实用氦气声学温度计初步研究

对高温气冷堆堆芯温度的可靠测量是目前的技术难题之一。传统温度计依靠实验室标定的材料特性与温度的关系进行测温,然而,长期暴露在高温、高辐照环境中,其测温材料的性质会发生改变且得不到及时校准,温度传感器易发生漂移甚至失效。气体声学温度计通过测量单原子气体的声速可以直接获得热力学温度;由于气冷堆内氦气介质相对稳定,利用氦气声速获得温度具有较高的可靠性。针对实用氦气声学温度计开展了初步研究,基于圆柱声学共鸣法设计了实用声学温度计测试系统,采用声波导管声学传感器测量了488 K至806 K圆柱共鸣腔内氦气的声学共振频率,修正了热边界层和粘性边界层的影响;基于量子力学从头算得到的氦气声学维里状态方程,获得了热力学温度。对氦气共振频率的测量相对标准偏差小于0. 07%,温度测量的信噪比可满足需求,声学温度计与热电偶测温结果差异小于1%。研究结果为未来持续开展极端环境下气体声学温度计的应用研究提供了支持。     

加筋圆柱壳声辐射特性研究及声学优化设计

为研究全频段加筋圆柱壳声辐射特性,基于VA-ONE建立FE-BEM混合法、FE-SEA混合法及SEA法低中高全频段的计算模型,并进行加筋圆柱壳辐射声功率的计算,从结构固有模态角度研究了各阶模态的声辐射效率。结果表明,加筋能够减小圆柱壳结构的总体辐射声功率,尤其可以减小低频段的辐射声功率;在中低频区,各阶模态的模态辐射效率具有较大差异,在中高频区,则相差不大。进一步研究了激励位置、壳厚、材质及辐射介质对加筋圆柱壳声辐射特性的影响。为减小加筋圆柱壳对外场点的辐射声功率,基于NCT模块及Design Optimization模块进行声学优化设计,结果表明,将GA算法与SQP算法或MMA算法组合使用不仅可以减少运算时间,而且可以获得较好的优化方案。     

非连续边界层对圆柱声学共鸣频率的影响研究

基于声学一阶微扰理论,建立了低压下由于气 固界面的温度阶跃和速度滑移带来的边界层不连续性对圆柱声学共鸣频率的扰动规律,进一步发展了圆柱声学共振频率的非连续边界层修正模型,计算了非连续边界层对4种惰性气体、不同声学模式和不同压力及温度的影响。分析研究显示,气体处于低压状态时,温度阶跃和速度滑移会使声学共振频率发生偏移,不引入声能损耗。在50 kPa时,非连续边界层对声学共鸣频率的影响可达10×10^-6,表明非连续边界层修正项对于10^-6不确定度水平的尖端声学共鸣测量,是一个重要的不确定性来源。     

基准声学温度计的研究进展

热力学温度是一切温度测量(包括国际实用温标)的基准,是国际上公认的最基本的温度.声学温度计是测量中低温区热力学温度精度最高的方法之一,也是定容理想气体温度计最有效的替代方法之一.综述了声学温度计测量热力学温度的研究进展,分析了目前建立声学温度计的最主要方法-球共鸣声学法的测量原理及其进展,并对声学温度计的未来发展进行了展望.     

一种高灵敏度光声光纤SO2气体传感器的研究

基于气体光声效应原理，研究了一种高灵敏度光纤SO2气体浓度传感器。用染料激光器作为激励源，激励出光声信号，采用光纤位移传感器测量光声信号。设计了光学长程装置以提高光声腔的灵敏度。用此装置测量SO2气体浓度，给出了实验数据并对结果作了分析。     

近临界区二氧化碳声速的精密测量研究

基于圆柱声学共鸣法原理,开展了303.10～303.18 K,压力从3.855 MPa至7.534 MPa的近临界区CO2测量研究。二氧化碳声速测量的相对标准不确定度结果为:当压力低于7.1 MPa时为0.035%,当压力高于7.3 MPa时为0.15%。与CO2国际标准状态方程计算得到的声速相对偏差分布在0.005%～-0.4%范围。所获得的测量结果可为CO2国际标准状态方程的改进提供重要数据来源,建立的实验系统和方法可用于更宽广温区CO2及其他工质的声速精密测量研究。     

水下圆柱壳声学代理模型优化设计

为了提高水下结构声学计算的效率,采用有限元软件进行水下圆柱壳结构声辐射分析,建立声学分析近似代理模型,给出壳体结构几何尺寸与水下声辐射特性的显式解析表达式,简化声学计算,建立高效的结构声学优化设计模型。利用拉丁超立方取样方法进行样本点的选取,分别采用多项式响应面法、Kriging函数和径向基函数法构造水下双层圆柱壳结构的声辐射代理模型。通过比较三种代理模型的拟合精度,选择三种代理模型建立双层圆柱壳结构水下声辐射优化设计模型,并采用Matlab进行尺寸优化,减轻了结构质量。该研究为水下结构声辐射预报和声学设计提供参考。     

潜艇典型结构的声振特性研究概况及声学设计构想

潜艇结构的振动与声辐射特性是声隐身研究的重点。对潜艇典型结构的声振特性研究现状进行综述,归纳总结典型结构声学设计的研究动态,论述开展结构声学设计的重要性和必要性,提出基于声学性能开展结构设计的流程及方法,为进一步研究潜艇结构声隐身设计提供参考。     

水声材料声学参数及其声管测量方法

简要阐述了水声材料产品研制过程中水声材料及其声学参数测量的重要意义和存在的问题,详细论述了水声材料声学参数分类及相应的测量方式,归纳了脉冲法、驻波法和行波法声管各自的测量原理和适用的条件,以及声管测量技术的发展趋势,最后总结了通过声管测量水声材料声学参数时,对测量声管和被测量样品的一般要求。     

热声发动机用声学放大器的改进研究

声学放大器是一种可显著提高热声发动机输出压力振幅和压比的装置,存在的主要问题是声功损失过大.通过理论研究,提出采用较大管径进一步提高声学放大器性能的方法,称为改进型声学放大器.实验结果表明:该声学放大器在大幅度提升输出压比的同时,没有明显降低发动机内的压比和破坏发动机内部声场,能使发动机工作在较高的品质状态.采用变负载法测量声功的实验结果也表明,改进型的声学放大器有效地解决了声功损失过大的问题.     

Thermodynamic Temperatures of the Triple Points of Mercury and Gallium and in the Interval 217 K to 303 K

We measured the acoustic resonance frequencies of an argon-filled spherical cavity and the microwave resonance frequencies of the same cavity when evacuated. The microwave data were used to deduce the thermal expansion of the cavity and the acoustic data were fitted to a temperature-pressure surface to deduce zero-pressure speed-of-sound ratios. The ratios determine (T–T₉₀), the difference between the Kelvin thermodynamic temperature T and the temperature on the International Temperature Scale of 1990 (ITS-90). The acoustic data fall on six isotherms: 217.0950 K, 234.3156 K, 253.1500 K, 273.1600 K, 293.1300 K, and 302.9166 K and the standard uncertainties of (T−T₉₀) average 0.6 mK, depending mostly upon the model fitted to the acoustic data. Without reference to ITS-90, the data redetermine the triple point of gallium T_g and the mercury point T_m with the results: T_g/T_w = (1.108 951 6 ± 0.000 002 6) and T_m/T_w= (0.857 785 5 ± 0.000 002 0), where T_w = 273.16 K exactly. (All uncertainties are expressed as standard uncertainties.) The resonator was the same one that had been used to redetermine both the universal gas constant R, and T_g. However, the present value of T_g is (4.3 ± 0.8) mK larger than that reported earlier. We suggest that the earlier redetermination of T_g was erroneous because a virtual leak within the resonator contaminated the argon used at T_g in that work. This suggestion is supported by new acoustic data taken when the resonator was filled with xenon. Fortunately, the virtual leak did not affect the redetermination of R. The present work results in many suggestions for improving primary acoustic thermometry to achieve sub-millikelvin uncertainties over a wide temperature range.     

超声脉冲测温技术初步研究

目前基于脉冲技术的超声测温研究主要侧重于超声换能器和系统硬件电路设计,而对高温敏感元件的研究较少。通过选取合适的敏感元件材料,以及对超声导波在杆中的频散特性和反射、透射分析,最终选用了一根长为1 m、直径1 mm左右的带反射凹槽的钍钨杆作为敏感元件,并在一个超声测温平台进行了初步的实验。实验结果表明,采用钍钨合金杆作为敏感元件,可有效测量12℃~1 600℃声速与温度的关系,所测得的高温下的声速与参考值相比误差不超过0.68%。     

单圆柱微波谐振法测量热力学温度的研究

利用氩气的量子力学“从头算”理论和相关实验测量结果,基于圆柱微波谐振法建立了气体折射率热力学温度计实验系统,测量了253~303 K范围内的热力学温度。通过测量圆柱微波谐振腔内4个横磁模式的微波谐振频率,获得了氩气在700 kPa附近的气体折射率,不同微波模式得到的氩气折射率一致性优于1×10^-8,进一步结合氩气的维里状态方程得到热力学温度。热力学温度T和ITS-90国际温标T90差异不确定度为11.6 mK,与国际温度咨询委员会的评估值具有良好的一致性。未来随着氩气理论计算和实验系统压力测量不确定度的深入研究,该方法测定热力学温度的不确定度会进一步改善。     

声学测温信号时延优化方法

为了优化发动机燃烧室声学测温信号的时延处理,提高温度测量的准确性和稳定性,提出了一种结合小波包分解变换重组和孤立森林算法的信号处理新方法。首先,通过热校准风洞实验,得到声学测温探头在高温气流环境中的数据;然后,采用小波包分解变换重组方法结合孤立森林算法对温度数据进行滤波和重构,消除噪声和提取有效信息;同时,为了提高数据质量和准确性,对重构后的数据进行异常值检测。热校准风洞试验结果表明：经过信号处理后的数据分布更平缓和对称、标准差显著降低、数据更集中于均值,从而提高了温度测量的准确性和稳定性。本研究为声学测温更准确的应用于发动机燃烧室提供了一种有效的技术方案。     

NBS/NIST Gas Thermometry From 0 to 660 °C

In the NBS/NIST Gas Thermometry program, constant-volume gas thermometers, a unique mercury manometer, and a highly accurate thermal expansion apparatus have been employed to evaluate temperatures on the Kelvin Thermodynamic Temperature Scale (KTTS) that correspond to particular temperatures on the 1968 International Practical Temperature Scale (IPTS-68). In this paper, we present a summary of the NBS/NIST Gas Thermometry project, which originated with planning activities in the late 1920s and was completed by measurements of the differences t(KTTS)-t(IPTS-68) in the range 0 to 660 °C. Early results of this project were the first to demonstrate the surprisingly large inaccuracy of the IPTS-68 with respect to the KTTS above 0 °C. Advances in several different measurement techniques, development of new, specialized instruments, and two distinct sets of gas thermometry observations have resulted from the project.     

Studies on a sealed-cell lambda-point device for use in low temperature thermometry

We report here the development of a sealed-cell lambda-point device which has been used to realize the lambda-point temperature of ⁴He, T_λ=2.1768 K, to a precision of 0.04 mK with simple automatic control. With this device, one can produce and maintain T_λ-plateaus for unlimited duration with no ascertained temperature drift. This unique performance is achieved by a design, which makes it possible to keep a HeI/HeII interface quasi-stationary inside a vertical variable-conductance capillary tube. The capillary connects a top HeII-cell and a bottom HeI-cell at its two ends, and acts as a sensitive heat switch which automatically adjusts a heat input to the bottom HeI-cell to compensate exactly the heat conducted out of the HeII-cell to the environment. The HeI/HeII interface thus stays at an equilibrium height determined by the magnitude of heat flow through the capillary and by the temperature difference along the capillary. The sharp difference between the thermal conductances of the interfacing HeII and HeI columns is the underlying physics of this self-adjusting function. Realization of T_λ is achieved after appropriate corrections to the thermometer reading at the HeII-cell, in particular, by extrapolating to zero heat flow through the device.     

声学高温计拓扑结构优化研究

声学高温计存在探头温度耐受不够,测温稳定性较差,易受气流速度影响的问题。为了提高声学高温计的测温可靠性,本文提出在Virtual. Lab中建立相应的气流温度场和声传播模型,改变现有的一套声学高温计的声探头分布直径、朝向和倾斜角度等拓扑结构,分析并研究减小声压级衰减的最佳拓扑结构参数,并进行试验对比。最终发现在常温至900℃、0～0.3 Ma的气流温度场环境中,直径15 cm,声探头与水平面倾角为30°的拓扑结构综合声压级减小数值最小;直径20 cm,声探头与水平面倾角为15°的拓扑结构次之。二者均比现有的拓扑结构数据标准差减小17%以上,提高了声源信号接收的性能,进而提高声学高温计在常温至900℃、0～0.3 Ma的气流温度场环境中测温的可靠性。     

Perturbations From Ducts on the Modes of Acoustic Thermometers

We examine the perturbations of the modes of an acoustic thermometer caused by circular ducts used either for gas flow or as acoustic waveguides coupled to remote transducers. We calculate the acoustic admittance of circular ducts using a model based on transmission line theory. The admittance is used to calculate the perturbations to the resonance frequencies and half-widths of the modes of spherical and cylindrical acoustic resonators as functions of the duct’s radius, length, and the locations of the transducers along the duct''s length. To verify the model, we measured the complex acoustic admittances of a series of circular tubes as a function of length between 200 Hz and 10 kHz using a three-port acoustic coupler. The absolute magnitude of the specific acoustic admittance is approximately one. For a 1.4 mm inside-diameter, 1.4 m long tube, the root mean square difference between the measured and modeled specific admittances (both real and imaginary parts) over this frequency range was 0.018. We conclude by presenting design considerations for ducts connected to acoustic thermometers.