The Effect of Chevrons on the Primary and Secondary Swirlers on the Dynamic Behavior of the Flow Generated by a Counter-Rotating Radial-Radial Swirler

Abstract

An experimental investigation was conducted to study the effect of chevrons on the dynamic behavior of the swirling flow generated by a counter-rotating radial-radial swirler. 3X models of a low swirl number swirler (SN ≈ 0.6) were used to achieve lower velocities for the same Reynolds number (Re) and enhanced visibility of the flow characteristics by enabling high spatial and temporal resolutions. Three swirler configurations were used, including the baseline with no chevrons. Configuration 2 features chevrons on the trailing edge of the primary swirler, and configuration 3 has chevrons on the trailing edge of both primary and secondary swirlers. The swirlers were tested in water flow at Reynolds number (Re) = 51,500 which corresponds to the typical operational pressure drop of 4% of atmospheric pressure for the corresponding 1X model of the swirler at ambient conditions. Water testing was used since it allows additional slowing down of the flow dynamic features so that they can be captured and analyzed. Measurements were conducted in a vertical plane passing through the swirler centerline, and two horizontal (cross-sectional) planes using a High-Speed, Two Dimensional, Particle Image Velocimetry (2D PIV) system to obtain the mean, turbulent and dynamic behavior of the flow. Results of this study introduce the concept of chevrons on swirlers as a promising approach to change the flow dynamic behavior and thus, affect combustion dynamics. The results show that the presence of chevrons break down the region of high modal energy into several smaller regions. However, configuration 2 has few regions of the highest modal energy among the configurations, whereas the modal energy values for configurations 3 has the lowest magnitudes. Thus, the secondary chevrons in configuration 3 play an important role to eliminate these high-energy local spots as well as meet the requirement to break down the large scale structures.