2. Steam expands in a two-stage adiabatic turbine (composed of a low pressure (LPT) and high
pressure turbine (HPT)) from a specified state to specified pressure shown below. Some (10%)
steam is extracted at the exit of the HPT and the remainder is piped (isobarically and
adiabatically) to the LPT and expanded. If the HPT inlet flow is 10kg/s, determine the total or
combined power output of the turbine for:
a) 100% LPT and HPT isentropic efficiencies. Ans. 10.86MW
b) 88% LPT and HPT isentropic efficiencies. Ans. 9.73MW
Your schematic must include a device diagram with state labels and corresponding T-s
diagram!
6 MPa
500°C
STEAM (HPT)
10 kg/s
1.2 MPa
STEAM (LPT)
9 kg/s
20 kPa
90%
10%
Hint: Note that $W_{Combined} = W_{LPT} + W_{HPT}$. Also, the mass-flow rates are not the same for each turbine,
thus, take care when calculating LPT and HPT powers!