STUDY OF THREE-DIMENSIONAL EFFECTS ON AEROELASTIC CHARACTERISTICS OF CASCADE

1.开发了吸声壁面衬板对亚、超音速振动叶栅非定常气动力的影响计算程序。吸声侧壁对非定常气动力的影响对于超音速叶栅比亚音速叶栅更为显著。如果像通常情况那样，壁面的声导纳依赖于声频，那么壁面对转子叶栅的影响与对定子叶栅的影响有很大的不同，因为简谐振动下的转子叶栅会产生多频声场。利用双线性化理论，编制了二维亚、超音速叶栅和三维亚声速叶栅的非定常气动力计算程序。通过与更精确的数值场法(有限元和逐次逼近法)计算结果的比较，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、弯曲度和叶片厚度对叶栅弯曲颤振边界的影响及其展向非均匀性，超音速叶栅弯曲颤振边界的临界入射角远小于亚音速叶栅。在亚音速叶栅的情况下，定常载荷的横向分布从轮毂到叶尖增大，有利于获得总定常载荷较大的稳定(无弯曲颤振)运行。正在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。有限元方法在三维振动叶栅中的应用也在进行中。

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.