In the maps for compressor, turbine and derived components (e.g. the fan), the beta parameter is used to avoid numerical convergence problems during iterations towards the operating point solutions. With the typical relations between corrected mass flow and pressure ratio for constant rotational speed for these turbo-machinery components, either one of the variables can become independent of the other. For example, the constant speed curve in a compressor map can be nearly horizontal or nearly vertical. This causes numerical problems, since for one rotor speed and pressure ratio, multiple values for mass flow are possible. To avoid these numerical problems, the beta parameter is added, representing a relation between pressure ratio and corrected mass flow for which constant beta lines or curves are virtually perpendicular to the constant corrected speed curves in the map graph. Beta values are equidistant, ranging between 0 and 1. The beta parameter is also used in GasTurb [1].
Beta parameter
