Abstract:
A compact, lightweight steam turbine is connected to a central shaft that drives a high pressure pump, a high efficiency generator and a blower. An igniter burns fuel exiting a fuel injector to generate heat in a cyclone combustion chamber. Water pumped through coils is heated in the combustion chamber to produce steam energy to drive the turbine. Exhaust steam is directed through a centrifugal condenser having an arrangement of flat plates to condense the steam to a liquid state. The turbine drives the generator at a high rpm, through the connected shaft, to generate electric power.

Description:
BACKGROUND OF THE INVENTION  
       [0001]    This non-provisional patent application is based on provisional patent application Ser. No. 60/840,786 filed on Oct. 28, 2006. 
     
     DISCUSSION OF THE RELATED ART  
       [0002]    Portable generators for producing electricity are typically powered by combustion engines fueled by gasoline or diesel. Combustion engine powered portable generators are known to be noisy (i.e. loud) and are not fuel efficient. For this reason, portable generators powered by combustion engines are primarily used for emergency power situations when more efficient conventional power sources are unavailable. Additionally, gasoline and diesel powered combustion engines are considerably heavy and bulky. This adds to the overall size and weight of portable generators, making them difficult to transport when used in mobile field operations. 
         [0003]    Accordingly, there remains an urgent need for a fuel efficient portable generator that is relatively quiet, compact in size, lightweight and easy to transport. Further, there is a need for a portable, fuel efficient generator that operates on multiple fuel types, including a mixture of different fuel types. Finally, there is a need for a portable, fuel efficient generator that uses heat regeneration for greater efficiency. 
       SUMMARY OF THE INVENTION  
       [0004]    The present invention provides a heat regenerative mini-turbine generator in a compact, lightweight unit. The unit includes a steam turbine connected to a central shaft that drives a high pressure pump, a high efficiency generator and a blower. An igniter burns fuel exiting a fuel injector to generate heat in a cyclone combustion chamber. Water pumped through coils is heated in the combustion chamber to produce steam energy to drive the turbine. Exhaust steam is directed through a centrifugal condenser having an arrangement of flat plates to condense the steam to a liquid state. The turbine drives the generator, through the connected shaft, to generate electric power. It is necessary to drive the generator at a high rpm to achieve the lightweight and small size. However, it is known that turbines in small sizes have poor efficiency. The use of heat regeneration helps this deficiency. The turbine heat exchanger, condenser and re-heaters are all contained in one small package. The unit is water lubricated and operates in a closed loop system. According to several preferred embodiments, the generator unit operates in a compact envelope at weight of approximately 10-25 lbs. The unit size can be scaled up or down to accommodate different power output requirements. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0005]    For a fuller understanding of the nature of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0006]      FIG. 1  is a top plan view, shown in partial phantom lines, illustrating the heat regenerative mini-turbine generator of the present invention; 
           [0007]      FIG. 2  is a side elevational view, in partial cross-section, showing the main component parts of the heat regenerative mini-turbine generator; and 
           [0008]      FIG. 3  is an isolated view of a steam ejector nozzle fitted to a turbine housing for ejecting a pressurized flow of steam against a cupped perimeter of a turbine wheel to forcibly drive rotation of the turbine wheel and a central shaft. 
       
    
    
       [0009]    Like reference numerals refer to like parts throughout the several views of the drawings. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0010]    Referring to the several views of the drawings, and initially  FIG. 2 , the heat regenerative mini-turbine generator is shown and is generally indicated a  10 . 
         [0011]    The generator  10  is supported on a base  12  that may include feet  14  on the bottom for supported engagement on a floor, ground or counter surface. A fuel tank  16  rests on the top of the base. In a preferred embodiment, the fuel tank  16  is circular (i.e. donut shaped) to provide an open central area above the base that accommodates a centrifugal blower  22  and an alternator  20 . A fill spout  18  with a cap  19  extends upwardly from the fuel tank to facilitate refilling of fuel. 
         [0012]    A condenser chamber  30  sits above the fuel tank  16  and alternator  20  and contains a centrifugal condenser  32  and a condensate collection pan  36  at the bottom of the condenser chamber. The centrifugal condenser has a spaced arrangement of condenser plates  34  that present a large surface area for maximizing heat transfer within a relatively compact space. A sight gauge  38  on the exterior of the condenser chamber indicates a working fluid level (i.e. water level) within the condensate collection pan  36 . Water can be added through a fill spout  37  at the top of the site gauge by removing a pressure relief cap  39 . When a desired working fluid level is indicated in the sight gauge  38 , the pressure relief cap  39  is replaced on the fill spout  37 . 
         [0013]    A fuel pump  40  pulls fuel from the fuel tank  16  and directs a supply of fuel through hose  42  leading to fuel injector  44 . The fuel injector  44  directs a spray of fuel past an igniter  46  to burn the sprayed fuel. The burning fuel is directed into a cyclone combustion chamber  50  that surrounds a tube bundle  54 . An igniter coil  48  connects to the igniter  46  and is powered by a battery (not shown). The blower  22  directs air flow from air intake  58  on the base  12  of the generator through the condenser chamber  30 , about the exterior of the centrifugal condenser plates  34 . A portion of the air flow (approximately 20%) from the blower  22  is directed to air duct  60  leading to the cyclone combustion chamber  50 , thereby providing sufficient airflow to promote combustion of the fuel. The directed airflow into the cyclone combustion chamber  50  helps to circulate the heat around the circular combustion chamber so that hot gases from combustion circulate around and over the tube bundle  54 . The cyclone combustion chamber  50  is surrounded by an insulated wall structure, including an insulated cover  64  and an insulated central section  65  partially surrounding a turbine housing  70 . The turbine housing  70  is centrally positioned above the centrifugal condenser  32  and contains a turbine wheel  72 . The central shaft  76  is fixed to the center of the turbine wheel  72  and is supported on bearings  78 . The shaft  76  extends downwardly from the turbine wheel  72  and into driven engagement with the alternator  20  and blower  22  at the lower end. Rotation of the shaft  76  drives the blower  22 , the alternator  20  and a centrifugal water pump  80  in the bottom of the condensate collection pan  36 . The water pump  80  directs a flow of water to bypass governor  84 . At normal operating pressure, water flow is directed to heat exchanger  86  at the top of the centrifugal condenser  32  for pre-heating the water. From the heat exchanger  86 , the water flow is directed to a conduit  87  leading to a splitter valve  88  at the top center of the combustion chamber. The splitter valve  88  directs the water flow through the tube bundle  54  leading to multiple steam ejector nozzles  90 . In a preferred embodiment, the splitter valve splits into four separate tubes  92  in the tube bundle  54 , with each tube  92  leading to one of four steam ejector nozzles  90 . In the tube bundle  54 , within the cyclone combustion chamber  50 , the pre-heated water is heated to produce steam which is directed to each of the steam ejector nozzles  90 . The steam ejector nozzles  90  are fitted to the turbine housing  70  and are arranged at an optimal angle and position to direct the ejected steam into cup shaped members  73  about the periphery of the turbine wheel  72 . The force from the ejected steam drives the turbine wheel  72  to rotate the shaft  76 . When the turbine wheel RPMs get above normal operating speed (i.e. too high), the increasing pressure of water flow from the water pump  80  causes a valve member in the bypass governor  84  to be operated to a bypass position, causing water flow to bypass the normal passage  85  leading to the heat exchanger  86  and, instead, going to a conduit  94  leading to the turbine housing  70 . In the bypass position, the pressurized water flow is directed into the turbine housing and against the turbine wheel  72 , with the impinging force of the pressurized water flow against the flat face of the turbine wheel  72  having the effect of slowing the turbine wheel, and, thereby, slowing the RPMs to a normal operating speed. 
         [0014]    Air flow through the condenser chamber  30  from blower  22  is exhausted through cooling exhaust port  96 . Combustion gases within the cyclone combustion chamber are exhausted through exhaust port  98  on the top of the cover. 
         [0015]    An electric control panel  100  includes an ON/OFF switch  102  to start and stop operation of the generator. Upon initial start up, the ON/OFF switch  102  is operated to energize the alternator  20 . During startup, the alternator  20  is motorized, using power from the battery (not shown) to turn the shaft  76  and turbine wheel  72 . This allows for initial operation of the blower  22 , water pump  80  and fuel pump  40 . The fuel pump  40  then directs the fuel supply to the injector  44  and igniter  46  assembly to generate hot gases in the cyclone combustion chamber  50 , while the water pump  80  directs water flow to the tube bundle  54 . Once steam is produced, the turbine wheel  72  is driven by the ejected steam and the alternator  20  switches from start up mode to normal alternator operation. 
         [0016]    A voltage regulator  104  on the side of the unit connects to the alternator  20 . The voltage regulator  104  provides DC voltage at connection terminals  106 , 108 . 
         [0017]    While the present invention has been shown and described in accordance with a preferred and practical embodiment, it is recognized that departures from the instant disclosure are contemplated within the spirit and scope of the invention which, therefore, is not to be limited except as defined in the following claims, as interpreted under the doctrine of equivalence.