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Showing 1 to 20 of 61 for “"Flame structure"”.
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The Flame Structure of AP /Htpb Sandwiches
The ultraviolet flame emissions observed in the experiments show a correspondence with the fuel-rich region of the flame, as determined with a Schvab-Zeldovich model. This is reasonable since the primary sources of ultraviolet emission in the 305--315 nm region, electronically excited OH and the CO …
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Flame Structure and Emissions of Strongly-Pulsed Turbulent Diffusion Flames with Swirl
This work studies the turbulent flame structure, the reaction-zone structure and the exhaust emissions of strongly-pulsed, non-premixed flames with co-flow swirl. The fuel injection is controlled by strongly-pulsing the fuel flow by a fast-response solenoid valve such that the fuel flow is …
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Thermal Diffusion and Flame Structure in a Laminar Hydrogen Jet Diffusion Flames
The steady, undriven flames were used to evaluate the thermal diffusion model. In addition to showing a premixed area inside the flame zone of the stabilization region, temperature and concentration measurements indicated that jet flame attachment is sensitive to nozzle and flow conditions. The …
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In Situ Flame Structure Imaging of Composite Propellants using High-Speed Planar Laser-Induced Fluorescence
… to determine how microscale propellant flame structure varies with propellant formulation and pressure. Propellants with monomodal AP particle size distributions, changing coarse-to-fine AP particle size ratios, and different sizes and locations of burning rate catalysts have been …
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Investigation of atomization mechanisms and flame structure of a twin-fluid injector for different liquid fuels
… kerosene, biodiesel, straight VO and glycerol flames at the combustor exit are reported using a novel flow blurring (FB) injector. The PDPA measurements in the FB sprays at least 1.0 cm downstream of the injector exit quantitatively show the superior fuel-flexibility and atomization capability …
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Laminar burning velocity of hydrogen and flame structure of related fuels for detailed kinetic model validation
The laminar burning velocity and the flame structure are common targets for combustion studies aimed at detailed kinetic model development. In the present work, fuels relevant to hydrogen combustion were considered. The laminar burning velocity of rich and lean hydrogen flames was studied …
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Modelling of Spray Combustion with Doubly Conditional Moment Closure
… regimes, where self-propagating premixed flames and diffusion-controlled non-premixed flames may occur simultaneously within the same flame. The physical processes involved in spray combustion and their interaction take place over a broad range of scales, which makes their modelling in …
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Development of Microcombustors and Characterization of Confined Sub-Millimeter Laminar Diffusion Flames
… devices and fundamental studies of microscale flame structure. A simple, robust, high endurance, high efficiency sub-millimeter hydrocarbon microscale combustor capable of producing an estimated 400W-cm-3 was built by reducing heterogeneous reactions in the combustor, tailoring the flow pattern …
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Development of a micro-FID using a diffusion flame
A micro-flame ionization detector (micro-FID) was developed operating with a diffusion flame with a folded flame structure. Unlike conventional FIDs, an air-hydrogen diffusion flame was developed and tested in an encapsulated structure of Quartz-Macor®-Quartz layers. Diffusion flames are generally …
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Flame stabilization and mixing characteristics in a stagnation point reverse flow combustor
… velocities, species mixing, heat release and flame structure in an atmospheric pressure SPRF combustor with the help of various optical diagnostic techniques: OH PLIF, chemiluminescence imaging, PIV and Spontaneous Raman Scattering. Results indicate that the combustor is primarily stabilized …
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Two-Dimensional Modeling of AP/HTPB Utilizing a Vorticity Formulation and One-Dimensional Modeling of AP and ADN
… AP and ADN, and a two-dimensional diffusion flame model has been developed to examine the flame structure above an AP/HTPB composite propellant. This work was part of an ongoing effort to develop theoretically based, <em>a priori</em> combustion models. The improved numerical model for AP …
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Numerical Solution of Buoyancy Induced Motion of a Hydrogen Flame Bubble (Combustion, Convection)
… standard flammability tube, exhibit a remarkable flame structure in the neighborhood of the lean limit. The subject of this dissertation is the investigation of this fine structure, referred to as "flame bubbles", brought about by cellular type instability. We consider the numerical simulation of …
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4D combustion and flow diagnostics based on tomographic chemiluminescence (TC) and volumetric laser-induced fluorescence (VLIF)
… tools for the study of turbulent flows and flames. However, optical diagnostics developed in the past have been primarily limited to measurements at a point, along a line, or across a two-dimensional (2D) plane; while turbulent flows and flames are inherently four-dimensional …
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LARGE EDDY SIMULATION OF TURBULENT HYDROGEN FLAMES
… use introduces important challenges related to flame stability, strong differential diffusion effects, and increased nitrogen oxides (NOx) emissions. These issues are particularly critical in lean premixed conditions, which are commonly used to limit emissions but lead to complex …
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Development and experimental analysis of a micro-flame ionization detector for portable gas chromatographs
… has been developed that utilized a diffusion flame encased in a micro-fabricated SOI structure. The micro-flame was fueled by a portable electrolyzer that provided the hydrogen and oxygen flow rates necessary for the device operation. The micro-FID was able to detect organic analytes with …
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Structure and Nitrogen Chemistry in Coal, Biomass, and Cofiring Low-NOx Flames
… work is an experimental investigation of the flame structure and nitrogen chemistry differences occurring between coal, biomass and cofiring flames. A pilot-scale facility was fired with a dual-feed low-NOx burner capable of independently conveying 2 separate fuels unblended to the burner. …
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Edge-Flames and Combustion at the Microscale
… relevant to the dynamic behavior of laminar flames in devices whose critical dimensions are at or below classical quenching limits. The behavior of premixed and nonpremixed edge-flames in tune-periodic counterflows is modeled using a constant-density approximation and a single-step Arrhenius …
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Electric field effects on chemi-ionization in droplet burning
… field are studied for a single isolated droplet flame under the spherically symmetric 1-D configuration. A reduced 3-step chemical kinetic mechanism is proposed to capture the production and destruction of ions inside the flame, which is then used for conducting analytical and numerical …
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Characteristics of flame-turbulence interactions in freely propagating turbulent premixed flames under decaying and forced isotropic turbulence conditions
Turbulent premixed flames observed in energy conversion and propulsion applications are characterized by highly nonlinear, unsteady, and multi-scale processes. Previous numerical studies of freely propagating flames have utilized either forced or decaying background isotropic turbulence to provide …
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Experimental Investigation of a Lean, Premixed Gas Turbine Combustor Using Advanced Laser Diagnostics
Flame structure and stabilization were studied using planar laser-induced fluorescence of the hydroxyl radical. Four operating conditions were examined---two equivalence ratios, 0.6 and 0.7, and two combustor pressure drops, 3% and 5%. Time-resolved images were acquired at two axial locations for …
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