一种基于活塞杆动态能量指数的故障监测诊断方法

活塞杆是往复机械核心运动部件,在大载荷气体力、往复惯性力作用下易发生疲劳断裂,进而导致活塞撞缸、压缩介质外泄、着火爆炸等恶性事故发生。活塞杆运行状态的有效监测是避免恶性故障发生的关键。本文基于在线监测系统数据提取了活塞杆轴心动态能量指数,用以评价活塞杆实际运行状态,通过实测活塞杆纵向与横向位移信号,计算活塞杆轴心运行轨迹,获得轴心在纵向与横向上的瞬时运动能量,结合常规活塞杆位移监测信号,可对典型的磨损故障、松动故障与断裂故障进行故障预警。实际故障案例数据验证了本文方法的有效性。     

Dynamic analysis of a reciprocating compression mechanism considering hydrodynamic forces

In this paper, a dynamic analysis of the reciprocating compression mechanism of a small refrigeration compressor is performed. In the problem formulation of the mechanism dynamics, the viscous frictional force between the piston and the cylinder wall is considered in order to determine the coupled dynamic behaviors of the piston and the crankshaft. Simultaneous solutions are obtained for the equations of motion of the reciprocating mechanism and the time-dependent Reynolds equations for the lubricating film between the piston and the cylinder wall and for the oil films on the journal bearings. The hydrodynamic forces of the journal bearings are calculated by using a finite bearing model along with the Gümbel boundary condition. A Newton-Raphson procedure is employed in solving the nonlinear equations for the piston and crankshaft. The developed computer program can be used to calculate the complete trajectories of the piston and the crankshaft as functions of the crank angle under compressor-running conditions. The results explored the effects of the radial clearance of the piston, oil viscosity, and mass and mass moment of inertia of the piston and connecting rod on the stability of the compression mechanism.     

Dynamic behavior analysis of reciprocating compressor with subsidence fault considering flexible piston rod

Subsidence wear is inevitable in a reciprocating compressor system, but how to induce body vibration is not clear. We investigated the dynamic behavior of a reciprocating compressor system with subsidence fault considering a flexible piston rod. The flexible piston rod was modeled as a cantilever beam. The dynamic model, in which the influence of the subsidence size, variational cylinder pressure, impact effects and piston rod flexibility are taken into account, was established. Influences of the four parameters including subsidence size, vertical force of flexible piston rod, cylinder pressure and crankshaft speed were analyzed in the dynamic response. Numerical results reveal that with the change of the four parameters, the existence of subsidence fault has a significant effect on the displacement, velocity and acceleration of the crosshead in the transverse direction, but only conspicuously affects the acceleration in the longitudinal direction. In addition to cylinder pressure, the larger the values of the other three parameters, the greater the influences. The cylinder pressure is a time-varying working load. Not only the cylinder pressure but also the open/close time of the valves and change rate of the pressure all affect the dynamic behavior of the system with subsidence. Meanwhile, the change in the vertical force of the flexible piston rod has a remarkable effect on the jump position of the crosshead, but the effect of other parameters is not obvious. In addition, the changes of parameters produce obvious influences on the impact force and the impact range of the crosshead. The stability of the reciprocating compressor system was studied using Poincaré portraits method. The result shows that the system with subsidence fault has chaotic behavior.     

压缩机的现状、发展及新型技术展望

扼要地提及了现有压缩机的技术现状、发展特点以及近年来专利文献中出现的新型设计概念。对活塞往复压缩机、螺杆式压缩机、旋涡式压缩机以及旋转式压缩机等典型的压缩机技术进行了概述,对上述典型压缩机的应用特点与前景进行了分析,并从结构原理解析了能够实现低成本、高效率的无余隙活塞往复压缩机的可行性。以使用压缩机数量最多的空调与制冷领域,尤其是其中的家用空调器与家用冰箱行业为例来阐述相关问题。     

Numerical analysis of the piston secondary dynamics in reciprocating compressors

In this study, a numerical analysis for the piston secondary dynamics of small refrigeration reciprocating compressors is performed. In general, the length of cylinder in this class of compressors is shortened to diminish the frictional losses of the piston-cylinder system. So, the contacting length between piston and cylinder wall is in variable with the rotating crank angle around the BDC of the reciprocating piston. In the problem formulation of the piston dynamics, the variation in bearing length of the piston and all corresponding forces and moments are considered in order to determine the piston trajectory, velocity and acceleration at each step. A Newton-Raphson procedure was employed in solving the secondary dynamic equations of the piston. The developed computer program can be used to calculate the entire piston trajectory and the lubrication characteristics as functions of crank angle under compressor running conditions. The results explored the effects of some design parameters and operating conditions on the stability of the piston, the oil leakage, and friction losses.     

Comparison of the Dynamic Behavior and Lubrication Characteristics of a Reciprocating Compressor Crankshaft in Both Finite and Short Bearing Models©

The compression force of refrigerant gas, the viscous and inertial force of the piston, and the centrifugal force of balancer weight induce rotating whirl of the crankshaft in a small reciprocating compressor. It is necessary to develop an analytical model for the accurate prediction of dynamic behavior of the compressor mechanism having coupled characteristics between the piston and crankshaft. The reciprocating compression mechanism is dynamically modeled by considering the viscous frictional force of a piston and the variation in the contact length of the piston-cylinder system, and then numerical analysis is performed for the coupled dynamic behavior of the piston and crankshaft. For the accurate predictions of the dynamic behavior and characteristics of lubrication of the crankshaft-journal bearing system, a finite bearing model is adopted. In addition, the dynamic trajectory and characteristics of lubrication of the crankshaft such as power consumption and oil leakage are compared between the finite bearing model and the short bearing approximation. The influences of the variation in the radial clearance of the journal bearings, lubricant viscosity, and mass and mass moment of inertia of the piston and connecting rod on the dynamic behavior and characteristics of lubrication such as power consumption and oil leakage are investigated.     

摆杆约束往复活塞式无油润滑空气压缩机的研究

提出一种新型往复活塞式无油润滑空气压缩机,在传统曲柄连杆机构的基础上增设一个摆杆机构,以此约束连杆和活塞以近乎直线往复的方式进行工作,从而缓解活塞及密封环对气缸的侧压力与敲击强度。与传统机型相比较,新型压缩机摩擦功减小了7.4%,噪声下降约1dB(A),密封环寿命提高约10%,高度降低24%。建立了新型压缩机的数学模型,对其摆杆约束机构的特性进行了分析。研究表明:增设摆杆可以大幅度地减小活塞及密封环相对于气缸的摆动幅度,有利于降低它们对气缸的侧压力和敲击强度;另外,曲柄的运转方向对摆杆机构的运动学特性和动力学特性影响较为明显,将机构的急回行程与压缩机的进气行程呼应设置有利于改善摆杆的受力状况。     

利用Excel与AutoCAD绘制活塞压缩机动力曲线及飞轮矩面积矢量图

活塞压缩机动力曲线及飞轮矩面积矢量图的绘制可以通过Excel与AutoCAD两个软件相互结合来实现.利用Excel中的函数来处理在动力计算中的众多数据,通过AutoCAD软件的绘图和曲线处理功能,自动生成动力曲线、飞轮矩矢量图从而求出压缩机组所能允许的最小飞轮矩.     

基于示功图的往复压缩机故障诊断技术

往复压缩机结构复杂、激励源多,常规的机械振动声学法难以满足压缩机故障诊断的需要.示功图是有效的参数法诊断手段,是反应设备内部能量循环的最佳方式,可在较深层次上诊断压缩机故障.介绍了往复压缩机气缸内动态压力的测取方法,比较了常用的示功图测试装置,详细阐述了基于示功图分析的故障诊断方法,并对常见的进气阀、排气阀、活塞环泄漏故障进行了基于示功图法的故障分析.     

往复压缩机气阀所受动态气体力的探讨

通过分析往复压缩机气阀的工作原理和阀片的运动规律,阐述了动态气体力对阀片开启阶段的影响,并把动态气体力和静态气体力做比较,说明动态气体力对阀片运动影响的重要。     

CFA34往复压缩机排气温度高原因分析及处理

针对高压空气系统中CFA34往复压缩机末级排气温度高报警故障,通过对往复压缩机排气温度高常见原因分析,从气阀、活塞环、中间水冷器、进气缓冲罐滤网、冷干机等进行故障排查,找到故障症结并提出处理措施,为此类往复压缩机故障分析与处理提供了参考。     

往复式变频压缩机在CNG子站系统中的应用

对定频、变频与液压3种往复活塞式压缩机在CNG子站系统中应用进行了对比分析。模拟了压缩机排气量、轴功率随吸排气压力的变化关系,得到了性能变化的曲线图。数值模拟结果与压缩机的实际运行特性表明,CNG子站用变频往复活塞式压缩机在排气量、能耗、运行时间和智能化等性能指标方面更具竞争性。     

时频域分析在往复压缩机活塞磨损故障诊断中的应用

采用振动波形的时频域分析法对往复压缩机气缸的活塞磨损故障进行诊断。通过采集往复压缩机气缸等部位的振动信号并进行时域特征求解和波形分析,利用傅里叶变换将时域信号转换为频域信号,结合信号的频谱图,实现对活塞磨损故障的诊断。实际应用中,首先对压缩机进行监测,提出故障原因,然后现场拆机检修,最后进行复测验证,这一闭环的监测过程取得了良好的效果。     

活塞式制冷压缩机活塞与汽缸间隙迷宫密封的理论研究

对活塞式制冷压缩机工作过程进行了数值模拟,建立了活塞与汽缸迷宫密封的数学模型,分析了泄漏量随活塞与汽缸间隙及迷宫槽间距变化的关系.     

Numerical Analyses of Hydrodynamic Lubrication and Dynamics of the Rolling Piston and Crankshaft in a Rotary Compressor

In this article, numerical analyses of hydrodynamic lubrication and dynamics of the crank, rolling piston, and vane were carried out to study the tribological performance of a rotary compressor. Dimensionless Reynolds equations of journal and thrust bearings in dynamic load condition were derived and solved numerically. To deal with the lubrication of the rolling piston, the effect of the nonuniformity of tangential velocity over the bearing surface on the Reynolds equation was taken into account. In addition, combined with the analyses of dynamics and kinematics of the crank, piston, and vane, the angular velocities of the crank and piston as well as the motion mode between the piston and vane were studied. Analysis results illustrate characteristic oil film pressure distributions of the crank and piston bearings, which are different from that of common journal bearings. Under the influences of dynamic load and eccentricity of the cam, the wedge effect as well as the stretch and squeeze effect contribute greatly to hydrodynamic pressure. The relative motion mode between the piston and vane tip is not always pure sliding but accompanies rolling in some cases, which depends on the magnitude of the friction coefficient between the piston and vane tip. The analysis results are helpful for the improvement of rotary compressor design.     

往复压缩机变工况下吸气阀运动及冲击特性研究

基于局部行程压开进气阀的往复压缩机无级气量调节系统采用液压系统驱动机械执行机构控制吸气阀的开启时间实现气量调节。本文通过建立气量调节工况下往复压缩机工作循环的数学模型与吸气阀阀片运动的数学模型,模拟了不同负荷下气缸内动态压力,分析执行机构外力瞬间撤销下吸气阀阀片自由关闭时的运动规律;利用AMESim软件对复位弹簧在不同的弹簧刚度下执行机构运动规律进行研究;通过实验与仿真结果对比分析,确定了气量调节工况下吸气阀运动规律和气量调节工况下缸体振动冲击的来源;为往复压缩机无级气量调节系统的研发和气量调节工况下往复压缩机吸气阀故障诊断提供理论依据。     

往复活塞式压缩机及其运动转换机构的发展

论述了当前压缩机的发展与运动转换机构发展的关系,对几种采用不同运动转换机构的新型压缩机的工作原理、机构特点、动力特性和应用范围作了分析。     

基于往复压缩机轴心轨迹特征的故障诊断方法研究

往复压缩机的故障诊断一直以来都是研究工作的重点问题,对其关键运动部件的监测诊断更是研究的热点之一.当往复压缩机发生运动部件磨损、撞缸等故障时,活塞杆的运行状态会发生改变,进而引起活塞杆轴心轨迹的变化.因此,提出了一种基于活塞杆轴心轨迹的往复压缩机智能诊断方法.首先,文章利用改进的离散点轮廓包络方法提取活塞杆轴心轨迹特征...     

碳化钨涂层活塞杆的研制

在往复压缩机中活塞杆的耐磨、耐蚀性的问题始终是提高产品质量的一大难题。作者研制出一种碳化钨涂层活塞杆,并经三年试车考验,效果良好。     

间隙密封高频往复运动活塞偏移特性研究

在间隙密封下的高频往复运动活塞组成的热力机械中,活塞平衡位置发生偏移的现象称为活塞偏移现象,这一现象普遍存在。对于线性压缩机和自由活塞斯特林发电机,活塞偏移将导致板簧容易断裂、输出效率下降甚至发生撞缸等严重后果。为研究间隙密封活塞偏移的内部机制以及其影响因素,建立间隙流场的流动泄漏模型,并通过数值模拟验证模型准确性。以百瓦级自由活塞斯特林发电机活塞的密封结构为研究对象,建立热力学和动力学耦合模型,分析间隙和外力对活塞偏移的影响规律。研究表明：一个周期内通过间隙的净泄漏量大于0是导致间隙密封活塞发生偏移的根本原因;在一定条件下,间隙和外力越大,活塞偏移越明显。