The conventional feedwater pump turbine is selected based on the unit maximum continuous output condition

so the efficiency of feedwater pump turbine will be much lower when the unit runs under and below THA condition. In order to improve the efficiency of the feedwater pump turbine

the optimization on selection of the feedwater pump turbine was carried out. According to the principle that the supplementary steam can increase the turbine output

taking the turbine output under THA condition as the type selection criteria for the feedwater pump turbine

higher output can be realized by opening the supplementary steam

thus it is possible to improve the operating efficiency of the feedwater pump turbine under and below THA condition. Combining with the actual case of type selection of feedwater pump turbine for a double-reheat unit

the parameters of the feedwater pump turbine before and after optimization were calculated to investigate the steam consumption of the feedwater pump turbine under different conditions and its influence on the unit heat consumptions. The results show that

after type optimization

under THA

75%THA and 50%THA conditions

the inlet mass flow of the feedwater pump turbine decreased by 1.9

1.2

0.8 t/h

separately

and the unit heat rate decreased by 3.08

3.42 and 3.62 k J/(k W·h) respectively. This optimization method for feedwater pump turbine's type selection can be applied in ultrasupercritical double-reheat units.