排序方式: 共有55条查询结果,搜索用时 46 毫秒
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Elias Al Sarraf Christophe Almarcha Joël Quinard Basile Radisson Bruno Denet Pedro Garcia-Ybarra 《Proceedings of the Combustion Institute》2019,37(2):1783-1789
Hydrodynamic flame instabilities are studied in a Hele-Shaw burner. By studying the development of perturbations, starting from a 2D Bunsen flame at the top of the burner, growth rates are measured for propane and methane–air mixtures, and compared to theoretical predictions. It is found that the dispersion relation in a Hele-Shaw cell has the same dependence with wavenumber as the one predicted in tubes. Markstein numbers relative to fresh gases are obtained for propane and methane flames and compared to the literature. 相似文献
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Rafael P. Bianchin Mariovane S. Donini Cesar F.C. Cristaldo Fernando F. Fachini 《Proceedings of the Combustion Institute》2019,37(2):1903-1910
The present work analyzes cylindrical diffusion flames (Tsuji burner) under low stretch condition, considering fuel injection also from the backward region of the burner. To highlight the fundamental aspects of this flame, some assumptions are imposed, like constant thermodynamic and transport coefficients, unitary Lewis number and no radiative heat loss. It is also considered potential flow model and incompressible Navier–Stokes model. Despite the simplicity of the former model, results from both models show good agreement. Also, an asymptotic analysis describing the problem far from the burner is able to capture the most important mechanisms controlling the flame, then the flame shape is determined and the dependence of the characteristic length scales on Peclet number (based on the burner properties), free stream velocity and stoichiometry is revealed. The results show that the flame width is proportional to the mass stoichiometric coefficient and reciprocal to the Peclet number the 1/4 power and free stream velocity the 3/4 power, and that the flame height is proportional to the square of the mass stoichiometric coefficient and to the square root of the ratio of Peclet number to free stream velocity. In addition, an asymptotic stability analysis reveals low-stretch flame extinction to be caused by reduction in fuel and oxidizer concentrations, which provides the range of the stoichiometric coefficient for stable regime, and at the same time the range of heat released. 相似文献
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B. Li E. Baudoin R. Yu Z.W. Sun Z.S. Li X.S. Bai M. Aldn M.S. Mansour 《Proceedings of the Combustion Institute》2009,32(2):1811-1818
The structure and dynamics of a turbulent partially premixed methane/air flame in a conical burner were investigated using laser diagnostics and large-eddy simulations (LES). The flame structure inside the cone was characterized in detail using LES based on a two-scalar flamelet model, with the mixture fraction for the mixing field and level-set G-function for the partially premixed flame front propagation. In addition, planar laser induced florescence (PLIF) of CH and chemiluminescence imaging with high speed video were performed through a glass cone. CH and CH2O PLIF were also used to examine the flame structures above the cone. It is shown that in the entire flame the CH layer remains very thin, whereas the CH2O layer is rather thick. The flame is stabilized inside the cone a short distance above the nozzle. The stabilization of the flame can be simulated by the triple-flame model but not the flamelet-quenching model. The results show that flame stabilization in the cone is a result of premixed flame front propagation and flow reversal near the wall of the cone which is deemed to be dependent on the cone angle. Flamelet based LES is shown to capture the measured CH structures whereas the predicted CH2O structure is somewhat thinner than the experiments. 相似文献
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齿形中心扩锥对旋流燃烧器气固流动影响的PDA试验研究 总被引:1,自引:0,他引:1
1前言旋流燃烧器依靠高温回流区做为稳定的热源,使煤粉气流及时着火并稳定燃烧,燃烧器单独组织燃烧,不互相影响,燃烧器区域的气固流动特性决定了燃烧器的性能。燃烧器的喷口结构对其气因流动特性有重要影响山。本文提出了齿形中心扩锥结构(如图l所示)。2实验方法及结果分析试验采用三维激光粒子动态分析仪(简称三维PDA),实验台系统主要由送风机、吸风机、给粉机、燃烧器模型、试验段、旋风分离器等组成,试验段为一竖直放置的筒体,直径为4800mm,燃烧器模型安装在简体上部中心位置,最外层扩口端部与筒体内壁平齐,沿射流流动方… 相似文献
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D. Lo Jacono P. Papas M. Matalon P.A. Monkewitz 《Proceedings of the Combustion Institute》2005,30(1):501-509
A unique burner was constructed to experimentally realize a one-dimensional unstrained planar non-premixed flame, previously considered only in idealized theoretical models. One reactant, the fuel mixture in the current experiments, is supplied through a porous plug at the bottom of the combustion chamber and flows vertically up towards the horizontal flame. The crux of the design is the introduction of the oxidizer from above in such a way that its diffusion against the upward product flow is essentially one-dimensional, i.e., uniform over the burner cross-section. This feature was implemented by introducing the oxidizer into the burner chamber from the top through an array of 625 closely spaced hypodermic needles, and allowing the hot products to escape vertically up through the space between the needles. Due to the injection of oxidizer through discrete tubes, a three-dimensional “injection layer” exists below the exit plane of the oxidizer supply tubes. Experimental evidence suggests that this layer is thin and that oxidizer is supplied to the flame by 1-D counterdiffusion, producing a nearly unstrained flame. To characterize the burner, flame position measurements were conducted for different compositions and flowrates of H2–CO2 and O2–CO2 mixtures. The measured flame locations are compared to an idealized one-dimensional model in which only diffusion of oxidizer against the product flow is considered. The potential of the new burner is demonstrated by a study of cellular structures forming near the extinction limit. Consistent with previous investigations, cellular instabilities are shown to become more prevalent as the initial mixture strength and/or the Damköhler number are decreased. As the extinction limit is approached, the number of cells was observed to decrease progressively. 相似文献