from the previous cycle. For example, depending on the particulars of various embodiments, mixing may be induced, e.g., due to viscous forces, turbulence induced by features (not shown) in combustion channel  32  (e.g., flame accelerators) for embodiments so equipped, turbulence induced by incidence at open ends  40  and/or  42 , motion of the mixtures and gases due to secondary flow patterns set up by combustion channel curvature, pressure gradients within the combustion channels in radial and/or tangential (circumferential) and/or axial directions, e.g., due to centrifugal and centripetal forces and/or by other interactions. The mixing of mixture  94  with oxidant  92 , with in some cases some portion of combustion products  98  mixed, forms the remainder R, and the presence of remainder R adversely affects the fuel/oxidant ratio of mixture  94  at open ends  42 , which may adversely affect the ignition of mixture  94  by ignition source  64 , and may adversely affect the combustion of mixture  94 . 
         [0028]    Embodiments of the present invention include one or more features to enhance fuel/oxidant ratio of the mixture in combustion channel  32  in the vicinity of open ends  42 , e.g., to overcome deficiencies in the fuel/oxidant ratio brought about by mixing with remainder R or due to the presence of remainder R. Some such fuel/oxidant ratio enhancing features are illustrated in  FIGS. 3A and 3B . It will be understood that various embodiments may include only one such enhancement feature, or may include any of or all of such enhancement features. 
         [0029]    In one form, an enhancement feature in the form of a cavity  68  is employed. Cavity  68  is disposed in end structure  60 , and is disposed between exhaust port  62  and ignition source  64 , downstream of exhaust port  62  in direction  86  of rotation of wave rotor  30 . In one form, a single cavity  68  is employed. In other embodiments, more than one cavity  68  may be employed. Cavity  68  is disposed opposite open ends  42  of combustion channels  32 . In one form, cavity  68  is configured with a width that spans a plurality of combustion channels  32 , wherein a plurality of combustion channels  32  are exposed to cavity  68  at any one time. In other embodiments, cavity  68  may be configured with a width that is less than that of a single combustion channel  32 , or may be configured with a width sufficient to span any number of combustion channels between exhaust port  62  and ignition source  64 . In the depiction of  FIG. 3A , cavity  68  has a width configured to simultaneously expose at least three combustion channels to cavity  68 . 
         [0030]    Operation of combustion system  14  includes relative motion between combustion channels  32  and end structures  50  and  60 ; wherein the relative motion includes open ends  42  of combustion channels  32  moving past exhaust port  62 , then past cavity  68 , and then past ignition source  64 . In one form, cavity  68  is configured, e.g., in size and shape, to promote fluid exchange between cavity  68  and one or more adjacent combustion channels  32  via open ends  42  during the operation of combustion system  14 . In other embodiments, cavity  68  may not be configured to promote such fluid exchange. 
         [0031]    In one form, cavity  68  is configured to induce turbulence in one or more adjacent combustion channels  32  via open ends  42 . For example, in some embodiments, an abrupt entry portion  68 A and a smooth exit portion  68 B induces turbulence in open ends  42 . Embodiments may also include turbulence inducing features, such as turbulators  69 A and/or  69 B. The shape of cavity  68  and of any turbulators may vary with the needs of the application. Cavity  68  may be shaped to span any desired number of combustion channels  32 . Fluid exchange between cavity  68  and combustion channels  32  in open ends  42  tends to equilibrate mixture  94  in the regions of combustion channel  32  adjacent to end structure  60 . In addition, achieving a desired level of turbulence in the regions of combustion channel  32 , adjacent to end structure  60 , helps to promote successful ignition and the resulting rapid combustion of mixture  94 . 
         [0032]    Another feature for enhancing fuel/oxidant mixture  94  in combustion channel  32  in the vicinity of open ends  42  includes a fuel injection port  70  in fluid communication with a fuel supply  72 . Fuel injection port  70  is disposed between exhaust port  62  and ignition source  64 , e.g., between final portion  62 F of exhaust port  62  and ignition source  64 , downstream of exhaust port  62  in direction  86  of rotation of wave rotor  30 . In one form, a single fuel injection port  70  is employed. In other embodiments, more than one fuel injection port  70  may be employed. In one form, fuel injection port  70  is in fluid communication with open ends  42  of combustion channels  32  via cavity  68 . In other embodiments, fuel injection port  70  may be directly exposed to open ends  42  in addition to or in place of cavity  68 . Fuel injection port  70  is operative to supply fuel to open ends  42  of combustion channels  32 , e.g., to modify the fuel/oxidant ratio of the gas mixture resulting from remainder R and mixture  94 , e.g., mixture  94  diluted with additional oxidant  92  and/or combustion products  98  (e.g., mixture  94  diluted with remainder R). By adding fuel to open ends  42  of combustion channels  32 , the desired fuel/oxidant ratio for ignition may be obtained, e.g., within chamber  32  at the aft end  42  (open end  42 ) as it approaches ignition source  64  due to rotation in direction  86 . The modified mixture is subsequently ignited using ignition source  64  during the operation of combustion system  14 . 
         [0033]    Another feature for enhancing fuel/oxidant mixture  94  in combustion channel  32  in the vicinity of open ends  42  includes a conduit  80  having an opening  82  and an opening  83 . Conduit  80  may be formed of one or more components, e.g., tubes, pipes, fittings, and/or cored passages. Opening  82  of conduit  80  is disposed between exhaust port  62  and ignition source  64 , downstream of exhaust port  62  in direction  86  of rotation of wave rotor  30 . In one form, a single conduit  80  is employed. In other embodiments, more than one conduit  80  may be employed. 
         [0034]    Opening  82  is in fluid communication with open ends  42  via an opening  84  in end structure  60 . In one form, opening  84  is in fluid communication with open ends  42  of combustion channels  32  via cavity  68 . In other embodiments, opening  84  may be directly exposed to open ends  42  in addition to or in place of cavity  68 . Conduit  80  is operative to receive fluid from open ends  42  of combustion channel  32 , e.g., directly and/or via cavity  68 . 
         [0035]    In one form, opening  83  of conduit  80  is in fluid communication with open ends  40  of combustion channels  32 . In one form, opening  83  is in fluid communication with open ends  40  via inlet port  52 . In other embodiments, other schemes may be employed to yield fluid communication between opening  83  of conduit  80  and combustion channels  32 , via open ends  40  or via other portions of combustion channels  32 . In still other embodiments, opening  83  may be in fluid communication with other features, e.g., with exhaust port  62 . In one form, conduit  80  is configured to transmit fluid from open ends  42  of combustion channels  32 . In one form, the fluid is transmitted to open ends  40  of combustion channel  32 , e.g., via inlet port  52 . In other embodiments, the fluid may be transmitted to other locations. In one form, gas dynamics generate higher pressures at open ends  42  in the vicinity of opening  84  than at locations upstream of open ends  40  when exposed to inlet port  52 , thereby providing motive force to transmit the contents of combustion channel  32  at open end  42  adjacent to opening  84  toward opening  83  of conduit  80 . In other embodiments, other means may be employed to generate flow. In some embodiments, conduit  80  may be configured to transmit fluid, e.g., mixture  94 , from upstream of open ends  40  to open ends  42 . 
         [0036]    By removing fluid from open ends  42  of combustion channels  32 , the gas mixture R is replaced with non-diluted mixture  94  that back-fills from portions of combustion channel  32  adjacent to open ends  42 . The non-diluted mixture  94  has the desired fuel/oxidant ratio for ignition and combustion, and is drawn into open ends  42  with the removal therefrom of the gas mixture R. The non-diluted mixture is subsequently ignited using ignition source  64  during the operation of combustion system  14 . In one form, a valve  88  is coupled to conduit  80  and is operative to control the amount of fluid withdrawn from open ends  42 , e.g., directly and/or via cavity  68 . In such embodiments, the amount of fluid transmitted toward open ends  40  of combustion channel  32  may be controlled by valve  88  based on the operating conditions of combustion system  14 , e.g., power output, inlet conditions, rotational speed of wave rotor  30 , etc. In some embodiments, valve  88  may be configured to be closed, thereby preventing fluid transfer from open ends  42 , e.g., under selected operating conditions. Still other embodiments may not employ a valve such as valve  88 . 
         [0037]    In various embodiments, one or more of the aforementioned features may be employed to enhance the fuel/oxidant ratio of the mixture in open ends  42 . In some embodiments, each of the aforementioned features may be employed. Some of the features may be activated at some operating conditions and deactivated under other operating conditions. In some embodiments, some features may remain active during all operating conditions. 
         [0038]    Embodiments of the present invention include an engine, comprising: a combustion system, including: a plurality of combustion channels, each combustion channel extending between a first open end and a second open end thereof; a first end structure disposed adjacent to the first open ends of the combustion channels, wherein the first end structure includes an inlet port configured to permit the first open ends to receive a fuel and an oxidant into the combustion channels; an ignition source operative to ignite the fuel and the oxidant; and a second end structure disposed adjacent to the second open ends of the combustion channels, wherein the second end structure includes an exhaust port configured to discharge combustion products from the combustion channels; and wherein the second end structure includes a cavity disposed between the exhaust port and the ignition source; wherein operation of the combustion system includes relative motion between the combustion channels and the first and second end structures; and wherein the relative motion includes relative movement between a second open end of a combustion channel and the second end structure, whereby the second open end is exposed to the exhaust port, then the cavity, and then the ignition source. 
         [0039]    In a refinement, the engine further comprises a wave rotor, wherein the plurality of combustion channels is disposed in the wave rotor. 
         [0040]    In another refinement, the first and second end structures are stationary seal plates. 
         [0041]    In yet another refinement, the cavity is sized to promote a gas mixture exchange between the cavity and an adjacent combustion channel via the second open end. 
         [0042]    In still another refinement, the cavity has a width configured to simultaneously expose at least three combustion channels to the cavity. 
         [0043]    In yet still another refinement, the engine further comprises a conduit in fluid communication with the cavity, wherein the conduit is operative to receive a fluid from the cavity. 
         [0044]    In a further refinement, the engine further comprises a valve coupled to the conduit and operative to control an amount of the fluid received from the cavity. 
         [0045]    In a yet further refinement, the conduit is also in fluid communication with the inlet port; and the conduit is operative to transmit the received fluid toward the inlet port. 
         [0046]    In a still further refinement, the engine further comprises a conduit operative to receive a fluid from a first combustion channel at the second end structure and transmit the fluid to a second combustion channel at the first end structure. 
         [0047]    In a yet still further refinement, the engine further comprises a fuel injection port disposed in the second end structure and operative to supply fuel to the second open ends of the combustion channels. 
         [0048]    Embodiments of the present invention include a combustion system, comprising: a wave rotor having a plurality of combustion channels, each combustion channel having a first open end and a second open end; an ignition source operative to ignite a fuel and an oxidant; a first end plate positioned adjacent to the first open ends of the combustion channels, wherein the first end plate includes an inlet port for receiving the fuel and the oxidant into the combustion channels; a second end plate adapted to receive the ignition source, wherein the second end plate is positioned adjacent to the second open ends of the combustion channels; wherein the second end plate includes an exhaust port operative to discharge combustion products; and means for enhancing a fuel/oxidant mixture in the combustion channels at the second open end, wherein the means for enhancing is operatively disposed at the second end plate. 
         [0049]    In a refinement, the means for enhancing includes means for transmitting a fluid from the second open ends to the inlet port. 
         [0050]    In another refinement, the means for transmitting includes a conduit operative to receive a fluid from the second open ends of the combustion channels. 
         [0051]    In still another refinement, the combustion system further comprises means for controlling flow of the fluid from the second open ends. 
         [0052]    In yet another refinement, the means for enhancing includes a fuel injection port operative to supply fuel to the second open ends. 
         [0053]    In yet still another refinement, the means for enhancing includes a cavity operative to exchange fluid with the second open ends of the combustion channels. 
         [0054]    Embodiments of the present invention include a combustion system, comprising: a wave rotor having a plurality of combustion channels, each combustion channel having a first open end and a second open end; a first end plate positioned adjacent to the first open ends of the combustion channels, wherein the first end plate includes an inlet port for receiving a fuel and an oxidant into the combustion channels; a second end plate positioned adjacent to the second open ends of the combustion channels; and wherein the second end plate includes an exhaust port operative to discharge combustion products; and a conduit extending between a first opening and a second opening thereof, wherein the first opening is in fluid communication with at least one second open end via the second end plate; wherein the second opening is in fluid communication with at least one first open end via the first end plate; and wherein the conduit is operative to transmit a fluid from the at least one second open end to the at least one first open end. 
         [0055]    In a refinement, the first opening of the conduit is disposed between the exhaust port and the ignition source, downstream of the exhaust port in a direction of rotation of the wave rotor. 
         [0056]    In another refinement, the second end plate includes a cavity in fluid communication between the first opening of the conduit and the at least one second open end. 
         [0057]    In yet another refinement, the cavity is configured to induce turbulence in the combustion channels adjacent the second open ends. 
         [0058]    In still another refinement, the combustion system further comprises a turbulator disposed in said cavity and operative to induce turbulence in the at least one second open end. 
         [0059]    In yet still another refinement, the combustion system further comprises a valve operative to control a flow of the fluid through the conduit. 
         [0060]    While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment(s), but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as permitted under the law. Furthermore it should be understood that while the use of the word preferable, preferably, or preferred in the description above indicates that feature so described may be more desirable, it nonetheless may not be necessary and any embodiment lacking the same may be contemplated as within the scope of the invention, that scope being defined by the claims that follow. In reading the claims it is intended that when words such as “a,” “an,” “at least one” and “at least a portion” are used, there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. Further, when the language “at least a portion” and/or “a portion” is used the item may include a portion and/or the entire item unless specifically stated to the contrary.