Aerodynamic optimisation of a low-pressure multistage turbine using the response-surface method

Steam turbine plays an important role in the power-generation industry. The power output of the low-pressure ( LP) cylinder accounts for about 50% of the total power output of a steam turbine. Therefore, improving the efficiency of the LP cylinder is important. The response-surface method is used in this work to optimise the seven-stage turbine in the LP cylinder of a 600 MW steam turbine. The LP cylinder's efficiency is chosen as the objective function and the samples needed to establish the response surface are obtained by solving the three-dimensional Navier-Stokes equations with the ANSYS CFX. The stators' stagger angles and stacking lines are selected as the design variables. The former is determined to redistribute the enthalpy drop among turbine stages more reasonably and the latter is used to improve each stage's efficiency by forming bent and twisted stators. The efficiency and power of this LP cylinder are increased by 0.43% and 0.72%, respectively. Meanwhile, the mass flow rate is maintained nearly unchanged.