Abstract:
In a turbine engine with an annular recuperator surrounding the turbine, exhaust gas is directed from the turbine to the recuperator by a generally curved exhaust dome. A vortex disrupter structure extends from the exhaust dome to a point distal of the turbine to evenly distribute the exhaust gas entering the recuperator and sustain diffusion of the exhaust gas to increase the expansion ratio across the turbine.

Description:
RELATED APPLICATIONS  
       [0001]    This application claims the priority of provisional patent application serial No. 60/245,488 filed Nov. 2, 2000. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    A turbogenerator electric power generation system is generally comprised of a compressor, a combustor including fuel injectors and an ignition source, a turbine, and an electrical generator. Often, the system includes a recuperator to preheat combustion air with waste heat from the turbine exhaust. A recuperator is most efficient if the mass flows through it are evenly distributed. A recuperator also reduces the expansion ratio of the turbine and thus the power extracted by the turbine. Therefore, what is needed is a turbine engine that promotes even mass distribution of the exhaust gas into the recuperator and maximizes the turbine expansion ratio.  
         SUMMARY OF THE INVENTION  
         [0003]    In one aspect, the present invention provides a turbine engine comprising a turbine rotationally driven by hot gas to exhaust the gas, a compressor rotationally coupled to the turbine to generate compressed air, an annular combustor for combusting fuel and the compressed air to generate the hot gas, the combustor extending coaxially away from the turbine to form a passage for the turbine exhaust gas therethrough, an annular recuperator surrounding the turbine for transferring heat from the turbine exhaust gas to the compressed air, a surface spaced from the combustor to direct the exhaust gas exiting from the passage into the recuperator, and an elongated structure extending from the surface into the passage toward the turbine to direct the exhaust gas flowing through the exhaust passage.  
           [0004]    In another aspect, the elongated structure is generally conical. In other aspects, the structure is spaced from the combustor to form an annular exhaust passage, wherein the exhaust passage may be configured to sustain diffusion of the exhaust gas flowing therethrough. The passage may also be configured for evenly distributing the exhaust gas entering the recuperator.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]    [0005]FIG. 1 is perspective view, partially in section, of a turbogenerator system according to the present invention;  
         [0006]    [0006]FIG. 2 is a simplified, partial sectional view of the turbogenerator system of FIG. 1 including a vortex disrupter according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0007]    Referring to FIG. 1, integrated turbogenerator system  12  generally includes generator  20 , power head  21 , combustor  22 , and recuperator (or heat exchanger)  23 . Power head  21  of turbogenerator  12  includes compressor  30 , turbine  31 , and common shaft  32 . Tie rod  33  to magnetic rotor  26  (which may be a permanent magnet) of generator  20  passes through bearing rotor  32 . Compressor  30  includes compressor impeller or wheel  34  that draws air flowing from an annular air flow passage in outer cylindrical sleeve  29  around stator  27  of the generator  20 . Turbine  31  includes turbine wheel or impeller  35  that receives hot exhaust gas flowing from combustor  22 . Combustor  22  receives preheated air from recuperator  23  and fuel through a plurality of fuel injectors  49 . Compressor wheel  34  and turbine wheel  35  are supported on common shaft or rotor  32  having radially extending air-flow bearing rotor thrust disk  36 . Common shaft  32  is rotatably supported by a single air-flow journal bearing within center bearing housing  37  while bearing rotor thrust disk  36  at the compressor end of common shaft  32  is rotatably supported by a bilateral air-flow thrust bearing.  
         [0008]    Generator  20  includes magnetic rotor or sleeve  26  rotatably supported within generator stator  27  by a pair of spaced journal bearings. Both rotor  26  and stator  27  may include permanent magnets. Air is drawn by the rotation of rotor  26  and travels between rotor  26  and stator  27  and further through an annular space formed radially outward of the stator to cool generator  20 . Inner sleeve  25  serves to separate the air expelled by rotor  26  from the air being drawn in by compressor  30 , thereby preventing preheated air from being drawn in by the compressor and adversely affecting the performance of the compressor (due to the lower density of preheated air as opposed to ambient-temperature air).  
         [0009]    In operation, air  110  is drawn through sleeve  29  by compressor  30 , compressed, and directed to flow into recuperator  23 . Recuperator  23  includes annular housing  40  with heat transfer section or core  41 , exhaust gas dome  42 , and combustor dome  43 . Heat from exhaust gas  110  exiting turbine  31  is used to preheat compressed air  100  flowing through recuperator  23  before it enters combustor  22 , where the preheated air is mixed with fuel and ignited such as by electrical spark, hot surface ignition, or catalyst. The fuel may also be premixed with all or a portion of the preheated air prior to injection into the combustor. The resulting combustion gas expands in turbine  31  to drive turbine impeller  35  and, through common shaft  32 , drive compressor  30  and rotor  26  of generator  20 . Expanded turbine exhaust gas  100  then exits turbine  31  and flows through recuperator  23  before being discharged from turbogenerator  12 .  
         [0010]    Referring to FIG. 2, combustor dome  43  is formed in a annular configuration to creating turbine exhaust gas passage  50 . Exhaust passage  50  channels expanded turbine exhaust gas and directs it to flow towards exhaust dome  42  disposed at the end of combustor dome  43  distal of turbine  31 . Exhaust dome  42  is formed with a generally semi-spherical configuration that directs exhaust gas to flow radially outward and reverse direction towards recuperator core  41 . To maximize the diffusion of exhaust gas and thus maximize the expansion ratio across turbine  31 , exhaust passage  50  is formed with a generally conical configuration that allows the exhaust gas to diffuse as it flows towards exhaust dome  42 .  
         [0011]    Exhaust gas exits turbine  31  at very high speed and with a rotational directional component due to the rotation of the turbine impeller  35 . Thus, the flow of exhaust gas resembles a vortex flow in which the primary or main flow travels along the outer annulus of passage  50  and the secondary flow travels in the center of passage  50  and is generally characterized as low energy or low velocity flow. In some cases the secondary flow can be in the reverse direction and travel back toward the turbine impeller. Most of the mass flow discharge from the turbine is contained in the primary flow. The primary flow in effect forms an acoustic cavity around the secondary flow. Due to the highly turbulent and unsteady nature of the flow, this acoustic cavity ca be excited to thereby create an acoustic resonance within the cavity created by the secondary flow.  
         [0012]    To facilitate the diffusion of the exhaust gas as it flows through passage  50 , one embodiment of the present invention provides exhaust vortex disrupter  200  disposed within exhaust passage  50 . Disrupter  200  is mounted to exhaust dome  42  and extends from the exhaust dome coaxially towards turbine  31  to terminate proximal to turbine impeller  35 . In the preferred embodiment illustrated, disrupter  200  is formed in a generally conical configuration that cooperates with combustor dome  43  to define passage  50  as an annular, generally conical passage for the exhaust gas. Disrupter  200  is configured and spaced from combustor dome  43  to displace the secondary core region of the flow in passage  50  and to promote a more even velocity distribution in the flow as well as sustained diffusion of the exhaust gas. A more even velocity distribution helps to reduce pressure losses created in passage  50 . By occupying the central volume of passage  50 , disrupter  200  guides the exhaust flow towards exhaust dome  42  with greater diffusion, lower pressure losses, and a consequent greater expansion ratio across the turbine and higher turbine power output.  
         [0013]    Furthermore, disrupter  200  continues to direct exhaust gas as it arrives at exhaust dome  42 , encouraging the gas to flow radially outward. In conventional systems, the exhaust gas would impinge generally perpendicularly upon exhaust dome  42  before being forced radially outward by the upstream exhaust gas that is being discharged by the turbine impeller. Furthermore, in conventional systems the effective flow area increases rapidly as the gas passage turns radially. The rapid area increase causes flow separation which prevents further diffusion. Additionally, the momentum of the flow tends to pull the flow off the wall of combustor dome  43  as the flow turns radially outward. This flow separation increases the pressure losses in passage  50  and promotes uneven velocity distribution as the exhaust gas flows towards the recuperator inlet. Thus, the base of disrupter  200  at which the disrupter is mounted to the exhaust dome is contoured with a generally conical surface to direct oncoming exhaust gas  100  radially outward and thus allow the exhaust gas to continue diffusing after it exits passage  50 . The contours of combustor dome  43  and exhaust dome  42  are designed to guide the flow radially outward through a smoothly varying cross-sectional flow area and thus prevent flow separation and promote continued diffusion through the passage.  
         [0014]    Disrupter  200  further acts to more evenly distribute exhaust gas as it exits passage  50  and is reversed by exhaust dome  42  to enter recuperator core  41 , thereby enhancing the heat transfer efficiency of the recuperator. Because exhaust dome  42  provides a stable platform onto which to mount disrupter  200 , there is no need for struts or similar structures to fasten and secure the disrupter. Avoiding the use of such struts is highly desirable because the struts cause pressure loss and noise. Noise is also reduced by the use of disrupter  200  because it displaces the potential acoustic cavity that may be created by the secondary flow downstream of the turbine and eliminates the noise associated with acoustic resonation of this cavity. An additional advantage of using disrupter  200  is that by enhancing the diffusion of exhaust gas  100 , passage  50  may be shortened and thus entire turbogenerator  12  may be constructed with a reduced footprint.  
         [0015]    Having now described the invention in accordance with the requirements of the patent statutes, those skilled in the art will understand how to make changes and modifications to the present invention to meet their specific requirements or conditions. Such changes and modifications may be made without departing from the scope and spirit of the invention, as defined and limited solely by the following claims.