共查询到20条相似文献,搜索用时 218 毫秒
1.
2.
用火焰图像分析方法,对一种多股射流燃烧器燃烧富含氢气的瓦斯产生的湍流扩散火焰的尺度进行了实验研究,研究了燃烧器结构参数和操作参数对火焰长度和长宽比等尺度特性的影响规律。结果表明,火焰长度随燃烧器喷孔总面积的增大和燃气流量的增大而增大,随助燃空气过剩系数的增大而减小;火焰长度和长宽比随上层喷孔位置角的增大而减小。同时发现,瓦斯中氢气含量对火焰尺度影响较大,随着氢气含量增大,火焰长度和长宽比都明显减小。 相似文献
3.
建立双介质低温等离子体(NTP)反应器预氧化柴油机NO台架试验系统,研究了放电电压峰峰值V_(p-p)、放电频率、排气流量及负荷对NTP预氧化NO性能的影响。试验结果表明:2 100r/min转速、0%负荷工况下,相同放电频率时,NO体积分数随V_(p-p)增大而先减小后增大,NO_2体积分数随V_(p-p)增大而增大,NO_x总量随V_(p-p)增大而先减小后增大;不同放电频率时均存在一个能使NO/NO_2比例为1∶1的V_(p-p)临界值点。排气流量对NTP氧化NO性能影响不大。随着负荷的增大,NTP氧化NO的能力逐渐减弱,其中0%负荷和25%负荷时,NTP能使NO/NO_2比例达到1∶1,协同选择性催化还原(SCR)系统可实现快速SCR反应,提高柴油机低温区间NO_x的转化率。 相似文献
4.
5.
《内燃机工程》2016,(6)
为研究双介质阻挡放电型低温等离子体反应器的性能,对自行设计的双介质阻挡放电型低温等离子体反应器进行静态试验,分析了不同空气流量和工作电压对放电区域温度、NO、NO_2体积分数的影响,采集了不同空气流量和工作电压时放电区域的光谱信息,探讨了低温等离子体化学反应机理。研究结果表明:相同空气流量时,放电区域温度及光谱强度均随工作电压增大而增大,NO体积分数随工作电压呈线性增长关系,NO_2体积分数在空气流量为2L/min和4L/min时随工作电压增大而增大,在6L/min、8L/min和10L/min时几乎保持不变。相同工作电压时,放电区域温度随空气流量增大而减小,光谱强度几乎不随空气流量的改变而改变,NO体积分数随空气流量增大而减小,NO_2体积分数先随空气流量增大而减小,当空气流量大于6L/min后趋于稳定。 相似文献
6.
7.
直流双阳极等离子体特性的研究 总被引:1,自引:0,他引:1
利用高性能数字示波器、发射光谱法以及热力学方法,对直流双阳极等离子体发生器的伏安特性、射流的温度与射流的比焓特性进行了实验研究.结果表明,当等离子体的工作气体为纯氩气时,其弧压随电流的增加显著升高,且不随气体流量的增加而单调地变化;当工作气体为氩氮混合气体时,弧压随氮气的比例增加而急剧增大;氩等离子体射流的比焓随着电流的增大而增大,随着氩气流量的增加而减少;在相近的条件下氩氮等离子体射流的比焓远大于纯氩等离子体射流的比焓;氩等离子体射流在出口处的温度超过10000 K. 相似文献
8.
基于微波等离子体辅助点火可视化试验台架和分离影响因素的研究思路,试验了不同脉冲频率和峰值功率下微波辅助火花塞的放电特性,以及当量比为0.6~1.0、环境压力为0.1~0.7 MPa下的甲烷-空气预混球形火焰的着火及传播特性.干放电试验结果表明:微波脉冲频率为1 kHz时,由于第一个微波脉冲正处于放电电子密度高峰时刻,微波对火花塞放电核心膨胀的加速作用最明显,随着微波脉冲频率的增大,微波强化放电的效果减弱;随微波源的峰值功率增大,微波脉冲对放电的强化作用愈发明显.点火试验结果表明:频率为1 kHz、峰值功率为1 kW微波脉冲的馈入,使当量比为0.6、环境压力为0.1 MPa下的早期火核生长速度提升了60%,随着当量比的增加,微波对火焰发展的增强幅度减小;随着环境压力的增加,微波对点火的增强作用减弱.总之,微波对火焰发展的增强作用主要是对初始火核发展的促进;在火焰后期,燃料燃烧的热能远大于微波能量,导致微波的馈入对后期燃烧过程没有明显影响. 相似文献
9.
10.
11.
Regular observations of atmospheric mixing-ratios of carbon dioxide and methane in the urban atmosphere, combined with analyses of their carbon-isotope composition (δ13C, δ14C), provide a powerful tool for assessing both the source strength and source partitioning of those gases, as well as their changes with respect to time. Intense surface fluxes of CO2 and CH4, associated with anthropogenic activities result in elevated levels of these gases in the local atmosphere as well as in modifications of their carbon-isotope compositions. Regular measurements of concentration and carbon-isotope composition of atmospheric CO2, carried out in Krakow over the past two decades, were extended to the period 1995–2000 and also to atmospheric mixing-ratios of CH4 and its carbon-isotope composition. Radiocarbon concentrations (δ14C) in atmospheric CO2 recorded at Krakow are systematically lower than the regional background levels. This effect stems from the addition of 14C-free CO2 into the local atmosphere, originating from the burning of fossil fuels. The fossil-fuel component in the local budget of atmospheric carbon calculated using a three-component mixing model decreased from ca. 27.5 ppm in 1989 to ca. 10 ppm in 1994. The seasonal fluctuations of this component (winter–summer) are of similar magnitude. A gradually decreasing difference between the 14CO2 content in the local atmosphere and the regional background observed after 1991 is attributed to the reduced consumption of 14C-free fuels, mostly coal, in southern Poland and the Krakow municipal area. The linear regression of δ13C values of methane plotted versus reciprocal concentration, performed for the data available for Krakow sampling site, yields the average δ13C signature of the local source of methane as being equal to −54.2‰. This value agrees very well with the measured isotope signature of natural gas being used in Krakow (−54.4±0.6‰) and points to leakages in the distribution network of this gas as the main anthropogenic source of CH4 in the local atmosphere. 相似文献
12.
使用自行研制的微型天然气燃烧装置,利用FTIR发射透射技术,借助傅立叶变换红外光谱仪在线测量了常温高预混度条件下甲烷火焰的温度和辐射力。通过试验得出了较高预混度条件下常温甲烷火焰的碳黑生成、火焰辐射和火焰温度等方面的燃烧特性。 相似文献
13.
An experimental investigation has been made with the objective of studying the limit of equivalent ratio (ϕ) on mixing enhancement in a tone excited jet rich flame. The jet is pulsed by means of a loudspeaker-driven cavity and experiments are limited to very rich flames (ϕ>1⋅5). The excitation frequency is chosen for the resonant frequency identified as a pipe resonance due to acoustic excitation. Methane, propane and butane are used to examine the effect of mixture property on the limit of equivalence ratio. Mixing is always enhanced in a methane/air flame as the excitation intensity increases. In the case of propane/air and butane/air flames, mixing enhancement can be obtained only when the equivalence ratio lies in the range from a certain value (the equivalence ratio limit) to infinity (non-premixed flame), irrespective of mean mixture velocities. It is also found that the equivalence ratio limit is related to flame instability; the lower the Lewis number, the higher the equivalence ratio limit. As the excitation intensity increases, flame separation occurs below the equivalence ratio limit; an inner (premixed) flame is transformed into a cellular flame which then moves upstream, but the height of an outer (non-premixed) flame is not decreased. Acoustic pressure measurements using a microphone are made to quantify the oscillating velocity. The oscillating velocity amplitude at the cellular flame position is proportional only to mean mixture velocity regardless of fuel type. © 1997 by John Wiley & Sons, Ltd. 相似文献
14.
The profiles of the species H, OH, CH, NH, CN, NCO, NO2, and CH3O are compared in a series of five premixed stoichiometric 15-torr CH4/O2/NO2/N2 flames with NO2 comprising between 0% and 40% of the oxidizer. Relative species concentrations were measured by laser-induced fluorescence (LIF) and these results are compared with calculations using measured temperature profiles. The reaction mechanism of Miller and Bowman incorrectly predicts the standoff from the burner in flames containing more than 20% NO2; addition of several reactions involving NO2 and HONO produces excellent agreement with experiment for most species. The reaction CH3 + NO2 → CH3O + NO is found to be particularly important in the reaction mechanism. LIF profiles of CH3O show this species to be present in far larger quantities in the NO2 supported flames than in the CH4/O2 system. The nitrogen-containing intermediates CN, NCO, and NH are all overpredicted by a factor of two in the 40% NO2 flame relative to the 10% NO2 flame. This indicates an inaccuracy in either the reburn reactions or the fuel nitrogen chemistry when large amounts of NO are present. The kinetic modeling shows that in the 40% NO2 flame, the dominant pathway to N2 formation is through N2O, which is produced primarily by the reaction of NCO with NO. Comparison of emission profiles of NO2* for the various flames indicates that the appearance of an orange-yellow luminous zone at the base of NO2 supported flames is caused by thermal excitation of NO2, not by a chemiluminescence mechanism. 相似文献
15.
利用分光成像系统,实时收集O2/CH4同轴射流扩散火焰辐射发光信息,重点讨论火焰中3种激发态自由基组分(OH*、CH*和C2*)的发光特征.探讨3种激发态自由基的产生机理;分析OH*、CH*和C2*的辐射强度随氧气/燃料当量比的变化,及其沿扩散火焰轴向分布特征等.结果表明:激发态自由基均由化学激发途径产生,其辐射发光为化学发光;OH*辐射发光强度随氧气/燃料当量比变化显著,可采用[OH*]/[CH*]表征当量比变化;OH*辐射强度可以作为扩散火焰化学反应区及高度的表征. 相似文献
16.
17.
Inspired by the promising hydrogen production in the solar thermochemical (STC) cycle based on non-stoichiometric oxides and the operation temperature decreasing effect of methane reduction, a high-fuel-selectivity and CH4-introduced solar thermochemical cycle based on MoO2/Mo is studied. By performing HSC simulations, the energy upgradation and energy conversion potential under isothermal and non-isothermal operating conditions are compared. In the reduction step, MoO2: CH4 = 2 and 1020 K<Tred<1600 K are found to be most favorable for syngas selectivity and methane conversion. Compared to the STC cycle without CH4, the introduction of methane yields a much higher hydrogen production, especially at the lower temperature range and atmospheric pressure. In the oxidation step, a moderately excessive water is beneficial for energy conversion whether in isothermal or non-isothermal operations, especially at H2O: Mo= 4. In the whole STC cycle, the maximum non-isothermal and isothermal efficiency can reach 0.417 and 0.391 respectively. In addition, the predicted efficiency of the second cycle is also as high as 0.454 at Tred = 1200 K and Toxi = 400 K, indicating that MoO2 could be a new and potential candidate for obtaining solar fuel by methane reduction. 相似文献
18.
The effect of nonthermal plasma on diffusion flames in coflow jets has been studied experimentally by adopting a dielectric barrier discharge (DBD) technique. The plasma reactor had wire-cylinder-type electrodes with AC power supply operated at 400 Hz. The effect of flame on the behavior of electrical discharge was first investigated to identify the regime of plasma generation, discharge onset voltage, and delivered power to the plasma reactor. The generation of streamers was enhanced with a flame by the increase in the reduced electric field intensity due to high-temperature burnt gas and by the abundance of ions in the flame region. The effect of streamers on flame behavior reveals that the flame length was significantly decreased as the applied voltage increased. The yellow luminosity by the radiation of soot particles was also significantly diminished. The temperature of burnt gases, the concentrations of major species, and the spatial distribution of OH radical, PAH, and soot have been measured. The formation of PAH and soot was influenced appreciably by the nonthermal plasma, while the flame temperature and the concentration of major species were not influenced much with the plasma generation. The results demonstrated that the application of nonthermal plasmas can effectively suppress PAH and soot formation in the flames with low power consumption even in the order of 1 W. 相似文献
19.
Ceramic systems of Bi2O3 and gadolinia-doped ceria (GDC) solid mixture were prepared as catalysts for direct methane oxidation. These systems were characterized by temperature-programmed reduction using hydrogen and carbon monoxide, temperature-programmed reaction of methane, fixed-temperature direct methane oxidation, and X-ray diffraction analysis. Adding Bi2O3 to GDC promotes both hydrogen and CO oxidation activities, because of the presence of surface Bi2O3 and the high content of mobile oxygen in Bi2O3. The reactivity of CO with surface lattice oxygen is enhanced to a higher extent than that of H2, and this enhanced extent shows a maximum in Bi2O3 content. Such a maximum also exists for the catalytic activity of direct methane oxidation. A synergistic effect occurs due to a combination of the high methane reactivity of GDC and the high content of mobile oxygen in Bi2O3. The CO2 selectivity of direct methane oxidation can be modulated by varying the Bi2O3 content. The mixing of Bi2O3 with GDC also increases the self-de-coking capability of the catalyst during direct methane oxidation, which stabilizes the activity. 相似文献
20.
燃料质量浓度分布在一定程度上影响混合气体的燃烧效率,能使燃气充分混合的同轴射流、旋片同轴、轴切结合、切向旋流等典型混合模式在航空发动机、燃气轮机及火箭发动机等先进燃烧技术应用中较为常见。因此,设计了甲烷/空气部分预混的燃烧实验装置,较为系统地实验研究了旋流数和轴向流速对混合气体在约束空间燃烧室内燃烧特性的影响。结果表明:对于有中心射流的混合结构,燃气轴向流速较低时产生黄色火焰,增大轴向流速,黄色火焰转为蓝色湍流火焰,且温度分布趋于均匀;纯切向旋流燃烧器的掺混效果较好,受燃气轴向流速的影响小,火焰结构稳定,均为蓝色火焰,温度轴/径向分布均匀且趋势一致,同当量比下燃烧产物中的污染物体积分数最小。 相似文献