Analysis of blowoff dynamics from flames with stratified fueling

A Comparison of the Characteristics of Planar and Axisymmetric Bluff-Body Combustors Operated under Stratified Inlet Mixture Conditions

“…Chemiluminescence measurements of the electronically excited OH * and CH * radicals are frequently employed to identify the topology of the flame front, since, for example, the electronically excited OH * exists mainly in the flame front region (e.g., [4][5][6][7]12]). Image acquisition and data reduction were performed using the Davis 8.0 software from LaVision.…”

“…Under both cases strong recirculation regions assist in flame stabilization under high stretch rates leading to a spread in the disposition of the flame front alongside the wake flanks. The wake development in the square is affected by periodically asymmetric vortex shedding with strength that drastically varies between isothermal and low or high fuel injection reacting conditions [6,11,12,17]. On the other hand the axisymmetric disk exhibits low frequency vortex rollup from the rim periphery, which is again stronger under isothermal conditions [13,18].…”

“…Moreover the growing combination of burner and mixture placement setups in lean combustors has increased current interest for a more complete description of such flame types. Therefore comparative examinations of the performance of the axisymmetric versus the slender two-dimensional bluff-body stabilization configuration under stratified conditions are warranted; these could provide useful information regarding the more effective control, exploitation, or even extension, for example, through appropriate placement of pilot injection, of the operational margin under both setups (e.g., [2,4,6,11,12]).…”

“…The above geometries were chosen because these comprise two of the most popular stabilizers, at the opposite end of the field of practical applications, and comparisons of their limiting performance could provide useful directions in the design process for a wide range of configurations. Identification of the individual characteristics such as, for example, flame and recirculation lengths, flame front topologies, turbulence levels, vortical activity, and under successively weakening stabilization within the same geometry arrangement may help determine suitable methodologies to extend stability in a fashion tailored not only for the particular flame geometries but also for a range of intermediate variants, upgrades, or retrofits [2,4,12]. Furthermore both of these setups have been systematically investigated under fully premixed conditions and their operation under stratified conditions could then be directly contrasted against such a range of well documented data.…”

Application of a Central Composite Design for the Study of NOx Emission Performance of a Low NOx Burner

“…When bluff body is used as a flame holder, the incoming fuel and oxidizer mixture is ignited by the hot combustion products recirculating in a wake structure formed behind the bluff body. This stabilization mechanism has been investigated extensively by many researchers [6][7][8][9][10][11][12]. Many studies associated with bluff body stabilization mechanism focus on premixed combustion systems, where premixed fuel and oxidizer are provided to the combustion zone and thus complex physics that controls mixing process can be neglected.…”