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QUESTION 7 [16] An inward flow vertical shaft reaction turbine with a specific speed of 150 (Nst US) (in units of rpm, kW and m) works under the following conditions: Net supply head : 60 m Rotational speed : 375 rpm. Runner external diameter 1 250 mm : 8.4 m/s : 7.2 m/s without whirl : 2.4 m/s Velocity of flow at runner entry Velocity of flow at exit of runner 2 Diffuser (Draft tube) exit velocity Pressure head at entrance to runner Pressure head at runner exit Mean height of runner entry surface : 28.8 m : -2.4 m : 1.8 m above tailrace level Mean height of runner at exit : 1.0 m above tailrace level : 90% Turbine hydraulic efficiency Turbine overall efficiency : 88% The entry angle of the runner blades, The loss of head in: (i) The volute casing and guide blades, (ii) The runner (iii) The draft tube ANDR 7.1 7.2 -anny (5) (5) (3) (3) Page 3 of 7