Numerical modelling of non-premixed biogas and LPG combustion to study carbon nanostructures formation in flame

Abstract EN

This work presents the numerical simulation of biogas and LPG fuelled diffusion flames in an axisymmetric chamber to study the formation mechanism of soot and carbon nanostructures in these flames.

The simulation is formulated on transport equations that involve conservation of mass (the continuity equation), momentum (Navier-Stokes equation), energy, and chemical species.

The governing equations are solved using ANSYS FLUENT, centred on the finite volume method.

To predict the soot formation, one step soot model has been incorporated.

The solution of these equations permits the estimation of the temperature field and species concentrations inside the flame.

Simulation is conducted at fixed fuel flow rates and varied oxygen flow rates.

The results reveal that the formation of soot and carbon nanostructures is strongly dependent on peak flame temperature and the concentration of precursor species formed in the flame.

Since two fuels produce an exclusive chemical environment in the flame, the flame temperature and CO concentration conducive to the growth of carbon nanostructures is higher for LPG fuel than for biogas.

Hence, the nucleation process of carbon nanostructures is faster for LPG than biogas.

Moreover, the reactions inside the flame at different locations can also be predicted from flame temperature and species concentration at that location.

First, pyrolysis of fuel occurs near the burner exit, followed by the nucleation and surface growth of carbon nanostructures in the nearby region and oxidation of formed carbon nanostructures near the flame tip.