Mixing of Coaxial Streams inside a Closed Conduit

Abstract

In this paper the linearized integral equations of motion are used to solve the problem of turbulent mixing of two coaxial streams inside a closed conduit. Similar to the problem of mixing of unbounded coaxial streams, the problem is too complicated to be solved by the equations of motion, but by specifying a shape for the velocity distribution across the streams at all normal sections, the solution has been simplified. For every region of the mixing regions, the radius of the core, the external radius of the inside stream and the velocity on the axis are determined by the integral equations of motion. The solutions are then joined by making the velocity and radius continuous at the transition sections. In this way a complete picture of the flow pattern is obtained. In order to test experimentally the formulated theory, the paper describes experimental data from a coaxial air to air jet-pump having a mixing chamber of constant diameter. The data consist of complete velocity traverses and wall static pressures taken at different flow ratios. The primary and secondary streams were of the same density, incompressible, subsonic and isothermal. The main conclusion from the experiments is that the theory gives an overall picture of the mixing process which is in the main correct, though it might be inaccurate in some of the details.