Stationary genset power system having turbo-compounding

A stationary genset power may have a combustion engine configured to produce a mechanical output, and a main generator driven by the combustion engine to convert a majority portion of the mechanical output to electricity directed to an external load. The stationary genset power system may also have a turbine fluidly connected to the combustion engine, a compressor operatively driven by the turbine to compress combustion air directed to the combustion engine, and a secondary generator operatively driven by the turbine to produce electricity directed to the external load. The stationary genset power system may further have a controller in communication with the primary and second generators. The controller may be configured to synchronize an electrical power output of the secondary generator with an electrical power output of the primary generator prior to connection of the secondary generator to the external load.

TECHNICAL FIELD

The present disclosure relates generally to a generator set (genset) power system and, more particularly, to a stationary genset power system having turbo-compounding.

BACKGROUND

The primary purpose of a stationary generator set (genset) is to produce electrical power directed for external use. A genset typically includes a main generator coupled to and driven by a combustion engine. As a mixture of fuel and air is burned within the engine of the genset, a mechanical rotation is created that drives the main generator to produce electrical power. Power electronics associated with the main generator then condition the electrical power according to needs of an external load. Byproducts of the combustion process are exhausted to the environment.

An amount of mechanical power produced by the engine is directly related to an electricity output capacity of the genset. For this reason, gensets are often equipped with one or more turbochargers that are driven by exhaust to compress combustion air entering the engine. By forcing air into the engine, more air becomes available for combustion than could otherwise be drawn into the engine by motion of the engine's pistons. This increased supply of air allows for increased fueling, resulting in an increased mechanical power output and a corresponding increased electrically output of the generator. A turbocharged engine typically produces more mechanical power than the same engine without turbocharging.

Unfortunately, turbochargers do not remove all of the energy contained within an engine's exhaust prior to the exhaust being discharged to the atmosphere. Thus, upon discharge to the atmosphere, some amount of energy may be wasted in the form of heat and/or pressure. If this energy could be recuperated, efficiency of the genset may be improved.

An attempt to recuperate exhaust energy in a stationary genset application is disclosed in U.S. Pat. No. 7,047,743 (the '743 patent) issued to Stahlhut et al. on May 23, 2006. Specifically, the '743 patent discloses an engine/electric generator system having an internal combustion engine, and a primary electric generator driven by an output shaft of the engine to provide electrical power. The system also includes a turbocharger having a first turbine driven by exhaust gasses from the engine, and a compressor driven by the first turbine to provide inlet air to the engine. The system further includes a secondary turbine, and an exhaust line which communicates exhaust gas from the first turbine to an input of the secondary turbine. A secondary electric generator is driven by the secondary turbine. An electric power combining circuit combines electric power from the primary electric generator and the secondary electric generator, and delivers the combined electric power to a transmission line. In this manner, energy from the exhaust may be used to generate electric power through turbo-compounding.

Although the engine/electric generator system of the '743 patent may have improved efficiency, it may still be less than optimal. Specifically, the system of the '743 patent requires a dedicated secondary turbine located downstream of and inline with the primary turbine to drive the secondary generator. The dedicated secondary turbine and associated ducting may increase a cost and a size of the system, and require complex controls for proper speed regulation of the secondary generator.

The stationary genset power system of the present disclosure addresses one or more of the problems set forth above and/or other problems of the prior art.

SUMMARY

In one aspect, the present disclosure is directed toward a stationary genset power system. The stationary genset power system may include a combustion engine having an air inlet and an exhaust outlet and being configured to produce a mechanical output, and a main generator driven by the combustion engine to convert a majority portion of the mechanical output to electricity directed to an external load. The stationary genset power system may also include a turbine fluidly connected to the exhaust outlet of the combustion engine, a compressor operatively driven by the turbine to compress combustion air directed to the air inlet of the combustion engine, and a secondary generator operatively driven by the turbine to produce electricity directed to the external load. The stationary genset power system may further include a controller in communication with the primary and second generators. The controller may be configured to synchronize an electrical power output of the secondary generator with an electrical power output of the primary generator prior to connection of the secondary generator to the external load.

In another aspect, the present disclosure is directed toward another stationary genset power system. This stationary genset power system may include a combustion engine configured to produce a mechanical output, a high-voltage synchronous generator driven by the combustion engine to convert the mechanical output to electricity directed to an external load, and a turbocharger connected to receive exhaust from the combustion engine and to compress combustion air. The stationary genset power system may also include a low-voltage variable speed generator operatively driven by the turbocharger to produce electricity directed to the external load, and a controller in communication with the high-voltage synchronous and low-voltage variable speed generators. The controller may be configured to synchronize an electrical power output of the low-voltage variable speed generator with an electrical power output of the high-voltage synchronous generator prior to connection of the low-voltage variable speed generator to the external load.

In yet another aspect, the present disclosure is directed toward a method of producing power. The method may include combusting a mixture of fuel and air to produce a mechanical power output, converting a majority portion of the mechanical power output to a first electrical power output, and directing the first electrical power output to an external load. The method may also include converting energy from an exhaust flow resulting from the combusting of the mixture of fuel and air to mechanical power at a single location, utilizing a portion of the mechanical power to compress combustion air, and utilizing a remaining portion of the mechanical power to generate a second electrical power output. The method may further include synchronizing the second electrical power output with a first electrical power output, and directing the synchronized second electrical power output to the external load.

DETAILED DESCRIPTION

FIG. 1illustrates a power system10configured to supply electricity to an external load12. Power system10may embody, for example, a stationary land-based power plant. In the embodiment ofFIG. 1, external load12may include any device or devices that require uninterrupted electricity to perform one or more tasks, including, but not limited to, electric lights, consumer devices, and industrial drive motors. In some embodiments, external load12may require electric power in a particular form, such as three-phase alternating current having a frequency of 50 or 60 Hz. Power system10may include a generator set (genset)14operable to generate electricity in the required form, and a power-transmission network such as a common bus16for transferring electricity from genset14to external load12.

Genset14may include an engine18drivingly coupled to a generator20. Engine18may be any type of heat engine operable to produce mechanical power by combusting a mixture of air and fuel, including, for example, a diesel engine, a heavy fuel engine, a gasoline engine, and a gaseous fuel-powered engine. Engine18may include components that cooperate to direct combustion air into engine18and to exhaust combustion byproducts from engine18. For example, engine18may include at least one main turbocharger22having a compressors24connected to and driven by a turbine26. In one example, engine18may include only a single turbocharger22. Both compressor24and turbine26may be supported by a common driveshaft28.

Turbine26may be a fixed or variable geometry turbine having any number of volutes and being configured to receive exhaust from an exhaust outlet30of engine18. As the hot exhaust gases exiting engine18move through turbine26and expand against blades (not shown) therein, turbine26may rotate and drive the connected compressor24via driveshaft28to pressurize air directed into engine18via an air inlet32. In one embodiment, turbine26may be oversized relative to compressor24. That is, throughout an operational range of engine18, turbine26may provide a greater mechanical power output than consumed by compressor24to pressurize the air to desired levels.

The extra mechanical power output from turbine26(i.e., the mechanical output not consumed by compressor24) may be converted to electricity directed to external load12and/or to other on- or off-board auxiliary loads36. Specifically, power system10may include a secondary or auxiliary generator34. In one embodiment, auxiliary generator34may be a low-voltage (e.g., about 4,000 V or lower), variable speed generator operatively coupled to and driven by driveshaft28. In this manner, as driveshaft28is rotated by turbine26, auxiliary generator34may absorb and convert the extra mechanical power output to electricity directed to external load12and/or to auxiliary load36via an internal bus38. Auxiliary generator34may have an electricity production capacity of about 10-20% of the electricity production capacity of main generator20.

Generator20may be any type of power producing device mechanically coupled to receive power from engine18and to convert at least a portion of that mechanical power into electricity. In one embodiment, generator20may be the main generator configured to convert a majority portion of the mechanical power output of engine18to electricity. For example, generator20may embody a high-voltage (e.g., about 4,000 V or higher) AC synchronous generator having a rotor (not shown) directly coupled to a crankshaft21of engine18. In one embodiment, generator20may include multiple pairings of poles (not shown), each pairing having three phases arranged on a circumference of a stator (not shown) to produce an alternating current with a frequency of 50 or 60 Hz as the rotor is driven to rotate by the mechanical output of engine18.

Power system10may also include a synchronizing and load sharing controller40to regulate operation of power system10. Controller40may include commonly known components that cooperate to synchronize the electrical output of auxiliary generator34and main generator20, and to combine the output into a common supply of power directed to external load12and/or to auxiliary load36by way of common bus16. For example, controller40may include, among other things, a power electronics module42and a transformer module44connected between internal bus38and common bus16to selectively synchronize, condition, and/or connect the electrical output from one or both of auxiliary and main generators20,34to common and/or internal buses16,38. Controller40may further include commonly known sensing devices (not shown) required to receive input regarding monitored characteristics of electricity generated by each of main and auxiliary generators20,34such as a current, frequency, phase, and/or voltage. Additionally, controller40may receive information relating to an amount of power required by external load12and/or auxiliary load36. For example, controller40may receive information such as the current, frequency, phase, and/or voltage along one or more portions of common bus16and internal bus38, and/or the current, frequency, phase, and/or voltage in one or more components of external load12and/or auxiliary load36.

In some embodiments, additional components may be associated with controller40to enhance the functionality of auxiliary generator34and turbocharger22. Specifically, controller40may further include an energy storage module46and/or a braking resister module48. With these modules, controller40may effectively operate auxiliary generator34as a motor (i.e., auxiliary generator34may be a motor/generator) to drive turbocharger22to compress more air or to slow turbocharger22to compress less air. Specifically, in some circumstances, it may be possible that turbocharger22responds to a demand for increased boost pressure slower than desired. In these circumstances, power from energy storage module46and/or from main generator20may be directed to auxiliary generator34to thereby motor turbocharger22at an increased speed. In other circumstances, it may be possible that turbocharger22responds to a demand for decreased boost pressure slower than desired. In these circumstances, braking resistor module48may be used to quickly absorb power from auxiliary generator34, thereby adding braking torque to driveshaft28that helps to slow turbocharger22.

INDUSTRIAL APPLICABILITY

The disclosed power system may have application in stationary electric power generation, where efficiency may be a concern. The disclosed power system may improve efficiency by converting a portion of the naturally occurring exhaust heat and pressure to electricity that may be used to power an external load. During operation of the disclosed power system, electrical synchronizing and transforming may be performed to produce a common electrical power supply from a main high-voltage AC synchronous generator and an auxiliary low-voltage variable speed generator driven by an existing turbocharger used to compress combustion air. Because power system10may utilize a single existing turbocharger to provide both compressed air to engine18and to generate electricity, power system10may be compact and simple.

It will be apparent to those skilled in the art that various modifications and variations can be made in the disclosed power system and method without departing from the scope of the disclosure. Other embodiments of the disclosed power system will be apparent to those skilled in the art from consideration of the specification and practice of the power system and methods disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.