Study Of The Compressible Gas Three Dimensional Flow Fields In The Vortex Tube

Vortex tube is a new device for energy separation, and has comprehensive applications. Though the structure of vortex tube is simple, the mechanism of energy separation is very complicated, so the researchers have not come to a conclusion. It is clearly that energy separation has closely relationship with the moving of compressed gas in the tube, which is the source of energy separation. The full map of flow fields and the distribution of three dimensional velocities are critical to the study of energy separation mechanism.This paper does research on the three dimensional turbulent flow fields of compressible air with highly rotation, using methods of mathematical analyze and CFD simulation. First, the traditional technique applied on measuring velocity in vortex tubes is summarized. Then basing on the free-vortex equation, potential equation and stream function of flow are achieved by mathematical analyze, and solving these equations gives flow fields. The H.H.Bruun's vortex tube is used to do CFD simulation. Subarea grids generation method, RNG k-ε turbulent model and second-order upwind scheme are selected.CFD code "Fluent" is appealed to mapping the flow fields, and the results give the distributions of tangential velocity, axial velocity, radial velocity and the pattern of flow streamlines. The distribution of tangential velocity is in accord with forced-free vortex model, the strength of which intensifies with the increasing of inlet pressure while the quality of which enhances with the addition of inlet nozzles. There is a face of zero axial velocity in the flow field, the location of which moves to the cold gas outlet with the weakening of cold mass ratio. The value of radial velocity is less than the others, and only changes acutely in the vortex chamber. The pattern of flow streamlines is same to Archimedes lines.The flow fields in the vortex tube can be described by three domain movements namely "periphery flow ","inner flow "and "secondary flow", and two important characters namely "zero axial velocity face" and "short-cutting flow".