Experimental Investigation of Elliptical Jet in Coflow

The objective of the present study is to investigate systematically the mixing characteristics of an Elliptical jet with varying large aspect ratio in a co-flow current using experimental technique. Laser-Induced Fluorescence (LIF) technique is employed to measure the quantitative time-averaged and turbulent concentration fields of an elliptic jet issuing into a co-flowing current and then get compared with the previous experimental results of a round jet in the present work. The spreading and mixing characteristics of an elliptical jet in a co-flow including centerline concentration, centerline dilution decay, turbulence intensity and axis-switching…etc are discussed and compared with circular jet. The experimental results with varying large aspect ratio (AR=3, 6 and 10) at different downstream distance indicate that: i) when x/D>1.33 in the major axis plane and x/D>1 in the minor axis plane, the mean concentration, the turbulence intensity, are self-similar and the mean concentration field appear to be Gaussian, ii) axis switching phenomena happens at about x/D ≈ 7; iii) The experimental results using LIF further verify that the Elliptic jet with varying large aspect ratio has also much higher dilution in a co-flow than an equivalent round jet under the same flow conditions (same momentum flux Me and same flow rate Q).