Mean Flow Characteristics Downstream of a Vortex Tube Separator Array

Vortex tube separator (VTS) arrays are used to filter foreign particles from turboshaft engine intakes. Arrays may consist of hundreds of separators that share a common surrounding plenum, potentially allowing for significant interactions between the devices. However, most VTS studies have been limited to individual separators acting alone. The current study first involves an experimental investigation of the fluid flow emerging from the outlets of a VTS array installed in a wind tunnel. Particle image velocimetry is used to measure the flowfield at planes 0.23DVTS, 0.58DVTS, and 1.77DVTS downstream of the outlets, where DVTS is the inlet tube diameter of a separator. The results indicate that the emerging vortices quickly merge into a single vortex with high circumferential velocity concentrated near the edges of the duct, and that a central recirculation zone (CRZ) develops. This is in contrast to the flow from a single VTS, which does not have a clear CRZ. Comparisons to similar combustion swirler flows lead to the hypothesis that VTS arrays may uniquely generate fast-developing CRZs that produce strong axial flow gradients near or even within some VTS outlets. Such gradients will alter the filtration performance of affected VTSs, which is highly sensitive to flow rates. To explain the onset of recirculation that is exclusive to the array configuration, the framework of a momentum integral model has been developed and is presented here. Additionally, computer-aided design files of the experimental geometry along with inlet/outlet boundary conditions are being made available for any future computational validation studies of this complex flowfield.