Abstract:
One embodiment of the present invention is an engine. Another embodiment 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 
     The present application claims benefit of U.S. Provisional Patent Application No. 61/427,584, filed Dec. 28, 2010, entitled Engine And Combustion System, which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to engines and combustion systems for engines. 
     BACKGROUND 
     Engines and combustion systems 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 
     One embodiment of the present invention is an engine. Another embodiment 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 
       The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein: 
         FIG. 1  schematically depicts a non-limiting example of a gas turbine engine in accordance with an embodiment of the present invention. 
         FIGS. 2A and 2B  schematically illustrate a non-limiting example of aspects of a combustion system in accordance with an embodiment of the present invention. 
         FIGS. 3A-3E  schematically illustrate non-limiting examples of shapes of discrete roughness elements in accordance with some embodiments of the present invention. 
         FIGS. 4A and 4B  schematically illustrate non-limiting examples of discrete roughness elements in accordance with some embodiments of the present invention. 
         FIGS. 5A-5F  schematically illustrate non-limiting examples of discrete roughness elements in accordance with some embodiments of the present invention. 
         FIGS. 6A and 6B  schematically illustrate non-limiting examples of an insert with discrete roughness elements in accordance with some embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     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. 
     Referring to the drawings, and in particular  FIG. 1 , a non-limiting example of an engine  10  in accordance with an embodiment of the present invention is depicted. In one form, engine  10  is a gas turbine engine configured as an air vehicle propulsion power plant. In other embodiments, engine  10  may be another type of gas turbine engine, e.g., an aircraft auxiliary power unit, a land-based engine or a marine engine. In one form, gas turbine engine  10  is a turbofan. In other embodiments, gas turbine engine  10  may be a single-spool or multi-spool turbofan, turboshaft, turbojet, turboprop gas turbine or combined cycle engine. In still other embodiments, engine  10  may be a wave rotor engine and/or a pulse detonation engine. 
     In one form, engine  10  includes a compressor system  12 , a combustion system  14  and a turbine system  16 . Combustion system  14  is fluidly disposed between compressor system  12  and turbine system  16 . During the operation of gas turbine engine  10 , air is drawn into the inlet of compressor system, pressurized and discharged into combustion system  14 . Fuel is mixed with the pressurized air in combustion system  14 , which is then combusted. The combustion products are directed into turbine system, which extracts energy in the form of mechanical shaft power to drive compressor system  12 . The hot gases exiting turbine system  20  are directed into a nozzle (not shown), and provide a thrust output of gas turbine engine  10 . 
     In one form, combustion system  14  is a wave rotor combustion system  12 , or a constant volume combustor. In other embodiments, combustion system  14  may be one or more pulse detonation combustors or a wave rotor employing pulse detonation combustors. In still other embodiments, combustion system  14  may be or may employ other types of combustors in addition to or in place of a wave rotor and/or pulse detonation combustors. In still other embodiments, combustion system  14  may be a wave rotor combustor or another type of combustor employing pulse deflagrative combustion. 
     Referring to  FIGS. 2A and 2B , a non-limiting example of some aspects of combustion system  14  are depicted. In one form, combustion system  14  is combined with turbomachinery (e.g., compressor system  12  and turbine system  16 ) to form a hybrid turbine engine. In other embodiments, combustion system  14  may be a direct propulsion engine. In various embodiments, combustion system  14  includes one or more combustion channels  20 . For example, in the form of a wave rotor, combustion system  14  includes a plurality of combustion channels  20 . In the form of a pulse detonation combustor and/or a pulse deflagration combustor, combustion system  14  may have a single combustion channel  20  or a plurality of combustion channels  20 . Combustion channel  20  may be rotating, or may be stationary. In some embodiments, combustion system  14  may be a wave rotor having a plurality of pulse detonation combustors and/or pulse deflagration combustors, each having one or more combustion channels  20 . 
     In one form, combustion channel  20  is an elongated tubular form. In other embodiments, combustion channel  20  may take other forms. In one form, combustion channel  20  has a circular cross-sectional shape, e.g., as depicted in  FIG. 2A . The cross-sectional shape of combustion channel  20  may vary with the application. In other embodiments, combustion channel  20  may have other cross-sectional shapes, such as circular, rectangular or other N-gon, or any desired shape. In one form, combustion channel  20  is an axial combustion channel, extending predominantly in an axial direction  22  that is parallel to the axis of rotation of compressor system  12  and turbine system  16 . In other embodiments, combustion channel  20  extends in any one or more of engine  10  and/or combustion system  14  radial, axial and circumferential directions. 
     In one form, combustion channel  20  includes a wall  24  that defines a combustion chamber  26  extending though combustion channel  20 . In other embodiments, e.g., having non-circular cross-sections, combustion channel  20  may include a plurality of walls  24 , e.g., N walls for an N-gon shaped combustion channel  20 , which define combustion chamber  26 . Wall  24  may be devoted to a single combustion channel  20 , or may be a joint wall used by more than one combustion channel  20 , e.g., as in a wave rotor. In one form, combustion chamber  26  is linear, extending linearly along axial direction  22 . In other embodiments, combustion chamber  26  may be linear, curved, segmented, or have any shape and configuration suited to the particular application for which combustion system  14  is intended. 
     In one form, combustion chamber  26  is configured to contain a transient pulse combustion event. In one form, the transient pulse combustion event is one in a series of combustion events contained within combustion chamber  26 , e.g., a repeating cycle of transient pulse combustion events. In other embodiments, combustion chamber  26  may be configured to contain a plurality of transient pulse combustion events, e.g., spaced apart along the length of combustion chamber  26  and occurring at the same time and/or different times, and/or to contain a continuous combustion event. 
     Combustion system  14  includes an ignition source  30  and a flame accelerator  32 . In one form, ignition source  30  is disposed within combustion channel  20 , in particular, inside combustion chamber  26 . In other embodiments, ignition source  30  may be disposed adjacent to combustion channel  20  and/or combustion chamber  26 , rather than being disposed within combustion channel  20  and combustion chamber  26 . In one form, ignition source  30  is an igniter, such as a spark plug. In other embodiments, ignition source  30  may take another form, e.g., a high energy ignition system, or one or more ports for injecting one or more fluids to initiate a combustion event or for injecting a mixture that is already in a state of combustion. 
     In one form, a single ignition source  30  is employed for each combustion channel  20 . In other embodiments, a plurality of ignition sources may be employed for each combustion channel  20 . In still other embodiments, no ignition source may be employed for combustion channel  20 . In one form, ignition source  30  is disposed at an exit end  36  of combustion channel  20 . In other embodiments, ignition source  30  is disposed at an inlet end  38  of combustion channel  20 . In still other embodiments, ignition source  30  may be disposed at any convenient location, including in, on or adjacent to combustion channel  20 , or remote from combustion channel  20 . 
     During operation, fuel and oxidizer are supplied to inlet end  38  of combustion channel  20  in a filling phase. The fuel and oxidizer are subsequently ignited by ignition source  30  to initiate a transient pulse combustion event  40 . The combustion products resulting from transient pulse combustion event  40  are then exhausted from combustion channel  20 . The mass flows of fuel, oxidizer and combustion products in the filling and exhausting processes within combustion channel  20  are in a predominant flow direction  42 , from inlet end  38  toward the exit end  36  of combustion channel  20 . Transient pulse combustion event  40  yields a front, e.g., a flame front and a compression wave, that travels in a combustion direction  44 , which is opposite to predominant flow direction  42 . An opposing front may proceed in the opposite direction. 
     Flame accelerator  32  is disposed in combustion channel  20 , and is configured to accelerate the combustion process. In one form, flame accelerator  32  is structured to transition the combustion process from deflagration combustion to detonation combustion, e.g., to initiate a deflagration-to-detonation transition. In other embodiments, flame accelerator  32  may be configured to accelerate the combustion process, but without transitioning the combustion process from deflagration combustion to detonation combustion. In addition, flame accelerator  32  is configured to yield a directionally-dependent pressure loss in flow inside combustion channel  20 . In one form, the directionally-dependent pressure loss yields a higher pressure loss in direction  44  than in direction  42 . In other embodiments, flame accelerator  32  may be configured to yield a higher pressure loss in direction  42  than in direction  44 . 
     In one form, flame accelerator  32  includes a plurality of discrete obstacles, otherwise referred to herein as discrete roughness elements  34 . Each discrete roughness element is configured to accelerate the combustion process. In one form, each discrete roughness element  34  is configured to yield a greater flow contraction in one direction than the opposite direction. In other embodiments, other means of accelerating the combustion process may be employed. In one form, each discrete roughness element  34  has a shape configured to yield a directionally-dependent pressure loss in a flow through combustion channel  20 . 
     In one form, it is the plurality of discrete roughness elements  34  that provide the directionally-dependent pressure loss of flame accelerator  32 , and that accelerate the combustion process. In other embodiments, other means may be employed to yield a directionally dependent pressure loss and accelerate the combustion process in addition to or in place of discrete roughness elements  34 , e.g., fluid injection ports that inject gases or liquids in a direction that has a component in direction  42  that is greater than any component in direction  44 . In addition, in other embodiments, other discrete roughness elements or other means for creating a pressure loss that is/are not directionally-dependent may be employed in conjunction with directionally-dependent discrete roughness element(s)  34  or other means for yielding a directionally-dependent pressure loss. 
     The number of discrete roughness elements  34  may vary with the application. For example, in various embodiments, only a single discrete roughness element  34  may be employed, or a larger number of discrete roughness elements  34  may be employed. The number of discrete roughness elements in any particular embodiment depends on various factors, for example and without limitation, the desired degree of flame acceleration, the passage dimensions, the size and shape of the elements such that there is the creation of regions of pressure wave reflection into regions of flame front arrival, the creation of regions of intense mixing between combusting and yet to combust fluid, and other means to promote the rapid creation of regions of intense combustion. Discrete roughness elements  34  may take a variety of forms, e.g., including different shapes. In one form, one or more discrete roughness elements  34  are obstacles that are disposed in combustion chamber  26 . In another form, one or more discrete roughness elements  34  are cavities in wall  24 . Various embodiments may include discrete roughness elements  34  in the form of obstacles and/or cavities. 
     In one form, one or more of discrete roughness elements  34  are formed integrally with wall  24  and extend therefrom into combustion chamber  26 . In other embodiments, one or more of discrete roughness elements  34  may be coupled to wall  24  and extend therefrom into combustion chamber  26 , in addition to or in place of one or more discrete roughness elements  34  formed integrally with wall  24 . In one form, one or more of discrete roughness elements  34  extends partially into combustion chamber  26 . In some embodiments, one or more of discrete roughness elements  34  may extend from wall  24  all the way through combustion chamber  26  to an adjacent and/or opposite wall  24  or portion thereof. In one form, discrete roughness elements  34  are arranged in a staggered relationship around combustion chamber  26 . In other embodiments, discrete roughness elements  34  may be arranged in a spiral and/or a ring in addition to or in place of a staggered relationship. In one form, discrete roughness elements  34  extend partially around the periphery of combustion chamber  26 . In other embodiments, discrete roughness elements  34  may extend around the entire perimeter of combustion chamber  26 , e.g., forming a ring or spiral, in addition to or in place of discrete roughness elements  34  that extend partially around the periphery of combustion chamber  26 . 
     In one form, one or more discrete roughness elements  34  are configured to yield a higher flow area contraction per unit length in the combustion direction than the flow area contraction per unit length in the predominant flow direction. The flow area contraction per unit length is a measure of the suddenness or gradualness of the contraction. In one form, one or more discrete roughness elements  34  are configured to yield a sudden contraction in combustion direction  44 , and a gradual contraction in predominant flow direction  42 , e.g., as depicted in  FIG. 2A . In other embodiments, one or more discrete roughness element  34  may be configured to yield a higher flow area contraction per unit length in the predominant flow direction than the flow area contraction per unit length in the combustion direction. In some embodiments, a sudden area change may be employed for certain area ratios (A/A), for example and without limitation, a flow area downstream divided by a flow area upstream having a value from about 0.01 to 0.2 for contracting flows, and a flow area downstream divided by a flow area upstream having a value near about 0.8 for expanding flows. In general the shape of the elements is selected to create greater drag to flow in direction  44  than in direction  42  by either or both boundary layer drag or form drag. 
     Referring to  FIGS. 3A-3E , some non-limiting examples of shapes for discrete roughness element  34  include, but are not limited to, those shapes depicted for discrete roughness elements  34 A- 34 E. The shape of each discrete roughness element  34  may vary with the needs of the application, and is not limited to the depictions of  FIGS. 3A-3E . In one form, each discrete roughness element  34  in combustion channel  20  has the same shape. In other embodiments, a plurality of different shapes may be employed in combustion channel  20 , e.g., one or more shapes illustrated in  FIGS. 3A-3E  and/or other shapes. In one form, discrete roughness elements  34 A- 34 E are obstacles disposed in combustion chamber  26 . In one form, each of discrete roughness element  34 A- 34 E is configured with a flow surface  46  and a flow surface  48 . Flow surface  46  is configured to provide a more gradual flow area contraction in predominant flow direction  42  than the less gradual flow area contraction in combustion direction  44  provided by flow surface  48 , to yield a higher pressure drop in flow in combustion direction  44  than the pressure drop in flow in predominant flow direction  42 . The degree of flow area contraction per unit length of each of flow surfaces  46  and  48  may vary with the needs of the application. Flow surfaces  46  and  48  may be planar or may be three-dimensional surfaces. In various embodiments, other shapes and/or types of discrete roughness elements  34  and/or other means of providing a directionally-dependent pressure loss may be employed in addition to or in place of discrete roughness elements  34 A- 34 E. 
     Referring to  FIGS. 4A and 4B , some non-limiting examples of shapes for discrete roughness element  34  include, but are not limited to, those shapes depicted for discrete roughness elements  34 F and  34 G. In one form, discrete roughness elements  34 F and  34 G are cavities disposed in wall  24 , which are exposed to combustion chamber  26 . The shape of each discrete roughness element  34  may vary with the needs of the application, and is not limited to the depictions of  FIGS. 4A and 4B . In one form, each discrete roughness element  34  in combustion channel  20  has the same shape. In other embodiments, a plurality of different shapes may be employed in combustion channel  20 , e.g., one or more shapes illustrated in  FIGS. 4A and 4B  and/or other shapes. 
     In one form, each of discrete roughness element  34 F and  34 G is configured with a flow surface  50  and a flow surface  52 . Flow surface  50  is configured to provide a more gradual flow area contraction in predominant flow direction  42  than the less gradual flow area contraction in combustion direction  44  provided by flow surface  52 , to yield a higher pressure drop in flow in combustion direction  44  than the pressure drop in flow in predominant flow direction  42 . The degree of flow area contraction per unit length of each of flow surfaces  50  and  52  may vary with the needs of the application. Flow surfaces  50  and  52  may be planar or may be three-dimensional surfaces. In the depictions of  FIGS. 4A and 4B , flow surfaces  52  are bluff surfaces, which present a sudden contraction to flow in combustion direction  44 . It will be understood that in other embodiments, flow surface  52  may be configured to yield a gradual contraction to flow in combustion direction  44  in place of a sudden contraction. In various embodiments, other shapes and/or types of discrete roughness elements  34  and/or other means of providing a directionally-dependent pressure loss may be employed in addition to or in place of discrete roughness elements  34 F and  34 G. 
     Referring to  FIGS. 5A-5E , some non-limiting examples of shapes for discrete roughness element  34  include, but are not limited to, those shapes depicted for discrete roughness elements  34 H- 34 K. The shape of each discrete roughness element  34  may vary with the needs of the application, and is not limited to the depictions of  FIGS. 5A-5E . In one form, each discrete roughness element  34  in combustion channel  20  has the same shape. In other embodiments, a plurality of different shapes may be employed in combustion channel  20 , e.g., one or more shapes illustrated in  FIGS. 5A-5E  and/or other shapes. In one form, discrete roughness elements  34 H- 34 K are obstacles disposed in combustion chamber  26 . In one form, discrete roughness elements  34 H- 34 K span combustion chamber  26 , e.g., as illustrated in  FIG. 5E , wherein discrete roughness element  34 K spans combustion chamber  26 , extending from wall  24 A to wall  24 B of a rectangular-shaped combustion channel  20  through combustion chamber  26 . 
     In one form, each of discrete roughness elements  34 H- 34 K is configured with a plurality of flow surfaces  54  and a flow surface  56 . At least one flow surface  54  is configured to provide a more gradual flow area contraction in predominant flow direction  42  than the less gradual flow area contraction in combustion direction  44  provided by flow surface  56 , to yield a higher pressure drop in flow in combustion direction  44  than the pressure drop in flow in predominant flow direction  42 . The degree of flow area contraction per unit length of each of flow surfaces  54  and  56  may vary with the needs of the application. Flow surfaces  54  and  56  may be planar or may be three-dimensional surfaces. In the depictions of  FIGS. 5A-5E , flow surfaces  56  are bluff surfaces, which present a sudden contraction to flow in combustion direction  44 . It will be understood that in other embodiments, flow surface  56  may be configured to yield a gradual contraction to flow in combustion direction  44  in place of a sudden contraction. In various embodiments, other shapes and/or types of discrete roughness elements  34  and/or other means of providing a directionally-dependent pressure loss may be employed in addition to or in place of discrete roughness elements  34 H- 34 K. 
     Referring to  FIGS. 6A and 6B , non-limiting examples of other embodiments in accordance with the present invention are depicted. In one form, combustion system  14  includes an insert  58  disposed within combustion channel  20  and combustion chamber  26 . In one form, one or more discrete roughness elements are formed into, coupled to and/or formed integrally with insert  58 . For example, in the depiction of  FIG. 6A , insert  58  includes discrete roughness elements  34 L, which extend from insert  58  into combustion chamber  26 . In the depiction of  FIG. 6B , insert  58  includes discrete roughness elements  34 M, which are cavities in insert  58  that are exposed to combustion chamber  26 . In other embodiments, other shapes and/or types of discrete roughness elements  34  and/or other means of providing a directionally-dependent pressure loss may be employed in addition to or in place of discrete roughness elements  34 L and  34 M. 
     Embodiments of the present invention include a combustion system, comprising: a combustion channel configured to contain a combustion process; and a flame accelerator disposed within the combustion channel, wherein the flame accelerator is configured to accelerate the combustion process; and wherein the flame accelerator is configured to yield a directionally-dependent pressure loss in a flow in the combustion channel. 
     In a refinement, the flame accelerator includes a discrete roughness element having a shape configured to yield the directionally-dependent pressure loss in the flow through the combustion channel; and the discrete roughness element is configured to accelerate the combustion process. 
     In another refinement, the combustion channel includes at least one wall configured to form a combustion chamber; and the discrete roughness element is a shaped obstacle disposed within the combustion chamber. 
     In yet another refinement, the discrete roughness element extends from the at least one wall into the combustion chamber. 
     In still another refinement, the combustion channel includes at least one wall configured to form a combustion chamber; wherein the discrete roughness element is a cavity formed in the at least one wall; and wherein the cavity is exposed to the combustion chamber. 
     In yet still another refinement, the combustion channel includes at least one wall configured to form a combustion chamber; and the combustion system further comprises an insert disposed in the combustion chamber, wherein the insert includes the discrete roughness element. 
     In a further refinement, the discrete roughness element is a cavity formed in the insert; and the cavity is exposed to the combustion chamber. 
     In a yet further refinement, the discrete roughness element extends from the insert into the combustion chamber. 
     In a still further refinement, the combustion system is configured as a pulse detonation combustor. 
     In a yet still further refinement, the combustion system is configured as a wave rotor. 
     Embodiments of the present invention include an engine, comprising: a combustion system, including a flame accelerator configured to interact with and accelerate a combustion process, wherein the flame accelerator is configured to yield a greater flow contraction in a first direction than in a second direction opposite the first direction. 
     In a refinement, the engine further comprises a combustion channel configured to contain the combustion process, wherein the flame accelerator is disposed within the combustion channel; and wherein the flame accelerator is configured to yield a directionally-dependent pressure loss in a flow in the combustion channel. 
     In another refinement, the flame accelerator includes a discrete roughness element having a shape configured to yield the directionally-dependent pressure loss in the flow through the combustion channel; and wherein the discrete roughness element is configured to accelerate the combustion process. 
     In yet another refinement, the engine further comprises a turbine in fluid communication with the combustion system. 
     In still another refinement, the flame accelerator is structured to transition the combustion process from deflagration combustion to detonation combustion. 
     In yet still another refinement, the combustion channel has a predominant flow direction and a combustion direction opposite the predominant flow direction; and the shape of the discrete roughness element is configured to yield a higher flow area contraction per unit length in the combustion direction than in the predominant flow direction. 
     In a further refinement, the shape of the discrete roughness element is configured to yield a sudden contraction in the combustion direction and to yield a gradual contraction in the predominant flow direction. 
     In a yet further refinement, the combustion channel has a predominant flow direction and a combustion direction opposite the predominant flow direction; and the discrete roughness element is configured to yield a greater pressure drop in the flow in the combustion direction than in the predominant flow direction. 
     Embodiments of the present invention include an engine, comprising: means for containing a combustion process; and means for accelerating the combustion process, wherein the means for accelerating is disposed in the means for containing, and wherein the means for accelerating is structured to yield a directionally-dependent pressure loss. 
     In a refinement, the means for accelerating is structured to transition the combustion process from deflagration combustion to detonation combustion. 
     In another refinement, the means for accelerating is not structured to transition the combustion process from deflagration combustion to detonation combustion. 
     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 words “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.