Novel transonic nozzle for Ranque-Hilsch vortex tube

The process of the vortex flow formation in the Ranque-Hilsch vortex tube is studied. Starting from deficiencies of the existing vortex tubes, a novel type for the transonic nozzle is suggested and designed. The proposed nozzle is different from the existing classical ones by the presence of additional supersonic section placed after the blades. This section creates controlled conditions for acceleration of the vortex flow to supersonic speed. Analysis of the gas flow in the transonic nozzle using 3D RANS simulations showed that slightly improper selection of nozzle dimensions may lead to destabilization of the vortex flow and deterioration of the vortex tube performance. Simplified semi-one-dimensional model of swirling gas flow was derived and utilized for correction of the nozzle dimensions in order to stabilize the flow. Detailed validation of this model against full 3D RANS simulations demonstrated its applicability for preliminary engineering computations. It was demonstrated that application of the novel transonic nozzle extends the region in the energy separation chamber occupied by the supersonic vortex. This results in increase of both temperature separation effect and vortex tube energy efficiency. Main advantages and disadvantages of the novel transonic nozzle are summarized in the concluding section.