Question

The rotor of a kaplan turbine is 2.8m in dia. at the blade tips and 0.9m at the hub. Its speed of rotation is 110r/min. Water enters the rotor without shock, making an angle of 37° to the axial direction at the mean dia and rotor has a blade exit angle of 58° to the axial direction at the mean diameter. The available pressure head is 6.5m .Determine 1) the inlet angle of the rotor blades at the mean dia. 2) the hydraulic efficiency and 3) the maximum mechanical power developed if the mechanical efficiency is 95%. make a neat drawing showing the layout and dimensions of the turbine and draw the inlet and exit velocity diagrams reasonably to scale

Answer 1

First we need to find out the absolute velocity from the given head. As the coefficient of velocity is not provided we will assume

   where

From velocity triangle the value of can be calculated by pythagoras theorem

Now blade angle at inlet is given by

...................(1)

velocity for mean diameter

2) Hydraulic efficiency

..............................(2)

= 73.33%

3) MAx mechanical power