Numerical Investigaton of Sand Erosion Phenomena in Rotor/Stator Interaction of Jet Engine Compressor

砂蚀是一种固体颗粒撞击壁面造成壁面严重机械损伤的现象。众所周知，各种机械设备，如飞机、船舶、燃气涡轮机、泵等，由于泥沙的侵蚀，其性能和寿命都严重下降。这是一个典型的气固两相湍流流动，是流场、颗粒运动轨迹和壁面变形相互作用的多物理问题。然而，传统的数值模拟方法没有考虑到冲蚀过程中流场的变化以及与之相关的颗粒运动轨迹。这种治疗在生理上是不现实的。因此，我们开发了数值计算程序的沙侵蚀现象，包括流场和壁面形状的时间变化。在本研究中，我开发了一个程序来模拟轴流压气机转子/定子干扰中的砂蚀现象，以澄清物理和对气动性能的影响。在2006年，我扩展了我们现有的旋转参考系计算转子/定子干扰的代码。然后将该程序应用于一个90度方形截面的弯曲，在弯曲处发生了砂蚀。将数值计算结果与实验数据进行比较，结果表明所开发的程序能够较好地再现湍流流动和冲蚀面随时间的变化。2007年，将所开发的程序应用于轴流压气机的动静叶干涉问题，以阐明其物理机制。通过对数值计算结果的分析，发现第一次撞击导致了转子前缘附近最严重的冲蚀，而在转子尾缘尖部附近，由于离心力的作用，使得大量的颗粒向该区域运动，从而导致了相对严重的冲蚀。

Sand erosion is a phenomenon where solid particles impinging to a wall cause serious mechanical damages to the wall surface. It is well-known that the performance and lifetime of various machines, such as airplane, ship, gas turbine, pump and so on, are severely degraded due to sand erosion. This phenomenon is E typical gas-particle two-phase turbulent flow and a multi-physics problem where the flow field, particle trajectory and wall deformation interact with among others. However, the change of the flow field and the relating particle trajectory during the erosion process have not been taken into account by conventional simulations. This treatment is physically unrealistic. Hence, we have developed the numerical procedure for sand erosion phenomenon, including the temporal change of the flow field and the wall shape. In the present research, I developed a code to simulate sand erosion phenomena in a rotor/stator interaction of an axial compressor, in order to clarify the physics and the effects on the aerodynamic performance.In 2006, I extended our existing code for rotational frame of reference to compute a rotor/stator interaction. Then the code was applied to a 90-degree bend with a square cross-section in which sand erosion took place. Comparing the numerical results with the experimental data, it was confirmed that the developed code can reproduce the temporal changes of the turbulent flow and eroded surface satisfactorily.In 2007, the code was applied to a rotor/stator interaction problem of an axial compressor, to clarify the physics. Investigating the numerical results, it was confirmed that the first impact leads to the most severe erosion around the rotor leading edge, and relatively severe erosion occurs around the tip of the rotor trailing edge, because centrifugal force makes a number of particles go towards the region.