If the water flows parallel to the axis of the rotation of the shaft, the turbine is known as axial flow turbine. If the head at the inlet of the turbine is the sum of pressure energy and kinetic energy and during the flow of water through runner a part of pressure energy is converted into kinetic energy, the turbine is known as reaction turbine.
a) Hydraulic efficiency: It is defined as the ratio of power developed by the runner of a turbine (runner is a rotating part of a turbine and on the runner vanes are fixed) to the power supplied by the water at the inlet of the turbine. Power at the inlet is more and this power goes on decreasing as the water flows over the vanes of the turbine due to hydraulic losses as the vanes are not smooth.
b) Mechanical efficiency: the power developed by the runner of a turbine is transmitted at the shaft of the turbine. Due to mechanical losses, the power available at the shaft is less than the power developed by the runner. The ratio of power available at the shaft to the power developed by the runner is known as mechanical efficiency of the turbine.
c) Volumetric efficiency: the volume of the water striking the runner of a turbine is slightly less than the volume of the water supplied to the turbine. Some water is discharged to the tail race without striking the runner. ...