Aerodynamics Study of a Linearly-Arranged 5-Swirler Array

Abstract

In this experimental work, a series of tests have been conducted to further study the aerodynamics of linearly-arranged 5-swirler arrays, using Laser Doppler Velocimetry (LDV). Two major parameters have been investigated for the 5-swirler arrays in this work, including the inter-swirler spacing, and the end wall distance. An additional effect of dome recession was studied for a single swirler in order to provide some insight into the results for the 5-swirler arrays. The 5-swirler arrays with an inter-swirler spacing of 1.75D, 2D, 2.5D, and 2.75D were studied, where D is the diameter of swirler exit. For the inter-swirler spacing of 1.75D or 2D, the center swirler is shown to have a weak, large center toroidal recirculation zone (CTRZ). The swirlers next to the center swirlers have strong, compact CTRZs whereas the outer swirlers have weak, large CTRZs. Thus, starting from the center swirler, the CTRZs exhibit a large – small – large pattern in either direction. For the swirler spacing of 2.5D or 2.75D, the trend is reversed, with a strong CTRZ for the center swirler and a small – large – small CTRZ pattern. The end wall distances of 0.75D, 1D, 1.25D, and 2D cases were studied. The end wall distances are seen to affect the strength of each CTRZ and the corner swirling flow pattern, though the bulk flow structure did not change significantly. The dome recession shows a clear impact on the expansion of swirling flow generated by a single swirler. As the dome recession distance increases, the expansion angle of the swirling jet reduces significantly for the unconfined cases. A phenomenological description is discussed to understand the reason for the periodically alternating CTRZ pattern observed in the experimental results of the 5-swirler arrays.