Structure and soot properties of nonbuoyant ethylene/air laminar jet diffusion flames

Smoke-point properties of non-buoyant round laminar jet diffusion flames

“…Thesedifferencesgenerallyhavebeenattributedto the different soot pathsin buoyantand nonbuoyant flames that were just discussedas well as increasedeffects of radiative quenching in nonbuoyant flames due to their increasedcharacteristic residencetimes comparedto buoyantflames. A concernabouttheseresults,however,is that limited testing using space-based microgravityfacilitiesyieldedsignificantlydifferentresultsthanobserved using ground-based microgravityfacilities [25]. Thus,theobjectiveof the present study was to more completelyaccessthesedifferencesby measuringlaminarsmoke-pointproperties during long-termexperiments(100-230s)at smallg-jitter conditionscarried out on orbit in the SpaceShuttleColumbia(flights STS-83and94).…”

“…Experimental methods ,,viii be described only briefly, see Urban et al [25] for details about the apparatus and instrumentation and Linet al [28] for a tabulation of test conditions. Monitoring measurements included the fuel flow rate, the fuel inlet temperature, the chamber pressure, and the chamber gas temperature [25,28].…”

“…Monitoring measurements included the fuel flow rate, the fuel inlet temperature, the chamber pressure, and the chamber gas temperature [25,28]. The flames were observed using a color CCD video camera …”

“…Because changes may be made before formal publication, this is made available with the understanding that it will not be cited or reproduced without the permission of the author. The potential differencesbetweenthe laminar smoke propertiesof buoyant and nonbuoyant flamescanbeattributedmainlyto thedifferenthydrodynamicpropertiesof these flames [24][25][26][27]. In particular,sootparticlesaretoo largeto diffuse like gasmoleculessothat they areconvectedby gasvelocitiesasidefrom minor effectsof thermophoresis [24].…”

Effects of structure and hydrodynamics on the sooting behavior of spherical microgravity diffusion flames

“…4 shows, upon ignition a premixed deflagration propagatesoutward quickly and then the flame contracts into nonpremixedconditions From about200-400ms after ignition until drop termination,the flames grow monotonically but do not reachsteadydiameters;this transient behavior is especially evident where nitrogen is supplied in the ambientgas. Microgravity tests in gas-jet flames indicate that althoughquasi-steady flame shapesappearwithin a few seconds [20,21], steady sooting behavior requires test times exceeding those of ground-basedfacilities [21].…”