INLET PRE-ROTATION INFLUENCE ON THE FLOW AND HEAT TRANSFER IN A ROTATING CAVITY

摘要

In order to get better knowledge of the flow and heat transfer in the rotating cavity an experimental rig is set up in the Institute of Steam and Gas Turbines at RWTH Aachen University. The rotating cavity with cooling air axial through flow is bound by two plane discs and a cylindrical shroud. The corresponding 3D time-dependent numerical investigation is carried out using a commercial CFD code, Fluent, with the RNG k-ε turbulence model. The influence of the inlet air pre-rotation on the flow pattern and the heat transfer in the cavity is analyzed. The sophisticated unstable flow patterns with cyclonic and anti-cyclonic circulations are captured in experiments and numerical simulations. Only one pair of circulations is observed in the simulations without inlet pre-rotation, two and three pairs of circulations are observed in the simulations of the inlet air with the same pre-rotational speed as the rotating cavity, i.e. full inlet pre-rotation. The numerical heat transfers are in reasonable agreement with the experiments. The local Nusselt numbers Nu on disks show basically an increasing radius distribution for the disks heated with radial increasing temperature profile. The simulations without inlet pre-rotation overestimate the heat transfer in the middle region of the disks and the simulations with full inlet pre-rotation overestimate the heat transfer in the region near the shroud. To get an accurate CFD simulation of the flow and heat transfer in rotating cavities, it is suggested that the inlet pre-rotation be a fraction of the rotational speed of the disks.