Abstract: As two common flow characteristics, the upper endwall separation and strong upper endwall secondary flow have great impact on the aerodynamic performance of large meridional expansion turbines. In the present study, forward-swept and wide-chord blade profiles were used to control the upper endwall separation. In blade profiles with different forward-swept and wide-chord schemes, three-dimentional numerical simulation, analysis of flow field topology, as well as comparison of various flow situations were conducted. What’s more, the application potentiality of forward-swept and wide-chord blade profile in the abovementioned turbine was investigated. The results show that with a properlydesigned forward-swept and wide-chord blade profile, the upper endwall separation can be effectively reduced or even eliminated, and then the streamwise pressure distribution at the upper wall can be improved. Meanwhile, the secondary flow at the upper endwall can also be well controlled, and thus the aerodynamic performance of the turbine is optimized.

Key words: meridional expansion, low-pressure turbine, numerical simulation, forward-swept and wide-chord blade profile