جستجوی مقالات مرتبط با کلیدواژه « احتراق متقارن محور » در نشریات گروه « مکانیک »

In this paper, the simultaneous study of the effects of the excess air ratio and the combustion mechanisms on the temperature and distribution of species in the porous medium burners with continuous porosity variation has been investigated. For this purpose, multi-step chemical kinetics have been used and their effects on the temperature profile, mass fraction of the main species and emission of pollutants for different values of the excess air ratio have been investigated. Problem-solving equations include continuity equation, momentum equations, gas, and solid phase energy equations, and chemical equilibrium equation are solved using the finite volume method and SIMPLE algorithm is used for the relationship between velocity and pressure. The results showed that for excess air ratio of 1.5, the results of combustion mechanisms have the same accuracy in predicting the temperature profile and mass fraction of the main species, and then, for additional values of the excess air ratio, the results of the combustion mechanisms Show a slight difference. This is while the greatest difference in the results is observed for the stoichiometric condition. Also in stoichiometric conditions, the NO emission rate using the GRI-3.0 combustion mechanism is predicted to be zero, and for the rest of the coefficients of the excess air ratio, its value will be of the order of magnitude 10-6.

In this paper, the results of the two-dimensional and axisymmetric modeling of the methane-air pre-mixed combustion with multi-step kinetics in a porous medium with continuous porosity change have been presented. In order to determine the thermophysical and thermochemical properties of species, the CHEMKIN II program and Basic information used. Continuity equations, Navier Stokes, gas and solid phase heat transfer equations, and chemical species governing equations are solved by using of finite volume method. The SIMPLE algorithm has been used for the relationship between speed and pressure. The burner under the studied includes two preheated and combustible areas. In this paper, we study the effects of divergence angle changes and length of burner preheating area on temperature profiles andemission of pollutants. The results showed that by increasing the divergence angle, the amount of NO contamination in the burner output increases dramatically, while by increasing the length of the preheating region, the amount of emission of this pollutant in the output decreases.

In this paper, a two-dimensional axisymmetric model for premixed methane/air combustion in porous media has been developed. For this aim, a numerical model with chemkinII library is used along with its database. This code solves the continuity, navier stokes, the solid and gas energy and the chemical species transport equations using the finite volume method. The pressure and velocity have been coupled with the simple algorithm. In this paper, an attempt is made to apply the profile of porosity instead of constant porosity for two zones of the burner. The results showed that by applying the varying porosity along the burner, the peak temperature can be decreased by about 4.5%, and subsequently, the amount of exhaust pollutants such as NOx can also be decreased while increase in pressure loss along the burner is negligible. The effects of increasing the inlet velocity and the wall temperature are also investigated. The results showed that by increasing the inlet velocity, the peak temperature and the emission of NOx will be decreased and also by increasing wall temperature, the peak temperature and the emission of NOx will be increased.

In this paper a two-dimensional axisymmetric numerical model with variable porosity for premixed methane/air combustion in porous media has been developed. For this purpose، multi step mechanisms such as GRI 1. 2، GRI. 2. 11، GRI. 3. 0، Skeletal and a mechanism with 17 species and 58 chemical reactions has been used and the effects of the mechanisms on the temperature profile، mass fraction of species and emission of pollutants have been investigated. This model solves the continuity، Navier Stokes، the gas and solid energy and the chemical species transport equations by using the finite volume method. The pressure and velocity have been coupled with the SIMPLE algorithm. The results showed that the combustion mechanisms have the same accuracy in predicting of temperature profile and mass fraction of species in order to the GRI. 1. 2، GRI. 2. 11، GRI. 3. 0 mechanisms are the same accuracy and also the skeletal and 17 species mechanisms are the same in predicting of temperature profile and mass fraction of species. Also the effects of increasing the inlet velocity and the volumetric heat transfer coefficient at combustion zone with variation porosity are investigated. The results showed that by increasing in inlet velocity، the peak temperature and the amount of NOx emission will be decreased and also by decreasing in volumetric heat transfer، the peak temperature will be decreased.