Investigation of flame structure and stabilisation characteristics of palm methyl esters diffusion flames

Experiment and numerical analysis were conducted to investigate the flame structure and stabilisation characteristics of palm methyl esters (PME) diffusion flame. In the experiment, nitrogen-diluted biodiesel mixtures with fuel mole fraction range from 0.02 to 0.03 were supplied to the nozzle through a pre-heated pipeline at a temperature of 550 K. The results showed that the stabilisation of the PME lifted flames was mainly controlled by the jet momentum, especially in the jet developed region, whereas the role of the buoyancy in the stabilisation of the lifted flame was not significant. In the simulation, biodiesel lifted flames were modelled using open-source tool, laminarSMOKE in OpenFOAM. Numerical analysis revealed that the stabilisation mechanism of the lifted flames at jet momentum dominated regime could be based on the factors that affect the edge flame propagation speed, such as mixture strength and fuel Lewis number. Additional numerical simulations were also carried out to investigate the role of each fatty acid methyl ester (FAME) component on the liftoff behaviour, and it was found that the unsaturated FAME, methyl oleate, has a lower liftoff height compared to the saturated FAME, methyl palmitate due to the higher reactivity of the methyl oleate.