航空发动机用聚四氟乙烯软管内压载荷下振动特性的研究

Study on Vibration Characteristics of Flexible Polytetrafluoroethylene Hoses Used in Aeroengines under Internal Pressure Load

为了分析用于航空发动机管路系统中的柔性软管的振动特性,搭建了激励振动试验台,采用锤击法测量七种规格聚四氟乙烯软管在空载条件和充液加压条件下的自由震荡衰减曲线,得到固有频率和阻尼比,以及测量了软管在不同压力载荷下的轴向应变和周向应变,得出软管应变分布随着压力载荷变化的规律。结果表明:充液加压工况下软管固有频率远小于空管的固有频率,在最大工作压力范围内,随着压力增加,固有频率仅小幅度增加,因此在对发动机管路系统进行调频时,应主要考虑管路介质因素而可以忽略压力的影响。随压力载荷增加,软管应变呈现非线性变化,沿管长方向分布比较均匀且以轴向拉应变为主,拉应力引起的弯曲刚度增强,导致固有频率下降。

In order to analyze the vibration characteristics of flexible hoses used in aeroengine pipeline systems, an incentive vibration test-rig was set up. Using the hammering pulse method, the natural frequency and the damping ratio of seven kinds of polytetrafluoroethylene hoses were obtained by measuring the free vibration attenuation curves under load-free and liquid-filled pressurized conditions. The axial and circumferential strains of the hoses under different pressure loads were measured, and the variation law of strain distribution with inner pressure was obtained. The results show that the natural frequency of the hose under inner pressure condition is far less than that of the empty pipe, and the natural frequency increases slightly with the increase of pressure within the range of maximum working pressure. Therefore, in frequency modulation of engine pipeline system, the pipeline medium should be mainly considered and the influence of pressure can be ignored. With the increase of the pressure load, the strain of the hose varies nonlinearly, the strain distribution becomes relatively uniform along the pipe axial direction, the axial strain is predominant, and the bending stiffness is enhanced, which leads to the decrease of natural frequency.