Numerical and Experimental Study of Inverse Diffusion LPG-Air Flames Pulsation

Abstract

This study uses Ansys 16 commercial package to investigate an accurate numerical model that can trace the flame shape from inverse diffusion combustion of LPG with a focus on the effect of air pulsation on the combustion characteristics. The simulation is based on solving the energy, mass and momentum equations. The large eddy simulation turbulence model and the non-premixed combustion model are used to simulate the pulsating combustion reaction flows in a cylindrical chamber with an air frequency of 10,20,50,100 and 200 rad/sec. The numerical results are in great agreement with the experimental results in the flame shape and the temperature distribution along the combustion chamber in both pulsating and non-pulsating combustion. Diffusion combustion responds positively to pulsating combustion and increases mixing in the reaction zone. Increasing the air frequency increases the temperature fluctuations, the peak turbulent kinetic energy and maximum velocity magnitude, respectively, by 27.3%, 300%, and 200%. Increasing the Strouhal number to 0.23 shortens the flame by 40% and reduces nitric oxide and carbon monoxide by 12% and 40%, respectively, including an environmentally friendly combustion product. The maximum average temperature dropped from 1800 K to 1582 K with a very homogeneous temperature distribution along the combustion chamber which is very important for furnaces.