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气相声速是流体的基础热物理性质,圆柱定程干涉法是最精确的气相声速测量手段之一。纯轴向共振模式(以下简称纯轴向模式)是圆柱定程干涉法测量声速的常用模式,但不同纯轴向模式测量结果间存在不一致性。本文从声学共振和耗散理论的基本原理出发,结合实验测量数据,分析实验测量中的各类非理想影响因素,揭示了纯轴向模式间出现不一致性的内在机理,为圆柱定程干涉法测量的模式选择提供了理论依据。研究结果表明:奇数和偶数模式在壳体开孔和壳体振动影响方面各有优势;对于奇偶性相同的模式,模式数越大的共振模式受到边界层效应影响越小而受到分子弛豫的影响越大:在远离共鸣腔固有频率的区域内,对于模式数相差不大的纯轴向模式,其测苗结果经修正后,不一致性可降至较低水平。
Gas-phase velocity is the basis of the thermophysical properties of the fluid, and cylindrical-range interferometry is one of the most accurate measurements of gas-phase velocity of sound. The pure axial resonance mode (hereinafter referred to as the pure axial mode) is a common mode for measuring the sound velocity by the cylindrical-range interferometry method, but there is an inconsistency between the measurement results of different pure axial modes. Based on the basic principles of acoustic resonance and dissipative theory, this paper analyzes all kinds of nonideal influencing factors in experimental measurement by combining with experimental measurement data, reveals the inherent mechanism of inconsistency between pure axial modes, The choice of measurement mode provides a theoretical basis. The results show that the odd and even modes have their own advantages in terms of the shell opening and the vibration of the shell. For the same parity mode, the larger the mode number is, the smaller the influence of the boundary layer effect is and the molecular relaxation The bigger the influence is, in the pure axial mode with little difference between mode numbers in the area away from the natural frequency of resonance cavity, the inconsistency can be reduced to a lower level after the result of measuring seedling is corrected.