瓦块固有频率对可倾瓦轴承频变刚度的影响

Effect of Pad Natural Frequency on Frequency-variation Stiffness of Tilting Pad Bearings

为研究轻载工况下可倾瓦块固有频率和振动频率对轴承刚度的影响,基于长轴承理论建立求解可倾瓦推力轴承瓦块固有频率和频变刚度的润滑和动力学耦合模型,推导润滑模型的解析解和频变动力学特性的表达式,并通过实例计算分析载荷、支点系数(瓦进油边到支点的距离与瓦长的比值)、瓦块转动惯量等结构参数对瓦块固有频率和频变刚度的影响。结果表明:瓦块的惯性、油膜的刚度和阻尼共同决定瓦块振动的固有频率,瓦块在固有频率附近振动可以使轴承的频变刚度出现负值,甚至正负无穷大;小载荷的瓦(如非承载瓦)容易出现瓦块振动频率接近其固有频率的状况,使瓦发生共振;可倾瓦轴承设计中有必要考虑瓦块的固有频率和频变刚度来设计非承载瓦的支点系数和转动惯量,使瓦块的振动频率跨过固有频率而产生大的刚度。

In order to research the effect of natural frequency and vibration frequency of pad on stiffness of tilting?pad bearing,lubrication and dynamic coupling model based on long bearing theory was established to solve natural frequency and frequency?variation stiffness of pad in tilting pad thrust bearing.Analytical solution of this lubrication model and formulae of frequency?variation dynamic characteristics were deduced,and the influence of load,pivot coefficient ( Ratio of the distance between oil inlet and pivot to the pad length) ,rotational inertia and other structural parameters on natural frequency and fre?quency?variation stiffness were analyzed through example calculation.The results show that vibration natural frequency of tilt?ing pad is codetermined by inertia,stiffness and damping of oil film.When the vibration frequency of pad is close to its natu?ral frequency,frequency?variation stiffness of bearing presents negative value even with positive and negative infinite.The sit?uation that vibration frequency is close to its natural frequency is easily appeared for the pad of light load ( unloaded pad for an example),which will cause resonance phenomenon.In order to ensure vibration frequency is greater than natural frequency of pad to produce high stiffness,it is necessary to take natural frequency and frequency?variation stiffness into consideration to design pivot coefficient and inertia of unloaded pads in design of the tilting pad bearings.