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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/45308

Title: Numerical Study of Spray Flame Characteristics
Authors: Likun Ma;Dirk Roekaerts
Contributors: 國立臺灣海洋大學:輪機工程學系
Keywords: Spray combustion;Flame structure;Large Eddy Simulation;Flamelet Generated Manifolds;Time scales
Date: 2017
Issue Date: 2018-03-08T08:17:15Z
Publisher: Proceedings of the Combustion Institute
Abstract: We investigate the multi-flame phenomenon often seen in spray combustion. To do so, simulations are made of two cases from the Delft Spray in Hot Coflow (DSHC) database. These two cases have the same fuel (ethanol) but differ in the type of coflow: room temperature air (case AII) or products of lean premixed combustion (case HII), and they exhibit remarkably different flame structure, respectively with a ‘double flame’ and a ‘single flame’. The two-phase flow was handled with an Eulerian–Lagrangian approach. Large Eddy Simulation (LES) with Flamelet Generated Manifolds (FGM) method was used to account for the turbulence and combustion. Validation was done by using available experimental data as well as information on similar systems reported in literature. Major features of these two cases were correctly reproduced. Simulation results revealed that four spatially separated reaction regions exist in the flame AII and two in the flame HII. These regions are of different types, premixed or non-premixed, and are formed by different species, major fuel (ethanol) or intermediate species, e.g. carbon monoxide. The mechanism underlying the multi-flame structure was investigated and explained in terms of the relative magnitude of different time scales, namely of droplet evaporation, dispersion, convection and reaction. Parametric studies on the effect of spray polydispersity and coflowing air temperature were carried out, demonstrating an even wider range of flame structures. An important observation is that the ‘single flame’ structure usually present in the hot-diluted coflow case (HII), is also generated in a case of room temperature air coflow, provided the injected droplets are small. This is attributed to the fact that representative droplets in all cases with single flame have similar evaporation time scale. Or stated more generally, by matching important time scales, similar flame structure can be created under considerably different conditions.
Relation: 36(2), pp.2603-2613
URI: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/45308
Appears in Collections:[輪機工程學系] 期刊論文

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