An Investigation of the Establishment of a Recirculation Zone by Swirling Flows Within a Conical Duct

This paper reports an investigation carried out on the recirculation zones established in conical chambers with radial vaned inlet swirlers. The boundaries of the recirculation zones established in various conical chambers of different cone angles are presented for different inlet swirl numbers and an optimum cone angle which gives a reasonably short length of the recirculation zone with maximum pressure recovery is suggested. The inlet swirl number is also optimized for a fairly high swirl strength within the recirculation zone and the inlet swirl number for which the recirculation completely disappears is also estimated. In addition to this, an equation is curve-fit to the experimental data which correlates the length of the recirculation zone for any given cone angle and inlet swirl number.