Abstract: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 analyzed. The governing equations including continuity, momentum, energy, and species are numerically solved with a coupled simple and Piso … Show more
“…As can be seen in the figure, the results of the current study and Wada et al, 6 with the strain rate of 150 s -1 , are compared which shows an acceptable agreement with the maximum error of 4% in the maximum temperature of the flame. As can be seen, the good agreement of this comparison confirms the accuracy of the presented model.Figure 2.Centerline temperature distribution versus longitude coordinates for the current study, as well as (10), and experimental data (6)…”
Section: Resultssupporting
confidence: 79%
“…6 similar to Figure 2 of Ref. 10. As can be seen in the figure, the results of the current study and Wada et al, 6 with the strain rate of 150 s -1 , are compared which shows an acceptable agreement with the maximum error of 4% in the maximum temperature of the flame.…”
Section: Resultssupporting
confidence: 74%
“…Centerline temperature distribution versus longitude coordinates for the current study, as well as (10), and experimental data (6)…”
Section: Resultsmentioning
confidence: 99%
“…These researchers applied multi-step modeling that simulated 133 species and 922 reactions. Edalati-nejad et al 10,11 numerically investigated counterflow methane flame, taking into account multi step reactions of methane combustion and GRI (Gas Research Institute) 3.0 mechanism. They found that the residence time factor is more sensitive to the inlet velocity compared to the inlet temperature.…”
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.
“…As can be seen in the figure, the results of the current study and Wada et al, 6 with the strain rate of 150 s -1 , are compared which shows an acceptable agreement with the maximum error of 4% in the maximum temperature of the flame. As can be seen, the good agreement of this comparison confirms the accuracy of the presented model.Figure 2.Centerline temperature distribution versus longitude coordinates for the current study, as well as (10), and experimental data (6)…”
Section: Resultssupporting
confidence: 79%
“…6 similar to Figure 2 of Ref. 10. As can be seen in the figure, the results of the current study and Wada et al, 6 with the strain rate of 150 s -1 , are compared which shows an acceptable agreement with the maximum error of 4% in the maximum temperature of the flame.…”
Section: Resultssupporting
confidence: 74%
“…Centerline temperature distribution versus longitude coordinates for the current study, as well as (10), and experimental data (6)…”
Section: Resultsmentioning
confidence: 99%
“…These researchers applied multi-step modeling that simulated 133 species and 922 reactions. Edalati-nejad et al 10,11 numerically investigated counterflow methane flame, taking into account multi step reactions of methane combustion and GRI (Gas Research Institute) 3.0 mechanism. They found that the residence time factor is more sensitive to the inlet velocity compared to the inlet temperature.…”
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.
“…Previous analytical, experimental, and numerical studies focused primarily on the stable and weak flame modes for various fuel mixtures and under various operating conditions. These studies provided insight to understand the concepts of low-temperature ignition (LTI), cool flames, and the influence of the negative temperature coefficient (NTC) region [4,12,[16][17][18][19][20][21]. It has been shown that cool flames are usually generated in the unburned fuel mixture region, while another conventional flame propagates through the reacting mixture.…”
Understanding and improving the performance of miniature devices powered by micro-combustion have been the focus of continued attention of researchers recently. The goal of the present work is to investigate the behavior of premixed methane–air combustion in a quartz microreactor with an externally controlled wall temperature. Specifically, the impacts of the flow inlet velocity, the equivalence ratio, and the microreactor channel size are examined. This study is conducted by means of computational simulations, and the results are validated against prior experimental data, as well as by other similar studies in the literature. Utilizing simulation results with detailed chemistry, the present work provides more in-depth insight into a variety of phenomena, such as ignition, flame propagation, flames with repetitive extinctions and ignitions (FREI), and flame stabilization. In particular, the ignition, the flame span, and the FREI-related characteristics are scrutinized to understand the underlying physics of the flame stability/instability modes. It is shown that the flames appear stable at higher inlet velocities, while the FREI mode is detected at a lower inlet velocity, depending on the equivalence ratio and the channel size. The findings also explain how different operating conditions impact the flame characteristics in both stability modes.
In this article, the effect of different boundary conditions and different thermal and physical properties of walls and gas on flame characteristics and stability of hydrogen–air mixture are investigated using an analytical method. This method solves the gas–wall energy equation, and the hydrogen mass conservation equations. The jump conditions are obtained by integrating the energy and mass equation into a small control volume around the flame. For validation of this model, the temperature distribution on the outer surface of the wall is compared with experimental data that show the maximum relative error of 3.5% for Q = 400 mL/min and 4.9% for Q = 200 mL/min. The maximum variation of gas temperature is nearly 6.5 times of wall temperature variation. The wall can be considered one‐dimensional for conventional wall materials with K > 10. For the existence of combustion inside the chamber, when the value of K is greater than 10, the Péclet number should also be considered greater than 10. In a constant equivalence ratio, increasing the medium temperature increases flame stability.
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