Multistage three-dimensional Navier-Stokes computation of off-design operation of a four-stage turbine

In this paper a three-dimensional computational methodology for multistage turbomachinery flows is developed, validated and applied in analysing the reduced mass flowrate operation of a four-stage turbine. The flow is modelled by the three-dimensional Favre-Reynolds-averaged Navier-Stokes equations using the Launder-Sharma near-wall k-epsilon turbulence closure, which are integrated using an implicit third-order upwind solver. The computation models the eight blade rows, including the tip clearance gaps of the rotors, using a 6 x 10(6) points grid, and computes the time-averaged flow using mixing planes between rows. Computational results are compared with measurements for various operating points. After this validation the method is used in a first attempt to analyse the three-dimensional flow at reduced-mass-flow operation.