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This non-provisional patent application is based on provisional patent application Ser. No. 60/840,786 filed on Oct. 28, 2006.
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.
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.
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.
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:
FIG. 1 is a top plan view, shown in partial phantom lines, illustrating the heat regenerative mini-turbine generator of the present invention;
FIG. 2 is a side elevational view, in partial cross-section, showing the main component parts of the heat regenerative mini-turbine generator; and
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.
Like reference numerals refer to like parts throughout the several views of the drawings.
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.
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.
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.
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.
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.
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.
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.
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.