10th European Conference on Turbomachinery Fluid dynamics & Thermodynamics
This paper addresses the unsteady formation of secondary flow structures inside a rotor passage. The first stage of a two-stage low pressure turbine is investigated at a Reynolds Number of 75000. The configuration represents the third and the fourth stages of an engine low pressure turbine. The vane-rotor interactions at hub are discussed in the relative frame of reference using the streamwise vorticity to identify the flow structures and interaction processes involved. A multi-stage URANS prediction which is validated by time-averaged fivehole probe data at inlet and exit of the rotor provides the time-resolved data set required. An interaction mechanism is revealed which is responsible for the creation of rotating structures which are fixed in space in the absolute frame of reference at rotor exit. The wakes and secondary flow structures of the nozzle guide vane transform the secondary flow structures at the rotor hub unsteadily. The time-averaged isentropic efficiency distribution at rotor exit is observed to be dominated by flow structures associated with the nozzle guide vane.