ROTODYNAMIC MACHINERY

QUESTION $2$

$[30$ MARKS$]$

The first stage of a turbine is a two$-$row velocity compounded wheel. The steam at $4000$ kpa $,$ and $400C$ is expanded in the nozzle to $1500$ kpa and has a velocity at the discharge of $700\frac{m}{s}.$ The inlet velocity to the stage is negligible. The relevant exit angles are the nozzle angle at $188$; the first$-$row blades at $21$; the inlet angle of fixed blades at $26\mathrm{.}5$; and the second$-$row blades at $35.$

Take the blade velocity coefficient for all blades as $0\mathrm{.}9.$ The mean diameter of the blading is $750$ mm $,$ and the turbine shaft speed is $3000re\frac{v}{m}in.$

Draw the velocity diagram for this wheel and Calculate:

$2\mathrm{.}1$ The diagram efficiency.

$2\mathrm{.}2$ The stage efficiency.l