Soot measurements in laminar flames of gaseous and (prevaporized) liquid fuels

A high pressure vessel and diffusion burner (HPVB) were designed, constructed and integrated with an evaporation system, to enable laminar flames studies of gaseous and vaporized liquid fuels. This experimental setup is designed to offer ample optical accessibility for laser diagnostics techniques; its capabilities and specifications are described. Soot volume fraction measurements are performed with line-of-sight attenuation (LOSA) and validated using data of ethylene flames from literature. The first measurements of a vaporized liquid fuel (n-heptane) are reported. A stable laminar n-heptane flame is achieved with a maximum standard deviation in soot volume fraction of 0.04 ppm

The effect of elevated pressures on the laminar burning velocity of methane + air mixtures

In spite of the large amount of research spent on the evaluation of the high pressure dependence of laminar burning velocity of methane + air flame, there still exists a large uncertainty in the data for various reasons. In order to reduce the scatter to acceptable levels, the Heat Flux Method (HFM), known as a potential method with high accuracy, has been extended to higher pressures. New measurements of the laminar burning velocity of methane + air flames are presented. Non-stretched planar flames were stabilized on a perforated plate burner which was placed in a high pressure environment. The experimental results are reported for a pressure range between 1 and 5 atm. The equivalence ratio was varied from 0.8 to 1.4. Comparisons with several recent literature sources (experiments) show good agreement. An exhaustive literature survey was performed to study the numerous existing laminar burning velocity correlations for its pressure dependence. It is indicated from the literature that many of the deduced correlations use stretched laminar burning velocity results. Many used only few data points for the pressure behavior and correlations and therefore show wide discrepancies. As the heat flux method furnishes quality results with reduced errors, the results were further utilized in deducing a power-law pressure dependence. Numerical simulations were also performed using two widely used chemical reaction mechanisms, which were further involved in comparing correlations. The proposed power exponent ß1 shows a non-monotonic behavior at equivalence ratio around 1.4 in experiments and simulations. Through species and reaction flux analysis it was observed that CH3 consumption through various reactions remain pressure dependent and show non-monotonic behavior at equivalence ratio around 1.4