宽带相干反斯托克斯喇曼散射法诊断固体燃剂燃烧场

报道了采用单次脉冲非稳腔空间增强探测 相干反斯托克斯喇曼散射（USED CARS）技术诊断常压下固体燃剂瞬态燃烧场温度和氮气浓度。采用宽带USED CARS技术,在固体燃剂瞬态燃烧场获得了较高信噪比的单次激光脉冲氮气Q支CARS实验谱,用CARS理论计算软件拟合CARS实验谱,给出了固体燃剂瞬态燃烧场温度和氮气浓度在不同高度的分布,固体燃剂燃烧场温度约2 250K、氮气相对浓度16%～20%。     

利用拉曼散射测量燃烧场的组分浓度及温度

介绍了利用拉曼散射测量燃烧流场温度及组分浓度的物理方法和实验测量结果。利用可调谐KrF准分子激光激发振动拉曼散射（VRS）测量了甲烷－空气燃烧火焰内不同空间的主要组分分子（CH4、N2、O2、H2O等）浓度及温度,测量误差小于10％;另外用N2的拉曼谱拟合测量了火焰的温度,测量精度高于5％。在实验中采用了偏振技术及波长调谐提高了信噪比和测量精度。     

宽带相干反斯托克斯喇曼散射法诊断固体燃剂燃烧场

 报道了采用单次脉冲非稳腔空间增强探测 相干反斯托克斯喇曼散射（USED CARS）技术诊断常压下固体燃剂瞬态燃烧场温度和氮气浓度。采用宽带USED CARS技术，在固体燃剂瞬态燃烧场获得了较高信噪比的单次激光脉冲氮气Q支CARS实验谱，用CARS理论计算软件拟合CARS实验谱，给出了固体燃剂瞬态燃烧场温度和氮气浓度在不同高度的分布，固体燃剂燃烧场温度约2 250K、氮气相对浓度16%～20%。     

BOXCARS测量燃烧场的温度

介绍了用BOXCARS技术测量CH4/air火焰的温度。给出了甲烷气体不同流量下和火焰不同高度处的温度测量结果,分析了温度随甲烷气体流量变化和火焰高度变化的变化趋势,根据实际的实验参数计算了相应的空间分辨率。实验结果表明：利用BOXCARS技术可进行高精度、高空间分辨的温度测量。     

BOXCARS测量燃烧场的温度

 介绍了用BOXCARS技术测量CH₄/air火焰的温度。给出了甲烷气体不同流量下和火焰不同高度处的温度测量结果，分析了温度随甲烷气体流量变化和火焰高度变化的变化趋势，根据实际的实验参数计算了相应的空间分辨率。实验结果表明：利用BOXCARS技术可进行高精度、高空间分辨的温度测量。     

单脉冲BOXCARS技术在瞬态燃烧场测温中的应用

 用单脉冲交叉相干反斯托克斯喇曼散射技术测量了两种不同固体燃剂的瞬态燃烧场的温度。对燃烧场进行了优化，给出了在燃烧场中取得的部分典型单脉冲CARS光谱及其理论拟合结果，得到了燃烧场的温度及其随高度的分布；稳定燃烧时两种燃剂燃烧场的温度基本保持不变，平均值分别为2 260，2 090K；测量了实验的纵向空间分辨率。结果表明，BOXCARS技术能较好地完成复杂的瞬态燃烧场温度的测量工作。     

混合溶液中CARS过程的非共振信号实验研究

相干反斯托克斯拉曼散射是一种非线性四波混频效应,但是通过探测共振信号不易进行物质成分的定量光谱分析。本文利用单频相干反斯托克斯拉曼散射光谱分析法,对不同体积比混合的乙醇溶液在远离双光子共振跃迁及其远离溶质与溶剂的特征拉曼共振态位置进行了光谱探测。通过对实验结果进行分析发现,在共振位置2 876 cm-1的信号强度随混合溶液中的乙醇的体积比增加而增加,呈二次方关系。而在远离共振态位置的非共振信号强度随混合溶液中乙醇的体积比增加而增加,且呈线性关系,进而说明了非共振信号强度随着分子数浓度N呈线性变化关系。因此,通过探测非共振信号强度与分子数浓度关系可以为混合物中特定成分的定量光谱分析提供一种研究途径。     

分时窄带CARS光谱技术在测量烯烃浓度方面的应用

基于相干反斯托克斯拉曼散射(CARS)光谱技术机理,针对甲醇制烯烃(MTO)产物中多种组分烃类的探测需求,搭建了一套扫描式窄带CARS光谱实验装置。采用该装置对甲烷,乙烷,乙烯,丙烯分别进行CARS光谱扫描,获得了各分子的特征拉曼谱;并在相同实验条件下进行比对试验,得到不同分子特征峰处的CARS信号强度与目标气体浓度及其他背景气体之间的关系。通过建立简化模型对不同分子的CARS信号特征峰强度信息进行解析,提出了一种分时窄带CARS光谱探测多种拉曼活性气体浓度的方法,用于快速在线分析催化化工等领域中各类流体的组分。利用这种方法探测了甲烷,乙烯,丙烯的浓度,将实验误差控制在9%以内。     

基于CARS技术的超燃冲压发动机点火过程温度测量

相干anti-Stokes Raman散射（coherent anti-Stokes Raman scattering,CARS）技术作为一种非接触测量手段,已广泛应用于多种发动机模型燃烧室温度测量及地面试验.然而,目前的工作主要集中在稳态燃烧场温度的测量,缺乏用高分辨率的单脉冲来测量瞬变的燃烧火焰温度及组分浓度的研究.基于CARS理论,结合多参数拟合算法,开发了基于MATLAB的CARS光谱计算和拟合程序CARSCF;利用McKenna平面火焰炉在不同工况下进行了温度测量,并与DLR测量结果进行对比,结果显示开发的CARSCF具有较高的测量重复性和准确性;最后将CARS技术应用于测量超燃冲压发动机点火过程中的温度测量,获取了点火过程中的温度.结果显示,在来流Mach数为3的条件下,H₂/air点火过程中温度呈现急剧上升然后缓慢下降,而CARS信号则呈现急剧上升然后急剧下降随后又缓慢上升的趋势,并且在点火过程中最高温度为1 511 K.      

基于LED光源的非相干宽带腔增强吸收光谱技术探测HONO和NO2

介绍了基于近紫外发光二极管LED (中心波长约372 nm,半高宽13 nm) 光源的非相干宽带腔增强吸收光谱技术,同时用于探测痕量气体HONO和NO₂. LED出射光经准直后耦合进入长度为70 cm,由两块高反射率镜片组成的高精密光学腔内. 分别测量了氮气消光谱和氦气消光谱,通过两者瑞利散射截面的差异而引起光谱强度的变化来标定镜片反射率.在360—390 nm反演波段内,镜片反射率在390 nm处最大且为0.99962, 对应测量NO₂/HONO混合物时的最大光程约1.71 km,并利用最小二乘拟合反演出了 HONO和NO₂的浓度值.当光谱采集时间为1000 s时, HONO和NO₂的探测灵敏度(1σ) 分别为0.6 ppbv和1.9 ppbv.实验结果表明,该技术为实现大气痕量气体的高灵敏度在线监测提供了另一种可能的途径.     

燃烧流场线CARS测温技术研究

常规CARS采用凸透镜聚焦多束激光于空间一点,在满足相位匹配条件下产生携带该点温度信息的CARS信号。常规CARS一次只能测量一个空间点的温度,难以满足燃烧流场深入研究需要。为了提高CARS测量能力,使得CARS在一次测量中获得更多信息,提出了线CARS测量方法。线CARS测量方法在常规CARS基础上采用柱面凸透镜替换普通凸透镜,使得聚焦位置由焦点变为焦线。由于焦线上的点大部分满足相位匹配关系,因此可以同时获得多点CARS信号。后续光路同样采用柱面凸透镜替换普通凸透镜,通过光谱仪和ICCD相机将CARS信号传输至计算机,解析出聚焦线上CARS信号对应的温度信息,实现CARS测量能力由“点”到“线”的提升。基于平面火焰炉的燃烧实验结果表明：线CARS可以一次有效测量200个空间点的温度信息,空间测量长度约3.6 mm,空间分辨率约18 μm,测量结果相对不确定度优于7%,在保持测量精度的同时有效丰富了单次测量信息。     

Validation experiments for spatially resolved one-dimensional emission spectroscopy temperature measurements by dual-pump CARS in a sooting flame

In this work, an emission spectroscopic (ES) technique for the determination of soot temperatures in an axisymmetric flame is validated against coherent anti-Stokes Raman spectroscopy (CARS) as preparation for a zero gravity measurement campaign. In order to reduce valuable measurement times during the parabolic flights, a setup for spatially resolved one-dimensional measurements along a line has been built up using an imaging spectrometer and a CCD-camera for data acquisition.In order to assess the performance of the ES technique, accurate coherent anti-Stokes Raman scattering (CARS) measurements have been performed at the same conditions. Hereby, great care has to be taken to minimize the known interferences in sooting flames. The non-resonant signal contribution was suppressed by a polarization technique and the signal wavelength was shifted to an interference free region. These modifications are discussed in detail. The temperatures obtained by both methods are in good agreement in most regions of the flame. It turned out that the described approach for ES is an appropriate and robust alternative for measuring temperatures in sooting axisymmetric flames, if more accurate techniques cannot be applied, e.g., during investigations in zero-g parabolic flight experiments.     

In-cylinder temperature field measurement with laser shearing interferometry for spark ignition engines

The temperature field in combustion chamber of spark ignition engine is measured using laser shearing interferometry and high-speed photography in this paper. A set of experimental facility is set up. The relationship equation between the interference fringe image and temperature distribution is deduced. Changing the shearing interferometry quantity, the two-dimensional temperature field of engine combustion chamber and flame propagation can be measured quantitatively by image processing. The test results indicate that the shearing interferometric method has a strong vibration resistance, and a simple and reliable optical path. The temperature distribution and the temperature gradient are different in different zones. The temperature is highest in the burning zone and the temperature gradient is large. The temperature is lower in the burned zone and the temperature gradient is smaller. The temperature is lowest in the unburned zone but the temperature gradient is large. At the initial period of combustion, the flame propagation velocity is low. In the combustion process, the flame front in the approximate spherical shape pushes toward the unburned zone, and the flame propagation velocity starts to decrease. It rapidly increases until it reaches the maximum value as the combustion process going on, and then it gradually decreases until it has burned in the entire combustion chamber.     

PLIF法定量测量甲烷-空气火焰二维温度场分布

利用平面激光诱导荧光(PLIF)技术,通过选择适合的OH自由基激励线,定量测量了甲烷-空气燃烧火焰的二维温度场分布。给出炉面中心上方火焰温度随离炉面高度的变化和距炉面12 mm高处沿炉面水平方向变化的实验测量结果并进行了讨论与分析。与利用相干反斯托克斯喇曼散射（CARS）技术进行测温的实验结果相比,该测量的相对不确定度优于5％。     

Temperature field of radiative equilibrium in a two-dimensional graded index medium with gray boundaries

In this paper, a numerical method is presented for the study of the radiative transfer in a two-dimensional graded index semitransparent medium with diffuse gray boundaries. The numerical method is a combination of the linear refractive index bar model, the discrete curved ray-tracing technique and the pseudo source adding method (LRIB-CRTP). In the traditional ray-tracing technique, it is difficult to deal with the diffuse gray boundary while solving the radiative transfer. Using the pseudo source adding method, the diffuse gray boundary of the medium can be treated as a black boundary. We have also studied the radiative equilibrium temperature field of the medium and analyzed the influence of some parameters involved. The results show that the directional discrete number is important for the medium having a large absorption coefficient. The results also show that the refractive index distribution greatly influences the temperature field, whereas the linear absorption coefficient distribution has little influence on the temperature field.     

Temperature field measurement of an array of laminar premixed slot flame Jets using Mach-Zehnder interferometry

An experimental study was performed to investigate the influence of Reynolds number (Re) and non-dimensional jet-to-jet spacing (S/D_h) on flame shape, structure and temperature field of an array of laminar premixed slot flame jets. Mach-Zehnder interferometry technique is used to obtain an insight to the overall temperature field between single, twin and triple slot flame jets. The slot jets with large aspect ratio (L/W), length of L=60 mm and width of W=6 mm were used to eliminate the three-dimensional effect of temperature field. The effect of jet-to-jet spacing was investigated on flame characteristics under the test conditions of 200≤Re≤400 and equivalence ratio (φ) of unity. The present measurement reveals that the variation of maximum flame temperature with increment of Reynolds number is mainly due to heat transfer effects and is negligible while the flame height is increased. For the cases of twin and triple flame jets by increasing Reynolds number and decreasing non-dimensional jet-to-jet spacing (S/D_h), the interferences between the jets are increased and the jets attracted each other. Strong interference was observed at S/D_h=1.15. For the case of triple jets at this S/D_h, the central jet was suppressed while the side jets deflected towards the inner jet. The interference between jets was found to reduce the heat flux in the jet-to-jet interacting zone due to incomplete combustion. Also the optimum jet-to-jet spacing of triple flame jets is obtained at each Reynolds number to enhance the heat transfer performance of the jets.     

The measurement of the electrical field distribution by external electro-optic measuring system with submicrometre spatial resolution

A GaAs solid immersion lens has been applied to the external electric-optic measuring system. The spatial resolution of the system is improved to 0.7 μm because of the increased effective number aperture. We measured the electrical field distribution of ceramic microstrip lines transversely. The variation of electrical field with a submicrometre interval has been revealed experimentally and the results are in good agreement with the theoretical analysis.