Gas Turbines CCYCLE
Gas Turbine Modeling
CCYCLE provides two methods for modeling gas turbines.
1. Performance Curves
2. Stage by Stage calculations
The performance is specified be defining the four parameters below, at a known design condition (typically ISO)
• Heat Rate
• Exhaust Flow
• Exhaust Temp
The "design" condition is defined by
• Inlet temperature
• Inlet Humidity
• Inlet Pressure
• Percent Load
• Inlet Pressure Drop
• Outlet Pressure Drop
• Injection Flows
• Bleed Flows
Correction data, for differences between the design condition and actual operating conditions are also specified in the form of either curves or constants:
Gas turbine performance curves can either be user supplied, or taken from a library of common engines using a menu shown below, or from engine data created and saved by the user.
Stage By Stage Calculations
Data describing the flow capacity and efficiency of the various sections of the compressor and turbine are supplied, or determined from a known design point. The partial heat balance diagram below shows a GT24 reheat gas turbine, with external cooling in once thru coolers, as well as internal cooling, modeled with 4 compressor sections and 4 turbine sections.
In modeling a gas turbine in the level of detail shown above, the following data is all that is typically needed
• <>Design Output
• <>Design Heat Rate
• <>Design Exhaust Flow
• <>Design Exhaust temperature
• <>Compressor Discharge Pressure
• <>A reasonable estimate of cooling and bypass flows
• <>An estimate of combustion chamber pressure drop
• <>Stage pressures of interest (where cooling flows originate and terminate, or where bleed flows are taken.)
CCYCLE will calculate "design point" gas turbine performance. The calculated performance (stage flows, temperatures, section efficiencies, etc.) gets saved as detailed inputs for accurate off-design predictions.
The firing control systems of the various manufacturers are modeled. These include:
• Firing Temp specified
• Exhaust Temp vs Compressor Inlet Temp specified
• Exhaust Temp vs Compressor Discharge Pressure specified
• Firing Temp is a function of (Exhaust Temp, Compressor Inlet Temp, and Pressure Ratio)
Gas Turbine Auxiliaries
A full range of gas turbine auxiliaries are supported. Among these are:
• Steam and water injection (up to 3 flows)
• Evaporative cooling
• Fuel heaters
• Inlet heating using steam (SHOWN BELOW) , hot water or compressor outlet air.
• Compressor bleeds
Steam Cooling System
CCYCLE supports modeling of steam cooled combustors (SHOWN BELOW) and turbine sections and external air coolers, including the kettle boiler type and the once through cooler type.