水下运动体尾流的浮升规律及其水面冷热特征的数值模拟

水下运动体尾流的浮升规律及其水面冷热特征是潜艇红外探测技术的基础。采用FLUENT软件中的多相流模型,对排放冷却水的水下航行潜艇尾流的浮升规律及其水面冷热特征进行了数值模拟,分别在温度均匀和温度分层及有、无气泡的海水中,获得了潜艇尾流不同横截面上和不同水平截面上的温度分布、尾流水平截面上的最大温差随水深的变化规律和尾流的浮升轨迹。结果表明:在温度均匀海水中,无论有、无气泡尾流都呈现"热"特征,尾流引起的水面热特征很微弱,但有气泡时的水面热特征比无气泡时要显著些;在温度分层海水中,无论有、无气泡尾流几乎都呈现"冷"特征,而且温度分层时的水面冷特征比温度均匀时的水面热特征要显著得多,但温度分层时尾流的浮升角比温度均匀时小得多。     

海水非温度分层条件下的舰船尾流红外探测可行性研究

在海面行驶时,舰船后面会形成一条清晰可辨且持续时间很长的尾流区, 其长度可达数千米。利用红外成像技术进行尾流探测已成为世界上各大军事 强国重点发展的一项军事侦察技术。首先,从空间分辨率和温度分辨率两方面考虑,推导出了舰 船尾流的红外探测条件。然后基于红外测温原理,推导出了海水非温度分层条件下舰船尾 流与周边海水之间的等效温差的表达式。最后,以阀值信噪比和目标等效条带数为基础,得出了 舰船尾流的红外探测概率。研究结果表明,在海水非温度分层条件下,只有当探测天顶角较大时, 才能以一定概率探测到尾流;而且随着天顶角的增大,探测概率逐渐提高。     

尾流气泡参数测量系统的光学设计

针对尾流气泡成像存在的难点,采用片光源切片扫描与高速摄影相结合的技术手段,研制了一套尾流气泡参数测量系统。该系统采用片光照明,避免了尾流区气泡图像层叠;设计了三组倍率可切换镜头,实现了对粒径是大动态范围的小气泡的成像;将镜头分裂成前后组,以平行光中继,通过片光与前镜组的同步移动,可实现尾流区一定体积内气泡图像的采样,同时还能保证扫描过程中始终成像清晰。还讨论了前组镜头移动对成像质量的影响、片光源厚度选择以及系统畸变校正等问题。设计结果表明,系统成像效果良好,满足项目技术要求。     

舰船尾流光特性分析

在远场尾流区气泡之间是不相关的,气泡光的散射是不相关散射.基于这一认识,利用Mie散射理论初步分析了远场尾流区光的散射特性,发现远场尾流区尾流光的背向散射强度明显增强,不同深度和不同长度光的背向散射强度都有一定的差别.尾流光的背向散射特性是水下航行体跟踪、识别和定位目标的重要参数.     

基于可调谐半导体激光吸收光谱技术的甲烷/空气预混平焰炉温度测量

燃烧场温度的测量对于燃烧诊断具有重要意义。开展了基于可调谐半导体激光吸收光谱 (Tunable diode laser absorption spectroscopy, TDLAS)的在 线测温方法研究,基于双光束分时扫描技术,实现了双激光器协同工作与燃烧产物水汽 7154.35 cm$^{-1}$ 和7467.77 cm$^{-1}$两条吸收谱线的同时测量,并利用双线积分吸光度比值关系完成温度的精确反演, 满足燃烧场温度在线检测应用需要。开展了针对甲烷/空气预混平焰炉火焰温度的实时检测实验研究, 并与热电偶进行了测温对比分析,两种方法的测量具有较好的一致性,相对误差小于3.8\%,验证 了TDLAS技术对燃烧场温度非侵入式快速测量的可行性和可靠性。     

潜艇热尾流的浮升扩散规律及海表温度特性

选取1/72龙鲨Ⅱ号核潜艇为研究对象,采用有限体积法建立外流域的三维计算模型,运用动参考系实现尾部螺旋桨高速旋转的仿真。基于该模型,评估下潜深度、航行速度、热尾流喷速、热尾流温度等因素对热尾流浮升扩散规律及海表温度特性的影响。研究表明:1)随着下潜深度和航行速度的增大,海表温度特性的后向延迟距离增大、海表温差减小;2)随着热尾流喷速和热尾流温度的增大,海表温度特性的后向延迟距离减小、海表温差增大;3)增大高温热尾流热容量或减小低温海水热容量均能促使海表温度特性趋于明显。本文结论可为某型号潜艇的红外探测与反演定位提供针对性的参考与借鉴。     

基于激光吸收光谱技术在线测量燃烧场温度研究

燃烧场温度的测量对研究燃烧机理、提高燃烧效率、降低污染物排放等至关重要。利用水在1397.75 nm和1397.87 nm处两条邻近的吸收线,采用波长扫描直接吸收法实现了单台二极管激光器对标定燃烧炉甲烷/空气预混火焰温度的测量。并利用基于Labview语言的数据采集卡对信号进行采集和实时处理,从而能够实时在线地获得测量结果,在温度1750 K时标准测量不确定度为2.3%。分析了火焰边界层对测量结果的影响,结果表明燃烧场非均匀性对路径积分测量结果影响较大,且其测量结果不是路径积分算术平均值。     

舰船尾流光特性分析

在远场尾流区气泡之间是不相关的，气泡光的散射是不相关散射．基于这一认识，利用Mie散射理论初步分析了远场尾流区光的散射特性，发现远场尾流区尾流光的背向散射强度明显增强，不同深度和不同长度光的背向散射强度都有一定的差别．尾流光的背向散射特性是水下航行体跟踪、识别和定位目标的重要参数．     

潜艇热尾流红外特征分析与计算

在建立海水的红外辐射模型的基础之上,综合考虑了海面发射率、天空辐射、阴影遮挡系数、环境大气等因素对探测器接收到的辐射能量的影响,模拟计算出8～14μm波段内探测器接收到的潜艇热尾流浮升到海面之后的辐射亮度.并根据热尾流与周围海水的平均温度差计算出红外探测器对潜艇热尾流的作用距离.分析得出热尾流的红外辐射特性分别与探测方位、风速、尾流温度、环境温度与湿度等因素密切相关,并且当采用温度分辨率达到0.001℃的红外热像仪,尾流温度与周围海水的温差达到0.02℃时,探测器对尾流目标的发现距离、识别距离、认清距离分别为8.84km,3.88km,2.74km.     

基于重叠网格技术和VOF模型的潜艇热尾流浮升扩散规律的数值与实验研究

研究潜艇热尾流的浮升扩散规律和水面红外特征对红外探潜具有重要意义。以潜艇缩比模型为研究对象,建立了潜艇热尾流三维计算模型。分别使用重叠网格、VOF （Volume of Fluid）模型方法和来流法,对潜艇热尾流的浮升扩散过程进行了数值模拟。分析了潜艇热尾流的浮升扩散规律和温度场特征。使用实验测得的水面红外热像图和热尾流浮升扩散图像对两种仿真方法的精度进行了对比验证。结果表明:基于重叠网格和VOF模型的数值模拟方法精度较高,模拟得到的热尾流最大温度出现时间相差0.2 s,温度偏差为0.003 K,能够很好地模拟潜艇热尾流的浮升扩散和温度分布特性。     

用单次脉冲非稳腔空间增强探测CARS技术测量火焰温度

采用宽带相干反斯托克斯拉曼散射(CARS)技术测量了甲烷-空气预混火焰温度场分布,并分析了温度测量的不确定度.建立的宽带CARS实验系统采用非稳腔空间增强探测(USED)相位匹配构造,其横向空间分辨率约0.1 mm,纵向空间分辨率约3 mm,该系统能实现10 Hz重复频率测量火焰瞬时温度.采用宽带非稳腔空间增强探测CARS在甲烷-空气预混火焰中获得了单次激光脉冲的高信噪比氮气Q支CARS实验谱,用CARS理论计算软件拟合理论谱和实验谱确定了预混火焰的温度随高度的分布,采用单次激光脉冲的氮气Q支CARS实验谱测量火焰温度的不确定度小于5%.     

激光诱导荧光技术燃烧诊断的研究进展

激光诱导荧光(LIF)技术具有非扰动、实时原位测量、组分选择性强、灵敏度好、时空分辨率高等优点,可用于燃烧诊断中测量火焰的重要特征参数。介绍了LIF技术的原理及其在燃烧诊断中的应用,重点阐述了LIF技术在成像火焰瞬时结构、定量测量组分浓度、混合场温度、火焰温度和流场速度方面的研究进展,讨论了LIF技术在测量燃烧流场参数时的技术特点和挑战,展望了高速平面LIF、体LIF和多场同步测量方面的发展趋势。     

双色平面激光诱导荧光瞬态燃烧场测温实验

在复杂的燃烧流场等试验研究中,平面激光诱导荧光技术（PLIF）被用于特定气体分子浓度分布、火焰构造和温度分布的测量。基于双色激光诱导荧光测温原理,设计了双激发PLIF 系统,选取两条合适的OH 自由基激励线,定量测量了甲烷-空气预混火焰的二维瞬态温度场分布。实验中,通过对两个激光脉冲功率和激光轮廓分布监控以及双ICCD 成像的空间位置校正,提高了测量的精细程度。给出了测量结果,并与稳态燃烧场火焰的热电偶测量结果进行了对比,不确定度优于5%,这种二维瞬态测温技术能够满足超声速燃烧诊断中的应用。     

汽油机缸内瞬时温度和空燃比的光电测量方法与装置

研制了一套高灵敏度、快速光电测量系统。分别利用燃烧火焰辐射在７９７ｎｍ，５０３ｎｍ处的光强度以及燃烧化学反应物ＣＨ，Ｃ２自由基的光辐射强度，测量了一台二冲程单缸汽油机燃烧过程中缸内的瞬时温度和过量空气系数的大小，实验结果给出了汽油机在不同工况下燃烧过程中的温度变化和过量空气系数的波动。     

Improving the Performance of HF Radio Networks in the Presence of Interference through Automatic Link Establishment with Frequency Hopping Technique

In the cement industry, a rotary kiln is a pyro-processing device that is used to measure temperature. Measuring and maintaining a certain range of temperature in the rotary kiln is important to ensure the production of quality clinker granules. The assessment of consuming zone temperature is acquired using radiation pyrometers from the temperature of a hotspot. However, it is a difficult task to measure the burning zone temperature due to the very high temperature developed in the turning furnace sintering process. Existing pyrometer and camera based techniques are not able to provide accurate temperature and temperature variations developed in the burning zone. This research work considers flame image processing using region of interest (ROI), fuzzy logic, and neural networks for efficient temperature measurement. Various temperature measurement and control techniques are utilized in the existing conventional (Prasanna and Bojja in ESCI (helix—the scientific explorer) 4843–4849, 2019) rotary kiln control techniques. In pyrometer-based measurements, the standard of radiation may lead to errors and inaccurate readings. Hence, the consuming zone temperature estimation got from the radiation pyrometer isn't solid and it is hard to get temperature data for a particular location. A colorimetric device-based intelligent control system measures the burning temperature of a specific point, but reading fluctuations are seen because of smoke and dust developed in the combustion process. In ROI based flame image processing, many factors, such as turbulent flame, brightness of flame zone, and dust, affect identifying the boundary for ROI based flame image analysis. In neural network models, variable selection plays a crucial role in designing effective systems with learning capabilities, but it is not an easy task to accomplish without certain rules. Hence, it is highly necessary to develop an improved control system. In view of the issues in variable and feature selection, a few neuro fuzzy systems are adopted in measurement and control. The consuming zone temperature estimation needs a lot of attention due to the very high temperature developed in the rotary kiln sintering process. Existing techniques have to be improved upon using advanced algorithms and intelligent approaches. A sintering state recognition system has been developed with features of flame images and fusion methodologies. In this approach, various flame image features and texture (Ren and Wang in Int J Autom Compu 11(1):72–77, 2014) features are extracted from the burning zone region. Though these methods address a few issues in flame image processing, the acquired image is largely affected by blurring and internal parameters of the sintering process. Charge coupled device (CCD) camera images and videos are applied to many image processing algorithms for better feature extraction and region extraction. The region of interest-based analysis is mainly focused on temperature assessment in this work. Intelligent control techniques are applied to measure the burning zone temperature in a rotary kiln. Fuzzy logic-based inference systems are combined with neural network algorithms in the development of neuro-fuzzy systems. The fuzzy surmising framework in light of mathematical models is the successful manner to anticipate the temperature esteems utilizing power measures. The fire pictures caught by the CCD cameras are handled utilizing fluffy rule-based picture investigation, which estimates temperature from a fire picture by contemplating RGB power planes. The arrangement of result temperature esteems is wanted to be a participation work. The Mamdani fluffy induction model is used to give planning of fluffy fire temperature. Exact temperature planning of fire pictures is performed to control the temperature inside the going stove to make top notch clinker. The fire picture examination is completed in different edges of three unique datasets, and temperature is estimated for various crude supper feed rates and coal feed rates. However there is a slight distinction in the acquired temperature, the general temperature evaluation process doesn't show a huge contrast as per the dataset.

     

Radiation from a circularly polarized antenna through the ionized wake of a Mars-entry capsule

The effects of the ionized wake-of a Mars-entry capsule on radiation from a circularly polarized antenna operating at 400 and 2295 MHz are studied. The circularly polarized antenna is represented by a turnstile antennalambda/4above a ground plane, while the ionized wake is approximated by a cylindrically stratified plasma consisting ofN-plasma regions. Integral expressions for the fields are obtained for the antenna located in the wake and are evaluated using saddle-point integration to yield the radiation patterns. Computed patterns for the two simplest configurationsN = 1andN = 2are presented. The radiation patterns for both near- and far-wake electron-density profiles develop a conical null region whose extent is proportional to the peak electron density in the wake. For the near-wake electron-density profile, sharp peaks which are attributable to leaky-wave radiation, appear within the null region of the patterns. The effect of the conical null region in the patterns is to prolong blackout time for communication cone angles that lie within the null region. There are no serious depolarization effects in the nonnull region and satisfactory communications can be carried out.     

基于射线跟踪算法的舰船尾迹波红外特征与探测

舰船驶过海面后会形成一条长度可达数千米且持续很长时间的尾迹区。这种显著特征为利用尾迹波的红外特征来探测舰船提供了依据。从舰船尾迹区特点出发,实现了尾迹波的可视化仿真。在Cook-Torrance光照模型的基础上建立了适用于舰船尾迹波的红外成像模型。采用射线跟踪算法,并综合考虑太阳辐射、天空背景辐射和大气传输等环境因素的影响,得到了不同探测条件下舰船尾迹波的红外成像特征。结果表明:俯仰角较小时海面整体较暗,舰船尾迹波特征明显;俯仰角较大时海面整体较亮,舰船尾迹波特征减弱;开尔文尾迹的成像特征受气温变化影响较小,湍流尾迹在低俯仰角低气温时为一条暗带,高气温时为一条亮带;海面风速增加,开尔文尾迹最终会无法分辨,湍流尾迹成为唯一可识别的舰船尾迹波特征。     

高纯高导热BeO陶瓷材料烧结工艺研究

选用两种高纯氧化铍(BeO)瓷料(一种为原生料,另一种为瓷件料),以不同的烧结工艺制备高纯BeO陶瓷。通过品红实验和扫描电镜(SEM)观察发现:采用原生料制备的陶瓷素坯在天燃气方式加热的钟罩炉中难以致密化,陶瓷容易吸红。这主要是由于高纯BeO的原生料的烧结是以蒸发-凝聚传质方式为主,扩散传质方式为辅,在一定的温度和压力下,有BeO(蒸汽) CH4易产生BeOH CH3或CH3OH Be。采用瓷件料制备的陶瓷素坯在天燃气热钟罩炉中能致密化,陶瓷不易吸红。这主要是由于高纯BeO的瓷件料的烧结是以扩散传质方式为主,以蒸发-凝聚传质方式为辅,烧结后期离子沿粒界作快速迁移,靠界面扩散使瓷体致密化。