Comparison of Predicted and Measured Velocities in a Compressor Disk Drum Model

The tangential velocity distributions in the bleed and the trapped cavities of an eleven-cavity, compresor drum model were measured and predicted. The measurements were obtained with a Laser Doppler Velocimeter (LDV) in experiments using Freon-113 as the working fluid. The experiments were conducted at disk tangential Reynolds numbers of approximately 2 × 10⁶ over a range of inward bleed flow rates through the center cavity. The experimental results show that the tangential velocity profiles in the bleed cavity vary from near-solid-body at low flow rates to near-free-vortex at the highest flow rate. The experimental results also showed a decrease in tangential velocity strength in the trapped flow cavities with distance from the bleed cavity. The flow in the bleed and trapped cavities were predicted using an analysis coupling the flow in a core region with the flow in the disk boundary layers. The secondary flow in the boundary layer was modeled using momentum integral equations. The core flow was determined by coupling the total flow with the boundary layer flow through the continuity equation, and the core tangential velocity was modeled with one dimensional viscous flow equations. Predicted results are presented for a range of flow conditions and cavity locations. The analytical model accurately predicted the tangential velocity distribution, and hence pressure drop, in both classes of cavities when the appropriate core turbulence model and boundary conditions were applied.