IECM 12.0 beta User Manual > Modules Included with the IECM > Natural Gas Combined Cycle (NGCC) Plant > SET PARAMETERS > Power Block >

Gas Turbine Perfornamce

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Inputs for the performance of the gas turbine are entered on the Gas Turbine Performance parameter screen . This screen is available for both the NGCC and IGCC plant types. The following parameters are available:

•Gas Turbine/Generator:

•Gas Turbine Model: This is a selection of the type of turbine model used. The type determines the inlet temperature, pressure ratio, and size parameters. The following options are available:

•GE 7FA: This is an older model found in many already constructed NGCC plants.

•GE 7FB: (This is the default.) This is an advanced turbine that has a higher inlet temperature, pressure ratio, and adiabatic efficiency, which result in a lower net heat rate.

•No. of Gas Turbines: This is the number of gas turbines. Since each turbine is able to produce a fixed output, the number of turbines will determine the plant size (e.g., gross plant size).

•Total Gas Turbine Output: This parameter is provided for reference purposes only. It provides the gross power generated from the gas turbines alone.

•Fuel Gas Moisture Content: (Only shown for IGCC) Steam is typically added to the fuel gas prior to being combusted. This increases the volume of the fuel gas and results in a higher power output in the gas turbine.

•Turbine Inlet Temperature: The turbine inlet temperature is carefully controlled to prevent damage or fatigue of the first stage stator and rotor blades. This temperature is one of the two most important parameters that impacts system efficiency.

•Turbine Back Pressure: The turbine exit pressure must be higher than atmospheric pressure to provide a positive pressure on the flue gas exiting the turbine.

•Adiabatic Turbine Efficiency: The adiabatic turbine efficiency adjusts for inefficiencies in real turbines. The ratio is an estimate of real to ideal performance.

•Shaft/Generator Efficiency: The combined shaft/generator efficiency adjusts for inefficiencies in generator and shaft between the compressor and the generator. The ratio is an estimate of real to ideal performance.

•Air Compressor:

•Pressure Ratio (outlet/inlet): This is the ratio of the compressor exit pressure to the inlet ambient air pressure. Compression takes place approximately adiabatically.

•Adiabatic Compressor Efficiency: The adiabatic compressor efficiency adjusts for inefficiencies in real compressors. The ratio is an estimate of real to ideal performance.

•Combustor:

•Combustor Inlet Pressure: The combustor inlet pressure is currently fixed at a single value. It is provided for reference purposes only.

•Combustor Pressure Drop: Although the combustor operates at essentially constant pressure, a small pressure drop is typically observed in the combustor exit from the compressor exit.

•Excess Air For Combustor: This is the excess theoretical air used for combustion. It is added to the stoichiometric air requirement calculated by the model. This value is based on the required mass flow rate of syngas through the combustor, the heat content of the syngas, and the flame temperature of the combustor.