燃烧温度测量的剪切干涉法

本文提出的测量燃烧气体温度的剪切干涉法,可测得全场温度分布,具有光路简单、对外界振动不敏感等特点。数据可由摄像机采集、计算机自动处理。     

非预混火焰中温度与全息干涉测得的折射率之间的新状态关系

通过对3个非预混火焰的详细数值模拟,获得了一个全新的温度和折射率之间的状态关系.利用该状态关系能直接从折射率计算温度,而不需要当地组分信息.利用全息干涉实验和数值模拟结果,对4个不同高度的横断面的温度计算表明,这个状态关系将空气组分假设带来的误差从48.8%降低到4%以下.分析表明,该状态关系具有应用于化学当量比较大的预混合部分预混火焰的潜力.     

用剪切干涉高速摄影法测量内燃机缸内温度场的实验研究

建立了一套用于火花点火发动机缸内燃烧研究的剪切干涉及高速摄影实验装置。利用图像处理系统对拍摄到的燃烧干涉图像进行处理 ,可以定量得到燃烧过程气缸内的温度场 ,并可估算出火焰传播速度。从温度场可以看出 ,在燃烧过程中缸内大致可以分为 3个区域 ,即已燃区、未燃区和燃烧区。燃烧区的温度最高 ,温度梯度大 ;已燃区的温度次之 ,梯度较小 ;未燃区的温度最低 ,但梯度较大。在燃烧过程中 ,缸内的火焰面以近似球面向未燃区推进 ,火焰传播速度开始较小 ,随着燃烧过程的进行而迅速增大 ,达到一最大值后 ,逐渐减小 ,直至燃遍整个燃烧室。剪切量是影响缸内燃烧温度测量精度的一个重要因素 :剪切量大 ,则干涉条纹密集 ,测量精度高 ,但图像处理工作量大 ,适用于温度梯度大的温度场的测量 ;剪切量小则相反。     

单光束激光散斑干涉法测量内燃机连杆的变形

本用单光束激光散斑干涉法测量了内燃机连杆的变形。中讨论了用激光散斑干涉法测量变形时，影响测量精度的各种因素，并认为变形测量的准确性主要取决于散斑干涉条纹间距和成像放大倍数的测量。为了准确测量条纹间距和成像放大倍数，中改进了测量方法，将再现的杨纸条纹用ＣＣＤ摄像机输入到计算机，用数字图像处理技术对条纹图进行处理，并用方法获取条纹间距，另外实物和散斑图像也摄入计算机，根据实物和像所占据的像素数得     

差分干涉法测量微重力环境蜡烛火焰的温度

从原理上介绍了用于测定微重力环境中蜡烛火焰温度分布的Ｗｏｌｌａｓｔｏｎ棱镜差分干涉仪,并给出了从差分干涉图计算轴对称蜡烛火焰温度分布的数学过程。测量与计算结果表明,微重力环境下的蜡烛火焰温度低于烟粒子的最小生成温度。由于自然对流消失,化学反应放热效率受到组分扩散速率的控制,辐射热损失的冷却作用相对增强,这是引起微重力环境中蜡烛火焰温度降低的主要原因。结论部分地证实微重力环境中蜡烛火焰出现暗蓝色无烟现象是由于火焰温度较低的推论。     

液相互扩散系数测量充注方法的改进

采用Mach–Zehnder干涉法测量液相互扩散系数有利于对扩散机理进行进一步分析。对于黏度值较小的溶液,人工充注溶液时容易引起扰流,由此会导致浓度场产生混乱,进而使得数据处理发生畸变。本文设计的溶液自动充注装置采用步进电机驱动注射器,能有效改善对溶液充注速度的控制,明显提升实验的成功率和测量精度。此外,本文还引入了带自动捕捉功能的矩形窗函数,将图像处理所需的时间大致由25分钟缩短至5分钟。最后,利用改进的实验系统测量了0.33 mol·L-1的氯化钾水溶液的互扩散系数,所得实验结果与文献值相比具有良好的一致性,二者的相对偏差绝对平均值为0.58%。     

液体比热的简易测量

<正> 化工企业在进行能量平衡测试时,要涉及到液体比热的计算,而很多物质,特别是混合物的比热在文献资料中很难查到,给计算带来不便。有些单位在类似计算中,常常是根据混合物中各组份的百分含量,将各组份的比热以加权平均法求得混合物的比热。对难以查到的有机     

利用激光干涉法和纹影摄影法进行燃烧室间隙内火焰传播与气体热力学性能的研究

应用激光干涉法测定火焰传播过程中燃烧室狭窄空间内气体的温度和密度场,利用火焰传播过程中所拍摄的纹影图像对火焰在间隙内的传播状态进行了分析。结果表明:燃烧室狭窄间隙内由于激冷效应其内部气体温度边界层逐渐增厚,气体温度迅速下降,如果狭缝间隙很小时火焰将在间隙入口处熄灭,从而造成排气中未燃碳氢化合物的大量排出。     

Temperature Measurement of Small Objects by Mach—Zehnder Interferometer

A Mach-Zehnder Interferometer incorporated with image processing has been set up to study the temperature field of small objects. Small objects with width to height ratios ranging from 0.33 to 1.0 subjected to natural convection are used to simulate the condition at which the end effects are significant. Interferogram representing the temperature gradient is captured, digitized, and image processed with the aid of an image processing unit. A simple correction model is proposed to treat the stored interferometric data. The interference data are found to compare well with those provided by the thermocouples.     

Azimuthally dependent radiative transfer in a slab with variable refractive index

Applying Fourier series expansion and a discrete ordinates method, we obtain accurate solutions of azimuthally dependent radiative transfer in an anisotropically scattering slab with variable refractive index and oblique irradiation. It is found that in a slab with a positive gradient of refractive index the optical distance traveled by incident rays decreases, and thus the value of transmittance increases. Besides, the increase of gradient of refractive index enhances the above effect. Influence of the optical thickness, scattering albedo and phase function of the medium, the incident angle of irradiation and the spatial variation of refractive index on the angular distribution of bidirectional reflectance is also investigated.     

Temperature distributions in an absorbing-emitting-scattering semitransparent slab with variable spatial refractive index

A Monte Carlo curved ray-tracing method is used to analyze the radiative heat transfer in one-dimensional absorbing-emitting-scattering semitransparent slab with variable spatial refractive index. A problem of radiative equilibrium with linear variable spatial refractive index is taken as an example in this paper. The predicted temperature distributions are determined by the proposed method and compared with the data in references. The results show that influences of refractive index gradient are important and the influences increase with the refractive index gradient, the temperature distribution approaches to the one obtained for a constant refractive index when the slab optical thickness is far greater than 1.0, and the effect of the scattering phase function is similar to that in the medium with constant refractive index.     

Finite element solution of radiative transfer across a slab with variable spatial refractive index

To avoid the complicated computation of ray trajectories, a finite element formulation is developed to solve the radiative transfer problem in a one-dimensional absorbing-emitting-scattering semitransparent slab with variable spatial refractive index. A problem of radiative equilibrium is taken as an example to verify this finite element formulation. The predicted temperature distributions are determined by the proposed method and compared with the data in references. The results show that the finite element formulation presented in this paper has good accuracy in solving the radiative transfer in one-dimensional absorbing-emitting-scattering semitransparent medium with variable spatial refractive index.     

Study on direct measurement method of vorticity from particle images

To overcome the shortcomings of conventional methods for vorticity measurement, a new direct measurement of vorticity (DMV) method extracting vorticity from particle images was proposed. Based on the theory of fluid flow, two matched particle patterns were extracted from particle images in the DMV method. The pattern vorticity was determined from the average angular displacement of rotation between the two matched particle patterns. The method was applied on standard particle images, and was compared with the second and third order central finite difference methods. Results show that the accuracy of DMV method is independent of the spatial resolution of the sampling, and the uncertainty errors in the velocity measurement are not propagated into the vorticity. The method is applicable for measuring vorticity of a stronger rotational flow. The time interval of image sampling should be shortened to increase the measurement ranges for higher shearing distortion flows. __________ Translated from Journal of Zhejiang University (Engineering Science), 2006, 40(9): 1 644–1 647 [译自: 浙江大学学报 (工学版)]     

Discrete ordinate solutions associated with the finite Legendre transform for radiative transfer in a slab with sinusoidal refractive index

In this work, we develop an alternative discrete ordinate approximation for radiative transfer in a refractive slab. The present method treats the angular derivative term of the radiative transfer equation for a planar medium with varying refractive index (VRI) by using a finite Legendre transform which gives a simple expression of the angular derivative term. Thus, the solution procedure does not march along direction, and so is not restricted to a monotonic variation of refractive index. We apply this method to study radiative heat transfer in a cold slab with anisotropic scattering, diffuse boundaries and sinusoidal VRI. We also solve the problems by the discrete curved ray tracing (DCRT). The hemispherical reflectance and transmittance of slabs with irradiation from the upper surroundings obtained by the present method and those obtained by the DCRT are in excellent agreement. For a slab of a sinusoidal refractive index with the minimum at the center plane, the gradient of refractive index causes the internal reflection of a part of irradiation, which reduces the transmittance of the slab. Other effects of the VRI, the optical thickness, the scattering albedo, the anisotropically scattering coefficient and the boundary reflection are also investigated.     

Solution of radiative heat transfer in a semitransparent slab with an arbitrary refractive index distribution and diffuse gray boundaries

On the basis of medium discretization and local linear approximation of refractive index distribution, the curved ray tracing technique is used in combination with the pseudo source adding method to numerically solve the radiative heat transfer in a semitransparent slab with an arbitrary refractive index distribution and two diffuse gray walls. The radiative equilibrium temperature field of a linear refractive index distribution is evaluated by this method and the results show excellent agreement with that of the previous research. For two types of sinusoidal refractive index distributions, the radiative equilibrium temperature field as well as the temperature and heat flux fields of coupled radiation-conduction are investigated in detail. The results show considerable significance of the gradient refractive index effect, and some important conclusions are to be obtained.     

Development of quasi common path phase-shifting interferometer for measurement of natural convection fields

A quasi common path phase-shifting interferometer for convection measurement was developed in this paper. This interferometer has a large measurement area of approximately 100 mm in diameter to visualize the spatial structure of natural convection. It also has a quasi common path to reduce the effects of air disturbance and vibration. In addition, a phase-shifting technique is introduced to improve the interferometer’s phase resolution and spatial resolution. Natural convection fields around a vertical flat plate with Rayleigh numbers from 1.9 × 10⁶ to 3.0 × 10⁶ were measured and the temperature profiles were estimated by the interferometer. The obtained temperature profiles were compared with the analytical solutions. Moreover, the three-dimensional effect of a thermal boundary layer was investigated. To validate the interferometer’s capability, the experimental results were compared with the calculated results in terms of changes in the optical path length of the test beam. It was confirmed that the quasi common path phase-shifting interferometer can measure the optical path length change accurately at high phase and spatial resolutions.     

300MW汽轮机轴承绝对标高测量装置的研究

引进型300MW汽轮机发电机组普遍存在低压缸轴承座刚度较差的问题，使得运行过程中机组轴承的绝对标高易于变化而导致机组振动增加。为此，现场往往需要精确地测出在运行时机组轴承绝对标高的变化以便准确地对机组进行异常振动故障诊断及正确地对机组进行调整、安装或维修。文章应用近代物理学中光学的干涉及微弱信号检测原理，设计了一套300MW汽轮机发电机组轴承标高测量装置，较精确地测量出轴承的绝对标高并利用计算机对标高进行现场实时统计、分析、记录。     

燃烧火焰特征的数字图像处理系统

介绍了一个作者自行开发的注蒸汽的燃气轮机燃烧室火焰特征分析软件，借助于数字图像处理技术和光学辐射理论对燃烧火焰的结构、层次和轮廓进行了分析和处理，同时依据火焰图像推算出其温度场，从而为燃烧室理论设计和实验处理提供一个强有力的分析工具。