The need for measuring laminar flame speeds for various fuels and blends is crucial for determining flame stabilization characteristics and design parameters for practical burner configurations. Various methodologies have been used over the years to estimate laminar flame speeds with axisymmetric Bunsen flames being one of the oldest and “simplest” techniques. Nonetheless, the cost of the instrumentation to measure laminar flame speeds with minimum experimental uncertainties remains noticeably high. The present work describes a low-cost flame speed estimation methodology and investigates its efficacy for methane and propane-air mixtures at different equivalence ratios. Flame propagation speeds with respect to the unburned gas were evaluated using both the cone angle and the surface area measurement methods. The experimental approach involves an automated image processing procedure that numerically processes plain photographic images of the flames and estimates the Bunsen cone borders, the cone angle, and the surface area in a straightforward manner. Those values are then used to extract the flame speed. Thus, it can be considered as an integrated experimental and numerical processing methodology that affords flame speed estimation, with reasonable accuracy, for a variety of gaseous fuel-oxidizer mixtures, relevant to industrial burner applications.

The work describes an experimental investigation of propane flames established through fuel injection and gradual premixing with preheated and vitiated oxidizing air, within a double-cavity arrangement, formed along a cylinder and two concentric disks. Ignition of the inlet stratified and vitiated mixture and flame stabilization is established at the recirculation region of the afterbody disk. Measurements of mean velocities, temperatures, OH* and CH* chemiluminescence and gas analysis provided information for the interpretation of the relative variations in flame structure and burner performance. The study illustrates some aspects regarding the influence of the preheated/vitiated conditions on the combustion of the inlet stratified fuel-air mixture profile, with respect to flame front stabilization, disposition, and burner emissions. Some important differences in the vitiated flame structure and topology are discussed in comparison to the unvitiated case characteristics, in an initial effort to e...

An investigation of the characteristics of turbulent prevaporized n-heptane-air flames, stabilized in the downstream wake region of a stratifier/bluff-body combustor configuration under the effect of inlet fuel-air mixture stratification and preheat, is presented. Experimental and computational results for different fuel-air mixing wake topologies have been obtained by regulating the fuel injection level and the incoming fuel-air ratio gradient. Fourier transform infrared analysis and particle image velocimetry measurements were taken to assess the mixing field characteristics in the near-wake region under nonreacting operation. Chemiluminescence measurements were also obtained to assess the flame topology under reacting conditions. In the computations, an implicit, finite-volume-based large eddy simulation method, coupled with a 25-species reduced $\mathrm{n}\text{-}{\mathrm{C}}_7{\mathrm{H}}_{16}$ kinetic scheme, was utilized for reproducing the mixing and the reacting field characteristics.