H. S. YANG ET AL.
Copyright © 2013 SciRes. EPE
The turbine choked back pressure result is shown in Ta-
ble 2 and Figure 3.
28 stages in the turbine, including 1 control stage and 9
pressure stages for the HP turbine, 6 pressure stages for
the IP turbine, and 2×6 pressure stages for the LP turbine.
The LP turbine last blade has a height of 939.8 mm. The
steam turbine is controlled by nozzles. The steam flow
into the four nozzle groups on the HP turbine is con-
trolled by the four mail control valves. The ACC system
is the mechanically drafted direct air-cooled system pro-
duced by the domestic manufacture.
Table 1. Main design data of the steam turbine.
Item Unit THA TRL
Unit Output kW 660.01660.00
Unit Heat Rate kJ/kWh 7778.318225.81
Main Steam Pressure MPa(a) 24.20 24.20
Hot Reheat Steam Pressur e MPa(a) 3.71 3.94
HP Turbine Exhaust Pr e ssure MPa(a) 4.12 4.38
Main Steam Temperature ℃ 566.00 566.00
Hot Reheat Steam Temperature ℃ 566.00 566.00
HP Turbine Exhaust Temperature ℃ 305.07 312.13
Main Steam Flow t/h 1878.422013.35
Reheat Steam Flow t/h 1600.901701.48
Turbine Back Pressure kPa 16 33
LP Turbine Exhaust Entha l py kJ/kg 2454.672550.0
LP Turbine Exhaust F l ow t/h 1254.781349.40
Makeup Water % 0 3
Final Feedwater Temperature ℃ 273 277.2
The main design data of the steam turbine is summa-
rized in Table 1.
3.1. The Calculation Result of the Steam
Turbines Choked Back Pressure
Based on the turbine last stage exhaust loss curve, the
turbine exhaust steam used energy end point enthalpy
and the exhaust loss and the final generator output are
calculated for various turbine back pressure operation
conditions. For each load condition, the turbine back
pressure corresponding to the maximum generator output
can be regarded as the turbine choked back pressure.
Using this method, the turbine choked back pressures
under different operation load conditions are calculated.
On Figure 2, the generator output change with the back
pressure is shown for various operation load conditions.
051015 20 25 3035 40
Turbine Back P re s sure (kP a )
Unit Output Relative Change (
Figure 2. Performance curves of the unit output with turbine back pressure.