Title

Acoustic Perturbation Effects On The Fluid Dynamics And Swirling Flame Response In A Non-Premixed Co-Flow Burner

Abstract

An investigation into the response of non-premixed swirling flames to acoustic perturbations at various frequencies (fp = 0 - 315 Hz) and swirl intensities (S = 0.09 and 0.34) is carried out. Perturbations are generated using a loudspeaker at the base of an atmospheric co-flow burner with resulting velocity oscillation amplitudes |u'/Uavg| in the 0.03 - 0.30 range. The dependence of flame dynamics on the relative richness of the flame is investigated by studying various constant fuel flow rate flame configurations. Flame heat release is quantitatively measured and simultaneously imaged using a photomultiplier (PMT) and a phase-locked CCD camera. Both of which are fitted with 430nm bandpass filters for observing CH* chemiluminescence. The flame response is observed to exhibit a low-pass filter characteristic with minimal flame response beyond pulsing frequencies of 200Hz. Flames at lower fuel flow rates are observed to remain attached to the central fuel pipe at all acoustic pulsing frequencies. PIV imaging of the associated isothermal fields show the amplification in flame aspect ratio is caused by the narrowing of the inner recirculation zone (IRZ). The Rayleigh criterion (R) is used to assess the potential for instability of specific perturbation configurations and is found to be a good predictor of unstable modes. Phase conditioned analysis of the flame dynamics yield additional criteria in highly responsive modes to include the effective amplitude of velocity oscillations induced by the acoustic pulsing. Highly amplified responses were observed in pulsed flame configurations with Strouhal numbers (St = fpU avg/dm) in the 1 - 3.5 range. Heat release to velocity perturbation time delays on the order of the acoustic pulsing period also characterized the highly responsive flames. Finally, wavelet analyses of heat release perturbations indicate sustained low frequency oscillations that become more prominent for low acoustic pulsing frequencies in lean flame configurations. Copyright © 2010 by ASME.

Publication Date

12-1-2010

Publication Title

Proceedings of the ASME Turbo Expo

Volume

2

Issue

PARTS A AND B

Number of Pages

1309-1321

Document Type

Article; Proceedings Paper

Personal Identifier

scopus

DOI Link

https://doi.org/10.1115/GT2010-23735

Socpus ID

82055207375 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/82055207375

This document is currently not available here.

Share

COinS