Adiabatic Combustion Waves in Sequential Exothermic-Endothermic Reactions

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Copyright: Qian, Chao
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Abstract
Combustion technology has been used in many areas today, such as in the synthesis of advanced materials, power generation and the production of engines. Combustion has been studied for a long time and many models have been developed to describe such combustion processes. However, most of those models focused on one-step combustion reaction schemes, with few considering more complex combustion reaction schemes. Our research interest is flame propagation in a two-stage reaction under adiabatic conditions in one-dimension. Specifically, we consider the following sequential reaction: A-->B+Q1-->P+Q2. Here both reactions are assumed to proceed at temperature-dependent rates. The first reaction transforms the fuel A into the intermediate product B and heat Q1, while the second reaction transforms the intermediate species B into the final product P and heat Q2. An exothermic-endothermic scheme is considered here, so that Q1>0 (exothermic) and Q2<0 (endothermic). The above reaction scheme has direct relevance to blast furnace chemistry, in particular to the process of iron ore reduction in iron ore/coal composites. In our study, the properties of travelling combustion waves were investigated numerically by solving a system of nonlinear differential equations subject to appropriate boundary conditions. We study the wave speed and extinction limits of the combustion wave. Throughout our numerical investigation, we have employed independent methods to check the accuracy of the numerical solutions to ensure that the dynamics of the system is observed rather than numerical artefacts. Instability in combustion waves has been detected by both experiments and numerical simulations of combustion models. In this thesis, we also present results from our preliminary investigation of oscillation and chaotic combustion profiles. The objective is to investigate how these properties vary as parameter values change. The parameters of interest include those describing the rates and activation energies of the exothermic and endothermic reactions, the ratio of thermal to mass diffusivities of the fuel and intermediates. The transitions from stable to unstable planar wave solutions as well as various bifurcations have been found and numerically analysed.
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Author(s)
Qian, Chao
Supervisor(s)
Sharples, Jason
Sidhu, Harvinder
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Publication Year
2013
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Thesis
Degree Type
Masters Thesis
UNSW Faculty
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