The numerical simulation was performed with a non-equilibrium condensing flow model to investigate the influences of the redesigned last stage turbine on the aerodynamic performance of the last stage
and the overall aerodynamic performance and condensation characteristics of the low pressure cylinder of a 300 MW steam turbine. The computation for the isolated last stage turbine shows that the flow capacity
power output and efficiency are obviously improved
and the leaving velocity loss is clearly reduced after redesign. The analyses of the low pressure cylinder were conducted when the redesigned last stage turbine was placed in its right place in the multi-stage environment. The results show that the power output and efficiency of the low pressure cylinder rise by 0.53% and 0.47%
respectively. The improvement of the low pressure cylinder performance is attributed to the significant decrease in the leaving velocity loss. The redesign can affect the enthalpy drop in the penultimate stage turbine as well as the aerodynamic performance of the last stage turbine. The supercooling degree drops by 3-5 K in the spanwise direction
and the nucleation region and the nucleation rate also decrease in the final rotor passage. The change of the condensation characteristics of the rest stages due to the redesign can be neglected. These results imply that the last stage can be isolated from the multi-stage turbine and optimized separately in the redesign process of a low pressure cylinder.
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references
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