Prime-mover dynamo plants – Electric control
Reexamination Certificate
1999-07-15
2001-09-25
Waks, Joseph (Department: 2834)
Prime-mover dynamo plants
Electric control
C060S039010
Reexamination Certificate
active
06294842
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to microturbine power generating systems as defined herein. Specifically, the present invention relates to unique and non-obvious methods of increasing the efficiency of microturbines and for providing beneficial cooling to various microturbine components.
BACKGROUND OF THE INVENTION
The United States Electric Power Research Institute (EPRI) which is the uniform research facility for domestic electric utilities, predicts that up to 40% of all new generation could be provided by distributed generators by the year 2006. In many parts of the world, the lack of electric infrastructure (transmission and distribution lines) will greatly expedite the commercialization of distributed generation technologies since central plants not only cost more per kilowatt, but also must have expensive infrastructure installed to deliver the product to the consumer.
Relatively small, multi-fuel, modular distributed power generation units commonly called “microturbines” could help alleviate current afternoon brownouts and blackouts prevalent in many parts of the world. Microturbines are a new technology being developed to serve as auxiliary power units, on-site generators, and automotive power plants. Microturbines typically have a maximum power output of about one megawatt. “Turbogenerators” are microturbines, characterized by the following features: (a) a single, integral shaft on which a compressor, turbine and generator are located; (b) the compressor and turbine are of single stage, radial design; (c) the shaft rotates at speeds in excess of 35,000 rpm at full power; (d) an inverter may be used to reduce frequency to typical utility-grade operating parameters, typically 50 or 60 hertz; and (e) a recuperator or regenerator is normally used to bolster efficiency. Both turbogenerators and microturbines can be further characterized as having high power density, compact design and the ability to burn a wide variety of fuels in an external combustor. Some microturbines may be more complex and have features that deviate from the features that characterize a turbogenerator—for instance, they may use multiple shafts, a gear reduction box, and may have an axial flow turbine wheel. Regardless, microturbines may all be characterized in that they are relatively compact gas turbine power generators having no more than one expansion stage, either radial or axial flow, per shaft.
The single moving part concept of a one-shaft microturbine can enable low technical skill maintenance, and the projected low overall cost of such microturbines is expected to allow for widespread purchase in those parts of the world where capital is sparse. In addition, given the United States' emphasis on electric deregulation and the world trend in this direction, consumers of electricity would have not only the right to choose the correct method of electric service but also a new cost effective choice from which to chose. U.S. Pat. No. 4,754,607, which is assigned to the assignee of the present invention, discloses a microturbine power generating system suitable for cogeneration applications.
Yet to make these units commercially attractive to consumers, improvements are needed in areas such as increasing fuel-efficiency, reducing size and weight, and lowering thermal signature, noise, maintenance and cost penalties. For example, increasing the amount of work extracted by the turbine would increase efficiency of the system and lower the cost of generating electrical power.
SUMMARY OF THE INVENTION
The present invention can be regarded as a microturbine power generating system including a compressor for compressing intake air during system operation; a recuperator for adding heat to air leaving the compressor; a combustor for producing hot, expanding gases by igniting fuel and air leaving a cold side of the recuperator; a turbine for converting the hot, expanding gases leaving the combustor into mechanical energy; and a power converter for converting the mechanical energy produced by the turbine into electrical energy. The system further includes components and controls for increasing the system's efficiency and for providing beneficial cooling of various components. These additional components and controls are used to accomplish injection of micronized fluid droplets into the combustion air stream at various locations within the system at various rates and droplet sizes. Water, which is the preferred injection fluid, adds mass to the hot, expanding gases entering the turbine, thus increasing the amount of work extracted by the turbine. It also increases the efficiency of the recuperator, and, in one embodiment, has the additional benefit of cooling the generator components.
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Allied-Signal Inc.
Slusher Steve
Starr Ephaim
Waks Joseph
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