Secondary Deviation and Unsteady Blockage in an LP Turbine due to Off-Design Operation

A two-stage low pressure turbine is tested at the aerodynamic design point and a strong off-design point representing flight idle conditions. The tests are performed on an altitude test facility at engine representative conditions. Time-resolved measurements are performed with dual-film probes up- and downstream of the second NGV row. The aim is to study the flow field for secondary deviation and the generation of losses in the NGV row. The experimental results are compared with multistage URANS predictions. The simulations match the measured data and allow for detailed analysis of the time-resolved flow field. With off-design operation a strong increase in cross-flow is observed due to radial migration. Wake fluid from the first stage tends to migrate towards the hub section and changes the blockage unsteadily in the NGV row. At off-design operation a distinction between a two-dimensional primary flow to the secondary flow areas is no longer possible.Copyright © 2015 by ASME