The effect of methyl pentanoate addition on the structure of premixed fuel-rich n-heptane/toluene flame at atmospheric pressure Artem M. Dmitriev a,b , Denis A. Knyazkov a,b,⇑ , Tatyana A. Bolshova a , Andrey G. Shmakov a,b , Oleg P. Korobeinichev a a Voevodsky Institute of Chemical Kinetics and Combustion, Institutskaya str. 3, Novosibirsk 630090, Russia b Novosibirsk State University, Pirogova str. 2, Novosibirsk 630090, Russia article info Article history: Received 18 December 2014 Received in revised form 19 December 2014 Accepted 22 December 2014 Available online 20 January 2015 Keywords: Methyl pentanoate n-Heptane Toluene PAH precursors MBMS abstract The effect of adding methyl pentanoate (MP) on the species pool in a rich premixed flame fueled by n- heptane/toluene blend (7/3 by volume of liquids) at atmospheric pressure is investigated. The emphasis of this work is on the effect of MP on the concentrations of intermediates, which are precursors of poly- cyclic aromatic hydrocarbons (PAH), in order to understand the processes responsible for reduction of concentration of PAH when biodiesel is added to diesel fuel in combustion devices. Two premixed fuel-rich n-heptane/toluene/O 2 /Ar (2.29/1.36/21.36/75%) and n-heptane/toluene/MP/O 2 /Ar (1.26/0.75/ 2.00/21.355/75%, 50% of liquid MP in liquid fuel mixture of n-heptane and toluene) fuel-rich flames with the same equivalence ratio u = 1.75 were stabilized on a flat burner at 1 atm. Molecular beam mass spec- trometric measurements of mole fraction profiles of reactants, the major products and many intermedi- ate species were performed. The experimental profiles were compared with those calculated using a detailed chemical kinetic mechanism, which was a combination of two detailed mechanisms proposed earlier in the literature for combustion of n-heptane/iso-octane/toluene mixture and for MP oxidation, respectively. Addition of MP was found to reduce mole fractions of many intermediates, which play an important role in formation of PAH, specifically, benzene, cyclopentadienyl, acetylene, propargyl, and vinylacetylene. Analysis of the reaction pathways responsible for formation of naphthalene, a typical rep- resentative of small PAH, was performed in order to elucidate the chemical effect of MP addition on its formation. To ascertain the effect of MP addition on the primary reactions of consumption of n-heptane and toluene, the analysis of the relative contributions of these reactions to the total rate of consumption of the fuels was carried out. Ó 2015 The Combustion Institute. Published by Elsevier Inc. All rights reserved. 1. Introduction Combustion of petroleum-based hydrocarbon fuels is currently the main source of energy used in the transport and industry. In this regard, considerable attention has been focused on solution of two main tasks: (1) reducing emissions of hazardous combus- tion products (soot, CO) and (2) finding alternative fuels, in partic- ular, biofuels, which could at least partially replace fossil fuels in order to cut down their consumption. One of the possible solutions is to use blends of traditional petroleum-based hydrocarbon fuels with biofuels. On the one hand, the biosystems used for production of biofuels consume CO 2 from air, therefore these biofuels do not contribute to emission of carbon dioxide. On the other hand, biofuels usually represent oxygenated hydrocarbons, and their addition to petroleum-based fuels is able to reduce the emission of soot particles and to decrease the concentration of CO in the combustion products. The common types of biofuels include alco- hols (methanol, ethanol, butanol) and biodiesel fuels, which as a rule represent blends of methyl esters of fatty acids. Over the recent years, the use of biodiesel fuels has been con- stantly growing, mostly as components of mixtures with conven- tional petroleum-based diesel fuels. Consequently, soot formation during combustion of biodiesel fuels and of their blends with con- ventional diesel fuel has been extensively studied, see e.g., [1–10]. This interest is associated with the fact that formation of soot in the combustion processes is of environmental and health concern, and results in reducing performance characteristics of internal combustion engines. Despite considerable progress in understanding the processes of soot formation during the combustion of hydrocarbon fuels http://dx.doi.org/10.1016/j.combustflame.2014.12.015 0010-2180/Ó 2015 The Combustion Institute. Published by Elsevier Inc. All rights reserved. ⇑ Corresponding author at: Voevodsky Institute of Chemical Kinetics and Combustion, Institutskaya str. 3, Novosibirsk 630090, Russia. Fax: +7 (383)3307350. E-mail address: knyazkov@kinetics.nsc.ru (D.A. Knyazkov). Combustion and Flame 162 (2015) 1964–1975 Contents lists available at ScienceDirect Combustion and Flame journal homepage: www.elsevier.com/locate/combustflame