Laminar Flame Speed

The atmospheric pressure laminar flame speeds of premixed ethylene/O2/N2 mixtures were experimentally measured over equivalence ratios ranging from 0.5 to 1.4 and mixture preheat temperatures varying from 298 to 470 K in a counterflow configuration. Ignition delay measurements were also conducted for ethylene/O2/N2/Ar mixtures using a rapid compression machine at compressed pressures from 15 to 50 bar and in the compressed temperature range from 850 to 1050 K. The experimental laminar flame speeds and ignition delays were then compared to the computed values using two existing chemical kinetic mechanisms. Results show that while the laminar flame speeds are reasonably predicted at room temperature conditions, the discrepancy becomes larger with increasing preheat temperature. A comparison of experimental and computational ignition delay times was also conducted and discussed. Sensitivity analysis further shows that the ignition delay is highly sensitive to the reactions of the vinyl radical with molecular oxygen. The reaction of ethylene with the HO2 radical was also found to be important for autoignition under the current experimental conditions.

472 Abstract-In this study, the laminar flame speed of biogas/H2 fuel mixtures is measured from pure biogas to biogas with an addition of 15% H2 in volume by using the method of the inner cone of combustion zone. The laminar flame speed is measured by mean of the geometric parameters of combustion cone capturing images of the flames. The aeration factors covers from stoichiometric conditions to lean conditions. Experimental results have been compared with numerical results obtained with CHEMKIN software, using GRIMECH kinetical mechanism, with good agreement between them and with previous works, showing the reliability of the method used. The trends on laminar flame speed experimental results obtained are explained by mean of numerical results on temperature profile and heat release rate. Hydrogen addition in biogas flames show an important effect, especially in zones near stoichiometric flames, decreasing its effects in lean mixtures combustion. Index Terms-Biogas-hydrogen, laminar flame speed, experimental and numerical study. Resumen-En este trabajo, se ha medido la velocidad de llama laminar de las mezclas de combustible biogás/H2, desde biogás puro hasta mezclas de este con una adición de 15% de H2 en volumen, utilizando el método del cono interno de la zona de combustión o método bunsen. La velocidad de la llama laminar se determina por medio de los parámetros geométricos del cono de combustión capturando imágenes de las llamas. Los factores de aireación abarcan desde condiciones estequiométricas hasta condiciones de mezcla pobre. Los resultados experimentales se han comparado con los resultados numéricos obtenidos con el software CHEMKIN, utilizando el mecanismo cinético de GRIMECH, con una buena concordancia entre ellos y con trabajos previos, mostrando la confiabilidad del método utilizado. Las tendencias en los resultados experimentales de la velocidad de la llama laminar se explican por medio de resultados numéricos sobre el perfil de temperatura y la tasa de liberación de calor. La adición de hidrógeno en las llamas de biogás muestra un efecto importante, especialmente en zonas cercanas a las llamas Acero, Mario J., is with Research estequiométricas, disminuyendo sus efectos en la combustión de mezclas pobres. Palabras claves-Biogás-Hidrógeno, velocidad de llama laminar, estudio numérico y experimental.

Laminar flame speeds of practical fuels including Jet-A1, diesel, palm methyl esters (PME) and blends of PME with diesel and Jet-A1 fuels are determined using the jet-wall stagnation flame configuration and particle imaging velocimetry (PIV) technique. The PME/Jet-A1 and PME/diesel blends are prepared by mixing 10%, 20% and 50% of PME with Jet-A1 and diesel fuels by volume respectively. The experiments are performed over a range of stoichiometries at elevated temperature of 470 K and atmospheric pressure under premixed conditions. The reference flame speed and imposed strain rates are determined from the two dimensional velocity profiles. Subsequently, laminar flame speeds are derived by extrapolating the reference flame speed back to zero strain rates. Experimental results are compared to experimental and simulation data from the literature for large n-alkanes and practical fuels. The results show that laminar flame speeds of Jet-A1 fuel are similar to those of n-decane and n-dodecane, indicating their potential use as surrogate fuels. Peak laminar flame speeds for diesel/air and PME/air mixtures at 470 K are similar, around 86.7 and 86.5 cm/s at equivalence ratios around 1.10 and 1.14 respectively, and that both mixtures exhibit lower flame speeds compared to n-decane and n-dodecane at fuel-leaner and stoichiometric conditions. Blending PME with Jet-A1 and diesel leads to reduced laminar flame speeds on the lean side but increased on the rich side.

Laminar flame speeds of practical fuels including Jet-A1, diesel, palm methyl esters (PME) and blends of PME with diesel and Jet-A1 fuels are determined using the jet-wall stagnation flame configuration and particle imaging velocimetry (PIV) technique. The PME/Jet-A1 and PME/diesel blends are prepared by mixing 10%, 20% and 50% of PME with Jet-A1 and diesel fuels by volume respectively. The experiments are performed over a range of stoichiometries at elevated temperature of 470 K and atmospheric pressure under premixed conditions. The reference flame speed and imposed strain rates are determined from the two dimensional velocity profiles. Subsequently, laminar flame speeds are derived by extrapolating the reference flame speed back to zero strain rates. Experimental results are compared to experimental and simulation data from the literature for large n-alkanes and practical fuels. The results show that laminar flame speeds of Jet-A1 fuel are similar to those of n-decane and n-dodecane, indicating their potential use as surrogate fuels. Peak laminar flame speeds for diesel/air and PME/air mixtures at 470 K are similar, around 86.7 and 86.5 cm/s at equivalence ratios around 1.10 and 1.14 respectively, and that both mixtures exhibit lower flame speeds compared to n-decane and n-dodecane at fuel-leaner and stoichiometric conditions. Blending PME with Jet-A1 and diesel leads to reduced laminar flame speeds on the lean side but increased on the rich side.