Abstract:
A pulse detonation engine contains a mechanically driven timing device coupled with a stator device, where the timing device has both an opening portion and a blocking portion. The opening and blocking portions open and close air flow access to a detonation chamber of the pulse detonation engine at appropriate times during the pulse detonation cycle.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates to pulse detonation systems, and more particularly, to an inlet airflow management system for use on a pulse detonation engine for supersonic applications. 
         [0002]    With the recent development of pulse detonation combustors (PDCs) and engines (PDEs), various efforts have been underway to use PDC/Es in practical applications, such as combustors for aircraft engines. Just as with any normal air breathing engine, inlet stability is an important aspect of maintaining proper operation of a pulse detonation engine. This is particularly true in applications with multiple combustors with a common inlet, where it is important to minimize or eliminate disruptions to the inlet. Such disruptions include pressure fluctuations, which have the potential to “un-start” or stall the airflow through the inlet, compressor, or other upstream devices. 
         [0003]    These problems are particularly prevalent in pulse detonation engines which use open inlet tubes. During operation, PDE&#39;s create a high pressure detonation wave used for propulsion (as it exits the PDE). However, it has also been observed that a forward propagating pressure wave, which may contain fuel-air reaction products, is generated. Because the pulse detonation process is a high pressure rise process, these forward propagating pressure waves may provide enough perturbation to “un-start” the PDE inlet, as well as expose some of the upstream components to high pressure pulses, which could cause damage to these components. 
         [0004]    Thus, it is desirable to provide some means or methodology to block these forward propagating pressure waves. Some efforts have been made to accomplish this by using conventional air flow valves. However, because of the operational pressures and frequencies involved (which can be as high as 100 Hz), such devices have had limited or no success. 
         [0005]    Therefore, there exists a need to block any upstream pressure waves generated by a detonation, using a relatively simple and robust system. It is noted that although the expression “pulse detonation engine” is used herein, this term is intended to describe all combustion type devices employing pulse detonation technology, including but not limited to pulse detonation combustors, and the like. 
       SUMMARY OF THE INVENTION 
       [0006]    In an embodiment of the invention, a pulse detonation engine (PDE) comprises a mechanically driven timing rotor in a cone or device configuration. The cone (or device) configuration is designed with a specially designed slot or slots, and blockages to open and close the pulse detonation engine at the appropriate times during the pulse detonation cycle. 
         [0007]    At the upstream most portion of the pulse detonation engine (upstream of the detonation chamber), a valve timing device is made rotatable around a central axis. The device contains a blocking portion and a slot portion, and as the device is rotated the detonation chamber of the PDE is either closed or opened to the upstream portions of the system. The device may be coupled to a sprocket or sprocket coupled to a drive motor or device, or may be directly driven by the motor, to provide the necessary rotation. The rotational speed of the timing device can be adjustable to coincide with operational changes in the PDE. 
         [0008]    At the forward end of the PDE the valve timing device is mated with a stationary slotted geometry herein referred to as a stator device, which is open to detonation chamber of the PDE. The configuration and mating of the valve timing and stator devices are such that as the valve timing device is rotated the detonation chamber is opened and closed to the upstream portions of the system. 
         [0009]    The present invention also contains an embodiment where a plurality of pulse detonation engines are coupled to each other and the valve timing devices of each respective PDE are rotated together or separately. 
         [0010]    A further embodiment of the present invention, is one where a plurality of pulse detonation engines are coupled to each other and a single valve timing device rotates along the centerline of the plurality of PDEs. 
         [0011]    This invention is not limited to the configuration of one or a plurality of PDEs connected to a single timing device. Alternatively, a single timing device may be connected to each PDE and rotated together or separately. 
         [0012]    As used herein, a “pulse detonation combustor” PDC (also including PDEs) is understood to mean any device or system that produces both a pressure rise and velocity increase from a series of repeating detonations or quasi-detonations within the device. A “quasi-detonation” is a supersonic turbulent combustion process that produces a pressure rise and velocity increase higher than the pressure rise and velocity increase produced by a deflagration wave. Embodiments of PDCs (and PDEs) include a means of igniting a fuelloxidizer mixture, for example a fuel/air mixture, and a detonation chamber, in which pressure wave fronts initiated by the ignition process coalesce to produce a detonation wave. Each detonation or quasi-detonation is initiated either by external ignition, such as spark discharge or laser pulse, or by gas dynamic processes, such as shock focusing, auto ignition or by another detonation (i.e. cross-fire). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The advantages, nature and various additional features of the invention will appear more fully upon consideration of the illustrative embodiment of the invention which is schematically set forth in the figures, in which: 
           [0014]      FIG. 1  shows a diagrammatical representation of a plurality of pulse detonation engines and a valve control device in accordance with an embodiment of the present invention; 
           [0015]      FIG. 2  shows a diagrammatical representation of a valve timing device in accordance with the embodiment of the present invention shown in  FIG. 1 ; 
           [0016]      FIG. 3  shows a diagrammatical representation of a stator device in accordance with the embodiment of the present invention shown in  FIG. 1 ; 
           [0017]      FIG. 4  shows a diagrammatical representation of a timing method used for the embodiment of the present invention shown in  FIG. 1 ; 
           [0018]      FIG. 5  shows a diagrammatical representation of the embodiment shown in  FIG. 1 , during operation; 
           [0019]      FIG. 6  shows a diagrammatical representation of a plurality of pulse detonation engines and a valve control timing device in accordance with an additional embodiment of the present invention; 
           [0020]      FIG. 7  shows a diagrammatical representation of a valve timing device in accordance with the embodiment shown in  FIG. 6 ; 
           [0021]      FIG. 8  shows a diagrammatical representation of a stator device in accordance with the embodiment shown in  FIG. 6 ; and 
           [0022]      FIG. 9  shows a graphical representation of the timing of air flow through the PDE that is controlled by the components of the present invention as it relates to a single detonation cycle. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    The present invention will be explained in further detail by making reference to the accompanying drawings, which do not limit the scope of the invention in any way. 
         [0024]    As used herein, the term “air” is to include any all oxidizers, including but not limited to air, that can be used as a fuel oxidizer. 
         [0025]      FIG. 1  depicts an assembly  100  of a plurality of pulse detonation engines  10  in accordance with the present invention. Each of the engines  10  have a detonation chamber  12  which is downstream of the inlet portion  14  of the engine  10 . The inlet portion  14  of each of the engines  10  contains a valve timing device  16 , a stator device  18 , and a mounting bracket  20 . Further, each of the valve timing devices  16  contain a shaft  22  and a sprocket  24 . 
         [0026]    Each of the stator devices  18  contain an open portion  26  which allows air flow to enter the stator devices  18  and valve timing devices  16  during operation. Although not shown, it is contemplated that the assembly  100 , shown in  FIG. 1 , is positioned downstream of a compressor in a typical gas turbine engine configuration. Further, the upstream portion of the assembly  100  is coupled to an air flow manifold structure which provides air flow to the pulse detonation engines  10 . It is contemplated that each pulse detonation engine  10  is coupled to the compressor stage (not shown) through a separate manifold structure, or that all engines  10  share a common supply manifold. 
         [0027]    Each of the valve timing devices  16  are rotated via the shaft  22  which has a sprocket  24  on and end thereof. Further, as shown in  FIG. 1 , shafts  22  are supported by mounting brackets  20 . The present invention is not limited, in any way, with regard to the structure or configuration of the mounting brackets  20  depicted in  FIG. 1 . The mounting brackets  20  are to be secured to the engine structure by any known conventional means. 
         [0028]      FIG. 2  shows a valve timing device  16  in accordance with an embodiment of the present invention. The timing device  16  is coupled to a shaft  22  which is supported by the mounting bracket  20 . At the end of the shaft  22  is a sprocket  24 , In an exemplary embodiment of the present invention, the timing device contains a blocking portion  28  and a slot portion  30 . During operation, as the timing device  16  is rotated by the shaft  22 , the air flow from the compressor stage (not shown) enters the detonation chamber  12  when the slot portion  30  rotates to allow the air flow to enter the chamber  12 . Air flow is then blocked by the blocking portion  28 , when the blocking portion  28  rotates to block the air flow from entering the detonation chamber  12 . Such an operation avoids the need for having complicated air flow control equipment to control air flow from the compressor stage (not shown). In fact, air flow from the compressor stage can be maintained constant, resulting in relatively minor pressure rises as the blocking portion  28  blocks air flow from entering the detonation chambers  12 . These pressure rises are relatively small when compared to the pressure rises which may be experienced due to forward propagating pressure waves from the pulse detonation process. 
         [0029]    Although the use of a sprocket  24  is shown with respect to the above embodiment, the present invention is not limited in this regard. It is contemplated that any known and conventional means to impart rotation or movement may be used. 
         [0030]    Additionally, the present invention is not limited to having a single blocking portion  28  and slot portion  30  on the timing valve  16 . Specifically, it is contemplated that the timing valve  16  may have more than one blocking portions  28  (for example two) which are separated from each other by slot portions. Such a configuration will increase the overall frequency of operation while keeping the rotation rate the same. 
         [0031]    Moreover, although  FIG. 2  (and the following  FIG. 3 ) shows the openings to be essentially rectangular in shape, the present invention is not limited in this way. It is contemplated that the openings and/or blocking portion be tapered or angled (or have any other geometric shape) to optimize performance of the device. By tapering or angling the openings, the amount of air flow can be regulated or controlled depending on the desired characteristics and performance 
         [0032]      FIG. 3  shows a stator device  18  in accordance with an embodiment of the present invention. The forward most end of the stator device has an open portion  26  which allows air flow to enter the volume of the timing device  16  and stator device  18 . The size and shape of the open portion  26  is to control the amount of air flow to ensure the desired performance and operation. Further, the open portion  26  is to be of a sufficient size to allow the shaft  22  to pass through. The stator device  18  also has a wall portion  34  and a slot portion  32 . During operation, the air flow passes through the slot portion  32  into the detonation chamber  12 . In the assembly of the present invention, the timing device  16  rotates partially within the stator device  18 . In an alternative embodiment of the present invention, this may be reversed. 
         [0033]      FIG. 4  shows an embodiment of a valve timing mechanism for the inlet air management system of the present invention. The view in this figure is the forward most end view of the assembly  100 . Further, although six pulse detonation engines  10  are shown, the present invention is not limited to this number, and although they are shown in a symmetrical circular patter, again the present invention is not limited to this, as the engines  10  can be distributed in any pattern or configuration. 
         [0034]    In  FIG. 4 , the sprockets  24  are engaged with a belts  40 , where the belts are driven by motors  42 . As the motors  42  drive the belts  40 , each of the sprockets  24  are rotated, thus rotating the shafts  22  and the timing devices  16 . In this embodiment, the motors can be operated at different speeds so that the operational frequency of the respective engines  10  are different. Additionally, this embodiment allows some of the engines  10  to be operated while the others are not, depending on the operational parameters. Further, the motors  42  can operate at the same speed as each other so as to ensure that the operational frequency of all of the engines  10  is the same. 
         [0035]    In an alternative embodiment, all of the sprockets  24  are coupled to the same belt  40 . In this embodiment, all of the timing devices  16  are rotated at the same rate. It is also contemplated that the sprockets  24  can be made of various sizes so as to adjust the rotation rates of the respective timing devices. Namely, by using sprockets  24  of different sizes the respective rotational rates of the timing devices will be different even though the motor  42  is providing a constant speed. 
         [0036]    In a further alternative embodiment, at least one of the motors  42  is a variable speed motor, which allows the rotational speed of the timing devices  16  (driven by that motor) to be adjusted based on the operational requirements and parameters. 
         [0037]    Additionally it is noted that although this embodiment is shown with two motors  42 , it is contemplated that more than two motors  42  can be used, such that the motor to engine ratio is less than that shown in  FIG. 4 . 
         [0038]    In a further alternative to the present invention, each of the respective engines  10  is coupled to its own individual motor  42  and belt  40 . In this embodiment, each of the motors  42  can be operated at the same speed, or can be operated at varying speeds so as to provide for asynchronous operation of the engines  10 . 
         [0039]    Additionally, in this embodiment (as also in the embodiments discussed above) each of the engines  10  may have the same operational frequency (for example 100 Hz) but are configured such that they are not pulsing at the same time. This is accomplished by having the timing devices  16  of respective engines  10  having different starting orientations such that even though they share the same rotational rate as the other engines  10 , the engines  10  respective operations (i.e. pulse detonations) are not occurring simultaneously. Further, as with the previous embodiments, the motors  42  may be variable speed motors such that the operation of each respective engine  10  can be varied based on operational characteristics and parameters. 
         [0040]      FIG. 5  depicts a cross-section of an engine  10  in accordance with the embodiment of the present invention discussed with regard to  FIGS. 1 through 4 . As shown in this figure, the stator device  18  and timing device  16  are positioned off-center with respect to the centerline of the engine  10  and the detonation chamber  12 . This is done to allow for the efficient flow of air from the stator and timing devices into the chamber  12  based on the configuration of the devices shown in  FIGS. 2 and 3 . However, the present invention is not limited to this configuration and it is contemplated that additional embodiments of the stator and timing devices can be used which allows for similar operation. For example, it is contemplated that the respective opening portions of the timing and stator devices be on the downstream end wall of each of these components, such that the devices can be positioned on the centerline of the detonation chamber. In any event, the present invention is not limited by the physical structure of the devices or their relative positioning with regard to the detonation chamber. 
         [0041]    As shown in  FIG. 5 , as the shaft  22  rotates the timing device  16  rotates. This allows the open portion  30  of the timing device  16  to communicate with the open portion  32  of the stator device  18  as the rotation occurs. This permits the air flow F to pass from the devices to the detonation chamber  12 . Then as the blocking portion  28  of the timing device  16  passes by the opening  32  of the stator device  18 , the air flow F is temporarily blocked from entering the detonation chamber. 
         [0042]    The size of the respective open portions ( 30  of the timing device  16 , and  32  of the stator device  18 ) are determined to optimize operation of the engine  10 . For example, in an embodiment of the invention, the opening  30  of the timing device  16  should be sufficient to allow the air flow F to sufficiently form an air buffer with any residual post-detonation products within the chamber  12  and refill the chamber  12  with the necessary amount of air flow for the next detonation. 
         [0043]    Turning now to  FIGS. 6 ,  7  and  8 , an additional exemplary embodiment of the present invention is shown. As with  FIG. 1 , the assembly  200  includes a plurality of pulse detonation engines  10  which are configured in a similar fashion to that described with regard to  FIG. 1 . Because their respective structure is similar, a detailed discussion of the engines  10  will not be repeated at this point. In this embodiment, a single valve timing device  60  and a single stator device  62  are used for the plurality of engines  10 . 
         [0044]    In this embodiment, the stator device  62  is secured to the inlet portion of the engines  10 . The present invention is not limited by the means of securing the stator device  62  to the engines. Within the stator device  62  are a plurality of channels  70 , which are configured so as to communicate with the respective inlet portions of the engines  10 . This ensures that air flow will pass along the channels  70  to the respective engines  10 , for engine operation. The shape and geometry of the channels  70  are such that operational efficiency and performance are optimized. 
         [0045]    Within an opening  72  of the stator device  62  is a valve timing device  60 . The valve timing device  60  rotates about an axis which corresponds to a centerline of the assembly  200 . As shown in  FIG. 7 , the valve timing device  60  has a plurality of openings  64  which allow the air flow to pass through to the channels  70 , and ultimately the engines  10 , for operation. As shown, the openings  64  are separated by support struts  66 , which provide for structural integrity of the device  60 . The embodiment shown in  FIGS. 6 and 7  has three openings  64  and two support struts  66 . However, the present invention is not limited to this embodiment. Namely, an embodiment of the present invention can have a single opening, two openings, or more than three, to provide the necessary air flow to each of the engines  10 . Moreover, another embodiment of the present invention has openings which are positioned 180 degrees from each other on the device  60 . This embodiment allows for the simultaneous operation of engines  10  which are opposite each other, as the valve timing device  60  rotates. 
         [0046]    In  FIGS. 6 and 7 , the valve timing device  60  is conical in shape. However, the present invention is not limited to this geometry. Further, unlike the embodiment shown in  FIGS. 1 to 4 , in this embodiment the centerline of the valve timing device  60  and stator device  62  is coincident with the centerline of the assembly  200 . 
         [0047]    Further, the pulse detonation system may be fueled either upstream, downstream, or from within the valve timing or stator devices. 
         [0048]    The valve timing device  60  includes a drive connection portion  68  ( FIG. 7 ). In this embodiment, a motor (not shown) is either coupled directly or via a drive shaft or mechanism to impart rotation on the timing device  60 . Again, the motor is a variable speed motor to control the timing of the detonations and operation of the engines. In an alternative embodiment, the valve timing device may be driven by a belt or similar mechanism, as shown in  FIG. 4 . In this configuration, a flange (or similar structure) may extend from the upstream portion of the valve timing device  60 , such that a belt may provide the necessary rotation. 
         [0049]    A diagrammatical representation of this timing is shown in  FIG. 9 , For the purposes of simplicity the time is shown from 0 to 1, with no units (i.e. seconds, ms, etc.) The selection of 0 to 1 is intended to merely reflect a single cycle of the device. At time 0 the valve system opens. This is when the opening  30  of the timing device  16  begins communication with the opening  32  of the stator device  18 . As these openings communicate with each other, the air flow F begins to purge the detonation chamber  12  of the engine. At some point after T=0, the purge process ends and fuel is injected into the chamber  12  to mix with the air flow F. It is noted that the present invention is not limited in any way with respect to the fuel injection and/or spark initiation methodology used, as any known methods may be used and employed. 
         [0050]    At some point after fuel fill begins the blocking portion  28  of the timing device  16  blocks the opening  30  of the stator device  18  and the fuel injection ends. Although it is shown in this figure that the fuel injection ends after the air flow is blocked, the present invention is not limited to this embodiment. Following these events, and when the opening  32  of the stator device  18  is blocked the spark/detonation occurs. Thus, any forward propagating pressure wave is blocked from entering the devices (and going further upstream). Thus damage to any upstream components is avoided. 
         [0051]    In the embodiment discussed above, the opening  32  of the stator device  18  is completely blocked by the blocking portion  28  when detonation occurs. However, the present invention is not limited to this embodiment, and it is contemplated that the opening  32  be nearly closed when detonation begins and be fully closed when the main bulk of the forward propagating pressure wave reaches the devices. In any event, the timing of the operation, and the overall sizing of the components are selected to avoid the forward propagation of any significant or appreciable amount of any pressure wave generated from the detonation process. This will protect any upstream components from high pressure waves generated by the pulse detonation process 
         [0052]    It is noted that although the present invention has been discussed above specifically with respect to aircraft applications, the present invention is not limited to this and can be in any similar detonation/deflagration device in which the minimization of forward propagating pressure waves is desired. 
         [0053]    While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.