Question $01-$ Previous Exams Pape

$1\mathrm{.}1$ A multi$-$stage axial flow turbine is to be designed with the impulse stage and is operated with an inlet pressure and temperature of $6$ bar and $900$ k and outlet pressure of $1$ bar. The isentropic efficiency of the turbine is $85\%.$ All the stages have a nozzle outlet angle of $75$ and equal inlet and outlet angles. The mean blade speed is $250\frac{m}{s},$ axial velocity is $150\frac{m}{s},$ and a constant is across the turbine.

$1\mathrm{.}1\mathrm{.}1$ Estimate the number of stages required for this turbine.