Question

Why whirl velocity at inet of compressor zero?

Answer 1

The Francis turbine is a type of reaction turbine, a category of turbine in which the working fluid comes to the turbine under immense pressure and the energy is extracted by the turbine blades from the working fluid. A part of the energy is given up by the fluid because of pressure changes occurring in the blades of the turbine,
quantified by the expression of Degree of reaction , while the remaining part of the energy is extracted by the volute casing of the turbine. At the exit, water acts on the spinning cup-shaped runner features, leaving at low velocity and low swirl with very little kinetic or potential energy left. The turbine's exit tube is shaped to help
decelerate the water flow and recover the pressure.
If we study Ideal velocity diagram,in ideal cases the whirl component of outlet velocity is "zero "and the flow is completely axial.