Abstract:
For the efficient design of transonic turbomachinery systems, understanding of the
complex flow phenomena inherent in the flow passages is essential. In the present
study, a computational technique is adopted to meet this formidable goal. A code using
a time-marching technique has been developed first for quasi three-dimensional cascades
(that is two-dimensional computation with the varying streamtube height in the third
dimension taken into consideration) and then extended to fully three-dimensional flows
within the rotating flow passages. Each code has a built-in switch for in viscid and
viscous flows. The basis of the codes is the conservative form of the Reynolds-
averaged Navier-Stokes equations in a rotating framework. This is supplemented by
either the Baldwin-Lomax (algebraic) or the k-e (two-equation) turbulence model. For
solving the hyperbolic type governing equations, spatial derivatives are first discretized
on the easily-constructed H-type grid system using a central-difference finite-volume
approximation with the flow variables stored at the cell centre. An explicit multistage
Runge-Kutta scheme is then employed for the time integration o f the resulting ordinary
differential equations.
The accuracy of the quasi three-dimensional code is initially evaluated by predicting the
flows through cascades with simple geometry. Its robustness is then confirmed by two
realistic configurations with a wide range o f operating conditions. Finally the fully
three-dimensional code is applied to two highly loaded transonic rotors with complicated
geometry at peak efficiency and near stall operating conditions. An extensive
comparison in terms of detailed flowfield and overall performance between the
predictions and experiments with laser anemometry and conventional probes shows the
accuracy o f the codes and also indicates that the present study has great potential to be
a viable aerodynamic design and analysis tool in the development of transonic
turbomachinery systems.
