Patent Application
20150315927
The invention relates generally to gas turbines and, more particularly, to a gas turbine including a heat exchange circuit utilizing cold energy for a coolant in a generator.
Gas turbines are widely used in commercial operations for power generation.
In an environment with hot ambient temperatures, the cooling water inlet to a generator can be higher than desired, thereby reducing the heat load and generator capability. For example, with high ambient temperatures around 55° C. (about 130° F.), the cooling water inlet to the generator will be 60° C. (about 140° F.), and the exit temperature will be about 65° C. (about 150° F.). Due to these high temperatures, the heat loads carried by the coolers are reduced, thereby reducing the capability of generators in the warmer climates. Even if the gas turbine is capable of producing higher output, due to reduced generator capability, the output may be limited.
It would be desirable to find a source of cold energy to reduce a temperature of the coolant in the generator.
In recent years, natural gas fuel prices have continued to increase dramatically, forcing combustion turbine power plants to explore alternatives to natural gas fuels. Many power plants are evaluating use of alternate fuels such as liquefied natural gas (LNG). The LNG is stored in a cylinder in liquid form at very low temperatures (e.g., about −260° F. to −160° F.) under pressure (about 400 psia). Also, in warm climates, gas turbine sites may be equipped with an inlet chiller to enhance performance during a hot day.
In an exemplary embodiment, a gas turbine includes a compressor, a combustor, a turbine, and a generator disposed upstream of the compressor. The gas turbine also includes a heat exchange circuit with a generator cooler circuit cooperable with the generator and circulating a coolant for cooling the generator, and with a water circuit circulating water in a heat exchange relationship with the generator cooler circuit. The coolant in the generator cooler circuit is cooled by the water in the water circuit.
In another exemplary embodiment, a heat exchange circuit is cooperable in a gas turbine and a generator. The heat exchange circuit includes a generator cooler circuit disposed upstream of the gas turbine compressor. The generator cooler circuit circulating a cooling medium to cool the generator. A cooling source containing fuel is coupled with a supply line that delivers the fuel to the one or more combustors. A water circuit circulating water includes a first section in a heat exchange relationship with the generator cooler circuit and a second section in a heat exchange relationship with a section of the supply line. The water in the water circuit is cooled by the fuel in the supply line, the cooling medium in the generator cooler circuit is cooled by the water in the water circuit, and the fuel is heated by the water in the water circuit. Subsequently, the supply line directs the heated fuel to the one or more combustors of the gas turbine.
In yet another exemplary embodiment, a gas turbine includes a compressor, a combustor receiving compressed air from the compressor, a turbine receiving combustion gases from the combustor, and a generator sharing a rotor with the turbine. A fuel source is in fluid communication with the combustor by a fuel supply line. The combustor injects fuel from the fuel source into the compressed air from the compressor and ignites the mixture to produce the combustion gases. The turbine also includes a heat exchange circuit with a generator cooler circuit disposed upstream of the compressor that circulates a cooling medium to cool the generator, and with a water circuit that circulates water. The water circuit includes a first section in a heat exchange relationship with the generator cooler circuit and a second section in a heat exchange relationship with a section of the fuel supply line. The water in the water circuit is cooled by the fuel in the supply line, the cooling medium in the generator cooler circuit is cooled by the water in the water circuit, and the fuel is heated by the water in the water circuit. The supply line subsequently directs the heated fuel to the combustor.
Both the LNG and condensate from the inlet chiller can be a source of cold energy for cooling. In
Cold energy in the embodiment shown in
A water circuit 24 circulates water and includes a first section or intercooler 26 in a heat exchange relationship with the generator cooler circuit 18 and a second section or fuel heater 28 in a heat exchange relationship with a section of the supply line 22. A pump 30 circulates water in the water circuit 24.
In use, the water in the water circuit 24 is cooled by the fuel in the supply line 22. The cooling medium in the generator cooler circuit 18 is cooled by the water in the water circuit 24. The fuel is heated by the water in the water circuit 24, and the supply line 22 directs the heated fuel to the one or more combustors 14 of the gas turbine 10.
Preferably, the fuel is LNG. The LNG is at a very low temperature (about −260° F. to −160° F.), depending on the pressure of the storage to keep it in a liquefied state. For power generation, the LNG is gasified by releasing the pressure, and the LNG is heated to a desirable temperature for combustion in the turbine combustor (about 80° F. to 120° F.)
Cooling generator performance can be enhanced by the exchange of cold energy from a cold energy source. In preferred embodiments, the cooled energy source may be LNG fuel or condensate from an inlet chiller.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
