共查询到18条相似文献,搜索用时 125 毫秒
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利用电荷耦合器件摄像机采用烟黑温度场和浓度场同时重建模型对自由火焰烟黑的三维温度场和浓度场进行了同时重建实验研究,所利用的重建模型是基于区域重建的方法.将重建的烟黑温度场和浓度场与文献结果进行了对比,而且还将重建温度场与热电偶所测量的温度场进行了对比.结果表明,重建的烟黑温度场和浓度场与文献结果趋势相一致,重建温度值与热电偶测量值符合较好.因此,同时重建模型可以较好地重建出火焰烟黑的三维温度场和浓度场.
关键词:
火焰烟黑
温度场
浓度场
三维同时重建 相似文献
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本文采用数值模拟方法研究了重力对甲烷/空气同轴射流层流扩散火焰烟黑生成特性的影响,数值分析中将详细的气相化学反应机理、复杂的热物性和输运特性关系、半经验的双方程烟黑生成模型和非灰体辐射模型耦合到燃烧场的计算中。同时考虑烟黑经O_2、OH和O的氧化途径。热辐射计算采用与统计窄波段调K(SNBCK)模型相耦合的离散坐标法求解。烟黑的谱带吸收系数根据小颗粒的Rayleigh理论计算。结果表明,随着重力水平的降低,火焰峰值温度降低,微重力下烟黑浓度的最大值约为正常重力下相应火焰的两倍。这一计算结果与已有的试验数据符合较好。计算结果还表明,重力也影响烟黑成核和表面生长的位置和强度。 相似文献
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基于烟黑热辐射传递过程,提出了非对称碳氢扩散火焰断面内烟黑浓度和温度分布的联合层析重建模型.应用最小二乘QR矩阵分解算法模拟分析了传感器数量和布置方式对重建结果的影响以及模型的抗噪能力.计算结果表明,当4个320像素线阵电荷耦合辐射投影传感器(CCD)成非正对布置时,浓度场重建结果最大误差小于2.5%,温度场重建结果最大误差小于0.2%.此外CCD正对布置将导致重建误差向中心聚集.从对含噪声数据的重建结果看,应用联合层析重建模型,辐射能传感器的信噪比不应低于60dB.
关键词:
非对称火焰
层析重建
最小二乘QR矩阵分解算法
联合重建 相似文献
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光场成像技术可以在一次曝光中,同时记录下入射光线的空间分布信息和传播方向信息,能够得到更丰富的热辐射信号。本文利用聚焦型光场相机对三维火焰进行了光场采集,并利用这些光场信息通过截断奇异值分解(TSVD)重建了不同火焰的三维温度场分布,在重建过程中考虑了光场相机白图像的特点,剔除了对重建不利的无效像素,并且分别对均匀分布、轴对称分布和非轴对称分布的火焰进行了温度场重建,重建结果表明均匀温度分布的重建结果最佳,轴对称分布的重建结果次之,非轴对称分布的重建结果最差。最后考察了不同测量误差下重建结果,重建结果表明在一定的测量误差范围内,TSVD方法的重建效果对测量误差不敏感。 相似文献
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通过理论分析和LARED多群辐射输运模拟研究了激光间接驱动聚变中黑腔辐射温度的角分布特点。研究发现,黑腔辐射温度角分布主要决定于光斑区与非光斑区的对比度、视野中光斑区的面积比例,以及体发射的份额。激光二维光环排布下黑腔辐射温度角分布与二维LARED模拟结果非常一致。研究还发现,二维的LARED模拟能够有效地用于研究神光Ⅲ原型黑腔实验中三维光斑排布下的辐射温度角分布。通过缩小FXRD测量面积能够有效地提高黑腔辐射温度随角度的变化,从而降低辐射流测量误差对辐射温度角分布的影响。 相似文献
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C. Schoemaecker Moreau E. Therssen X. Mercier J.F. Pauwels P. Desgroux 《Applied physics. B, Lasers and optics》2004,78(3-4):485-492
Laser-induced incandescence is a technique which enables the measurement of soot volume fractions. However, the laser-induced soot emission might be affected by a fluorescence background generally ascribed to the polycyclic aromatic hydrocarbon compounds (PAHs) present at the soot location. In this paper, spatially resolved distributions of PAH absorbance and soot are obtained in sooting diffusion flames. The original method developed here consists in comparing the emission distributions induced by two different laser wavelengths: (1) at 1064 nm emission signals are exempt from PAH fluorescence and (2) at 532 nm both soot incandescence and PAH emission contribute to the total signal. In addition, the absolute absorption coefficient of the PAH mixture is determined by comparing absorption measurements obtained by cavity ring-down spectroscopy (CRDS) at 1064 nm and 532 nm. The proposed method can provide highly sensitive 2D imaging of PAHs and soot using the fundamental and the second-harmonic frequencies of a single YAG laser. Finally, 2D distributions of PAH absorbance and soot volume fraction calibrated by CRDS are obtained in two diffusion flames, particularly in a very low-sooting flame exhibiting a maximum PAH absorbance of 6×10-4 cm-1 and a maximum soot volume fraction of 3 ppb only. The respective spatial distributions of PAHs and soot are shown to vary with the initial C/O ratio. PACS 33.20.Lg; 42.62.Fi; 44.40.+a 相似文献
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Yu-hua Ai 《Journal of Quantitative Spectroscopy & Radiative Transfer》2005,91(1):11-26
For visualizing non-uniform absorbing, emitting, non-scattering, axisymmetric sooting flames, because conventional two-color emission methods are no longer suitable, a three-color emission method for the simultaneous estimation of temperature and soot volume fraction distributions in these flames is studied in this paper. The spectral radiation intensities at wavelengths of red, green, and blue, which may be derived from color flame images, are simulated for the inverse analysis. Then the simultaneous estimation is carried out from the spectral radiation intensities by using a Newton-type iteration algorithm and the least-squares method. In this method, a factor is used to balance the wide variation of spectral radiation intensities due to both the wide ranges of temperature and wavelength of the flame radiation. The results indicate that the three-color method is suited for the reconstruction of flame structures with single or double peaks with small difference between the peak and valley. For a double-peaked flame structure with larger peak and valley difference, reasonable result can be obtained just when the mean square deviations of measurement data are small, for example, not more than 0.01. 相似文献
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Experimental determination of distributions of soot particle diameter and number density by emission and scattering techniques 下载免费PDF全文
《中国物理 B》2019,(1)
A diagnostics method was presented that uses emission and scattering techniques to simultaneously determine the distributions of soot particle diameter and number density in hydrocarbon flames. Two manta G-504 C cameras were utilized for the scattering measurement, with consideration of the attenuation effect in the flames according to corresponding absorption coefficients. Distributions of soot particle diameter and number density were simultaneously determined using the measured scattering coefficients and absorption coefficients under multiple wavelengths already measured with a SOC701 V hyper-spectral imaging device, according to the Mie scattering theory. A flame was produced using an axisymmetric laminar diffusion flame burner with 194 mL/min ethylene and 284 L/min air, and distributions of particle diameter and number density for the flame were presented. Consequently, the distributions of soot volume fraction were calculated using these two parameters as well, which were in good agreement with the results calculated according to the Rayleigh approximation,demonstrating that the proposed diagnostic method is capable of simultaneous determination of the distributions of soot particle diameter and number density. 相似文献
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Jun Hayashi Nozomu Hashimoto Noriaki Nakatsuka Hirofumi Tsuji Hiroaki Watanabe Hisao Makino Fumiteru Akamatsu 《Proceedings of the Combustion Institute》2013,34(2):2435-2443
Soot formation characteristics of a lab-scale pulverized coal flame were investigated by performing carefully controlled laser diagnostics. The spatial distributions of soot volume fraction and the pulverized coal particles were measured simultaneously by laser induced incandescence (LII) and Mie scattering imaging, respectively. In addition, the radial distributions of the soot volume fraction were compared with the OH radical fluorescence, gas temperature and oxygen concentration obtained in our previous studies [1], [2]. The results indicated that the laser pulse fluence used for LII measurement should be carefully controlled to measure the soot volume fraction in pulverized coal flames. To precisely measure the soot volume fraction in pulverized coal flames using LII, it is necessary to adjust the laser pulse fluence so that it is sufficiently high to heat up all the soot particles to the sublimation temperature but also sufficiently low to avoid including a too large of a change in the morphology of the soot particles and the superposition of the LII signal from the pulverized coal particles on that from the soot particles. It was also found that the radial position of the peak LII signal intensity was located between the positions of the peak Mie scattering signal intensity and peak OH radical signal intensity. The region, in which LII signal, OH radical fluorescence and Mie scattering coexisted, expanded with increasing height above the burner port. It was also found that the soot formation in pulverized coal flames was enhanced at locations where the conditions of high temperature, low oxygen concentration and the existence of pulverized coal particles were satisfied simultaneously. 相似文献
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Hyun I. Joo 《Proceedings of the Combustion Institute》2009,32(1):769-775
The effects of pressure on soot formation and the structure of the temperature field were studied in co-flow methane-air laminar diffusion flames over a wide pressure range, from 10 to 60 atm in a high-pressure combustion chamber. The selected fuel mass flow rate provided diffusion flames in which the soot was completely oxidized within the visible flame envelope and the flame was stable at all pressures considered. The spatially resolved soot volume fraction and soot temperature were measured by spectral soot emission as a function of pressure. The visible (luminous) flame height remained almost unchanged from 10 to 100 atm. Peak soot concentrations showed a strong dependence on pressure at relatively lower pressures; but this dependence got weaker as the pressure is increased. The maximum conversion of the fuel’s carbon to soot, 12.6%, was observed at 60 atm at approximately the mid-height of the flame. Radial temperature gradients within the flame increased with pressure and decreased with flame height above the burner rim. Higher radial temperature gradients near the burner exit at higher pressures mean that the thermal diffusion from the hot regions of the flame towards the flame centerline is enhanced. This leads to higher fuel pyrolysis rates causing accelerated soot nucleation and growth as the pressure increases. 相似文献
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Reconstruction model for temperature and concentration profiles of soot and metal-oxide nanoparticles in a nanofluid fuel flame by using a CCD camera 下载免费PDF全文
This paper presents a numerical study on the simultaneous reconstruction of temperature and volume fraction fields of soot and metal-oxide nanoparticles in an axisymmetric nanofluid fuel sooting flame based on the radiative energy images captured by a charge-coupled device(CCD) camera. The least squares QR decomposition method was introduced to deal with the reconstruction inverse problem. The effects of ray numbers and measurement errors on the reconstruction accuracy were investigated. It was found that the reconstruction accuracies for volume fraction fields of soot and metaloxide nanoparticles were easily affected by the measurement errors for radiation intensity, whereas only the metal-oxide volume fraction field reconstruction was more sensitive to the measurement error for the volume fraction ratio of metaloxide nanoparticles to soot. The results show that the temperature, soot volume fraction, and metal-oxide nanoparticles volume fraction fields can be simultaneously and accurately retrieved for exact and noisy data using a single CCD camera. 相似文献
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Andrea D’Anna Mario Commodo Cristophe Allouis 《Proceedings of the Combustion Institute》2007,31(1):621-629
Spectral optical techniques are combined to characterise the distribution of large-molecule soot precursors, nanoparticles of organic carbon, and soot in two turbulent non-premixed ethylene flames with differing residence times. Laser-induced fluorescence, laser-induced incandescence and light scattering are used to define distributions across the particle size distribution. From the scattering and laser-induced emission measurements it appears that two classes of particles are formed. The first ones are preferentially formed in the fuel-rich region of the flame closer to the nozzle, have sizes of the order of few nanometers but are not fully solid particles, because the constituent molecules still maintain their individual identity exhibiting strong broadband fluorescence in the UV. The second class of particles constituted by solid particles, with sizes of the order of tens of nanometers are able to absorb a sufficient number of photons to be heated to incandescent temperatures. These larger particles are formed at larger residence times in the flame since they are the result of slow growth processes such as coagulation or carbonization. The flames are also modeled in order to produce mixture fraction maps. A new discovery is that nanoparticles of organic carbon concentration, unlike soot, does correlate well with mixture fraction, independent of position in the flame. This is likely to be a significant benefit to future modelling of soot inception processes in turbulent non-premixed flames. 相似文献