Multi-factor optimization study on aerodynamic performance of low-pressure exhaust passage in steam turbines

The influence of multiple factors on low-pressure exhaust passages in a 600-MW steam turbine was investigated by orthogonal experiment. Numerical optimization of the exhaust-passage installed guide devices was performed according to the major factors. The compressible three-dimensional Navier-Stokes equations and standard k-ε turbulence model were solved by the CFX numerical simulator. The results show that the last-stage blades (LSBs), boiler feed-pump turbine, and steam-extraction pipeline as well as their interactions have some influence on the aerodynamic performance of the exhaust passage, in which the LSB is the most significant. This influence should be considered in the optimization. Installing guide devices in the condenser throat can reduce the fluctuation degree of the velocity at the condenser-throat outlet. Under a 100% turbine heat-acceptance condition, the total pressure drop in the exhaust passage increases by only 0.72%, whereas the static-pressure recovery coefficient is improved by 19.49%. In addition, the optimization can be applied to different loads, which can obviously improve the aerodynamic performance of an exhaust passage with small energy loss.