1 - Basic equations and dimensional analysis

Abstract

This chapter introduces an overall framework for the thermo-fluid dynamic design and performance analysis of turbomachines. Turbomachines are rotodynamic devices that are specifically designed to transfer energy to or from a so-called working fluid through the action of forces that are generated fluid-dynamically by a rotor. Fluid deflection in passing through the stator blade row is produced in Newtonian reaction to blade lift forces akin to those of an aerofoil. In the same manner, the rotor blades also generate lift forces that further modify the swirl distribution, thus, producing rotor torque and therefore, a demand for shaft input power. Whether it is a fan, pump, compressor or turbine, it is evident that the design and performance analysis of a turbomachine must invoke principles of mass flow continuity, steady flow energy transfer, and finally, momentum changes and their associated reaction forces. Two extremely important and useful fields of particular study have been introduced— namely, aerodynamics or hydrodynamics and dimensional analysis, because these provide an enormous range of helpful practical engineering tools, emerging from applications of the basic laws of thermo-fluid dynamics.