甲烷-空气预混V形火焰的CARS实验研究

本文将相干反斯托克斯(CARS)理论光谱计算和实验光谱分析的方法应用于预混V形火焰燃烧的温度测量实验,利用N2的Q支CARS谱线,使用单脉冲宽带方法获得了预混V形火焰的CARS信号光谱强度特性,测量了V形火焰水平方向和竖直方向上的温度分布特征,从中得出了火焰锋面的厚度,分析了火焰锋面的皱褶与摆动对CARS信号的影响。同时测量了不同燃料系数下V形火焰燃烧产物的温度,得出了温度随燃料系数的变化趋势,为进一步研究预混 V形火焰的结构提供了依据。     

多色宽带相干反斯托克斯拉曼散射过程的理论与实验研究

宽带相干反斯托克斯拉曼散射(coherent anti-Stokes Raman scattering,CARS)光谱技术能够同时获取完整的分子CARS光谱信息,以准确识别和定量分析混合物中的不同成分或未知成分.在宽带CARS光谱技术中,由于超连续谱激光有效光谱范围内各光谱成分的作用不同,分别会产生双色和三色CARS过程.这里我们在理论上分析了宽带激发条件下两种CARS过程的产生条件,以及不同CARS光谱信号强度与各激发光功率之间的关系.在此基础上,搭建了基于SC激光的宽带CARS光谱系统,分别实现了双色和三色CARS过程.通过对获得的苯甲腈样品的CARS光谱信号进行函数拟合分析,实验验证了上述两个过程中CARS信号的强度与各激发光强度之间的函数关系.理论和实验研究结果为进一步优化宽带时间分辨CARS光谱探测和显微系统,实现同时获取物质分子完整的CARS光谱信号提供了指导.     

利用辐射光谱法在线测量固体火箭推进剂燃烧温度（英文）

针对固体火箭发动机恶劣环境下的高温燃烧测量问题,提出了利用辐射光谱法来开展固体火箭推进剂燃烧温度在线测量的方法,采用200～1 100nm光纤光谱仪测量了高压实验燃烧器下固体火箭推进剂燃烧火焰辐射光谱,总结了其光谱特性,并基于普朗克定律和光谱拟合方法获得了相应的推进剂燃烧温度,这对固体火箭推进剂燃烧诊断与燃烧机理研究具有重要的参考价值。     

1维非稳腔空间增强探测CARS技术对稳态燃烧场温度的测量

 建立了1维非稳腔空间增强探测CARS实验系统，该系统由光源（YAG激光器、染料激光器）、实验光路和信号采集系统组成。分别测量了空气和化学平衡比为1，甲烷流量为0.7 L/min的甲烷-空气预混火焰中的氮气Q支的CARS实验谱。给出了火焰不同高度处小范围内的温度分布结果，并对实验结果进行了分析，结果表明：预混火焰温度随高度的增加呈下降趋势，测量结果的不确定度优于7%。该技术可用于稳态燃烧场温度的测量。     

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。     

可调空间分辨USEDCARS技术研究

相干反斯托克斯拉曼散射（CARS）技术是一种非常重要的燃烧诊断技术,该技术具有非常强的抗干扰能力和非常高的测量精度。但空间分辨力不足会使CARS技术产生很强的空间平均效应,引起成CARS光谱畸变,进而造成CARS光谱分析困难,无法通过CARS光谱反演燃烧场参数。针对非稳腔空间增强探测CARS（USEDCARS）技术存在的空间分辨不足以及空间分辨力不易改变的特点,分析了影响USEDCARS技术测量空间分辨力的各种因素,采用一组轴棱锥对USEDCARS系统中的泵浦激光进行环状光束整形,并通过调节轴棱锥之间的距离获得了不同直径的环状光束,在此基础上,建立了空间分辨可调USEDCARS诊断系统。开展了空间分辨力分析实验,获得了CARS信号强度随空间位置的分布数据,以CARS信号总强度95%包含的空间区域代表CARS的纵向空间分辨力,以此计算得到了CARS系统空间分辨力为1.7～6.5 mm连续可调。其中,高分辨力情况,达到了现有BOXCARS技术的空间分辨力。利用所建立的空间分辨可调USEDCARS诊断系统测量了酒精/空气预混火焰温度参数,获得了不同空间分辨条件下的CARS光谱。空间分辨力为1.7 mm时,获得了高质量CARS光谱,通过光谱拟合给出了所测火焰的温度信息。分辨力分别为4.9和6.5 mm时获得了较强的CARS信号,但存在光谱畸变。结果显示,空间分辨力对CARS信号的强度和空间平均效应有很大地影响,提高测量的空间分辨力可以有效消除空间平均效应,获得准确的CARS光谱,增强光谱拟合精度,同时空间分辨可调的特性使该系统能够更好地适应不同实验条件下的诊断工作。     

CARS光谱测温技术应用于燃油炉火焰温度场的测量

一、引言 由于CARS光谱测量技术具有高度的时间和空间分辨率以及无接触测量等优点,特别适用于燃烧动力过程的研究,如火焰温度、温度波动以及燃烧产物浓度的测量。这项技术在国际燃烧研究领域发挥了越来越大的作用。目前,我国在这项测量技术的开发利用方     

利用辐射光谱法在线测量固体火箭推进剂燃烧温度

针对固体火箭发动机恶劣环境下的高温燃烧测量问题,提出了利用辐射光谱法来开展固体火箭推进剂燃烧温度在线测量的方法,采用200～1 100 nm光纤光谱仪测量了高压实验燃烧器下固体火箭推进剂燃烧火焰辐射光谱,总结了其光谱特性,并基于普朗克定律和光谱拟合方法获得了相应的推进剂燃烧温度,这对固体火箭推进剂燃烧诊断与燃烧机理研究具有重要的参考价值。     

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。     

TDLAS与CARS共线测量发动机温度

发动机燃烧室设计以及计算流体动力学模型的建立和验证需要对燃烧室流场温度等参数进行精细化测量。本文提供了一种TDLAS与CARS技术共线的测温装置,解决了两种技术在联合测量时探测区域不一致的问题,同时使二者共用发射端与接收端,降低了系统的复杂性。利用建立的测量系统在超燃发动机试验台不同位置处开展了温度测量实验,结果表明发动机燃烧段的凹槽区域内(距流道下壁面30mm)煤油燃烧时期温度最高(约2400 K),而发动机燃烧段下沿(距流道下壁面10 mm)煤油燃烧时期温度上升不明显。     

CARS temperature measurement in a LOX/CH4 spray flame

Coherent anti‐Stokes Raman scattering (CARS) spectroscopy has been used to investigate cryogenic liquid oxygen/gaseous methane (LOX/CH₄) flames on a medium‐size test facility at a pressure of 0.24 MPa and mass flow of 0.025 kg/s. Single‐shot, broadband CARS spectra with simultaneous detection of the Q‐branches of hydrogen and water molecules were recorded with good signal‐to‐noise ratio. Temperature was deduced from the H₂ and H₂O CARS profiles. The spatial temperature distribution in a comparatively harsh environment has been measured successfully. The measurements took place in the windowed combustion chamber of the DLR M3 test facility, aiming to provide data for validation of rocket combustor modeling. Copyright © 2010 John Wiley & Sons, Ltd.     

CARS thermometry in high temperature gradients

CARS is an effective non-intrusive technique for measuring gas temperature in combustion environments. In regions of high temperature gradient, however, the CARS signal is complicated by contributions from gas at different temperature. This paper examines theoretically the uncertainty associated with CARS thermometry in steep temperature gradients. In addition, the work compares the temperature predicted from CARS with the adiabatic mixed temperature of the gas resident in the measurement volume. This comparison helps indicate the maximum sample volume size allowed for accurate temperature measurements.     

Single-pulse CARS spectra in solid propellant combustion at atmosphere pressure

The unstable-resonator spatially enhanced detection (USED) coherent anti-stokes Raman spectroscopy (CARS) measurements of temperature and N2 concentration in the combustion of solid propellant at atmosphere pressure are reported. The USED CARS measurement system has a high spatial solution of ~ 0.1 mm in diameter and 3 mm in length, and permits instantaneous measurement at 10-Hz rate. The single-pulse N2 Q-branch CARS spectra have been obtained from the propellant combustion. The temperatures and N2 concentrations of the propellant flame at different height have been achieved by fitting the experimental data to theoretical spectra. The results indicate that the temperature is up to ~ 2500 K with N2 concentration in a range from 10% to 26%.     

Theoretical modeling of single-laser-shot, chirped-probe-pulse femtosecond coherent anti-Stokes Raman scattering thermometry

Chirped-probe-pulse (CPP) femtosecond (fs) coherent anti-Stokes Raman scattering (CARS) spectroscopy for single-laser-shot temperature measurements in flames is discussed. In CPP fs CARS, a giant Raman coherence is created in the medium by impulsive pump-Stokes excitation, and the temperature-dependent temporal decay of this initial coherence is mapped into the frequency of the CARS signal using a CPP. The theory of the CPP fs CARS technique is presented. A computer code has been developed to calculate theoretical CPP fs CARS spectra. The input parameters for the calculation of the theoretical spectra include the temperature, probe time delay, ratio of the resonant and nonresonant susceptibilities, and parameters for characterizing the pump, Stokes and probe pulses. The parameters for characterizing the pump, Stokes and probe pulses are determined from the best fit of theoretical spectra to experimental spectra acquired from calibration flames at a known temperature. For spectra acquired in subsequent measurements, these laser parameters are fixed and temperature is determined as one of the fit parameters from the best fit of theoretical spectra to experimental spectra. For single-laser-shot CPP fs CARS temperature measurements performed in steady, near-adiabatic flames, the best-fit temperature distribution width is typically less than 1.5% of the mean temperature. The mean temperature is accurate to within approximately 3% with respect to the adiabatic flame temperature. The most significant limitation on temperature measurement accuracy is associated with the evaluation of the theoretical laser parameters. Significant improvements in the temperature measurement accuracy are expected once monitoring equipment capable of characterizing the spectrum and phase of each laser pulse is incorporated in the experiments.     

Combined coherent anti-Stokes Raman spectroscopy and linear Raman spectroscopy for simultaneous temperature and multiple species measurements

The simultaneous application of pure rotational coherent anti-Stokes Raman spectroscopy (CARS) and vibrational linear Raman spectroscopy (LRS) for the measurement of temperature and species concentrations in combustion systems is demonstrated. In addition to the standard rotational CARS experimental setup, only one detection system (spectrometer and intensified CCD camera) for the collection of the LRS signals was applied. The emission of the broadband dye laser used for CARS was shifted to the deep red to avoid interferences with the LRS signals located in the visible region. First experimental results from a vaporizing propane spray using an engine injection system are shown.     

燃气轮机燃烧室空气加湿燃烧的实验研究

空气加湿燃烧是HAT循环的关键技术。本文通过中压全尺寸燃气轮机燃烧室空气加湿燃烧实验,研究了加湿度对燃烧特性的影响。实验中发现,燃烧室内温度分布、出口温度场、污染物生成(即NOx、CO、UHC)及燃烧稳定性都受到加湿度的影响。研究结果表明,空气加湿燃烧导致NOx排放显著下降, CO和UHC排放略有上升,燃烧室中压力振荡的频谱产生了变化,燃烧室出口温度场畸变加剧。作者从水蒸气影响燃烧的机理出发对实验结果进行了分析和解释。     

Effect of ignition energy on the uncertainty in the determination of laminar flame speed using outwardly propagating spherical flames

The initial propagation processes of expanding spherical flames of CH₄/N₂/O₂/He mixtures at different ignition energies were investigated experimentally and numerically to reduce the effect of ignition energy on the accurate determination of laminar flame speeds. The experiments were conducted in a constant-volume combustion bomb at initial pressures of 0.07???0.7?MPa, initial temperatures of 298???398?K, and equivalence ratios of 0.9???1.3 with various Lewis numbers. The A-SURF program was employed to simulate the corresponding flame propagation processes. The results show that elevating the ignition energy increases the initial flame propagation speed and expands the range of flame trajectory which is affected by ignition energy, but the increase rates of the speed and range decrease with the ignition energy. Based on the trend of the minimum flame propagation speed during the initial period with the ignition energy, the minimum reliable ignition energy (MRIE) is derived by considering the initial flame propagation speed and energy conservation. It is observed that MRIE first decreases and then increases with the increasing equivalence ratio and monotonously decreases with increasing initial pressure and temperature. As the Lewis number rises, MRIE increases. The results also suggest that during the data processing of the spherical flame experiment, the accuracy of determination of laminar flame speeds can be enhanced when taking the flame radius influenced by MRIE as the lower limit of the flame radius range. Then the flame radius influenced by MRIE was defined as RFR. It can also be found that there exist nonlinear relationships between RFR and the equivalence ratio and Lewis number, and the RFR decreases with increasing initial pressure and temperature.