共查询到16条相似文献,搜索用时 200 毫秒
1.
天然气-氢气-空气混合气火焰传播特性研究 总被引:3,自引:0,他引:3
在定容燃烧弹内研究了初始条件为常温常压的灭然气-氢气-空气混合气火焰传播规律,得到了不同掺氢比例和燃空当量比下混合气的层流燃烧速率、质量燃烧流量和马克斯坦长度,结合火焰传播照片,分析了火焰的稳定性并预测了大尺寸火焰稳定性的演变趋势。研究结果表明,随着天然气中掺氢比例的增加,混合气的燃烧速率增加,且增长速率逐渐加快,马克斯坦长度值减小,火焰的稳定性下降。各种掺氢比例下,随当量比的增加,马克斯坦长度值增加,火焰的稳定性增加。掺氢比例高于80%时,随着火焰的传播,其不稳定性将明显增加。 相似文献
2.
在定容燃烧弹内研究了不同初始压力下天然气-氢气-空气混合气的火焰传播规律,得到了不同掺氢比例和初始压力下,不同燃空当量比时混合气的层流燃烧速率,并分析了火焰的稳定性及其影响因素.研究结果表明,随着天然气中掺氢比例的增加,混合气的燃烧速率增加,且增长速率逐渐加快,而马克斯坦长度值则随着掺氢比例的增加而减小,即火焰的稳定性下降.不同初始压力下,随着燃空当量比的增加,马克斯坦长度值在不同掺氢比例下均增加,显示火焰的稳定性增加.无拉伸层流燃烧速率随着初始压力的增加略有减小,且在化学当量比附近,变化的初始压力和掺氢比对无拉伸层流燃烧速率的影响最为明显. 相似文献
3.
高温高压下掺氢天然气的燃烧特性 总被引:2,自引:0,他引:2
在定容燃烧弹内研究了高温(450,K)、高压(0.75,MPa)条件下天然气-氢气-空气混合气的火焰传播过程,获得了不同掺氢比和不同当量比下掺氢天然气的无拉伸层流燃烧速率,并分析了火焰的稳定性。结果表明,高温高压下随着掺氢比的增加,掺氢天然气的燃烧速率增加,且增长速率逐渐加快;马克斯坦长度则随着掺氢比的增加而减小,即火焰的稳定性下降。随着当量比的增加,无拉伸层流燃烧速率呈现先增大后减小的趋势,且最大无拉伸层流燃烧速率所对应当量比的位置随着掺氢比的提高而向浓混合气移动;马克斯坦长度随当量比的增加而增大,即火焰稳定性随当量比的增加而提高。 相似文献
4.
初始压力对天然气-氢气-空气混合气火焰传播特性的影响 总被引:2,自引:0,他引:2
使用定容燃烧弹研究了不同初始压力下天然气-氢气-空气混合气的火焰传播规律,得到了初始压力、掺氢比和燃空当量比对无拉伸层流燃烧速率、质量燃烧流量的影响,结合高速纹影图片分析了影响火焰稳定性的因素(马克斯坦长度、火焰面两侧密度比和火焰厚度).结果表明,掺氢天然气无拉伸层流燃烧速率以及火焰的不稳定性受掺氢比、初始压力和燃空当量比的综合影响.结合高速纹影图片,得出火焰的稳定性会随初始压力的增加而减小;在相同的燃空当量比和掺氢比下,初始压力对密度比的影响不大,但是对火焰厚度的影响比较明显. 相似文献
5.
利用高速纹影摄像法和球型发展火焰研究了常温常压下丙烷-空气,丙烷-空气-稀释气预混层流燃烧特性,获得了不同稀释系数(0、10%、20%、30%)和燃空当量比(0.6~2.0)下混合气的层流燃烧速率和马克斯坦长度值,分析了拉伸对火焰传播速率的影响.结果表明:丙烷-空气混合气的无拉伸火焰传播速率和无拉伸层流燃烧率在当星比1.1时达到最大值,随当量比的增加,马克斯坦长度值降低,火焰前锋面不稳定性趋势增加.当量比为1.4时,马克斯坦长度值由正值转为负值.丙烷-空气-稀释气混合气随稀释系数的增加,火焰传播速率和层流燃烧速率降低,在当量比小于1.4时,随稀释系数的增加,马克斯坦长度值增加,火焰前锋面的稳定性趋势增加.有无稀释气时无拉伸层流燃烧速率的比值仅与稀释系数有关并成线性关系而与混合气浓度无关. 相似文献
6.
为了更深入地理解废气中二氧化碳对掺氢燃料燃烧特性的影响,在定容燃烧弹中利用高速摄像系统研究了不同燃空当量比φ(0.6~1.4)和稀释比(0%~40%)下CO2稀释氢气-空气混合气的层流燃烧特性.结果表明:氢气-空气混合气的火焰传播速率随着燃空当量比的增大而增大;马克斯坦长度随着当量比的增大而增大,即火焰的稳定性增强;随稀释比的增大,无拉伸火焰传播速率S1明显减小;同时得到层流火焰燃烧速率,并分析了稀释比对火焰稳定性的影响.通过对试验结果数据拟合,获得了计算氢气-CO2-空气混合气的无拉伸层流燃烧速率的拟合多项式. 相似文献
7.
《燃烧科学与技术》2016,(5)
在定容燃烧弹内研究了相同的掺氢比、不同的二氧化碳体积分数下,天然气-氢气-二氧化碳-空气的预混气体层流火焰燃烧特性;分析了二氧化碳体积的增加对火焰燃烧特性的影响.结果表明:随着二氧化碳体积分数的增加,二氧化碳气体的稀释作用和吸热作用使混合气燃烧速率降低,火焰半径随时间的增长率明显减小;同时火焰前锋出现"ω"形的火焰锋面,减小了已燃区和未燃区接触面积,拉伸火焰传播速率明显下降.当二氧化碳体积分数?CO_2≤5%,时,拉伸火焰传播速率随拉伸率的增加而减小,马克斯坦长度为正值,火焰前锋面趋于稳定;当?CO_2≥10%,时,马克斯坦长度随二氧化碳体积分数的增加没有统一的规律可循,由于氢气和天然气的马克斯坦长度随着稀释度的增加有相反的变化规律,所以其变化规律取决于可燃混合气中占主导地位的可燃气体是氢气还是天然气. 相似文献
8.
二甲醚-空气混合气层流燃烧速度的测定 总被引:1,自引:0,他引:1
在定容燃烧弹中利用高速纹影摄像法系统地研究了不同燃空当量比和初始压力下二甲醚-空气混合气的层流燃烧特性.利用球形扩散火焰理论分析纹影照片,获得了不同初始压力和当量比下的二甲醚-空气混合气层流燃烧速率.结果表明:随着初始压力的增大,层流燃烧速率显著减小,层流燃烧速率的峰值向浓混合气侧偏移.拉伸层流燃烧速率随拉伸率的增加而增加,拉伸层流质量燃烧速率随拉伸率的增加而减小.根据球形扩散火焰模型得到混合气的马克斯坦长度值表明:在各初始压力下,随着当量比的增加,二甲醚-空气混合气的马克斯坦长度值逐渐减小,火焰前锋面的不稳定性增加. 相似文献
9.
在定容燃烧弹内研究了初始压力为0.5 MPa时,不同初始温度和燃空当量比下二甲醚-空气混合气预混层流火焰的层流燃烧速率和马克斯坦长度,分析了火焰拉伸对火焰传播速率的影响.基于容弹燃烧的双区模型计算了预混层流燃烧的燃烧特性参数.结果表明:随着初始温度的增加,二甲醚-空气预混合气的无拉伸火焰传播速率和无拉伸层流燃烧率增加;对于给定的初始温度,在化学当量比偏浓混合气一侧存在一个层流燃烧速度的峰值;随初始温度和当最比增加,马克斯坦长度值减小,火焰前锋面的不稳定性增加;最大燃烧压力随初始温度的增加而下降,压力升高率随初始温度的增加而降低. 相似文献
10.
11.
In this study, the experiment study about the laminar burning velocity and the flame stability of CO2 diluted natural gas–hydrogen–air mixture was conducted in a constant volume combustion vessel by using the high-speed schlieren photography system. The unstretched laminar burning velocity and the Markstein length at different hydrogen fractions, dilution ratios and equivalence ratios and with different initial pressures were obtained. The flame stability was studied by analyzing the Markstein length, the flame thickness, the density ratio and the flame propagation schlieren photos. The results showed that the unstretched laminar burning velocity would be reduced with the increase of the initial pressure and dilution ratio and would be increased with the increase of the hydrogen fraction of the mixture. Meanwhile, the Markstein length would be increased with the increase of the equivalence ratio and the dilution ratio. Slight flaws occurred at the early stage. At a specific equivalence ratio, a higher initial pressure and hydrogen fraction would cause incomplete combustion. 相似文献
12.
Study of laminar combustion characteristics of gasoline surrogate fuel-hydrogen-air premixed flames 总被引:1,自引:0,他引:1
《International Journal of Hydrogen Energy》2019,44(26):13910-13922
This paper investigated the effects of hydrogen addition to gasoline surrogates fuel-air mixture on the premixed spherical flame laminar combustion characteristics. The experiments were carried out by high speed Schlieren photography on a constant-volume combustion vessel. Combining with nonlinear fitting technique, the variation of flame propagation speed, laminar burning velocity, Markstein length, flame thickness, thermal expansion coefficient and mass burning flux were studied at various equivalence ratios (0.8–1.4) and hydrogen mixing ratios (0%–50%). The results suggested that the nonlinear fitting method had a better agreement with the experimental data in this paper and the flame propagation was strongly effected by stretch at low equivalence ratios. The stretched propagation speed increased with the increase of hydrogen fraction at the same equivalence ratio. For a given hydrogen fraction, Markstein length decreased with the increase of equivalence ratio; flame propagation speed and laminar burning velocity first increased and then decreased with the increase of equivalence ratio while the peaks of the burning velocity shifted toward the richer side with the increase of hydrogen fraction. 相似文献
13.
The laminar flame characteristics of natural gas–hydrogen–air–diluent gas (nitrogen/CO2) mixtures were studied in a constant volume combustion bomb at various diluent ratios, hydrogen fractions and equivalence ratios. Both unstretched laminar burning velocity and Markstein length were obtained. The results showed that hydrogen fraction, diluent ratio and equivalence ratio have combined influence on laminar burning velocity and flame instability. The unstretched laminar burning velocity is reduced at a rate that is increased with the increase of the diluent ratio. The reduction effect of CO2 diluent gas is stronger than that of nitrogen diluent gas. Hydrogen-enriched natural gas with high hydrogen fraction can tolerate more diluent gas than that with low hydrogen fraction. Markstein length can either increase or decrease with the increase of the diluent ratio, depending on the hydrogen fraction of the fuel. 相似文献
14.
Zhiyuan Zhang Xiangang Wang Jun Xiang Xibin Wang Haiyan Miao 《Combustion and Flame》2008,155(3):358-368
The laminar burning velocities and Markstein lengths for the methanol-air mixtures were measured at different equivalence ratios, elevated initial pressures and temperatures, and dilution ratios by using a constant volume combustion chamber and high-speed schlieren photography system. The influences of these parameters on the laminar burning velocity and Markstein length were analyzed. The results show that the laminar burning velocity of the methanol-air mixture decreases with an increase in initial pressure and increases with an increase in initial temperature. The Markstein length decreases with an increase in initial pressure and initial temperature, and increases with an increase in the dilution ratio. A cellular flame structure is observed at an early stage of flame propagation. The transition point is identified on the curve of flame propagation speed against stretch rate. The reasons for the cellular structure development are also analyzed. 相似文献
15.
Xuan Zhang Zuohua HuangZhiyuan Zhang Jianjun ZhengWu Yu Deming Jiang 《International Journal of Hydrogen Energy》2009
The laminar burning velocities and Markstein lengths for the dissociated methanol–air–diluent mixtures were measured at different equivalence ratios, initial temperatures and pressures, diluents (N2 and CO2) and dilution ratios by using the spherically outward expanding flame. The influences of these parameters on the laminar burning velocity and Markstein length were analyzed. The results show that the laminar burning velocity of dissociated methanol–air mixture increases with an increase in initial temperature and decreases with an increase in initial pressure. The peak laminar burning velocity occurs at equivalence ratio of 1.8. The Markstein length decreases with an increase in initial temperature and initial pressure. Cellular flame structures are presented at early flame propagation stage with the decrease of equivalence ratio or dilution ratio. The transition positions can be observed in the curve of flame propagation speed to stretch rate, indicating the occurrence of cellular structure at flame fronts. Mixture diluents (N2 and CO2) will decrease the laminar burning velocities of mixtures and increase the sensitivity of flame front to flame stretch rate. Markstein length increases with an increase in dilution ratio except for very lean mixture (equivalence ratio less than 0.8). CO2 dilution has a greater impact on laminar flame speed and flame front stability compared to N2. It is also demonstrated that the normalized unstretched laminar burning velocity is only related to dilution ratio and is not influenced by equivalence ratio. 相似文献
16.
Xiangang Wang Zhiyuan Zhang Zuohua Huang Xibin Wang Haiyan Miao 《Frontiers of Energy and Power Engineering in China》2010,4(2):223-233
The outward propagation and development of surface instability of the spark-ignited spherical premixed flames for methanol-air-nitrogen
mixtures were experimentally studied by using a constant volume combustion chamber and a high-speed schlieren photography
system. The laminar burning velocities, the mass burning fluxes, and the Markstein lengths were obtained at different equivalence
ratios, dilution ratios, initial temperatures, and pressures. The laminar burning velocities and the mass burning fluxes give
a similar curve versus the equivalence ratios. They increase with the increase of initial temperature and decrease with the
increase of dilution ratio. The laminar burning velocity decreases with elevating the initial pressure, while the mass burning
flux increases with the increase of the initial pressure. Markstein length decreases slightly with the increase of initial
temperature for the rich mixtures. High initial pressure corresponds to low Markstein length. Markstein length increases with
the increase of dilution ratio, which is more obvious when the mixture becomes leaner. Equivalence ratio has a slight impact
on the development of the diffusive-thermal cellular structure at elevated initial pressures. The initial pressure has a significant
influence on the occurrence of the flame front cellular structure. At the elevated pressures, the cracks on the flame surface
branch and develop into the cell structure. These cells are bounded by cracks emitting a bright light, which may indicate
soot formation. For very lean mixture combustion, the buoyancy effect and cooling effect from the spark electrodes have a
significant impact on the flame propagation. The hydrodynamic instability, inhibited with the increase of initial temperature
around the stoichiometric equivalence ratio, is enhanced with the increase of initial pressure and suppressed by mixture dilution. 相似文献