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. ...

Operating principles of common turbomachines

Introduction

Turbomachines or turbines are defined as the hydraulic machines which convert hydraulic machines into mechanical energy. This mechanical energy is used in running an electric generator which is directly coupled to the shaft of the turbine.

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.

Efficiencies of a 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. Thus, the ratio of the volume of water actually striking the runner to the volume of water supplied to the
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