Thermal and fluid flow analysis of swirling flameless combustion

Flameless combustion is a novel combustion mode that is also to achieve ultra-low emissions of NOx and CO while producing a uniform temperature distribution and a stable combustion. In this work, a newly designed Internally Preheated Swirling Flameless Combustor (IPSFC) has been developed at the High Speed Reacting Flow Laboratory (HiREF), Faculty of Mechanical Engineering, Universiti Teknologi Malaysia (UTM) to achieve high performance combustion and low emission. The study examines the sequential development of a low emission swirling flameless vortex combustor operating from a thermal load of 7 kW to 15 kW. The swirling flameless combustor has been modified to include preheating where the fresh air passes through a helical tube that is fixed inside the combustion chamber before being injected into the flameless combustor for some experiments. The objective of this study is to investigate in detail the role of air inlet geometry with and without air preheating on the performance of the swirling flameless combustion without the addition of diluted gas. Investigation on the effect of multiple air–fuel injection configuration found that the case of SFR42 to be the best configuration for optimum flameless combustion performance. SFR42 is a swirling combustor with 4 inlets of tangential air and 12 inlets axial air with 11 inlets coaxial fuel. The lowest NOx and CO emissions are observed at the equivalence ratio of 0.8 with the value of 4 ppm and 24 ppm, respectively. In general temperature uniformity which is an important characteristic of flameless combustion is observed to vary from 0.03 to 0.06 at the different equivalence ratio. This work also demonstrated the achievement of swirling flameless combustion with and without preheated tangential air. Overall, preheated air has contributed to the increase of 5% thermal efficiency compared to the non-preheated case at the expense of 4 ppm maximum increment of NOx emission. In this thesis some simulation study is also performed to investigate the detail flow field inside the swirl combustor. The numerical investigation confirms the experimental finding on the outstanding performance of SFR42 configuration. It is found that in this configuration the bulk swirling motion was produced in the combustor for good mixing between fuel and oxidizer which in turn lead to complete combustion at low peak temperature. This results in the combustion process with low emission

Numerical calculation of the recirculation factor in flameless furnaces

This paper performs calculations of the recirculation factor in simulations of a flameless combustion furnace with different percentages of oxygen in air (from 21% to 100% O2). Results are compared with Magnussen’s recirculation theory and show that when there are chemical reactions, the recirculation results are overpredicted. An alternative correlation to Magnussen’s theory is proposed, useful in calculating the recirculation factor in flameless furnaces. Also, calculation of the recirculation factor obtained through numerical simulation for different configurations of confined jets taken from literature which do not involve chemical reactions, when compared with the recirculation confined jet theories of Craya-Curtet, Thring-Newby and Magnussen show that as recirculation increases, all the theories overpredict the recirculation factor

Numerical calculation of the recirculation factor in flameless furnaces

This paper performs calculations of the recirculation factor in simulations of a flameless combustion furnace with different percentages of oxygen in air (from 21% to 100% O2). Results are compared with Magnussen's recirculation theory and show that when there are chemical reactions, the recirculation results are overpredicted. An alternative correlation to Magnussen's theory is proposed, useful in calculating the recirculation factor in flameless furnaces. Also, calculation of the recirculation factor obtained through numerical simulation for different configurations of confined jets taken from literature which do not involve chemical reactions, when compared with the recirculation confined jet theories of Craya-Curtet, Thring-Newby and Magnussen show that as recirculation increases, all the theories overpredict the recirculation factorEn este trabajo es realizado el cálculo del factor de recirculación en simulaciones de un horno de combustión sin llama con diferentes porcentajes de oxígeno en el comburente (de 21% a 100% de O2).Los resultados se comparan con la teoría de recirculación de Magnussen, teniéndose que cuando hay reacciones químicas los resultados de recirculación son sobrepredecidos por esta teoría, entonces en lugar de usar la teoría de Magnussen, se propone usar una correlación obtenida por medio de simulaciones, para calcular el factor de recirculación en hornos de combustión sin llama. También se presentan los resultados obtenidos del cálculo del factor de recirculación por medio de simulación numérica para diferentes configuraciones de jets confinados tomadas de la literatura, las cuales no involucran reacciones químicas, cuyos resultados son comparados con teorías de recirculación de jets confinados de Craya-Curtet, Thring-Newby y Magnussen, obteniéndose que a medida que la recirculación es mayor, los resultados numéricos se van alejando de estas teoría

Numerical calculation of the recirculation factor in flameless furnaces

This paper performs calculations of the recirculation factor in simulations of a flameless combustion furnace with different percentages of oxygen in air (from 21% to 100% O2). Results are compared with Magnussen’s recirculation theory and show that when there are chemical reactions, the recirculation results are overpredicted. An alternative correlation to Magnussen’s theory is proposed, useful in calculating the recirculation factor in flameless furnaces. Also, calculation of the recirculation factor obtained through numerical simulation for different configurations of confined jets taken from literature which do not involve chemical reactions, when compared with the recirculation confined jet theories of Craya-Curtet, Thring-Newby and Magnussen show that as recirculation increases, all the theories overpredict the recirculation factor

Numerical Simulation of Convective-Radiative Heat Transfer

This book presents numerical, experimental, and analytical analysis of convective and radiative heat transfer in various engineering and natural systems, including transport phenomena in heat exchangers and furnaces, cooling of electronic heat-generating elements, and thin-film flows in various technical systems. It is well known that such heat transfer mechanisms are dominant in the systems under consideration. Therefore, in-depth study of these regimes is vital for both the growth of industry and the preservation of natural resources. The authors included in this book present insightful and provocative studies on convective and radiative heat transfer using modern analytical techniques. This book will be very useful for academics, engineers, and advanced students