Wednesday, November 19, 2008

LM6000 Gas Turbine

The General Electric LM6000 gas turbine is a stationary gas turbine which is derived from the family CF6 jet engines. The aircraft version of the engine is called CF6-80C2 turbofan engine that is used to drive several types of commercial aircraft like the Boeing 740-400.

The LM6000 gas turbine was developed in 1992 by General Electrics, who was one of the first developers of the aeroderivative; a gas turbine designed first as a flight engine, then redesigned for industrial use. The following have been changed to convert the CF6-80C2 to the LM6000:

  • Front fan removed and inlet guide vanes added.

  • Low pressure compressor from the CF6-50/ LM used.

  • Front and rear frames adapted.

  • Output shafts added to the front of the low pressure compressor.

  • Bearing 7R added.

  • Balancing disk added to the low pressure turbine.

  • Hydraulic control system for the variable geometry added.
The LM6000 gas turbine is a dual-rotor, concentric drive shaft gas turbine, capable of driving a load from the front and rear of the low-pressure rotor. The main components consist of a variable inlet guide vanes assembly, a 5-stage low-pressure compressor, a 14-stage variable-geometry high-pressure compressor, an annular combustor, a 2-stage high-pressure turbine, a 5-stage low-pressure turbine, an accessory gear box assembly, and accessories.

The low-pressure rotor consists of the low-pressure compressor and the low-pressure turbine that drives it. Attachment flanges are provided on both the front and the rear of the the low-pressure rotor for connection to the packager-supplied power shaft and load. The high-pressure rotor is made up of the 14-stage high-pressure compressor and the 2-stage high-pressure turbine that drives it. The high and low-pressure turbines drive the high and low-pressure compressors through concentric drive shafts.

Air enters the gas turbine at the variable inlet guide vanes and passes into the low-pressure compressor. The low-pressure compressor compresses the air by a ratio of aproximately 2.4:1. Air leaving the low-pressure compressor is directed into the high-pressure compressor. Variable bypass valves are arranged in the flow passage between the two compressors to regulate the airflow entering the high-pressure compressor at idle and at low power. To further control the airflow, the high-pressure compressor is equipped with variable stator vanes.

High-pressure compressor compresses the air to a ratio of 12:1, resulting in a total compression ratio of 30:1, relative to ambient. From the high-pressure compressor the air is directed into the signal annular combustor section, where it mixes with the fuel from the 30 fuel nozzles. An igniter initially ignites the fuel-air mixture and, once combustion is self-sustaining, the igniter is turned off. The hot gas that results from the combustion is directed into high-pressure turbine that drives the high-pressure compressor. This gas further expands through the low-pressure turbine, which drives the low-pressure compressor and the output load.