The stabilized methane–air counterflow flame into a plus-shaped chamber with platinum catalyst–coated walls: An emission estimation

Analysis of unsteady CH4/Air counterflow premixed flame into a newly designed plus-shaped channel is investigated in this study. The main objective is to explore the impact of platinum catalytic–coated walls of the combustion chamber on the flame characteristics and pollutant emissions. The OpenFOAM platform is used as a numerical simulation tool to investigate the effects of various equivalence ratios, from the range of lean to rich flames, and passing the reaction time on the counterflow flame characteristics and pollutant emissions of a plus-shaped chamber with the platinum catalyst–coated wall. Results show that the integrated temperature over the proposed geometry with platinum surfaces increases by 18% compared to the non-catalytic case. The numerical simulation revealed that presence of the platinum catalyst on the wall of the chamber has significant impact on reducing the pollutant emissions. This is evident as a 99.5% decrease on NO2 emission and a 58% reduction on CO2 formation are found.

Non-Premixed Filtered Tabulated Chemistry: Filtered Flame Modeling of Diffusion Flames

The flame front filtering is a well-known strategy in turbulent premixed combustion. An extension of this approach for the non-premixed combustion context has been proposed by means of directly filtering counterflow diffusion flamelets. Promising results were obtained for the non-premixed filtered tabulated chemistry formalism on 1-D and 2-D unresolved counterflow flame configurations. The present paper demonstrates the soundness of this approach on a 3-D real laminar non-premixed coflow flame. The model results are compared against the direct filtering of the fully resolved laminar diffusion flame showing that the formalism adequately describes the underlying physics. The study reveals the importance of the one-dimensional counterflow flamelet hypothesis, so that the model activation under this condition is ensured by means of a flame sensor. The consistent coupling between the model and the flame sensor adequately retrieves the flame lift-off and satisfactorily predicts the profile extension due to the filtering process.

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.