An Experimental and Analytical Study of Vortex-Flow Temperature Separation by Superposition of Spiral and Axial Flows: Part 1

This paper reports on an experimental and analytical study of compressible flow in a uniflow vortex tube. Part 1 deals with an experimental study, Part 2 with the analytical study. Its purpose is to provide a better understanding of the separation of a gas stream into regions of high and low stagnation temperatures, there being at present little agreement as to the theory of operation. The problem is first approached from the experimental standpoint. A large, multipurpose vortex tube is so designed and built that pressure, temperature, and velocity traverses can be taken at six different stations throughout the length of the tube. Pressure, temperature, and velocity traverses are taken by means of hypodermic probes. Velocities are checked by means of a miniature hot-wire anemometer. Data are taken for different runs of inlet pressures and plotted against radial distance. Flow visualization is obtained by means of liquid injection. The analytical study consists of using superposition for the solution of the flow equations. It begins with potential vortex flow in the plane. The solution of this flow is characterized by the existence of sonic or limit circles. Superposition of a sink flow to the vortex solution yields a spiral flow in the plane. The general solution in space is obtained by addition of a uniform axial velocity to the spiral flow. When viscosity effects are considered, the potential vortex changes into a forced vortex, and the solution becomes a superposition of a viscous compressible sink to a forced vortex. Performance or stagnation temperature separation is expressed as function of the ratio of vortex strength to sink strength.