Numerical Study On Laminar Premixed Flames

Laminar premixed flames are common combustion phenomena, and have wide application in our daily life and industrial production. Study on laminar premixed flames has important significance for their applications, but perhaps more importantly, it is the foundation of understanding turbulent flames. Many turbulent flame theories are based on an underlying laminar flame structure, because laminar premixed flames are fundamental combustion phenomena which embody the fluid flow, molecular transport, chemical reaction and so on, and both in laminar and turbulent flames, there are similar chemical process. Therefore, combustion process could be understood better by study on laminar premixed flames. The study can also provide theoretical support for improving combustion technique, reducing combustion pollution, enhancing combustion process control level. Therefore, laminar premixed flames have been becoming hot topics in combustion theory research.In this thesis, one-dimensional steady laminar premixed freely propagating flames are numerically simulated with detailed chemical reaction mechanisms. Firstly, the physical model of the problem is given, and then the governing equations are presented correspondingly, hence the domain, the equations together with the specified conditions are discretized, finally the resultant algebraic equations are solved. The extensive analysis for the detailed chemical reaction mechanisms of hydrogen-air, carbon monoxide-air, methane-air and blast furnace gas-air are made. After that, the numerical computations for one-dimensional steady laminar premixed freely propagating flames of methane-air and blast furnace gas-air are finished to understand the combustion characteristics of methane and blast furnace gas, and further to provide theoretical support for their practical application.The present calculation contains two aspects:(1) One-dimensional steady laminar methane-air premixed freely propagating flames are numerically simulated with the chemical reaction mechanism of GRI3.0. Mass flux, temperature profiles, species concentration profiles and gas velocity profiles in laminar methane-air premixed flames are researched. The effect of equivalence ratios and initial temperatures on laminar methane-air premixed flames is also analyzed.(2) A new chemical reaction mechanism for blast furnace gas-air combustion is presented based on intensively studying on the chemical reaction mechanisms of hydrogen-air, carbon monoxide-air and methane-air. One-dimensional steady laminar blast furnace gas-air premixed freely propagating flames are numerically simulated with the new chemical reaction mechanism. Mass flux, temperature profiles, species concentration profiles and gas velocity profiles in laminar blast furnace gas-air premixed flames are researched. The effect of equivalence ratios and initial temperatures on laminar blast furnace gas-air premixed flames is also analyzed.