Simulation of Particle Synthesis by Premixed Laminar Stagnation Flames
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Simulation of Particle Synthesis by Premixed Laminar Stagnation Flames Abhijit Modak, Karthik Puduppakkam, Chitralkumar Naik, Ellen Meeks Reaction Design, 5930 Cornerstone court west, Suite 230, San Diego, CA 92121, U.S.A. ABSTRACT A sectional method for determining particle size distributions has been implemented within the particle tracking module included with CHEMKIN-PRO. The module is available for use with many types of reactor models, ranging from 0-D batch reactors to laminar flame simulations. Coupled with the Burner-stabilized Stagnation Flame (BSSF) Model, the sectional model offers a high-fidelity, robust, and efficient computational framework for simulating flame synthesis of particles in a laminar, premixed stagnation flame environment. The CHEMKIN-PRO coupling allows inclusion of detailed gas-phase chemistry that determines key particle-formation precursors, along with physical processes such as nucleation and coagulation of particles. These capabilities are demonstrated for two flame-particle systems of practical importance, viz. nanocrystalline titania synthesis and soot formation. The results are compared with experimental data obtained at the University of Southern California (USC) flame facility. Computed particle size distributions show good agreement with experimental data. Simulations have led to exploration of the parameter space for particle production and particle-size influences. INTRODUCTION Flame synthesis is one of the actively used techniques for commercial production of nanoparticles. Stringent requirements on properties, such as size, phase etc., of the synthesized particles demand fundamental understanding of the influence of various process parameters on the particles produced. High scalability of flame synthesis processes has motivated investigations in a laboratory set-up, which can then be scaled-up to production level equipment [1]. Among the laboratory configurations, the burner-stabilized stagnation flame (BSSF) configuration has attracted attention due to its ability to allow systematic measurements of particle evolution without affecting the flow field by an external probe and while retaining a relatively simple 1-D flame structure. In addition, this configuration directly corresponds to deposition systems that can be used in thin film growth from nanoparticles. Recently, the BSSF configuration has also been used to investigate soot particle formation [2]. Computational modeling of such experiments is an invaluable tool that facilitates underlying theoretical development and/or efficient parametric analysis. A simulation tool used for such calculations needs to model the chemical reactions happening in gas-phase as well as at the gas-particle interface, along with physical processes such as particle nucleation and agglomeration. These processes furthermore must be handled in a computationally efficient manner. Even for simplified systems such as 1-D flame reactors, the simulation time can be long. The main reasons for this can be attributed to the size of the gas-phase reac
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