Showing papers on "Diffusion flame published in 2020"
TL;DR: In this article, the authors present a comprehensive analysis of the thermal runaway characteristics of type 21700 cylindrical lithium-ion batteries with a specific energy of 266 W∙h/kg.
51 citations
11 Aug 2020
TL;DR: In this article, the authors provide experimental evidence of the occurrence of dimerization of polycyclic aromatic hydrocarbons in the gas phase before soot formation in a laminar diffusion methane flame, supporting the hypothesis of stabilization of dimers through the formation of covalent bonds.
Abstract: The role of polycyclic aromatic hydrocarbons (PAHs) in the formation of nascent soot particles in flames is well established and yet the detailed mechanisms are still not fully understood. Here we provide experimental evidence of the occurrence of dimerization of PAHs in the gas phase before soot formation in a laminar diffusion methane flame, supporting the hypothesis of stabilization of dimers through the formation of covalent bonds. The main findings of this work derive from the comparative chemical analysis of samples extracted from the gas to soot transition region of a laminar diffusion methane flame, and highlight two different groups of hydrocarbons that coexist in the same mass range, but show distinctly different behavior when processed with statistical analysis. In particular, the identified hydrocarbons are small-to-moderate size PAHs (first group) and their homo- and heterodimers stabilized by the formation of covalent bonds (second group). A comprehensive understanding of soot nucleation in flame combustion is still lacking. Here the authors identify homo- and heterodimers of small-to-moderate size polycyclic aromatic hydrocarbons in the gas to soot transition region of a laminar diffusion methane flame as viable intermediates in the soot nucleation process.
38 citations
TL;DR: In this article, the authors investigated the effect of various natural gas substitution ratios on the combustion and soot emission characteristics experimentally in an optical diesel engine and found that higher substitution ratio leads to cleaner combustion trends and more desirable flame characteristics.
37 citations
TL;DR: In this paper, the authors investigated the effect of hydrogen blending in natural gas on the combustion and soot emission characteristics experimentally in an optical engine and found that when hydrogen is added, flame propagation speeds up, the flame distribution is more extensive especially in the first stage combustion, the heat release rate and pressure rise rate increase accordingly.
32 citations
TL;DR: In this article, the effect of inlet air swirl number of a Methane-Air Diffusion Flame on dynamic flow behavior, temperature, and radiation heat flux distribution was investigated using ANSYS-Fluent CFD code.
31 citations
TL;DR: In this paper, a Lattice-Boltzmann model for low-Mach reactive flows is presented, built upon our recently published model (Comb & Flame, 196, 2018).
26 citations
TL;DR: In this article, the effects of adding H2 to fuel on the formation of soot are studied numerically and experimentally in a laminar coflow C2H4 diffusion flame burning in 30%O2-70%CO2 atmosphere by applying the open source flame code CoFlame and two-dimensional light-of-sight attenuation (2D-LOSA) diagnostic, respectively.
23 citations
TL;DR: In this paper, the effects of oxygen-enriched atmosphere on the morphological evolution of soot emitted from a methane co-flow laminar diffusion flame were studied using a 12-μm SiC fiber deposition sampling method combined with field emission scanning electron microscopy (FESEM) analysis.
Abstract: The effects of oxygen-enriched atmosphere on the morphological evolution of soot emitted from a methane co-flow laminar diffusion flame were studied using a 12-μm SiC fiber deposition sampling method combined with field emission scanning electron microscopy (FESEM) analysis. The temperature distribution and the soot morphological evolution along the flame radial and axial directions at different oxygen concentrations were systematically investigated. Results showed that the soot morphology was strongly dependent on its position and oxygen concentration in flames. At the same flame height, the soot morphology changed significantly when the oxygen concentration increased from 21% to 31%. The soot generation rate increased rapidly under the elevated oxidative condition, and the position of soot inception was closer to the burner nozzle. As the flame height and oxygen concentration increased, soot particles in the flame centerline were enlarged and evolved to fiber-like depositions. Furthermore, the large clusters of soot particles gradually evolved to even denser spongy and fibrous particles around the flame edges. In addition, unique sponge-like soot deposits were observed for the first time in methane flames.
23 citations
TL;DR: In this paper, the effect of oxygen concentration on flame characteristics and soot formation in diffusion and partially premixed flames was comprehensively analyzed, and the results showed that both the peak temperature and the OH increase monotonically whether oxygen is added into co-flow or fuel flow.
23 citations
TL;DR: In this article, the impact of cyclic fuels on the nanostructure, nucleation and overall production of soot in an n-heptane (C7H16) laminar coflow diffusion flame was investigated.
22 citations
TL;DR: In this article, the evolution and combustion of H2 jets were investigated in an optically-accessible constant-volume chamber under simulated direct-injection (DI) compression-ignition (CI) engine conditions.
TL;DR: In this paper, the combustion regimes of iron particles in a laminar pre-mixed flame (LPF) and in an axisymmetric LDF were studied, respectively.
Abstract: In the work, the combustion regimes of iron particles (d10 = 4.7 µm) in a laminar pre-mixed flame (LPF) and in an axisymmetric laminar diffusion flame (LDF) are studied. For (LPF), we studied the ...
TL;DR: In this paper, numerical calculations were conducted to explore the various effects of hydrogen blending on flame properties and soot behaviors in an ethylene coflow diffusion flame, based on a fully step-by-step decoupling method, by introducing several virtual species into the gas-phase mechanism.
TL;DR: In this paper, the response of burning gaseous fuel jets to prescribed transverse acoustic excitation as a means of exploring the coupling of reactive, acoustic, and flow proces.
Abstract: The present experiments focused on the response of burning gaseous fuel jets to prescribed transverse acoustic excitation as a means of exploring the coupling of reactive, acoustic, and flow proces...
TL;DR: In this article, a planar two-color time-resolved laser-induced incandescence (TiRe-LII) technique and analysis of transmission electron microscope images was used to collect samples of soot particles.
TL;DR: In this article, the effects of blending rate of biodiesel surrogates of saturated methyl butyrate (MB) and unsaturated methyl crotonate (MC) were discussed, with the increasing of MB additions, the flame temperatures is lifted, and soot production increases firstly and then decreases because of a comprehensive effect depending on the oxygen content from oxygenated saturated MB.
TL;DR: In this article, the evolution, nanostructure, and oxidation reactivity of the soot particles for RP-3 kerosene in normal and inverse diffusion flames, were investigated by high-resolution transmission electron microscopy, X-ray diffraction, and thermogravimetric analysis.
Abstract: RP-3 kerosene is the most important hydrocarbon fuel used in civilian airplanes in China. Up to date, there are few experimental literatures on soot formation and oxidation of RP-3 kerosene available. In this experimental study, the evolution, nanostructure, and oxidation reactivity of the soot particles for RP-3 kerosene in normal and inverse diffusion flames, were investigated. The n-decane was selected as a base fuel for the comparison. Thermophoretic techniques followed by transmission electron microscopy were used to study the evolution of the soot particles in the different locations at the centerline and radial stream of the flames. Nanostructure, lattice parameters, and oxidation reactivity of the soot particles were examined by high-resolution transmission electron microscopy, X-ray diffraction, and thermogravimetric analysis. The results showed that the size of RP-3 kerosene flame soot particles was bigger than n-decane flame at 20 m m and 30 m m height above the burner surface for normal diffusion flame. In inverse diffusion flame, RP-3 kerosene flame had bigger soot aggregates than n-decane flame. Moreover, RP-3 kerosene flame nanostructure had larger fringe length and shorter fringe tortuosity than n-decane flame in normal and inverse diffusion flames, which reflect lesser oxidation reactivity of the RP-3 kerosene flame. X-ray diffraction spectrum and thermogravimetric curves displayed good agreements with the high-resolution transmission electron microscopy images. Finally, the nanostructure of soot particles had a strong relation to their oxidation reactivity.
TL;DR: In this article, the authors investigated the effect of the conical flame zone and the flame root on the stability and structure of a lifted jet-like flame at a critical swirl intensity, Scr.
TL;DR: In this paper, the effects of wind flow and sidewall restriction on the geometric characteristics of turbulent diffusion flames in tunnels were performed in a bench-scale wind tunnel, and the results suggest that the flame tilt angles of two fire source positions both increase faster first and then increase slowly with increasing ventilation velocity.
TL;DR: In this paper, the effects of non-octane enhancer bio-fuel lemon peel oil (LPO) on the combustion, performance and emission characteristics of the gasoline engine were investigated.
TL;DR: In this article, the effect of operating pressure (up to 8m) on the moderate or intense lowoxygen dilution (MILD) combustion of methane was investigated, and it was shown that increasing the operating pressure tends to increase both peak value and spatial gradient of the combustion temperature, and reduce the width of the reaction zone, indicating the departure of MILD combustion regime when using the identical burner.
TL;DR: In this paper, experiments of nano-scale polymethyl methacrylate dust explosions were conducted to reveal the flame propagation characteristics and evolution mechanism, and the results showed that the flame preheat zone front was approximately smooth.
TL;DR: In this article, a time-domain 2D numerical model of a jet diffusion flame is developed to gain insights on its dynamic response to acoustic disturbances at either resonant or non-resonant frequencies.
TL;DR: In this article, the effects of hydrogen enrichment of methane are investigated numerically from the diffusion flame structure and emissions aspect, and the results show that the hydrogen-enriched flames become broader and shorter with respect to the pure methane flame.
TL;DR: In this paper, the effect of tripropylene glycol methyl ether (TPGME) and two polyoxymethylene dimethyl ethers (POMDME or OMEs) on soot formation in a laminar diesel diffusion flame was investigated.
Abstract: Emissions from diesel engines can be limited and potentially decreased by modifying the fuel chemical composition through additive insertion. One class of additives that have shown to be particularly efficient in the reduction of the particulates from the combustion of diesel fuels are oxygenated compounds. In the present study we investigate the effect of tripropylene glycol methyl ether (TPGME) and two polyoxymethylene dimethyl ethers (POMDME or OMEs) on soot formation in a laminar diesel diffusion flame. From the evaluation of soot volume fraction by laser-induced incandescence (LII) measurements we could observe that OME additives have a substantial capability (higher compared to TPGME) to decrease the particle concentration, which drops by up to 36% with respect to the pure diesel fuel. We also note a reduction in particle aggregate size, determined by wide-angle light scattering (WALS) measurements, which is more pronounced in the case of OME–diesel blends. The effects we observe can be correlated to the higher amount of oxygen content in the OME molecules. Moreover, both additives investigated seem to have almost no impact on the local soot temperature which could in turn play a key role in the production of soot particles.
TL;DR: In this paper, the effects of oxygen-rich combustion on soot formation in the propane/(O2+N2) laminar flow coaxial jets diffusion flame were numerically investigated by using the detailed gas-phase chemical reaction model with the mechanism of tetracyclic aromatic hydrocarbons and the complex thermodynamic properties and transport characteristics parameters.
Abstract: Oxygen-rich combustion is a new type of clean combustion technology with important application prospects. In this work, the effects of oxygen-rich combustion on soot formation in the propane/(O2+N2) laminar flow coaxial jets diffusion flame were numerically investigated by using the detailed gas-phase chemical reaction model with the mechanism of tetracyclic aromatic hydrocarbons and the complex thermodynamic properties and transport characteristics parameters. Soot surface growth follows the hydrogen-abstraction-carbon-addition (HACA) model. A hybrid gas-phase mechanism was adopted, which contains a DLR-based polycyclic aromatic hydrocarbons (PAHs) formation, growth model and a gas-phase model. Results show that the oxygen-rich combustion has a great influence on the flame temperature, especially the high temperature region. With the increase of oxygen concentration, the soot formation region of flame broadens and the maximum of soot volume fraction increase from 3.95 ppm to 10.87 ppm. The extra oxygen makes PAHs increased around the nozzle, leading to larger rate in early soot nucleation and surface growth, eventually more soot yield.
TL;DR: In this paper, the authors extended the conservative finite element convective scheme proposed by Charnyi et al. originally formulated for incompressible flows to the low Mach regime, where stabilisation is only introduced for the continuity equation by means of a non-incremental fractional step method, modified in order to account for variable density flows.
TL;DR: In this paper, errors in soot predictions associated with flamelet-based combustion models are isolated and quantified in a combined a-priori and partial a-posteriori analysis using large-scale Direct Numerical Simulation (DNS) data of a sooting turbulent jet diffusion flame.
TL;DR: In this article, a simplified radiation reabsorption model was given based on the properties of the radiative re-absorption energy at T =1500-2000 K, P = 1-100 K, and the critical strain rate was calculated for eight C1-C6 hydrocarbon species at T=2000k, P=1-100k, at pressures from 1 to 100k.
TL;DR: In this paper, the interaction of two adjacent diffusion flames (dual flame) was experimentally investigated using the direct imaging method and particle image velocimetry (PIV) measurements for varied distances between the two flames under the influence of the co-flow.