EFFECTS OF SOUND ABSORBING WALL ON BLADE ROW FLUTTER AND SOUND GENERATION UNDER INTERACTION OF MULTIPLE BLADE ROWS

本文提出了一种非定常升力面理论，用于一个有振动叶片的三排叶栅模型，以考虑位于上游和下游的相邻叶栅的同时作用。编制了计算程序，计算了给定频率、叶间相位角等设计参数下的非定常气动力和叶片做功。通过将本程序的计算结果与K.C.教授的CFD欧拉程序计算结果进行比较，证实了程序的有效性。杜克大学大厅。两种结果完全一致。进行了参数研究，以研究上游和下游相邻叶片排对叶片振动引起的非定常载荷的同时影响。本文还研究了两个下游叶排和两个上游叶排的影响。 ...更多信息 涡轮风扇发动机的风扇音噪声。在真实三维升力面理论的基础上，考虑了动、静叶间相互气动声学干扰的影响，提出了一种预测方案。将该格式进一步改进为一种混合格式，该格式基于CFD技术处理静叶与上游转子来流涡干扰，基于非定常升力面理论处理两排叶栅的气动声学干扰。编制了计算程序，对上述模型进行了推广，包括吸声墙的影响，并建立了综合模型。(1)上游和下游叶片排的同时影响不能通过两个叶片排之间的相互作用的简单叠加来解释。在叶片排之间的距离非常短的情况下，下一个叶片排的影响也很大。(2)转子与定子之间的声相互作用对辐射声功率的影响是非常显著的。该效应在很大程度上取决于叶片通过频率的谐波数。少

An unsteady lifting surface theory was developed for a model of three blade-rows with vibrating blades, to account for the simultaneous effects of adjacent blade rows situated upstream and downstream. A program was coded to compute unsteady aerodynamic force and work on blades for specified frequency, inter-blade phase angle and other design parameters. The validity of the program was confirmed by making a comparison for a model condition between the results from the present program and those of CFD Euler code computation conducted by Professor K.C. Hall of Duke University. Both results were in complete agreement.Parametric studies were conducted to investigate the simultaneous influences of the upsteam and downstream neighboring blade rows on unsteady loading caused by blade vibration. The effects of two downstream blade rows and two-upstream blade rows are also investigated.It is a common understanding that interaction of stator vanes with oncoming rotor wakes is the primary source o … More f the fan tone noise of turbofan engines. A prediction scheme on the basis of genuine 3-dimensional lifting surface theory including the effect of mutual aeroacoustic interaction between the rotor and the stator was developed. The scheme was further modified into a hybrid scheme, which deals with vortical interaction of stator vanes with oncoming vortical wake disturbances from the upstream rotor on the basis of CFD technique and deals with aeroacoustic interaction of the two blade rows on the basis of the unsteady lifting surface theory. A computation program was coded to predict the generated sound power.The above models were further generalized to include the effect of the sound absorbing walls, and the comprehensive models were mathematically formulated.New findings are summarized as follows.(1) The simultaneous influence of the upstream and downstream blade rows can not be accounted for by a simple superposition of interactions between two blade rows. The effect of the next blade row but one is also substantial in the case of very short distances between blade rows.(2) The effect of the acoustic interaction between the rotor and the stator on the radiated sound power is very substantial. The effect heavily depends on the harmonic number of the blade passing frequency. Less