Computation of flow between two disks rotating at different speeds

Abstract

Disks rotating at different speeds are found in the internal cooling-air systems of most gas turbines. Defining F as the ratio of the rotational speed of the slower disk to that of the faster one then Gamma = -1, 0 and +1 represents the three important cases of contra-rotating disks, rotor-stator systems and co-rotating disks, respectively. A finite-volume, axisymmetric, elliptic, multigrid solver employing a low-Reynolds-number k-epsilon turbulence model, is used for the fluid-dynamics computations in these systems. The complete Gamma region, +1, is considered for rotational Reynolds numbers of up to Re-phi=1.25X10(6), and the effect of a radial outflow of cooling air is also included for nondimensional flow rates of up to C-w=9720. As Gamma-->-1, Stewartson-flow occurs with radial outflow in boundary layers on both disks and between which is a core of nonrotating fluid For Gammaapproximate to0, Batchelor-flow occurs, with radial outflow in the boundary layer on the faster disk, inflow on the slower one, and between which is a core of rotating fluid. As Gamma-->+1, Ekman-layer flow dominates with nonentraining boundary layers on both disks and a rotating core between. Where available, measured velocity distributions are in good agreement with the computed values.