【作者】 刘亦安；

【导师】 黄志尧； 闫勇；

【作者基本信息】 浙江大学 ， 控制科学与工程， 2010， 博士

【摘要】 多相流广泛地存在于自然界和工业生产过程中。随着科学技术的发展,多相流动现象在化工、石油、动力、原子能、环保、轻工等许多工业应用场合中变得越来越重要,深入研究多相流动过程对于工业生产和人类的生活都具有极其重要的意义。但是,由于多相流流动特性复杂,多相流参数检测的难度相当大,现有的多相流检测技术大都还局限于实验室研究阶段,远未能满足科学研究和实际工业应用要求。因此,多相流参数检测技术已经成为多相流研究和发展的制约性因素。太赫兹波通常是指频率在0.1-10THz(1THz=1012Hz)范围内的电磁波,与其它波段的电磁波相比,太赫兹波段是电磁波谱中最后一个有待全面研究的重要频段。太赫兹波具有安全性好,穿透力强,光谱灵敏度高等诸多特点。但是由于太赫兹波段的辐射源和检测手段在技术上实现非常困难,所以太赫兹波段的相关研究曾一度处于停滞不前的状态。然而,随着半导体技术和超快激光技术的飞速发展,太赫兹技术在20世纪90年代后期开始得到了蓬勃的发展。太赫兹技术作为一种新兴检测手段,它在基础研究、天文观测、安全检查、生物医学、环境检测,乃至现代通信技术等领域都展现出巨大的应用潜力。然而,太赫兹技术在多相流领域的检测研究还处在探索的阶段,相关的研究和文献报道极其有限。本文尝试将太赫兹技术应用于多相流的检测中,探索太赫兹技术应用于多相流领域的可行性与潜在应用前景。重点研究了将太赫兹技术应用于气固两相流固相浓度的检测和燃烧温度场和浓度场重建这两方面内容。论文的主要工作和创新点如下：1)提出了基于太赫兹时域光谱技术的气固两相流固相浓度测量新方法。该方法克服了光学测量方法在高颗粒浓度的气固两相流体(>1%)中不再适用的困难,能够实现高颗粒浓度条件下气固两相流固相浓度的测量。研究结果表明,基于太赫兹时域光谱系统的固相浓度测量方法无论是衰减模式还是时间延迟模式都能够有效地实现高浓度颗粒条件下气固两相流固相浓度的测量。同时,基于时间延迟模式的气固两相流固相浓度测量方法精度更高,线性度更好。2)应用ISA、EFA和QCA理论模型对高颗粒浓度条件下稠密相气固两相流中的电磁波的传播和散射规律进行了理论分析,并与实验测量结果进行了对比。研究结果表明,在三种模型中QCA模型的理论预测结果与实验测量结果最为相符,QCA模型是一种比较适合于稠密相气固两相流测量结果分析的模型。3)本文研究了颗粒的粒径和颗粒的相对介电常数对气固两相流固相浓度的测量产生的影响。研究结果表明,在稠密相气固两相流中颗粒粒径对基于衰减模式或基于时间延迟模式的测量方法不产生明显的影响。但是颗粒的相对介电常数会对基于衰减模式和基于时间延迟模式的测量方法产生明显的影响。当颗粒材料的相对介电常数的虚部较大时,基于衰减模式的测量方法的误差也会相对较大；当颗粒材料的相对介电常数的实部较大时,基于时间延迟模式的测量方法的误差相对较小。4)针对太赫兹光谱对极性气体分子的变化极为敏感的特点,提出了基于太赫兹时域光谱技术的分子振动-转动光谱的双光谱火焰温度测量新方法。该方法不依赖于火焰燃烧组分并且不干扰燃烧的流场。同时,根据HITRAN分子数据库提供的光谱数据,建立太赫兹波段双谱线测温法中双谱线的选择准则。5)基于双谱线测温方法提出了一种基于太赫兹时域光谱技术的燃烧温度场重建新方法。选取了三对太赫兹波段的水分子谱线,利用ART算法对温度场进行了重建。同时,本文分析了温度场重建过程中,谱线强度比值和谱线强度比值的相对灵敏度变化对温度场重建产生的影响。根据灵敏度变化的范围,给出了不同谱线对的有效测温区间。提出了选用大转动量子数和大能级差的分子谱线对来提高测温精度的方法。研究结果表明,基于太赫兹时域光谱技术的温度场重建结果与实际燃烧情况一致,是一种可行的温度场重建方法。6)对太赫兹光谱技术应用于燃烧温度场和浓度场的重建进行了研究。提出了一种基于太赫兹时域光谱技术的燃烧温度场和浓度场同时重建的新方法。研究结果表明,本文所提出的基于太赫兹时域光谱技术的温度场和浓度场同时重建的方法是有效的,太赫兹时域光谱技术可以为燃烧温度场和浓度场的重建提供一种新方法,其在火焰燃烧诊断领域有较好的应用前景。更多还原

【Abstract】 Multiphase flow phenomenon exists widely in nature and industrial processes. With the development of science and technology, understanding the phenomenon of multiphase flow becomes more and more important in chemical engineering, petroleum, power generation, nuclear energy, environment monitoring, metallurgy and so on. Therefore, fully understanding multiphase flow process is vital to the operation of industry and human lives. Meanwhile, due to the inherent complexity of multiphase flow system, it is difficult to measure the parameters of multiphase flow. Until very recently, most of the multiphase flow measurement techniques are still in labs, the urgent need of multiphase flow measurement from industries can hardly be satisfied. As a result, multiphase flow measurement techniques has already been an restriction for the further developing of multiphase flow research.Terahertz radiation is loosely defined by the frequency range of 0.1 to lOTHz (lTHz=1012Hz). Comparing with other region of the electromagnetic spectrum, the terahertz (THz) region of the electromagnetic spectrum has proven to be one of the most elusive. Terahertz radiation has attracted a lot of attention with its extremely safety radiation, non-absorbing in dry dielectric substances feature and high spectrum sensitivity. However, with the difficulties in the generation and detection of terahertz radiation, this region has been unexplored for a long time. From the late of 90s, the revolution in semiconductor industry and ultrafast laser technique welcome a prosperous era for the development of terahertz technique.As a rapid developing technique, terahertz technique have shown great potentials in fundamental science study, astronomy, safety insurance, medical biology, environment monitoring, telecommunication and so on. However, applications of terahertz technique in multiphase flow measurement are still in preliminary state, very limited research appears in scientific or engineering literature.The overall objectives of this thesis are exploring the possibility and practicability of terahertz technique to the measurement of multiphase flow. Three main applications have been under study:(1) Using terahertz time domain spectroscopy(THz-TDS) technique to investigate solids volume fraction in gas solids two phase flow measurement; (2) Using THz-TDS technique to reconstruct temperature distribution of combustion process; (3) Using THz-TDS technique to reconstruction of combustion temperature distribution and H2O concentration distribution. The main work of the dissertation includes:1) A new solids volume fraction measurement method of gas solids two phase flow based on THz-TDS technique have been proposed. This method overcomes the shortage of optical method which have limited optic depth in high concentration of particles(>1%). While this method can implement measurement of solids volume fraction of gas solids two phase flow in high concentration of particles. Static experiment have shown that both attenuation mode and time delay mode could implement the measurement of solids volume fraction with high concentration of particles. Meanwhile, experimental results show that he measurement of solids volume fraction with time delay mode is more accurate and with better linearity.2) Theoretical models of ISA, EFA and QCA have been investigated and compared with experimental results in dense gas solids two phase flow. Experimental results show that within three models, QCA is the best model to predict the propagation and scattering of terahertz wave in the gas solids flow, and this model is suitable for the analysis of gas solids flow with high concentration of particles.3) The effect of particle size and particle permittivity on the measurement of solids volume fraction have been investigated. Experimental results show that in high concentration of particles, particle size effect is not significant on both attenuation measurement mode and time delay measurement mode. But the permittivity of particles will affect both two measurement modes. If the imaginary part of the permittivity of particle is relatively large, the error of attenuation measurement mode will increase. On the contrary, if the real part of the permittivity of particle is larger, the error of time delay measurement model is smaller.4) With high spectra sensitivity of gas molecular, a new temperature measurement method based on THz-TDS have been proposed. This new method use two vibration and rotation spectra lines to obtain the temperature of gas molecular in combustion process. The method will not depend on component of combustion and not affect the combustion flow field. Base on the molecular spectra data from HITRAN database, the criterion of spectra line selection is setup. 5) Based on two spectra line temperature measurement, a new temperature distribution reconstruction method is established using THz-TDS technique. Applying ART reconstruction algorithm, three pairs of H2O spectra line are used to reconstruct the temperature field. The spectra line relative sensitivity and strength sensitivity are analyzed and the effective temperature sensing range is provided. Theoretical and experimental results demonstrate the proposed method of choosing large rotational quantum number and large differential molecular energy have been proved. The experimental results show that the proposed method based on THz-TDS is applicable for the temperature distribution reconstruction.6) A preliminary study on the temperature field reconstruction and chemical component concentration reconstruction are carried out based on THz-TDS technique. Experimental results show that based on THz-TDS the simultaneous reconstructing the temperature distribution and concentration distribution are possible. And application of terahertz technique in combustion temperature reconstruction and concentration reconstruction have a foreseen future.更多还原