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research-article

FORMATION OF SOOT IN ETHYLENE-AIR PARTIALLY PREMIXED FLAMES OVER A WIDE RANGE OF PREMIXEDNESS

[+] Author and Article Information
Aritra Chakraborty

Department of Aerospace Engineering and, National Centre for Combustion Research and Development (NCCRD), IIT Madras, India
aritra.1991@gmail.com

S. R. Chakravarthy

Department of Aerospace Engineering and, National Centre for Combustion Research and Development (NCCRD), IIT Madras, India
src@ae.iitm.ac.in

1Corresponding author.

ASME doi:10.1115/1.4037580 History: Received June 26, 2017; Revised July 05, 2017

Abstract

This paper reports an investigation of soot formation in ethylene-air partially premixed flames over a wide range of premixedness. An axisymmetric co-flow configuration is chosen to establish partially premixed flames from the fully non-premixed to fully premixed conditions. Reducing the fuel flow rate as a percentage of the maximum from the core stream and supplying the same to the annular stream leads to stratification of the reactant concentrations. The thermal power, overall equivalence ratio, and the average velocity in the both streams are maintained constant under all conditions. The soot volume fraction is estimated by light attenuation method, and LII is performed to map the soot distribution in the flow field. When traversing from the non-premixed end, below 60% fuel flow rate in core, the soot volume fraction drops drastically. The onset of sooting in the PPFs is clearly seen to be at the tip of the rich-premixed flame branch of their triple flame structure, which advances upstream towards the base of the flame as the premixing is reduced. Drop in sooting is clearly the effect of partial premixing, more specifically due to the presence of lean premixed flame branch of the triple flame. LII is incapable to capture the upstream advance of the soot onset with decreased premixedness beyond a point. A quick and inexpensive technique to isolate soot through flame imaging is also presented involvinging quasi-simultaneous imaging with a 650 nm and a BG-3 filter using a normal color camera.

Copyright (c) 2017 by ASME
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