Turbine and Compressor Cascade Flow Forces

The last chapter was dedicated to the energy transfer within turbomachinery stages. The stage mechanical energy production or consumption in turbines and compressors were treated from a unified point of view by introducing a set of dimensionless parameters. As shown in Chapter 4, the mechanical energy, and therefore the stage power, is the result of the scalar product between the moment of momentum acting on the rotor and the angular velocity. The moment of momentum in turn was brought about by the forces acting on rotor blades. The blade forces are obtained by applying the conservation equation of linear momentum to the turbine or compressor cascade under investigation. In this chapter, we first assume an inviscid flow for which we establish the relationship between the

lift force

and

circulation

. Then, we consider the viscosity effect that causes friction or drag forces on the blading.