包含转/静干涉影响的叶轮机颤振稳定性数值模拟研究

In order to simulate the relative motion of rotor/stator, considerable progress has been made by using interface model. The rotor/stator interaction cannot be simulated accurately because it is very difficult to obtain the unsteady information between blades rows. Meanwhile, in order to predict the flutter stability, considerable progress has been made by using the interactive coupled method to simulate the fluid-structure interaction. However, the efficiency and reliability of the body-fitted grid become one of the important factors of restricting the coupling calculation. Therefore, how to connect the rotor/stator interaction with the fluid-structure interaction is still a problem of great concern in both industry and academic study. In the present investigation, the goal of our work is to establish a fast simulation associated with the rotor/stator interaction and fluid-structure interaction and gain insight into the mechanism of blade flutter based on the immersed boundary method. We hope that this method may become an effective way to solve the fluid-structure interaction problem. The technology route is to develop a numerical simulation of multistage compressor flutter stability including the effects of rotor/stator interaction on the basis of the existing program. After a parallel computation program of high performance will be developed to carry on the prediction work of the flutter stability. The above simulate model can be straightly computed, and give a deeper insight into the significant model of rotor/stator interaction related to the flutter prediction over a broad range of the parameters of interest. This work could provide a reasonable technical approach to assess the flutter margin during the design phase of future compressors.

一方面，为了模拟转子、静子相对运动，国内外学者大多采用界面模型，不能获得叶片排间非定常流信息，难以精确模拟转/静干涉问题。另一方面，为了预测颤振失稳，国内外学者主要围绕迭代耦合方式开展流固耦合模拟，依赖贴体网格，计算效率不高。因此，如何将转/静干涉问题与流固耦合问题相关联，并快速给出转/静干涉对颤振预测的参数分析，是当前亟待解决的科学和工程实践问题。本项目将利用浸入式边界法，寻找切实可行的转静干涉/流固耦合数值模拟方法，克服传统方法的不足，完善和提高我们对复杂界面流动问题的物理认识。拟采取的技术路线是在已建立的流固耦合数值模拟平台基础上，发展可以考虑转/静干涉影响的叶轮机流固耦合数值模拟平台，并在此基础上开发高效的并行程序，开展颤振稳定性预测工作。这种数值模拟方法既可以在数值解法上快速实现，又能够包含多因素的影响，有可能在未来压气机设计阶段提供有意义的颤振稳定性预估。

对照本项目任务，顺利完成了各年度的结点任务和承诺的学术成果，主要工作体现在以下几个方面：.（1）建立在单一坐标系和网格上的包含任意转子/静子轴向间隙的计算模型..基于浸入式边界法，改进了现有的流固耦合数值模拟平台，使之可适用于包含转/静干涉影响的叶轮机颤振问题研究。..为了验证程序以及算法的可靠性，对圆柱绕流、静水振荡圆柱以及两自由度振荡圆柱等算例进行了数值模拟。通过与现有的实验或数值结果的对比，证明本文发展的方法是快速、有效并且可靠的。..利用该平台首先进行了单独转子叶片及前方有静子叶片时振荡转子叶片的数值模拟。.（2）揭示转/静干涉引起叶轮机颤振失稳的物理机理及其关键影响参数.通过不同轴向间距和静子不同攻角下对转子振荡影响的模拟，证明静/转轴向距离和静子攻角是影响转子振荡的重要因素。此外，转子振荡频率有两部分，分析认为，转子振动的高频部分是由于静子尾迹诱导产生的强迫响应，而低频部分跟转子本身的脱落涡诱导相关。.（3）多叶片排下的颤振控制方法研究.通过研究静子不同安装角对转子颤振的影响，证明静子的安装角对转子颤振有关键影响，可通过设置不同的静子安装角，达到抑制转子颤振的目的。.此外，提出了一种自相关预警分析的信号处理方法，并且对这种方法进行分析证明了本方法可以反映出叶片压力信号中非定常扰动的能量强度。由此我们建立了压气机工作时，叶片通道内部流动分离、涡脱落等非定常流动强度与压气机气动失稳之间的联系，通过相关性分析预警的方法提供了足够长的预警时间。.