Answer Happy

EXAMPLE 9.3 In a vertical-shaft Francis turbine the available head at the inlet flange is 150 m of water and the vertical distance between the runner and the tailrace is 2.0 m. The runner tip speed is 35 m/s, the meridional velocity of the water through the runner is constant at 10.5 m/s, the flow leaves the runner without whirl and the velocity at exit from the draft tube is 3.5 m/s. The hydraulic losses for the turbine are as follows: AHN = 6.0 m, AHR = 10 m, AHDT = 1.0 m. Determine (i) the specific work, AW, and the hydraulic efficiency, nh, of the turbine; (ii) the absolute velocity, C2, at runner entry; (iii) the pressure head (relative to the tailrace) at inlet to and exit from the runner; (iv) the absolute and relative flow angles at runner inlet; (v) if the flow discharged by the turbine is 20 m³/s and the power specific speed is 0.8 (rad), the speed of rotation and diameter of the runner. Z Tailwater === C4 Draft tube FIGURE 9.16 Location of Draft Tube in Relation to Vertical Shaft Francis Turbine