燃气轮机周向拉杆转子连接刚度对转子振动特性影响的研究

Impact of Connection Stiffness on Vibration Characteristics of Rotor in Circumferential Tie Rod Rotor of Gas Turbine

为研究燃气轮机周向分布式拉杆转子轮盘间存在的连接刚度对轴系转子振动特性产生的影响,提出一种基于六自由度的弹簧单元等效方法。首先,将轮盘接触刚度与拉杆弯曲刚度同时等效进连接界面,便于使用一维梁单元求解其临界转速与振动响应变化,验证其与全三维有限元法吻合度在3%以内。然后,改写了非线性动力学方程,采用谐波平衡法对其进行求解,使用经典Newmark方法验证其准确性。最后,使用该等效方法计算了某模拟转子连接刚度对其临界转速、响应特性、非线性特性等的影响。计算结果表明:当连接面剪切刚度与弯曲刚度减小3个数量级时,均造成了临界转速的降低和振动响应的提高,而其影响程度可由各阶振型大致推测,且响应幅值受剪切刚度影响较大;使用临界转速趋于收敛时的连接刚度与试验值的对比误差<2%,较连续模型提升显著;在连接刚度各向异性时,每一阶临界转速均出现两个响应峰值,轴心轨迹变成椭圆;考虑刚度随位移变化(非线性刚度)后,转子的响应峰值发生“歪扭”特性,且该峰值特征随不平衡量、无量纲阻尼等因素变化而呈现“波浪形”变化。

In order to study the effects of the connection stiffness between the disks of the gas turbine cir⁃cumferential distributed rod rotor on the vibration characteristics of the rotor,an equivalent method based on sixdegree-of-freedom spring element is proposed.Firstly,the contact stiffness of the disks and the bending stiffness of the tie rod are equivalently entered into the connection interface at the same time,which is convenient to use a one-dimensional beam element to solve the change of its critical speed and vibration response,and verified that the coincidence between the method and the full three-dimensional finite element method is less than 3%.Then rewritten the non-linear dynamic equation,solved it with the harmonic balance method,and verified its accuracy using the Newmark method.Finally,the equivalent method was used to calculate the influence of the connection stiffness of a simulated rotor on its critical speed,response characteristics,nonlinear characteristics,etc.The calculation results show that:When the shear stiffness and bending stiffness of the joint surface decrease by three orders of magnitude,the critical speed decreases and the response increases,the degree of influence can be roughly estimated from the various modes and the response amplitude is greatly affected by the shear stiffness.The comparison error between the critical rotational speed when the value tends to converge and the test value is less than 2%,which is significantly higher than that of the continuous model.In the case of anisotropic connec⁃tion stiffness,two response peaks appear at each order of critical speed,and the axis trajectory becomes ellipti⁃cal.After considering stiffness as a function of displacement(non-linear stiffness),the response peak of the rotor has a‘torsional’characteristic,and the characteristics of the peak show a‘wavy’change with the changes of im⁃balance and dimensionless damping.