A set of steam nozzles in an impulse turbine stage is supplied with steam at 20 kgf/ cm2 and 230° C. The mass flow rate of steam of 60 kg/s. The steam is expanded mass flow rate of steam is 60 kg/s. The steam is expanded from rest to a back pressure of 14 kg / cm2 with an efficiency of 98%. The mean diameter of the nozzle disc is 800mm and the nozzle angle is 20 degrees. Assuming that steam is admitted all around the periphery of the nozzle disc determine
(i) whether a convergent or a convergent-divergent nozzle is to be used,
(ii) the velocity of flow of steam at the exit of the nozzle,
(iii) the area of flow normal to the axis of the stage and
(iv) the height of the nozzles.
Assume adiabatic index for superheated steam to be 1.3. What would be the mass flow through the set of nozzles when the back pressure is reduced to 9 kgf/cm2 keeping the upstream conditions same as before.