The growth characteristics of transient impinging axisymmetric turbulent jets

This paper presents a study performed to evaluate the growth characteristics of transient impinging axisymmetric turbulent jets at a Reynolds number of 7500 for three different impingement angles (30, 45, and 60 deg). Previous studies have beat performed on a single transient turbulent jet as well as steady-state turbulent impinging jets. However, in the case of internal and diesel combustion engines, mixing of the fuel and oxidizer occurs under a transient condition just prior to ignition. This mixing application results from the impingement of these two fluid streams. Therefore, the current study utilizes smoke visualization to characterize the vertical and horizontal mixing layer widths of two identical turbulent air jets impinging at three different angles; as well as the time it takes for the mixture to travel downstream from the jets origin. The current results show an increase in the mixing layer width by approximately 3 diameters near the impingement point in both the vertical and horizontal directions when the transient case is compared to the steady-state cases. Also, by increasing the impingement point from 30 to 60 deg the maximum growth in both the horizontal and vertical directions is increased by approximately 30% (i.e., 1 diameter). Finally, by increasing the impingement angle from 30 to 60 deg the time it takes for the mixture to travel downstream from the jet origin to x/D = 15 increases by more than a factor of two. © 2015 by Begell House, Inc.