Uniform Conversions of Operating Points and Characteristics of   Compressor
  In the paper, some aspects of the polytropic analysis are developed that concerned with various processes changing the thermodynamic state of flow of a real fluid and with reduction of these processes to processes having a given temperature and pressure of a given real mixture at the inlet. It is shown that all parameters of the process can be converted under condition of full similarity of flow that is formulated in the paper. An operating point of a compressor represents such process. It is to emphasize that parameters of the reduced point include not only volume flow, speed and polytropic head, for which a requirement of similarity of flow at inlet is sufficient, but also polytropic exponent, polytropic efficiency, outlet pressure and outlet temperature. This allows a conversion of all compressor characteristics. A method for that is described. 
L. A. Ostromuhov
physics.flu-dyn cond-mat.stat-mech