A method and an apparatus for simulating the operation of a pressured air
source or sink such as a compressor or a turbine for a vehicle internal
combustion engine calculates momentum sources at interfaces in the
compressor or the turbine. A model stores steady state values of mass
flux and enthalpy change related to rotational speed, inlet pressure and
temperature and outlet pressure. The simulation can be an input to an
engine control module for controlling the operation of the vehicle engine
connected with the compressor or turbine.