共查询到19条相似文献,搜索用时 218 毫秒
1.
2.
微细通道内可燃气体预混燃烧实验与微型发动机燃烧方案 总被引:10,自引:0,他引:10
针对微型涡轮气体发动机的研制现状,讨论了微细通道稳定燃烧面临的难题。开展了微细通道内燃气与空气预混燃烧的火焰稳定性实验研究,通过测试获得了氢气和乙炔燃烧的着火浓度极限。结果表明:微细通道内可燃气体与空气的预混燃烧具有可行性,但可燃浓度范围明显缩小;采用增压燃烧,可以扩大其可燃浓度范围,提高燃烧稳定性;与大通道相比,微细通道不易发生回火,但容易发生火焰吹熄,而燃气浓度较高的混合气流相对不易被吹熄,燃烧稳定性较好。 相似文献
3.
4.
5.
6.
7.
本发展了一种新的预混湍流火核生成及初期发展的模型,该模型基于准维模型的基本思想,摒弃了湍流燃烧速度模型,以数值生成的湍流场对火焰前锋面的客观影响推动燃烧计算过程。模型考虑了很多对火核生成及初期发展有影响的因素,如已燃区的传热,非绝热效应,曲率和伸展效应等等;通过利用模拟得到的3维湍流速度场,首镒实现了对火核几何形状的3维模拟;模型的模拟结果和试验结果有很好的吻合性,这说明模型是合理的。 相似文献
8.
9.
10.
燃气轮机在更高参数下的低污染排放限制和宽工况范围稳定运行的需求,对燃烧室燃烧提出了新的要求。柔和燃烧作为一种新型燃烧技术,具有燃烧稳定和污染物排放低的优势。高速射流引射掺混是实现柔和燃烧所需条件的一种可行方式。本文主要研究不同燃料掺混方式对柔和燃烧器污染物排放和稳定工作范围的影响。在前期工作基础上设计了可实现燃料不同掺混方式的天然气柔和燃烧器。在常压条件下,通过实验研究了不同当量比、不同燃料/空气掺混方式下天然气柔和燃烧器的污染物排放,并研究了不同掺混方式对燃烧贫燃极限的影响,通过OH~*自发荧光、OH平面激光诱导荧光测量和数值模拟对反应区和流场结构进行了观察和分析。实验结果表明,在相同当量比下,全预混模式下的NO_x排放最低,全预混模式下稳定燃烧的贫熄火当量比为0.57;扩散模式下NO_x排放相对高,但贫熄火当量比可低至0.15,燃烧稳定范围更宽;混合模式下污染物排放水平介于预混和扩散模式之间;非预混模式下较好的贫燃火焰稳定性得益于燃烧室头部扩散燃料周围形成的低速稳定反应区。 相似文献
11.
Much work is reported in the literature pertaining to premixed burners using hydrocarbon fuels. However, very little work is available on similar burners using producer gas as a fuel. The present work aims at testing and optimization of a premixed burner with producer gas as a fuel.A burner of 150 kW capacity is used in the experimental investigations. The burner is of concentric tube type fully premixed in which air is supplied through central pipe and gas is supplied through annular passage. Swirl vane is provided to air and gas for thorough mixing. The bluff body is provided for flame stabilization. The premixed burner was tested on open core throat-less down draft gasifier for flame quality. A stable and uniform flame was observed with this premixed burner. Thereafter, an instrumented test set up to evaluate burner performance was installed on an open core gasifier. The burner was experimentally optimized for size and location of bluff body and flammability limits. The burner was optimized by using bluff bodies of 46, 61, 73, 80, 85, 98, 110 and 122 mm diameters. The burner was operated in batch operation of 6–8 h for optimization of various parameters. The experiment reveled that the uniform and high-temperature premixed flame was observed at conventional bluff body having blockage ratio of 0.65. The flammability limits for producer gas fired burner was established in the range of 40–55. 相似文献
12.
13.
《International Journal of Hydrogen Energy》2022,47(15):9156-9168
In order to study the influence of nitrogen on the deflagration characteristics of premixed hydrogen/methane, the explosion parameters of premixed hydrogen/methane within various volume ratios and different dilution ratios were studied by using a spherical flame method at room temperature and pressure. The results are as follows: The addition of nitrogen makes the upper limit of explosion of hydrogen/methane premixed gas drop, and the lower limit rises. For explosion hazard (F-number), hydrogen/methane premixed fuel with a hydrogen addition ratio of 10% has the lowest risk, and nitrogen has a greater impact on the dangerous degree of hydrogen and methane premixed gas whose hydrogen addition ratio does not exceed 30%. In terms of flame structure, the spherical flame was affected by buoyancy instability as the percentage of nitrogen dilution increased, but the buoyancy instability gradually decreased as the percentage of hydrogen addition increased. The addition of diluent gas reduces the spreading speed of the stretching flame and reduces the stretching rate in the initial stage of flame development. The laminar flame propagation velocity calculated by the experiment in this paper is consistent with the laminar flow velocity of the hydrogen/methane premixed gas calculated by GRI Mech 3.0. Considering the explosion parameters such as flammability limit, laminar combustion rate and deflagration index, when hydrogen is added to 70%, it is the turning point of hydrogen/methane premixed fuel. 相似文献
14.
Experiments have been carried out in which very small lean premixed flames closely representative of those formed by modern multiport domestic gas burners have been subjected to controlled acoustic perturbation. PLIF from CH has been used to visualise the flame response and the heat-release-rate fluctuations have been evaluated directly from the flame images. It is shown that small laminar flames can amplify the effects of acoustic velocity fluctuations by mechanisms that do not involve resonant heat loss to the burner and that the fluctuations in flame-front area are not adequately characterised by a Strouhal number alone. The measured transfer function is compared with the predictions of various analytical formulations and a new model of the flame oscillation is proposed which applies specifically to situations in which the design of the burner renders the flame base immobile. 相似文献
15.
An experimental study has been performed to detect the occurrence of nanosized carbon particulates below the soot laden zone of a co-flowing partially premixed flame. Samples have been extracted from different points across the flame and passed through DI water. Absorption and fluorescence spectroscopies have been performed with the collected water suspensions. The occurrence of carbon nanoparticles is evident across the inner flame front. In addition, evidence of naphthalene has also been found inside the inner rich premixed flame. The concentration of naphthalene decreases while that of the carbon nanoparticles increases as the inner flame front is reached. The stability of the nanoparticles in the sample has been ensured by observing that the change in fluorescence quantum yield from the sample over a long duration is small. The band gap energy has been evaluated using the absorption data to characterize the likely structures of the particles in the collected suspension. Two kinds of particles having different zones of band gap energy are found in the flame. Dynamic light scattering measurements show that the particle size grows with the increase in height in the lower part of the flame. While, at 3 and 6 mm elevations the particles are observed to be below 2.5 nm in diameter, the particles at 10 mm elevation are found in the size range of 2.5-5.5 nm. 相似文献
16.
Han S. Kim Vaibhav K. ArghodeMartin B. Linck Ashwani K. Gupta 《International Journal of Hydrogen Energy》2009
The effect of hydrogen addition in methane-air premixed flames has been examined from a swirl-stabilized combustor under confined conditions. The effect of hydrogen addition in methane-air flame has been examined over a range of conditions using a laboratory-scale premixed combustor operated at 5.81 kW. Different swirlers have been investigated to identify the role of swirl strength to the incoming mixture. The flame stability was examined for the effect of amount of hydrogen addition, combustion air flow rates and swirl strengths. This was carried out by comparing adiabatic flame temperatures at the lean flame limit. The combustion characteristics of hydrogen-enriched methane flames at constant heat load but different swirl strengths have been examined using particle image velocimetry (PIV), micro-thermocouples and OH chemiluminescence diagnostics that provided information on velocity, thermal field, and combustion generated OH species concentration in the flame, respectively. Gas analyzer was used to obtain NOx and CO concentration at the combustor exit. The results show that the lean stability limit is extended by hydrogen addition. The stability limit can reduce at higher swirl intensity to the fuel-air mixture operating at lower adiabatic flame temperatures. The addition of hydrogen increases the NOx emission; however, this effect can be reduced by increasing either the excess air or swirl intensity. The emissions of NOx and CO from the premixed flame were also compared with a diffusion flame type combustor. The NOx emissions of hydrogen-enriched methane premixed flame were found to be lower than the corresponding diffusion flame under same operating conditions for the fuel-lean case. 相似文献
17.
为研究燃气轮机模型燃烧室的非预混燃烧流场,采用大涡模拟方法分别结合火焰面生成流形模型(FGM)和部分预混稳态火焰面模型(PSFM)对甲烷/空气同轴射流非预混燃烧室开展了数值模拟研究,并与试验结果进行对比。结果表明:FGM所预测的速度分布、混合分数分布、燃烧产物及CO分布与试验结果更符合;两种模型均能捕捉到燃烧室中的火焰抬举现象;燃烧过程中的火焰结构较为复杂,同时存在预混燃烧区域和扩散燃烧区域,扩散燃烧主要分布在化学恰当比等值线附近,预混燃烧区域主要分布在贫油区。 相似文献
18.
19.
In gas turbines, lean premixed combustion is executed in strongly turbulent flow fields and under high-pressure to allow large thermal loads within small-size combustors. Previous research on turbulent premixed flames has revealed the vital importance of flame-vortex interactions, but most of these investigations have been performed only at atmospheric pressure disregarding the large pressure dependency of the flame front dynamics. We report about spatially high-resolved laser-induced predissociation fluorescence imaging of OH (OH-LIPF) in premixed, high-pressure bluff-body stabilized methane/air flames. For each of the two measurement series with different equivalence ratio (φ = 0.7 and φ = 1.0), the planar flame topology at different pressures (0.1 to 1.1 MPa) but constant exit velocity was detected and stored for analysis. As the pressure was increased, the flame front contour of both equivalence ratios became strongly wrinkled with formation of highly curved flame front elements. For quantification of this phenomenon, the probability density function of flame curvature was evaluated with definition of the mean curvature radius as representative folding scale. To discuss different mechanisms of flame front disturbances according to their relevance, the flame curvature is compared with characteristic turbulence scales of the flow field and with the expected folding scale derived with Sivashinsky‘s formulation of linear flame instability theory. Significant changes become obvious especially if the pressure is increased up to 0.5 MPa. The mean curvature radius decreases distinctly and can be linked to the decreasing size of the Taylor length. Additionally, the formation of highly convoluted flame front elements is enforced by the increasing flame instability behavior. As the results show, the flame stoichiometry has a strong impact on the flame front topology at increasing pressures due to the differences of their flame dynamics. 相似文献