A bifurcation analysis for limit flame phenomena of DMEair in perfectly stirred reactors.pdf

Combustion and Flame xxx (2014) xxx–xxxContents lists available at ScienceDirect Combustion and Flame journal homepage: www.elsevier .com/locate /combustflameA bifurcation analysis for limit flame phenomena of DME/air in perfectly stirred reactors0010-2180/$ - see front matter  2013 The Combustion Institute. Published by Elsevier Inc. All rights reserved. /10.1016/bustflame.2013.12.025 ? Corresponding author. E-mail address: Ruiqin.Shan@ (R. Shan). Please cite this article in press as: R. Shan, T. Lu, Combust. Flame (2014), /10.1016/bustflame.2013.12.025Ruiqin Shan ?, Tianfeng Lu Department of Mechanical Engineering, University of Connecticut, Storrs, CT 06269-3139, United States a r t i c l e i n f o a b s t r a c tArticle history: Received 29 August 2013 Received in revised form 1 December 2013 Accepted 24 December 2013 Available online xxxx Keywords: Bifurcation analysis Bifurcation index Limit phenomena Dimethyl ether Model reductionA bifurcation analysis was developed to systematically detect limit flame phenomena, including ignition, extinction and changes in flame stability, and to understand the underlying physicochemical processes that control the limit phenomena. The bifurcation analysis was demonstrated with steady-state perfectly stirred reactors (PSRs) using dimethyl ether (DME) with the negative temperature coefficient (NTC) chemistry. Flame stability was first analyzed to identify ignition and extinction states based on the eigen- values of the Jacobian of the governing equations. It was found that for DME–air mixtures, extinction may not occur at the turning points on the S-curves. A bifurcation index (BI) was then defined at each bifur- cation point on the S-curves to quantify the contribution of each reaction and the mixing process to the limit flame phenomenon. Results show that extinction of the strong flames of DME–air is primarily con- trolled by the reactions involving small molecules, such as HCO and CO, while extinction of the cool flames i