Research on a Rigid Rotor-Sliding Bearing System with a Squeeze Film Damper

In this paper, a dynamic model on a rigid rotor sliding bearing system with a SFD is established. The stability and bifurcation behaviors of the system are studied. On the basis of the differential equations of fluid momentum and mass continuity, the distribution pressure function is derived by taking oil film inertia force into consideration. Damping force, clearance excitation force, interference force of different frequencies and static load are also considered in the model. Finally, the governing equations of the stability and bifurcation behaviors of the system are solved by Floquet theory. Simulation of dynamic model shows that the rigid rotor sliding bearing system can maintain stability and exhibit a Hopf bifurcation phenomenon in a certain range.

Bifurcation of Periodic Motion of Rigid Rotor System Supported by Angular Contact Ball Bearings

Rotor systems supported by angular contact ball bearings are complicated due to nonlinear Hertzian contact force. In this paper, nonlinear bearing forces of ball bearing under five-dimensional loads are given, and 5-DOF dynamic equations of a rigid rotor ball bearing system are established. Continuation-shooting algorithm for periodic solutions of the nonlinear non-autonomous dynamic system and Floquet multipliers of the system are used. Furthermore, the bifurcation and stability of the periodic motion of the system in different parametric domains are also studied. Results show that the bifurcation and stability of period-1 motion vary with structural parameters and operating parameters of the rigid rotor ball bearing system. Avoidance of unbalanced force and bending moment, appropriate initial contact angle, axial load and damping factor help enhance the unstable rotating speed of period-1 motion.

Studies of Rigid Rotor-Rigid Surface Scattering in Dynamical Lie Algebraic Method

The dynamical Lie algebraic method is used for the description of statistical mechanics of rotationally inelastic molecule-surface scattering. It can give the time-evolution operators about the low power of and by solving a set of coupled nonlinear differential equations. For considering the contribution of the high power of and , we use the Magnus formula. Thus, with the time-evolution operators we can get the statistical average values of the measurable quantities in terms of the density operator formalism in statistical mechanics. The method is applied to the scattering of (rigid rotor) by a flat, rigid surface to illustrate its general procedure. The results demonstrate that the method is useful for describing the statistical dynamics of gas-surface scattering.

Alternating Parity Band in Octupole-Soft ^(140)Xe with Axial Vibrational-Rotational Model and Triaxial Rigid Rotor Model

Energies of the yrast positive-and negative-parity excited states in140 Xe are reproduced by two different models considering quadrupole-octupole deformations, namely the axial vibrational-rotational model and the triaxial rigid rotor model, and compared with the stable octupole-deformed222 Th. The origin of the energy difference between the opposite parity sequences is considered from two different mechanisms, the vibration in axial deformed energy minima and the rotation considering the effective triaxial deformation. The success of reproducing the data in both the models implies that these two mechanisms are equivalent on some level for the octupole-soft nuclei. By investigating the probability distributions for projection of total angular momentum in the triaxial rigid rotor model, it is found that such an energy difference is associated with the difference of orientation of the rotational axis.

STUDY ON AUTOMATIC BALANCE TECHNOLOGY FOR THE RIGID ROTOR

The theory and application of automatic balance technology for the rigid rotor is re- searched. New analysis about the mechanical model of vibratory system is done in view of feature of automatic balance, and the result is that the accurate model of system can be gained by compensa- tion method and the traditional principle error of balance machines both for soft and hard bearing can be overcome. The automatic balance testing theory for sofi and hard bearing machines is pro- posed. The automatic balance system has been developed and the function and technical key is also introduced in detail.

Bifurcation on synchronous full annular rub of rigid-rotor elastic-support system

An aero-engine rotor system is simplified as an unsymmetrical-rigid-rotor with nonlinear-elastic-support based on its characteristics. Governing equations of the rubbing system, obtained from the Lagrange equation, are solved by the averaging method to find the bifurcation equations. Then, according to the two-dimensional constraint bi- furcation theory, transition sets and bifurcation diagrams of the system with and without rubbing are given to study the influence of system eccentricity and damping on the bi- furcation behaviors, respectively. Finally, according to the Lyapunov stability theory, the stability region of the steady-state rubbing solution, the boundary of static bifurcation, and the Hopf bifurcation are determined to discuss the influence of system parameters on the evolution of system motion. The results may provide some references for the designer in aero rotor systems.

Experimental study and numerical simulation of isothermal closed die forging for aluminium alloy rotor

The closed die forging(or fully-enclosed die forging) method was employed to form a rotor instead of the conventional machining method. A combined female die was designed so that the rotor could be released easily from the female die after forging. In order to improve the metal flow ability, the isothermal forming technique was introduced to the closed die forging process. On the basis of the rigid-viscoplastic FEM principle, the DEFORM 3D software package was employed to simulate the forming process. The simulation results illustrate that the deformation of different part of the billet is not the same. The material near the entrance of the die cavity is deformed greatly whose strain rate and strain are both large, while the deformation of the material at the billet center is much smaller.

基于特征结构配置的电磁轴承-刚性转子系统动态补偿器的设计

由于电磁轴承-转子系统的动力学特性与控制器的结构和参数密切相关,若要使系统安全、稳定及可靠地运行,控制器的设计尤为重要。针对电磁轴承-刚性转子系统,提出一种基于特征结构配置的动态补偿器的设计方法。首先,通过模态解耦,将平动和锥动运动相互耦合的四自由度电磁轴承-刚性转子系统解耦为2个单自由度平动子系统和2个单自由度锥动子系统。然后,基于特征结构配置,建立引入动态补偿器后的闭环系统的特征值和特征向量与补偿器参数之间的关系。之后,限定特征值的变化范围,以使系统具备稳定性和良好的动态性能,构造优化目标函数,以同时抑制转子系统的不平衡位移和不平衡控制电流,从而使系统具备所需的动力特性。最后,通过数值仿真和试验,验证所设计的动态补偿器的有效性。

共轴刚性旋翼气动特性试验与分析

共轴刚性旋翼直升机是高速直升机的主要发展方向之一,为了深入了解前进比及升力偏置对共轴刚性旋翼气动特性的影响,在航空工业气动院FL-52风洞开展了共轴刚性旋翼气动特性风洞试验,通过合理的操纵与配平策略,实现了共轴刚性旋翼配平,并对悬停、多种前飞状态下气动特性及升力偏置对旋翼操纵特性及性能的影响机理进行了研究。结果表明,试验取得了比较好的配平效果,桨毂力矩、合扭矩及升力偏置配平误差分别优于±2 N·m、±0.5 N·m、±0.01;悬停状态扭矩配平与非配平状态下,上旋翼效率都大于下旋翼,差动总距效率随联动总距的增大而增大;前飞状态升力偏置可有效提升大前进比时旋翼气动效率而小前进比时则并不明显,升力偏置的增大会使上下旋翼的桨毂滚转力矩大幅增加。

共轴刚性旋翼振动载荷影响分析

针对共轴刚性旋翼建立了气动弹性分析模型,开展旋翼载荷影响分析。气动弹性分析模型中采用几何精确桨叶结构动力学模型和旋翼自由尾迹模型,并结合松耦合方法计算共轴刚性旋翼载荷。通过XH-59A和X2悬停及前飞试验状态,验证了理论模型。分析了旋翼桨叶片数、交叠方位角、轴前倾角等结构参数和飞行状态参数对共轴刚性旋翼振动载荷的影响。结果表明:同等实度下旋翼桨叶片数增加,振动载荷降低;奇偶片桨叶交叠角相对机身的分布,显著影响横向和纵向振动载荷水平;相同升力和升力偏置(LOS)下轴前倾角增加,振动载荷增加。

机架柔性对双风轮风电机组传动链固有特性的影响

双风轮风电机组是一种新型水平轴式风电机组,可以利用前风轮尾流发电,风能利用系数高,但为了减少前后风轮间流场干涉效应,传动链轴向跨距较单风轮机组更长,造成长跨距柔性机架多点弹性支撑下双风轮风电机组传动链模态特性复杂,潜在共振风险高。文中考虑机架柔性及其与传动链间弹性支撑,利用多体动力学方法建立了双风轮风电机组传动链刚柔耦合动力学模型,分析了传动链耦合振动模式,研究了机架柔性对传动链固有特性的影响。研究结果表明:双风轮风电机组传动链前2阶扭振固有频率分别为5.63 Hz和6.01 Hz,分别对应后、前风轮传动链第1阶扭振固有频率;双风轮风电机组传动链共存在3类系统振动模式,包括前或后风轮传动链局部振动模式、前或后风轮传动链耦合振动模式,以及前与后风轮传动链耦合振动模式;当系统各构件的模态能量主要集中在非扭振方向时,机架柔性会使各构件模态能量朝同侧传动链其余构件或异侧传动链构件转移。

基于力传感器的刚性转子动平衡实验方法

针对刚性转子动平衡问题,提出了一种基于拉压力传感器的综合实验平衡方法。首先,基于动平衡原理,构建了转子不平衡等效模型,求解了理论不平衡量,确保了实验的严谨性和合理性;然后,进行了结构设计、仪器与设备选择,搭建了转子动平衡实验平台以保障测试数据的稳定性和可重复性;最后,利用该平台,采集了力学性能数据,分析了轴系不平衡量的幅值和相位,采用了添加平衡质量的方式进行了转子动平衡实验,对基于拉压力传感器的综合实验平衡方法的可行性和有效性进行了验证。研究结果表明:平衡前左右两端不平衡质量幅值分别为2.2 kg、-3.8 kg,平衡后左右两端不平衡质量幅值分别为1.2 kg、-1.4 kg,转子系统不平衡量减小1.4 kg,平衡率为87.5%,这说明拉压力传感器和编码器相互配合以消除不平衡量的方法具有可行性。该实验平台使用拉压力传感器和编码器精确测量不平衡质量和相位,为解决旋转机械动平衡问题提供了新思路,有助于提高旋转机械的运行效率,并延长其使用寿命。

高速线材吐丝头结构仿真与优化设计研究

针对高速线材轧制生产中吐丝机普遍存在振动值较大、连续运转稳定性较低、吐丝圈形不稳定等问题,对吐丝机关键部件吐丝头进行仿真优化研究。采用模态分析动力学控制方程、动平衡计算方程等,建立几何模型、有限元模型、运动学模型等并进行临界转速分析、模态分析和动平衡仿真分析,掌握吐丝头振动值较大的主要原因。为在设计阶段尽可能消除吐丝头的动平衡量,利用有限元仿真软件对原吐丝头进行模态分析,获得原吐丝头的第1阶临界转速为72.2 r/s,高于最高转速40 r/s,可按刚性转子对吐丝头进行动平衡。利用动力学仿真软件建立吐丝头的虚拟样机,对其进行双面动平衡仿真分析,获得吐丝头在两个校正面上所需的校正质量,并根据安装位置设计配重结构。通过对吐丝头进行动平衡优化,吐丝头在两个校正面的动不平衡质量分别由优化前的8.199 1 kg、6.655 4 kg下降为4.843 9×10^(-4) kg、3.603 8×10^(-4) kg,且1阶临界转速由72.2 r/s提升为72.75 r/s,满足设计要求。最后,将优化后的吐丝头安装在吐丝机空心轴上进行现场在线动平衡测试实验,吐丝头在线动平衡初始不平衡量为27.4 g,相位为232°,两个轴承位置测点的水平振动幅值分别为1.02μm、6.63μm,均小于10μm,满足设计要求。

构型参数对共轴刚性旋翼悬停气动干扰的影响机理

基于非定常雷诺平均Navier-Stokes方程和嵌套网格法建立了共轴刚性旋翼流场模拟方法,通过与单旋翼对比,深入分析了其气动干扰特征和形成机理,并探究了旋翼间距和转速对共轴刚性旋翼悬停气动干扰的影响机制。结果表明:桨叶相遇干扰引起的拉力波动主要取决于桨叶附近诱导流场的梯度,在悬停状态,桨叶上方、桨尖附近的流场梯度较大,因此上旋翼拉力脉冲幅值大于下旋翼,桨尖附近剖面的拉力波动大于桨根处;随着间距从基准间距逐渐增大,桨叶相遇干扰迅速减弱然后消失,周期诱导效应则逐渐减弱,但在大间距时仍然存在;旋翼转速增加会增强诱导流场强度,从而引起更大的拉力波动。

转子偏心效应下大范围转动弹性梁外激励非线性动力学行为与振动机制

为实现大范围转动弹性梁类柔性机械的高速、安全、平稳运行,综合应用Galerkin模态截断法和Hamilton原理建立弹性梁刚-柔耦合动力学模型,并建立转子偏心运动微分方程;基于行波叠加原理,应用高阶Runge-Kutta法完成非线性动力学解耦;应用时、频域分析法解析转子偏心效应下弹性梁的振动机制以及外激励下的频谱响应特性。研究结果表明:外激励响应在转子偏心效应下会衍生新的低频谐波分量,转速和激励幅值的增加会导致频域内多个低频谐波分量高于主振,易引发不同程度的间歇性振动;外激励频率提高会引起频域谱峰后移,数值仿真5~35 Hz频段的外激励,当频率为25 Hz时其低频谐波分量是主振幅值的2倍,高达0.181 mm,进而呈现明显的外激励突发性激振。因此,借助时、频域分析可有效解析具有随机性的间歇性或突发性振动产生机制,可为大型旋转柔性机械的动力学优化设计提供重要的理论基础和数据支持。

倾转旋翼无人机过渡段控制策略研究

针对倾转旋翼无人机过渡段的纵向控制问题,以某型倾转旋翼无人机为研究对象,综述了国内倾转旋翼机的发展趋势。利用Rotorlib软件建立倾转旋翼无人机的6自由度刚体模型;通过频域和时域对过渡段的特性进行分析,设计出过渡段的舵面操纵分配策略;对总距控制通道的控制结构进行设计。由于倾转旋翼在过渡过程中总距控制通道存在严重的耦合,根据动力学方程分析提出余弦分配的策略来改进耦合问题。通过仿真验证了余弦分配对于总距控制通道的耦合问题有明显的改善。

共轴刚性旋翼直升机桨毂阻力特性试验

共轴刚性旋翼直升机在突破常规直升机前飞速度极限的同时会产生巨大的桨毂阻力。为研究共轴刚性旋翼直升机桨毂的阻力特性,采用天平测力的方式在1.4m×1.4m直流风洞中对不同的共轴双桨毂组合模型进行了风洞试验。试验状态变量包括桨毂转速、模型各部件间缝隙和不同整流模型组合。试验结果表明:共轴双桨毂试验模型的阻力受对称光滑桨毂旋转运动的影响基本可忽略;各整流部件间缝隙对模型所受阻力影响较大,大缝隙会使试验模型阻力增大;各整流部件分离尾流存在较大的气动干扰,使模型所受阻力明显增加。

刚性转子动平衡的关键技术分析

阐述了刚性转子双面硬支承动平衡的工作原理,介绍了转子不平衡量的提取算法和数字滤波方法,分析了动平衡系统标定方法、去重校正策略及误差补偿等关键技术。

磁悬浮刚性转子系统振动机理分析与动力学建模

磁悬浮惯性执行机构采用磁轴承支承,可通过主动控制实现极微振动,但磁悬浮惯性执行机构仍存在频谱分量丰富的振动.首先在转子动静不平衡和Sensor Runout振动机理分析的基础上,重点分析了Magnet Runout产生振动机理;然后,建立包含多振动源的系统动力学建模,并将整个动力学模型分解为平动和转动子系统,分析表明转子动静不平衡、Sensor Runout和Magnet Runout是通过不同的途径产生振动,不仅产生同频振动还包含倍频振动;最后,提出磁悬浮刚性转子系统主动振动控制的要求,为以后的主动振动控制研究奠定基础.

共轴刚性旋翼飞行器配平特性及验证

针对共轴刚性旋翼与常规旋翼的区别,从挥舞运动、变距操纵和诱导速度3方面建立共轴刚性旋翼的气动力模型。采用等效挥舞运动概念,建立共轴刚性旋翼的挥舞运动方程;引入提前操纵角概念,建立与共轴刚性旋翼挥舞频率相适应的变距操纵模型;引入上下旋翼干扰因子,建立共轴刚性旋翼的诱导速度模型。在此基础上,建立共轴刚性旋翼飞行器飞行动力学模型,并以XH-59A直升机为例计算纯直升机飞行模式的配平特性,使用飞行试验数据验证了理论模型的正确性,同时讨论了共轴刚性旋翼飞行器与常规直升机配平特性的异同点。