Combustion instability is a process which involves unsteady chemical kinetic, fluid mechanic, and acoustic processes. It can lead to unstable behavior and be detrimental in ways ranging from faster part fatigue to catastrophic system failure. In terms of combustion methodology, combustion instability has been a key issue for lean premixed combustion. The primary objective of this work is to imp...

This study presents results on the detection of CH, in low-pressure methane-oxygen flames using resonance-enhanced multiphoton ionization (REMPI) techniques. Experiments in a discharge-flow reactor were performed for optimization purposes. Excitation wavelengths near 286 and 333 nm were examined: the former is not recommended for flame applications, although it may be preferable under flow reac...

The interaction of a vortex pair with a premixed flame serves as an important prototype for premixed turbulent combustion. In this study, we investigate the interaction of a counterrotating vortex pair with an initially flat premixed methane flame. We focus on characterizing the mechanical nature of the flame-vortex interaction and on the features of the interaction strongly affected by fuel eq...

The chemical structure of an opposed flow, methane diffusion flame is studied using a chemical kinetic model and the results are compared to experimental measurements. The chemical kinetic paths leading to aromatics and polycyclic aromatics hydrocarbons (PAHs) in the diffusion flame are identified. These paths all involve resonantly stabilized radicals which include propargyl, allyl, cyclopenta...

Vertically well-aligned multi-walled carbon nanotubes (MWNTs) with uniform diameters ( 15 nm) were grown on catalytic probes at high yield rates in an inverse diffusion flame (IDF) of a co-flow jet configuration using methane as fuel. Varied parameters investigated included: alloy composition (e.g. Fe, Ni/Cu, Ni/Cr/Fe), sampling positions within the flame structure, and voltage bias applied to ...

Laminar flame speeds of mixtures of ethane, ethylene, acetylene, and carbon monoxide with small amounts of hydrogen addition at both atmospheric and elevated pressures were experimentally and computationally determined. It was found that the approximate linear correlation identified previously between the laminar flame speeds and an appropriate definition of the amount of hydrogen addition for ...

Plasma-induced combustion (PIC) has been shown to improve the reliability, efficiency, and delay time of ignition in flight systems like augmentors and scramjets. These high-velocity systems are mostly used in military applications, and improvement may help commercial viability. To understand this chemical process, the concentration of radicals, particularly H radicals, must be tracked through ...

New combustion systems based on ultra-lean premixed combustion have the potential for dramatically reducing pollutant emissions in transportation systems, heat, and stationary power generation. However, lean premixed flames are highly susceptible to fluiddynamical combustion instabilities, making robust and reliable systems difficult to design. Lowswirl burners are emerging as an important tech...

The shapes (flame-sheet and luminous-flame boundaries) of steady nonbuoyant round hydrocarbon-fueled laminar-jet diffusion flames in still and coflowing air were studied both experimentally and theoretically. Flamesheet shapes were measured from photographs using a CH optical filter to distinguish flame-sheet boundaries in the presence of blue CO2 and OH emissions and yellow continuum radiation...

Methane is a climatologically important greenhouse gas, which plays a key role in regulating water vapour in the stratosphere and hydroxyl radicals in the troposphere. Recent findings that vegetation emits methane have stimulated efforts to ascertain the impact of this source on the global budget. In this work, we present the re-5 sults of high frequency (ca. 1 min −1) methane measurements cond...