Tabular characteristics can be scaled in order to be able to use them for different gas turbines. If the parameter values of the map design point do not match those in the design point of the gas turbine to be modeled, scaling factors are determined during the design point calculation. These scaling factors are used to convert the input parameters to the map scale before the map data is accessed, and then to convert the map output parameters back to the gas turbine scale. For example, a compressor map with a nominal 100 kg/s mass flow and a pressure ratio PR of 5 can be used to represent a slightly larger but geometrically similar compressor with higher pressure ratio (e.g. 110 kg/s and PR = 6 results in scaling factors 1.1 and (6-1)/(5-1)=5/4 respectively). Scale factors for map output parameters such as isentropic efficiency are determined from the ratio of the user specified component design value (e.g. design efficiency) and the map efficiency in the map design point.
For small differences (<25%), scaling usually does not add large errors (i.e. deviations from actual component performance). Scaling for larger difference will introduce large error margins due to the changing Reynolds number.
Linear interpolation is used to obtain map parameter values from the tables. This requires attention to the resolution of the table parameter step size, especially with very non-linear relations. The SmoothC and SmoothT [6, 7] , and GasTurb [2] programs can be used to quickly increase map table resolution.
Note: The default GSP installation copies all model and map (*.map) files to the GSP projects directory. Map filenames paths are relative to the GSP directory. Therefore, when copying models and maps from one computer to another, an error may appear due to a change in path.
Component map scaling
