Enumeration to define polynomial models for calculating isentropic efficiency
type IsentropicPolynomialModels = enumeration(DarrAndCrawford1992 "DarrAndCrawford1992 - Function of rotational speed and densities", Karlsson2007 "Karlsson2007 - Function of pressure ratio and rotational speed", Engelpracht2017 "Engelpracht2017 - Function of pressure ratio and rotational speed");