Experimental and Numerical Study on the Sooting Behaviors of Furanic Biofuels in Laminar Counterflow Diffusion Flames

Furanic biofuels have received increasing research interest over recent years, due to their potential in reducing greenhouse gas emissions and mitigating the production of harmful pollutants. Nevertheless, the heterocyclic structure in furans make them readily to produce soot, which requires an in-depth understanding. In this study, the sooting characteristic of several typical furanic biofuels, i.e., furan, 2-methylfuran (MF), and 2,5-dimethylfuran (DMF), were investigated in laminar counterflow flames. Combined laser-based soot measurements with numerical analysis were performed. Special focus was put on understanding how the fuel structure of furans could affect soot formation. The results show that furan has the lowest soot volume fraction, followed by DMF, while MF has the largest value. Kinetic analyses revealed that the decomposition of MF produces high amounts of C3 species, which are efficient benzene precursors. This may be the reason for the enhanced formation of polycyclic aromatic hydrocarbons (PAHs) and soot in MF flames, as compared to DMF and furan flames. The major objectives of this work are to: (1) understand the sooting behavior of furanic fuels in counterflow flames, (2) elucidate the fuel structure effects of furans on soot formation, and (3) provide database of quantitative soot concentration for model validation and refinements.

Investigation of unsteady premixed micro/macro counterflow flames for lean to rich methane/air mixture

In the current work, an unsteady analysis of methane/air premixed counterflow flame is carried out for different flame conditions and stability parameters considering different strain rate values. The results are presented at unsteady and final steady conditions and the impact of time-dependent regimes and variations in equivalence ratio, from lean flame to rich one are analysed. The governing equations including continuity, momentum, energy, and species are numerically solved with a coupled of simple and Piso algorithm. It is also found that when the strain rate value is 1000s-1, for flame stability, the hydraulic distance of the microchannel must be at least 0.05mm. Increasing the strain rate results in decreasing the time of stabilizing temperature distribution with a faster quasi-steady equilibrium. The necessity of time dependent analysis is to comprehend the variations in main factors of flame structure before reaching the finalized steady state condition. Therefore, by designing an intermittent automatic valve, if the flow stops in time period of 0.0025s and starts again, the formation of NO2 and CO2 will be reduced about 50% and 9%, respectively, in a case with a=100s-1.