Effect of Chamber Length With Converging Exhaust on Swirling Flow Field Characteristics of a Counter-Rotating Radial-Radial Swirler

An experimental study has been conducted to examine the effect of chamber length on the aerodynamic characteristics of an enclosed, non-reacting, swirling, flow field. The swirling flow was generated by a counter-rotating radial-radial swirler consisting of an inner, primary swirler generating counter-clockwise rotation and an outer, secondary swirler generating clockwise rotation. The enclosures used were square cross-section chambers of differing lengths. The internal cross section of all chambers was 50.8 mm × 50.8 mm (2 inch × 2 inch). 3 different lengths of chamber used for the tests were 76.2 mm (3″), 101.6 mm (4″), and 152.4 mm (6″) respectively. A nozzle was used at the downstream end of the enclosure to ensure the absence of reverse flow back to test chamber and to simulate the area reduction in typical combustor. The nozzle reduced the cross-section area from 50.8 mm × 50.8 mm (2″ × 2″) to 22.2 mm × 22.2 mm (0.875″ × 0.875″) via 45° slope. A two-component laser doppler velocimetry (LDV) system was used to measure the velocities in the flow fields. The chamber length has been observed to have a clear influence on the mean and turbulent velocity profile near the exit of swirler. However, this effect is not as evident further downstream in the flow field. For the short chamber length, higher values of axial and tangential velocities were observed in the swirling jet due to the proximity of the downstream nozzle to the swirler. For this chamber length, higher turbulence intensities were observed in the swirling jet and inside center toroidal recirculation zone. The magnitudes of the swirling jet velocity and the turbulence intensities decreased with an increase in the chamber length. Two counter-rotating flows could merge more complete in the exit of swirler with the chamber length decreasing.Copyright © 2013 by ASME