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research-article

Flames of Swirling Double-Concentric Jets Subject to Acoustic Excitation at Resonance

[+] Author and Article Information
Omid Ali Zargar

Department of Mechanical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan 10672, R.O.C.
omid.alizargar@gmail.com

Rong Fung Huang

Department of Mechanical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan 10672, R.O.C.
rfhuang@mail.ntust.edu.tw

Ching Min Hsu

National Formosa University, Yunlin, Taiwan 632, R.O.C.
cmhsu@nfu.edu.tw

1Corresponding author.

ASME doi:10.1115/1.4041685 History: Received August 15, 2018; Revised October 03, 2018

Abstract

The effects of acoustic excitation at resonance on the flame appearances, flame lengths, flame temperatures, and combustion product concentrations of combusting swirling dual-disk double-concentric jets were studied. The Reynolds number of the annular swirling air jet was varied, while it was fixed at 2500 for the central propane jet. The central fuel jet was acoustically forced by a loudspeaker, which was installed using downstream longitudinal irradiation. The central jet pulsation intensities were measured by a calibrated, one-component hot-wire anemometer. The instantaneous full-length and close-up flame images were captured to identify the characteristic flame modes. Long-exposure flame images were taken to measure the flame lengths. The axial and radial temperature distributions of flames were measured using a homemade, fine-wire R-type thermocouple. The concentrations of combustion products were measured by a gas analyzer. Four characteristic flame modes, blue-base wrinkled flame, yellow-base anchored flame, blue-base anchored flame, and lifted flame, were observed in the domain of central jet pulsation intensity and annular swirling jet Reynolds number. The lifted flame, which was formed at large central jet pulsation intensities, presented characteristics of a premixed flame due to significant mixing induced by violent, turbulent flow motions. It was short and stable, with high combustion efficiency and low toxic emissions, when compared with the unexcited flame and other excited characteristic flame modes, which presented characteristics of diffusion flame.

Copyright (c) 2018 by ASME
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