Numerical Study of Deposition in a Full Turbine Stage Using Steady and Unsteady Methods

A computational study was performed to investigate deposition phenomena in a high-pressure turbine stator and rotor stage. Steady mixing-plane and unsteady sliding mesh calculations were utilized. 3D, steady and unsteady RANS calculations were performed in conjunction with published experiments completed on identical turbine geometry in order to extract boundary conditions and to validate flow solutions. Particles were introduced into the flow domain and deposition was predicted using a Lagrangian particle tracking method with the critical viscosity model to predict deposition. For the steady method, in order to track particles from the mixing plane through the blade domain, particle positions were saved after passing through the vane domain and inserted into the blade domain using two different methods: averaged and preserved. Both methods yielded nearly identical results. For the unsteady simulation particles were tracked through a sliding mesh interface with particle position, velocity, and temperature preserved at exit of the vane domain and inlet of the blade domain. Deposition results for the steady mixing plane using both particle averaging techniques and unsteady sliding interface were compared for particles of different sizes. Large particles produced localized impact and deposit zones near the hub and tip of the pressure surface for all methods. Steady methods overpredicted impacts and deposits relative to unsteady methods by averaging out discrete unsteady vane wake motion which caused particle motion towards blade surfaces.Copyright © 2015 by ASME