© 2015 N.R. Caetano et al., licensee De Gruyter Open. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 License. Open Eng. 2015; 5:213–219 Research Article Open Access Nattan R. Caetano*, Diego Soares, Roger P. Nunes, Fernando M. Pereira, Paulo Smith Schneider, Horácio A. Vielmo, and Flávio Tadeu van der Laan A comparison of experimental results of soot production in laminar premixed flames Abstract: Soot emission has been the focus of numerous studies due to the numerous applications in industry, as well as the harmful effects caused to the environment. Thus, the purpose of this work is to analyze the soot for- mation in a flat flame burner using premixed compressed natural gas and air, where these quasi-adiabatic flames have one-dimensional characteristics. The measurements were performed applying the light extinction technique. The air/fuel equivalence ratio was varied to assess the soot volume fractions for different flame configurations. Soot production along the flame was also analyzed by measure- ments at different heights in relation to the burner surface. Results indicate that soot volume fraction increases with the equivalence ratio. The higher regions of the flame were analyzed in order to map the soot distribution on these flames. The results are incorporated into the experimen- tal database for measurement techniques calibration and for computational models validation of soot formation in methane premixed laminar flames, where the equivalence ratio ranging from 1.5 up to 8. Keywords: soot volume fraction; light extinction tech- nique; premixed flat flame DOI 10.1515/eng-2015-0016 Received September 05, 2014; accepted January 20, 2015 1 Introduction Soot can be defined as the solid particulate matter pro- duced during combustion [1]. The process of formation is *Corresponding Author: Nattan R. Caetano: Dept of Mechanical Engineering, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brazil, E-mail: nattan@ufrgs.br Diego Soares, Roger P. Nunes, Fernando M. Pereira, Paulo Smith Schneider, Horácio A. Vielmo, Flávio Tadeu van der Laan: Dept of Mechanical Engineering, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brazil based in the conversion and agglomeration of the carbon atoms contained in the hydrocarbon fuel molecules. The formation of soot is not completely understood due to the complexity and velocity of this transformation. Soot is of great interest in engineering, insofar as its formation in- creases the radiated heat transfer, which can be a positive to the considered system. The excessive presence of partic- ulate in diesel engines is, an example, where soot is harm- ful. These particles resulted from an inadequate combus- tion process can become logged in the seat of valves, pre- venting a proper seal in the combustion chamber and lead- ing to a loss of compression in the cylinder. Another exam- ple is gas turbines, where the presence of soot affects the life of the blades due to abrasion for the contact. The emission of this type of particulate matter into the atmosphere causes great harm to the environment, since there is a significant deterioration in air quality. Also, in- duce respiratory problems in humans and is associated with the occurrence of cancer. On the other hand, in in- dustrial heating equipment such as a boiler, the presence of soot increases the heat exchange by radiation from the flame to the system walls, whereas the solid material re- sulting from the process absorbs and emits radiation at a wide range in the wavelengths spectrum [2]. Thus, where a large and uniform heat transfer is required, the presence of soot in combustion is purposely induced. To control the emission of soot in real combustion sys- tems, it is necessary to understand the soot formation and oxidation mechanisms. The basis of knowledge is the de- velopment of models that can predict the particulate mat- ter formation, and the validation of these models requires information about the soot volume fraction. In this way, optical techniques are generally employed to perform the measurement of these quantities due the non- intrusive probing. The necessity for such information in the study of com- bustion was what motivated the present work, which was developed in order to produce significant results for future calibration of measurement techniques and validation of theoretical models in this subject. Hence, the main objec- tive of this study is to analyze the production of soot in pre- mixed laminar flat flames of natural gas and air, measur-