STUDY OF THREE-DIMENSIONAL EFFECTS ON AEROELASTIC CHARACTERISTICS OF CASCADE

1. 在亚声速和超声速流动中，已经开发了用于预测振动的静、转子叶栅非定常力的计算机程序。超音速叶栅吸声侧壁对非定常气动力的影响要比亚音速叶栅大得多。如果壁面的声导纳与声频有关，那么壁面对转子叶栅的影响与对定子叶栅的影响就大不相同，因为转子叶栅在简谐振动中会产生多频声场。非均匀定常加载条件下叶栅振动的气动特性利用双线性化理论，开发了二维亚音速、超声速叶栅和三维亚音速叶栅的计算机程序，用于定常加载条件下振动叶片的非定常气动力预测。通过与更精确的数值场方法（有限元法和逐次逼近法）的结果比较，证实了双线性化理论的有效性。通过大量的数值研究，明确了入射角、弧度和叶片厚度及其展向非均匀性的影响。超声速叶栅在弯曲颤振边界上的临界入射角比亚音速叶栅小得多。在亚音速叶栅的情况下，从轮毂到叶尖的稳定载荷沿展向分布有利于在总稳定载荷较大的情况下获得稳定（无弯曲颤振）运行。将双线性化理论推广到三维超音速叶栅和旋转环形叶栅模型。三维振荡叶栅的有限元方法也进行了应用。

1. Effects of sound absorbing wall linings Computer programs have been developed for the prediction of unsteady aerodynamic forces on vibrating stator and rotor cascades in subsonic and supersonic flows. Effects of sound absorbing side walls upon unsteady aerodynamic forces are much more significant for supersonic cascades than for subsonic ones. If the acoustic admittance of the wall is dependent on sound frequency as is usually the case, the wall effects on rotor cascades are much different from those on stator cascades, because a rotor cascade in simple harmonic vibration generates a multi-frequency sound field.2. Aerodynamic characteristics of cascade vibrating with nonuniform steady loadingComputer programs for 2-dimensional subsonic and supersonic cascades and 3-dimensional subsonic cascades have been developed for the prediction of unsteady aerodynamic forces on vibrating blades with steady loadings, using the double linearization theory. The validity of the double linearization theory has been confirmed by comparison of the results with those by more accurate numerical field methods (FEM and a successive approximation method). Effects of incidence, camber and blade thickness and their spanwise nonuniformity have been made cleary by extensive numerical studies.The critical incidence angles on the bending flutter boundary for supersonic cascades are much smaller than those for subsonic cascades. In the case of subsonic cascades a spanwise distribution of steady loading increasing from hub to tip is favourable for attaining stable (free from bending flutter) operation with large total steady loadings.Extension of the double linearization theory to 3-dimensional supersonic cascade and rotating annular cascade models is being developed. Application of a finite element method to 3-dimensional oscillating cascades is also being conducted.