Numerical Simulation of the Effect of Equivalence Ratio and Turbulence Intensity on the Combustion Characteristics and Pollutants Production in a Liquid Fuel Combustor

Due to the increasing development of thermal power stations with fossil fuels, optimizing the combustion process in boilers and combustion chambers are important to reduce the amount of environmental pollutants. This paper examines the equivalence ratio parameter and its effect on maximum temperature of exhaust gases from the combustor and the rate of production and emission of Nitrogen Oxides (NOx) and soot ollutants as well as the turbulence effect on these pollutants. Finite volumes method was used to solve the equations of flow field of gasoil fuel turbulent combustion. Tesner’s two-stage model and Magnussen- Hjertager’s combustion model were used for modeling the process of soot formation and combustion. The amount of NOx was calculated prompt and thermal mechanisms. RNG K-ε model was used for modeling the oscillating terms in the conservation equations and an eddy dissipation model was used to calculate the combustion rate. Results indicate that by increasing the equivalence rate from 0.6 to 1 due to the complete combustion, the maximum temperature of combustor and consequently, NOx increase; also, by increasing the maximum temperature of flame, the rate of soot formation in flame increases. On the other hand, high temperature of combustion chamber causes soot combustion and decreases in output.Considering the turbulence effect also increases the amount of NOx and soot due to the better combustion.

Keywords:

liquid fuel combustion , turbulence , equivalence ratio , soot , NOx