Numerical investigation on damping coefficient of the integral squeeze film damper

The elimination of rotor vibration is usually achieved by applying additional damping to the system.Squeeze film dampers are widely used in various aerospace and turbine equipments.The research is carried out on flow characteristics in the integral squeeze film dampers(ISFDs).The dynamic response to the operation condition is investigated through the computational fluid dynamics(CFD) model of ISFD.Due to the large pressure loss at the oil inlet,the oil film force only changes slightly with the increase of oil supply pressure,and the damping increases slightly.The vibration amplitude only affects the film force,but has no effect on the damping.The oil film force and damping show an upward tendency with the decrease of thickness of the end seal clearance.

Experimental study of suppressing the unbalanced response vibration of rotor system with a G-type integral squeeze film damper

Conventional squeeze film dampers have numerous challenges including lock up,bistable response and incoordinate precession.In order to resolve these nonlinear problems,a novel G-type integral squeeze film damper(GISFD)is proposed in this research.The experimental test rig is provided to investigate the rotor system with an unbalanced single disk.Numerical simulation results show that the structural design of GISFD is reasonable,which can ensure its safe and stable operation.The influence of different support stiffnesses on the first-order speed of the rotor system is analyzed.Experimental results show that GISFD can effectively suppress the unbalanced response vibration of the rotor.In a certain range,it is found that the suppression effect of GISFD increases with the increase in the kinematic viscosity of the damping fluid.When the silicone oil with kinematic viscosity coefficients v=30.0 cm^(2)/s is employed,the vibration reduction of GISFD is approximately 71.51%.Furthermore,the experimental results show that with the increase of the unbalance,there is a linear relationship between the unbalance and the corresponding amplitude of the unbalanced response.It is concluded that GISFD has excellent linear damping characteristics and reduces the sensitivity of the rotor system to the unbalanced mass.

退行性腰椎管狭窄症的诊断和中西医治疗进展

退行性腰椎管狭窄症(DLSS)是一种全球范围内普遍存在的脊柱疾病,对于重度的退行性腰椎管狭窄症患者,手术治疗是首选方案,然而,对于轻度和中度的患者,更合适选择中医保守治疗。这2种治疗策略在临床上都已证明能够取得良好效果,但它们仍面临挑战,特别是关于DLSS的诊断以及中西医治疗方案的确定,目前在临床上仍存在分歧和争议。现对DLSS的诊断以及中西医治疗方法的最新研究进展进行综述,以期为临床实践提供参考。

Research on suppress vibration of rotor misalignment with shear viscous damper

A new type of shear viscous damper for rotating machinery is designed. The new damper with good stability and reliability can inhibit all kinds of frequency multiplication vibration caused by misalignment in the condition of nonstop machine. It analyzes and discusses the use of the shear viscous damper for misalignment vibration response inhibition with a finite element method, and experi ments are extensively carried out with a laboratory test rig. Both the simulation and experimental re suits basically agree well in that, the damper can effectively control the misalignment vibration of the rotor system and improves the stability of the plitude of one time running speed component bration has been basically eliminated. entire rotor system. Experimental results show the am decreases by 30% , and the two time running speed vibration has been basically eliminated.

Effect and sensitivity analysis of the rotational speed on the fluid-induced force characteristics of the straight-through labyrinth gas seal

The effects of the rotational speed on the fluid-induced force characteristics of a straight-through labyrinth gas seal( STLGS) are numerically investigated using the steady computational fluid dynamics( CFD) method based on a three-dimensional model of the STLGS. The fluid-induced force characteristics of the STLGS for five rotational speeds at a pressure drop of △P = 5000 Pa with and without eccentricity are computed. The grid density analysis ensures the accuracy of the present steady-CFD method. The effect and sensitivity analysis show that the changes in rotational speed affect the pressure forces,viscous forces and total pressure distributions on the rotor surface,velocity streamlines,leakage flow rates,and maximum flow velocities. The results indicate that the rotational speed inhibits the pressure forces,leakage flow rates and maximum flow velocities and promotes the viscous forces and total pressure on the rotor surface.

某重型燃气轮机压气机动叶弯曲变形故障分析

针对国内某热电厂首次发生的燃气轮机压气机第二级动叶顶部弯曲变形故障,从压气机进出口压力、叶片通道温度、排气温度、进口导叶(IGV)阀开度、轴承振动、余热锅炉出口烟气流量等多个监测参数入手,多参数协同分析可能造成故障的原因。在燃气轮机运行过程中,压气机出现进口静压增大0.0012 MPa,出口压力减小0.0782 MPa,叶片通道温度增#大14.09℃,排气温度增大6.12℃,2轴承振动增大10.69μm,余热锅炉出口烟气流量减少了0.25×106 Nm3/s等异常现象。揭示了轴流式压气机第二级动叶叶顶弯曲变形机理,判断动叶叶顶局部弯曲与压气机旋转失速现象密切相关。若出现压气机进口压力增大,压气机出口压力减小,叶片通道温度及排气温度升高,轴承振动增大,余热锅炉出口烟气流量减小等参数的异常变化,可初步判断压气机发生旋转失速。

基于整体式挤压油膜阻尼器的离心水泵传动轴减振研究

针对离心水泵传动轴的振动问题,提出了运用整体式挤压油膜阻尼器(ISFD)减小水泵传动轴振动的方法。对设计的ISFD的刚度和阻尼系数进行了仿真计算,并根据刚性支承和ISFD支承的动力学特征对离心泵传动轴进行了仿真分析;搭建了模拟水泵工作环境的试验台,通过对比水泵轴承座分别安装刚性支承和ISFD阻尼支承来分析整个系统的振动特性。结果表明,ISFD有着良好的阻尼减振性能,对于传动轴的高频外传力振动有着明显的抑制效果;在不同转速条件下,ISFD都能对振动有着良好的抑制效果,加速度降幅在50%以上,能够有效抑制水泵传动轴的振动。

基于ISFD的滑动轴承转子系统不平衡振动抑制研究

由于高转速和大功率的需要,现有很多转子设备往往是基于滑动轴承设计的,因而由不平衡故障引起的振动成为影响这些设备安全运行的关键因素。为了探究整体式挤压油膜阻尼器(ISFD)对滑动轴承转子系统因不平衡故障产生振动的抑制效果,对安装有ISFD阻尼支承后的转子系统的不平衡振动响应进行了研究。首先,以实验室现有的转子试验台为基础,设计了安装有滑动轴承的ISFD阻尼支承结构,对ISFD的减振机理进行了介绍;然后,运用有限元方法,研究了ISFD弹性体的径向刚度特性;最后,搭建了单跨对称转子试验台,采用试验的方式,研究了该ISFD阻尼支承结构对转子不平衡振动的抑制效果。研究结果表明:在较宽的载荷范围内,ISFD弹性体的位移值与静载荷呈线性关系,具有优良的线性刚度特性;ISFD具有优良的阻尼特性,可以较好地抑制不同转速工况下滑动轴承转子系统的不平衡振动,在1 800 r/min的工况下,转子在x和y方向的振动降幅分别为38.4%和49.4%;ISFD阻尼支承可以有效抑制滑动轴承转子系统不平衡故障导致的工频振动,在1 600 r/min的工况下,转子在x和y方向的工频振动降幅分别为19.5%和29.4%,其减振效果良好。该研究成果可以为ISFD在滑动轴承转子系统中的实际工程应用提供借鉴,具有良好的应用前景。

聚丙烯酸酯和水性聚氨酯阻尼涂料的减振性能研究

若能够有效阻隔振动和噪声的传递或在其传递过程中对其能量进行快速衰减,可显著提高乘客的舒适度。将聚丙烯酸酯和水性聚氨酯涂料作为阻尼层涂覆在薄壁结构上,基于单输入单输出(SISO)模态试验方法和正弦扫频激励试验方法探究阻尼层的涂覆厚度、外界激励力频率和激励力幅值对薄壁结构动力学特性的影响规律。首先,将薄壁结构的模态测试结果与使用有限元法计算得到的结果进行对比,发现两者差值较小,验证了SISO模态试验方法的准确性。随后将SISO模态测试方法应用于测试不同涂覆材料和不同涂膜厚度后复合结构阻尼比的变化情况,揭示涂覆阻尼层后复合结构阻尼比的变化情况。试验结果表明:随着涂覆厚度的增加,复合结构的阻尼比随之增大,但不同频率下阻尼比的增加幅度并不相同。另外,对比相同涂覆厚度的阻尼层,聚丙烯酸酯阻尼涂料提供的阻尼比更加稳定。为进一步验证聚丙烯酸酯阻尼涂料的减振能力,对涂覆厚度为1.5 mm的复合结构进行10~500 Hz频率范围内的扫频激励试验。试验结果表明:聚丙烯酸酯涂料能够有效降低薄壁结构在不同激励力频率、不同激励力幅值下薄壁的动态响应幅值,快速耗散振动的能量,提高薄壁结构的稳定性。研究成果可为聚丙烯酸酯和水性聚氨酯阻尼涂料在薄壁结构振动控制中的应用提供指导。

新型IDG不同阻尼液黏度控制齿轮轴系振动噪声的试验研究

开发设计了一种新型整体式阻尼齿轮(Integral Damping Gear,IDG),研究IDG不同阻尼液黏度对齿轮传动系统减振降噪特性的影响规律。建立了IDG减振力学模型,分析了IDG控制齿轮系统振动的有效性;搭建一级直齿圆柱齿轮传动系统试验台,对普通圆柱直齿轮系统和不同阻尼液黏度的IDG系统支承处的振动进行了对比。结果表明,IDG能够有效控制齿轮传动轴系的振动;在本试验所用的阻尼液黏度范围内,随着IDG所用阻尼液黏度的增大,齿轮轴系的振动逐渐减小,最大黏度下的IDG平均减振幅度大于50%;同时,IDG能够有效降低齿轮系统的噪声,最大黏度下能够降低7.6 dB(A)的噪声,进一步说明IDG具有优良的减振降噪特性,可保证齿轮传动系统的平稳运行。研究为齿轮系统的减振降噪提供了一种新思路。

齿轮箱箱体高精度模态识别方法研究及结构优化设计

考虑到齿轮箱箱体结构的复杂性,使用单点激励-多点响应模态识别技术对其前6阶模态进行识别,模态置信度即模态识别精度高。以试验获得的齿轮箱箱体前6阶模态为指标,提出了兼顾计算精度和计算效率的模态有限元计算方法;使用拓扑优化方法对齿轮箱箱体结构进行优化设计,优化后齿轮箱箱体在不同固有频率处的变形均得到了减小。研究为齿轮箱箱体结构优化设计提供了新思路。

偏心工况下梳齿、蜂窝与蜂窝-梳齿密封的泄漏特性

针对化工行业中透平机械运行过程中梳齿及蜂窝密封存在的偏心问题,本文搭建了高速旋转密封试验装置,通过试验真实还原化工行业高速旋转机械不同密封径向偏心和角向偏心工况,开展了不同径向与角向偏心状态下的不同结构密封的泄漏特性试验研究,揭示了偏心下梳齿密封、蜂窝密封及蜂窝-梳齿组合密封的封严机理,为化工透平机械的梳齿密封与蜂窝密封的设计与优化提供理论支撑。本文主要对比了梳齿密封、蜂窝密封及蜂窝-梳齿组合密封在径向偏心与角向偏心工况下的泄漏特性。主要结果表明:蜂窝-梳齿结构在所有测试条件下泄漏率最大,但其对偏心的敏感程度最低,受偏心的影响程度最小;蜂窝-光轴结构在所有测试条件下泄漏率最小,可以有效阻碍气体流动;梳齿-光轴结构在所有测试条件下对偏心的敏感程度最高,受偏心的影响程度最大,体现出显著的不稳定性。

基于GISFD的斜齿轮轴系减振实验研究

齿轮是机械传动装置中的重要元件,但是,齿轮传动产生的振动和噪声会危害到传动设备的正常运行,严重时甚至会造成设备损坏。为了减小和隔离斜齿轮轴系的振动,提出了一种结构新颖的G型整体式挤压油膜阻尼器(G-type Integral Squeeze Film Damper,GISFD),探究了GISFD对斜齿轮的振动特性影响。搭建基于GISFD的一级斜齿轮试验台,开展了GISFD对斜齿轮轴系的减振实验。此外,还进行了GISFD对齿面磨损斜齿轮的振动抑制实验。结果表明,GISFD对不同转速下斜齿轮轴系有较好的减振效果,在1200 r/min时,GISFD对斜齿轮主从动轴的振动降幅最高可以达到59.61%;同时,GISFD可以抑制斜齿轮啮合频率及其2倍频处的振动,振动降幅最高可以达到85.71%;GISFD对磨损斜齿轮也有较好的振动抑制效果,主动轴水平方向振动降幅在1200 r/min时可以达到83.99%。

Experimental study on vibration suppression of gear shaft misalignment with ISFD

Misalignment faults in gear systems lead to violent vibration and noise, shortening the life of equipment. The aim of this work is the demonstration of vibration suppression of parallel-misaligned gear shafts using an integral squeeze film damper(ISFD). Using a first grade spur gear in engineering for reference, an open first-grade spur gear system is built and the vibration characteristics of the gear system with rigid supports and ISFD elastic damping supports are studied under different degrees of misalignment. The experimental results show that ISFD supports have excellent damping and vibration attenuation characteristics, which have improved control of the gear system vibration in horizontal, vertical and axial directions under different degrees of misalignment. This work shows that an ISFD structure can effectively suppress vibration of characteristic frequency components and resonance modulation frequency components. The test results provide evidence for the application of ISFD in vibration control of gear shaft misalignment faults in engineering.

Experimental study on vibration suppression in a rotor system under base excitation using an integral squeeze film damper

Base excitation is one of common excitations in rotor system.In order to study the dynamic characteristics of rotor systems under base excitation and the effect of integral squeeze film dampers(ISFDs)on their dynamic characteristics,a single-disk rotor test rig,where mass imbalance and base excitation could be applied,is developed.Experimental research on the rotor system response under sinusoidal base excitation conditions with different frequencies and excitation forces is performed and the effect of ISFD on the dynamic characteristics of the rotor is investigated.The experimental results demonstrate that when the sinusoidal base excitation frequency approaches the first critical speed of the rotor system or the natural frequency of the rotor system base,strong vibration occurs in the rotor,indicating that the base excitation of the two frequencies has a greater impact on rotor system response.In addition,with the increase of the base excitation force,the vibration of the rotor will be increased.ISFDs can significantly inhibit the vibration due to unbalanced forces and sinusoidal base excitation in rotor systems.To a certain extent,ISFDs can improve the effect of sinusoidal base excitation with most frequencies on rotor system response,and they have a good vibration reduction effect for sinusoidal base excitation with different excitation forces.

Effect of integral squeeze film damper on vibration and noise of spur gear with center-distance error

When the actual installation center distance between a pair of spur gears is greater than the theoretical center distance,backlash increases,leading to increased vibration and noise.The structural parameters of an integral squeeze film damper(ISFD)were designed with the stiffness of rigid support as reference to investigate the effect of an ISFD on the dynamic characteristics of a spur gear transmission system with center-distance installation error.A spur gear test bench with center distance-error was built to investigate the vibration and noise reduction characteristics of ISFD.The experimental results indicate that,compared with a rigid support,the ISFD can reduce vibration by approximately 40%and noise by approximately 5 d B.ISFD can effectively absorb the impact energy caused by an increase of in backlash,which is conducive to the stable operation of the spur gear transmission system.

人工自愈与动力机械振动故障靶向抑制

人工自愈是在故障机理和风险分析的基础上,通过仿生设计赋予机器自发作用的维持健康状态的能力,从而使机器储存、补充和调动自愈力以维持机体的健康状态。透平压缩机、发电机组和航空发动机等动力机械是工业和国防的心脏设备,一旦发生故障将导致事故和巨大损失,在运行中通过自监测、自诊断和主动控制来抑制故障的发生以实现自愈化,是机器向高级智能阶段发展研究中的一个重要方向。本文总结了北京化工大学诊断与自愈工程(DSE)研究中心在人工自愈与动力机械振动故障靶向抑制方面的主要研究工作及成果,并以转子轴系不平衡和压缩机转子失稳振动为例,证明了靶向抑制方法的有效性。以上成果可为自主开发具有自愈功能的智能动力机械提供科学依据。

Experimental study on integral axial squeeze film damper to suppress longitudinal vibration of propulsion shafting

This paper aims at investigating the effectiveness of squeeze oil film in suppressing the longitudinal vibration of propulsion shaft systems through a novel integral axial squeeze film damper(IASFD).After designing the IASFD,a propulsion shafting test rig for the longitudinal vibration control is built.Longitudinal vibration control experiments of the propulsion shafting are carried out under different magnitude and frequency of the excitation force.The results show that both IASFD elastic support and IASFD elastic damping support have excellent vibration attenuation characteristics,and can effectively suppress the longitudinal vibration of the shaft system in a wide frequency range.However,IASFD elastic damping support has a more significant vibration reduction effect than the other supports,and increasing the damping of the system has obvious effect on reducing the shafting vibration.For an excitation force of 45 N,the maximum reduction of the vibration amplitude is 89.16%.Also,the vibration generated by the resonance phenomenon is also significantly reduced.

物理模拟及DEFORM仿真技术在大型锻件镦粗工艺中的应用

通过模拟实验及DEFORM仿真模拟,对比研究了普通镦粗和凹型坯料镦粗的变形规律,探讨了孔洞缺陷闭合的机理,提出了定量评定锻造效果的技术指标,可用于实际大锻件工艺的优化制定。

1例新型冠状病毒肺炎疑似患儿急诊支气管镜检和异物取出术的护理及防护

本文总结1例新型冠状病毒肺炎疑似患儿行急诊支气管镜检异物取出术的护理及防护经验,包括术前防护物资准备和感染控制、手术间消毒隔离、术中配合、术后物品消毒、转运等。