Abstract:
A pulse combustion device has a number of combustors with upstream bodies and downstream nozzles. Coupling conduits provide communication between the combustors. For each given combustor this includes a first communication between a first location upstream of the nozzle thereof and a first location along the nozzle of another. There is second communication between a second location upstream of the nozzle and a second communication between a second location upstream of the nozzle of a second other combustor and a second nozzle location along the nozzle of the given combustor.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates to pulse combustion devices, and more particularly to pulse combustion engines.  
         [0002]     Diverse pulse combustion technologies exist. Pulse detonation engines (PDE&#39;s) represent areas of particular development. In a generalized PDE, fuel and oxidizer (e.g. oxygen-containing gas such as air) are admitted to an elongate combustion chamber at an upstream inlet end. The air may be introduced through an upstream inlet valve and the fuel injected downstream thereof to form a mixture. Alternatively, a fuel/air mixture may be introduced through the valve. Upon introduction of this charge, the valve is closed and an igniter is utilized to detonate the charge (either directly or through a deflagration to detonation transition process). A detonation wave propagates toward the outlet at supersonic speed causing substantial combustion of the fuel/air mixture before the mixture can be substantially driven from the outlet. The result of the combustion is to rapidly elevate pressure within the chamber before substantial gas can escape inertially through the outlet. The effect of this inertial confinement is to produce near constant volume combustion as distinguished, for example, from constant pressure combustion. Exemplary pulse combustion engines are shown in U.S. Pat. Nos. 5,353,588, 5,873,240, 5,901,550, and 6,003,301.  
         [0003]     Additionally, pulse combustion devices have been proposed for use as combustors in hybrid turbine engines. For example, the device may replace a conventional turbine engine combustor. Such proposed hybrid engines are shown in U.S. Pat. No. 3,417,564 and U.S. Publication 20040123583 A1.  
       BRIEF SUMMARY OF THE INVENTION  
       [0004]     One aspect of the invention involves a pulse combustion device having a circular array of combustion conduits. Each conduit includes a wall surface extending from an upstream inlet to a downstream outlet. At least one valve is positioned to admit at least a first gas component of a propellant to the combustion conduit inlets. The device includes an outlet end member. The array and outlet end member are rotatable in at least a first direction relative to each other. Means are provided at least partially in the outlet end member for directing combustion products from at least a first of the conduits to at least a second of the conduits to initiate combustion of the propellant in the second conduit as the array rotates relative to the outlet end member.  
         [0005]     In one or more implementations, the outlet end member may be essentially fixed and the array may rotate. Alternatively, the array may be essentially fixed and the outlet end member may rotate. The means may include a passageway within the outlet end member. The outlet end member may further include an igniter. The outlet end member may further include means for introducing at least one of the start-up propellant and a supplemental propellant. The device may be used as a turbine engine combustor. The inlet valve may comprise an inlet end member non-rotating relative to the outlet end member.  
         [0006]     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  
       [0007]      FIG. 1  is a schematic side view of a gas turbine engine.  
         [0008]      FIG. 2  is a sectional view of a combustor of the engine of  FIG. 1 , taken along line  2 - 2 .  
         [0009]      FIG. 3  is a partially schematic unwrapped longitudinal circumferential sectional view of the combustor of the engine of  FIG. 1 . 
     
    
       [0010]     Like reference numbers and designations in the various drawings indicate like elements.  
       DETAILED DESCRIPTION  
       [0011]      FIG. 1  shows a gas turbine engine  20  having a central longitudinal axis  500 . From upstream to downstream, the exemplary engine  20  includes a fan section  22 , at least one compressor section  24 , a pulse combustion combustor section  26 , and a turbine section  28 . The exemplary combustor  26  includes a circumferential array of longitudinally-extending conduits  30  ( FIG. 2 ) mounted within an engine case  32  for rotation about the axis  500  (e.g., supported on a carousel structure  34  which may be on one of the compressor/turbine spools or a separate free spool).  
         [0012]      FIG. 3  shows further details of the exemplary combustor  26  during steady-state operation. The exemplary combustor array includes eighteen combustor conduits  30  (shown for illustration as straight circular sectioned tubes oriented longitudinally). Alternative cross-sections including annular sectors are possible, as are non-longitudinal orientations and non-straight configurations. The direction of rotation is labeled as  506 . Positions of the tubes at an exemplary point in the cycle are respectively designated as  30 A- 30 R. Each exemplary tube  30  has an upstream inlet  36  and a downstream outlet  38 . For ease of reference, the tubes will be identified by the reference numerals associated with the illustrated positions. At the illustrated instance in time, a last bit of a purge flow  50  of combustion products is exiting the outlet  38  of the tube  30 A. A slug of a buffer gas  52  is in a downstream end portion of the tube  30 A following right behind the purge flow  50 . A propellant charge  54  follows behind the buffer slug  52 , being delivered by a propellant fill flow  56  through the inlet  36 . An exemplary propellant flow includes a gaseous oxidizer (e.g., air) and a fuel (e.g., a gaseous or liquid hydrocarbon). In the exemplary turbine engine embodiment, the air may be delivered from the compressor  24  and the fuel may be introduced by fuel injectors (not shown).  
         [0013]     At the illustrated point in time, the next tube  30 B has just had its outlet closed by passing in front of an upstream face  58  of a relatively non-rotating combustor downstream member  60 . At the point of closure/occlusion, some or all of the buffer slug  52  may have exited the tube outlet. The buffer slug  52  serves to prevent premature ignition of the charge  54  due to contact with the combustion gases. The closure of the outlet port causes a compression wave  62  to be sent in a forward/upstream direction  510  through the charge  54  leaving a compressed portion  63  of said charge in its wake.  
         [0014]     This compression process continues through the position approximately shown for tube  30 C. At some subsequent point (e.g., as shown for the tube  30 D) the tube outlet becomes exposed to a port  64  in the member  60 . The port  64  is an outlet port for a passageway  66 . The passageway  66  has an inlet port  68 . The inlet port  68  is positioned to be open/exposed to the outlet of one or more tubes in a later position (e.g., approximately the position shown for tube  30 G). As is discussed in further detail below, by the time a tube has reached this later position, combustion is already occurring. Accordingly, a flow  70  of combustion products  71  from such tube may pass through the passageway  66  from the inlet port  68 . When these hot combustion products exit the outlet port  64 , they come into contact with the compressed portion  63  of the charge  54  behind the compression wave  62 . The hot combustion products produce combustion of the compressed charge  63  causing detonation and sending a detonation wave  72  forward/upstream after the compression wave  62  (e.g., as shown for tubes  30 E,  30 F, and  30 G). The newly-formed combustion products  71  are left in the wake of the detonating wave.  
         [0015]     In the exemplary engine, the member  60  includes a blocking wall portion  74  between the passageway inlet  68  and outlet  64 . This helps prevent combustion gases from leaking from the tube outlets as the tubes pass between the passageway outlet  64  and the passageway inlet  68 . This blockage also helps direct the detonation wave  72 .  
         [0016]     A surface  80  of a main portion of a relatively non-rotating combustor upstream member  82  is positioned to block the tube inlets during a main portion of the combustion process. In the exemplary implementation, the surface  80  (a downstream face) is positioned to block the inlets  36  to prevent upstream expulsion of the charge  54  as the compression wave  62  approaches. The surface  80  is also positioned to prevent upstream discharge of combustion products during a high pressure interval thereafter. An exemplary circumferential extent of the surface  80  is between 40° and 160° (more narrowly, 90° and 120°).  
         [0017]     In the exemplary combustor, there is a brief interval shown for the tube  30 H wherein both its inlet and outlet are blocked after the outlet has passed out of exposure to the passageway inlet  68 . Alternative configurations may lack this interval. Shortly thereafter (e.g., as shown for the tube  30 I) the tube outlet clears the surface  58  and is thus opened. A blow down flow  84  of high pressure combustion gases then exits the tube outlet. This blow down interval may continue (e.g., for the tubes shown as  30 J,  30 K, and  30 L).  
         [0018]     After the blow down interval, there may be a buffer filling interval wherein an inlet buffer flow  90  generates the buffer slug  52  upstream of the combustion gases  71 . The exemplary flow  90  may be of unfueled air. In the exemplary combustor, this flow  90  is isolated from the flow  56  by a narrow segment  92  of the upstream member  82  (thereby defining a port through which the flow  90  passes). Alternative configurations could lack such a segment  92  and rely on injector positioning to keep the flow  90  relatively unfueled. Thereafter, through several further stages (e.g., for tubes  30 M,  30 N,  30 O,  30 P,  30 Q,  30 R, and finally returning to  30 A) the tube may be recharged with propellant.  
         [0019]     At start-up, engine spool rotation may be commenced by conventional pneumatic or electric drive. The start-up condition may lack the flow  70 . Accordingly, additional start-up means may be provided. In one example,  FIG. 3  shows fuel and oxidizer lines  100  and  102  extending to the passageway  66  and controlled by valves  104  and  106 . These lines  100  and  102  may be used to introduce start-up amounts of fuel and oxidizer to the passageway which, in turn, are ignited by an igniter  108  (e.g., a spark igniter) to provide a start-up flow of combustion products.  
         [0020]     The fuel and oxidizer lines  100  and  102  (or other separate lines) may also be used to introduce supplemental amounts of fuel and/or oxidizer during steady-state operations and/or transient conditions. Depending on circumstances, such supplemental quantities may be lean, rich, or stoichiometric.  
         [0021]     Operation of the exemplary combustor may tend to be self-timing. However, additional timing control may be provided. For example, means may be provided to change the relative phases of the downstream and upstream members  60  and  82  (e.g., by shifting their orientational phase about the axis  500 ). Alternatively, means may be provided for varying the attributes of either of these members individually. For example, there may be multiple passageways in the downstream member  60  or a single passageway may have multiple outlets or inlets which may be selectively opened or closed individually or in combinations. Similarly, the circumferential extent of blocking provided by the upstream member  82  might be made adjustable as might be the circumferential extents and positionings of the respective fueled and unfueled flows  56  and  90 .  
         [0022]     In alternative embodiments, the tube array may be fixed and at least the downstream member may be rotating. An upstream member rotating synchronously with the downstream member will provide a similar operation as discussed above for  FIG. 3 . However, the valving interaction of the upstream member with the tubes could easily be replaced with discrete valves at the inlet ends of each tube. Such discrete valves would provide greater flexibility in timing control of the combustion process.  
         [0023]     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, even with the basic construction illustrated, many parameters may be utilized to influence performance. Accordingly, other embodiments are within the scope of the following claims.