物理学报2016，Vol.65Issue(13)：134302-1-134302-9,9.DOI:10.7498/aps.65.134302
可激发气体振动弛豫时间的两频点声测量重建算法∗
Algorithm for reconstructing vibrational relaxation times in excitable gases by two-frequency acoustic measurements
摘要
Abstract
Vibrational relaxation time is a parameter describing the macroscopic behavior of vibrational energy transition rate between molecular internal degrees of freedom (DOF) and external DOF in excitable gas, which determines the relaxation frequency of the maximum point in acoustic absorption spectrum. To measure the vibrational relaxation time, the traditional methods are used to obtain the acoustic absorption spectra by changing the ambient pressure at several operating frequencies. However, these traditional methods are not suitable for real-time measurement due to the complexity of equipment implementation and the non-ideality of test gas under high pressure. In order to solve those problems, we have developed an algorithm [2013 Meas. Sci. Technol. 24 055002] to capture the primary vibrational relaxation processes only based on the measurements of sound absorption and sound speed at two operating frequencies and a single pressure. But the algorithm only can reconstruct the absorption maximum and it cannot capture the relaxation time with high precision. To measure the frequency dependence of the complex effective specific heat of the relaxing gas, an algorithm synthesizing relaxation processes is given by Petculescu and Lueptow [2005 Phys. Rev. Lett. 94 238301]. In its derivation process, relaxational angular frequency was set to be the inverse ratio to relaxation time. However, the relaxational angular frequency was measured in the adiabatic process of transmission thermodynamic, while the relaxation time was obtained in the thermodynamic isothermal process, the derivation confused the two thermodynamic processes, making the algorithm unable to capture the relaxation frequency with high precision. In order to estimate the relaxation time with higher accuracy, in this paper we first obtain the theoretical relationship among the relaxation times under the three types of thermodynamics conditions, i.e., isothermal, adiabatic constant pressure and adiabatic constant volume. Then we correct the relaxation time derivation and propose our corrected algorithm to reconstruct the relaxation frequencies and relaxation times under the conditions of isothermal, adiabatic constant pressure and adiabatic constant volume. In experiments and simulations, the relaxation times and relaxation frequencies reconstructed by our corrected algorithm for various gas compositions including carbon dioxide, methane, chlorine, nitrogen, and oxygen around room temperature are consistent with the experimental data.关键词
弛豫时间/声弛豫吸收/弛豫过程/弛豫频率Key words
relaxation time/sound relaxational absorption/relaxation process/relaxation frequency引用本文复制引用
张克声,朱明,唐文勇,欧卫华,蒋学勤..可激发气体振动弛豫时间的两频点声测量重建算法∗[J].物理学报,2016,65(13):134302-1-134302-9,9.基金项目
国家自然科学基金(批准号:61461008,61371139,61571201,61402122)、贵州省科学技术基金(批准号:黔科合J字[2015]2065,黔科合LH字[2014]7361)和贵州理工学院高层次人才引进项目(批准号：XJGC20140601)资助的课题.* Project supported by the National Natural Science Foundation of China (Grant Nos.61461008,6137113961571201,61402122), the Natural Science Foundation of Guizhou Province, China (Grant Nos.[2015]2065,[2014]7361), and the Recruitment Program of Guizhou Institute of Technology (Grant No. XJGC20140601) （批准号:61461008,61371139,61571201,61402122）
