Abstract
The aim of the present study is to investigate effects of the axial gap
between rotor and stator upon the stage performances and flow field
of a single axial flow turbine stage. In this paper experimental and
numerical studies are performed for three axial gaps by moving the
stator vane axially. Five-hole probe measurements are made to obtain
total pressure loss and time-averaged flow field upstream and downstream
of the rotor blades. In addition, large-scale unsteady three-dimensional
RANS-based numerical simulation, in which blade-count
ratio is almost the same as that of the actual turbine stage, is executed
to understand interaction between the stator and the rotor. These results
show that overall turbine stage efficiency with the smallest axial
gap is the highest among the three gaps. This is because the stator
wakes are diffused by expanding axial gap, inducing the growth of the
secondary flow near the endwall.
