压力突变诱发的波流互动激发气流脉动机理的研究

The interaction of wave and flow during the pressure jump of compressor cause gas pulsation and vibration of the piping system, and serious gas pulsation and piping vibration will degrade the economy and reliability of the compressors and lead to other safety problems. In order to solve its adverse effects, controlling the generation of gas pulsation or reducing gas pulsation amplitude from the source is the fundamental way. The existing theories and methods all focus on propagation and response of the gas pulsation, but there is almost no research on the instantaneous microscopic processes of gas pulsation formation which caused by the interaction of wave and flow during the pressure jump. In this project, the theoretical and experimental study will been studied which focus on the flow process during the pressure jump. Moreover, to research on the wave phenomenon, the analysis on the comparison between the process of shock wave formation in the shock tube and the process of gal pulsation formation will be taken. A method to descript the gas pulsation formation mechanism will be presented. The physical nature of gas pulsation will be revealed by applying the classical shock tube theory, and some pulsation rules will be also inducted. Furthermore, the main factors of the gas pulsation formation will be studied and the mathematical equations will be presented to explain the influence of the main factors on the gas pulsation. Finally, according to the mathematical equations, the control method and improved structure focus on the generation of the gas pulsation will be designed to solve the adverse effects of the gas pulsation.

压缩机吸排气过程中的压力突变诱发的波流互动会激发气流脉动，由此导致管道振动及管道附加交变应力，每年因此引起的事故占到总毁损事件的19%。从源头控制气流脉动的产生或降低气流脉动的幅值是解决其不良影响的根本途径。现有的气流脉动研究理论及方法主要针对脉动的传播及响应，而对压力突变诱发的波流互动激发气流脉动本身这一瞬时微观过程并未涉及。本项目在前期研究的基础上，首先对压力突变瞬时的流动过程进行理论和实验研究，同时通过对气流脉动产生过程与激波管中激波形成过程的类比性分析，研究压力突变瞬时的波动现象，并用实验手段实现压力突变诱发的波流互动激发气流脉动过程的可视化，从而提出一套描述波流互动激发气流脉动机理的方法。在此基础上，理论研究气流脉动产生过程中的影响因素对脉动幅值的敏感度并提炼出相应的简化数学关系，提出气流脉动产生过程中的控制方法及控制结构并进行验证。最终从根本上有效的解决气流脉动造成的不良影响。

本项目在前期研究发现的基础上，首先对压力突变瞬时的流动过程进行理论分析，以压缩机气阀为研究对象，数值模拟了气阀打开压力突变瞬时，气阀两侧膨胀波与压缩波的产生与运动，并通过对气流脉动产生过程与激波管中激波形成过程的类比性分析，理论研究气流脉动产生过程中的影响因素对脉动幅值的敏感度并提出简化数学关联式。在理论研究的基础上，首先提出了外插管型容-管-容脉动衰减器结构，数值模拟了其脉动衰减特性，实测了不同参数的脉动衰减效果，并与缓冲罐衰减效果进行了比较。随后又提出在往复压缩机阀腔处安装亥姆赫兹共鸣器，来消减阀腔及管路中气流脉动的脉动控制方法，并应数值模拟了亥姆赫兹共鸣器的衰减特性，对安装亥姆赫兹共鸣器前后的脉动进行了比较。结果表明：所设计的脉动衰减器对下游管路脉动的衰减效果明显优于相同容积缓冲罐，脉动衰减幅度最大增加了91.76%；该脉动衰减器能够有效衰减特征频率以上的各倍频脉动分量，脉动衰减幅度比同容积缓冲罐均提高了至少65%以上；保持特征频率不变或降低的情况下，增大容积、喉管长度及喉管内径，均能增强其衰减效果；同时，提出的亥姆赫兹共鸣器结构能够有效衰减阀腔及管路内的脉动压力，可将阀腔内的脉动压力衰减40.1%，且下游管路内脉动压力得到有效衰减，最高衰减幅度达33.3%。另外研究还发现亥姆赫兹共鸣器的脉动衰减作用具有很强的频率选择特性，且共振频率互不干扰，在阀腔安装两个共鸣器能够同时有效衰减2、4 倍频的压力脉动，而对其它频率脉动不产生影响。