The Distortion of a Jet by Coil Inserts

Abstract

Results of experimental investigations of the effects of distortion caused by coil inserts on a turbulent jet are presented. The coils have different wire diameters with constant pitch spacing. The ratios of the coil wire diameter to the tube inside diameter, d/D, are 0.06, 0.08, 0.11, 0.13, and 0.16 and the ratio of the pitch spacing to the tube inside diameter, p/D, is 1.2. Results show that the coil inserts enhance the mixing process. At the jet-outlet, mixing enhancement is increased when d/D<0.1. However, further downstream, the highest mixing is achieved for the coil with the largest d/D ratio. Results suggest that the streamwise vortices generated by the coil inserts are the mechanism behind the high entrainments and the mixing process.

The distortion of a round jet by coil inserts of various lengths

“…The present study is a continuation of our previous investigations [8][9][10] where the effects of coil with variable pitch spacing, and constant wire diameter or variable wire diameter and constant pitch spacing on the mixing process of a turbulent jet were investigated. These investigations have shown that maximum mixing enhancement in a turbulent jet can be obtained when the ratios of the coil pitch spacing and coil wire diameter to the tube inside diameter, p=D and d=D respectively, are near 1.0 and 0.1.…”

“…These investigations have shown that maximum mixing enhancement in a turbulent jet can be obtained when the ratios of the coil pitch spacing and coil wire diameter to the tube inside diameter, p=D and d=D respectively, are near 1.0 and 0.1. Hoang and Rahai [10] also suggested that when d=D > 0:1, the forced vortices generated by the coils play a major role in the initial development of the jet. The weak swirl generated by the coil delays the mixing process until further downstream where the free vortices become dominant and increased entrainment and mixing are attained.…”