Analytical and CFD modeling of the fluid flow in an eccentric-tube centrifugal oil pump for hermetic compressors

A model is presented for calculating the volume flow rate in an eccentric-tube centrifugal oil pump for reciprocating compressors. The oil pump assembly consists of a pick-up tube with an inclined inlet that is mounted off-center with the crankshaft symmetry axis. The pick-up tube is connected to the shaft channel, a helical groove machined on the crankshaft that facilitates the supply of lubricant to the bearings. The analytical models for the pick-up tube and shaft channel were developed independently and were coupled via a numerical procedure to determine the steady-state volume flow rate in the assembly. The steady-state results were verified against a CFD model, which was also used to evaluate the fluid flow in the oil pump assembly during a start-up transient. A parametric analysis was conducted to quantify the influence of some oil pump geometric parameters, such as the pick-up tube diameter and the shaft eccentricity.     

The helix seal: Sealing concept and rib design

The helix seal is a radial shaft seal with enhancements for better sealing performance. A low angular torque is necessary to minimize kinetic energy loss of the shaft. This is achieved by a lubricating oil film, which is a potential source of leakage. To overcome this, the seal has moulded helix ribs to pump any leaked oil back to the sump. The design of these ribs therefore is a critical element in the seal's design. Here, the authors from NOK Corporation present an analytical method of assessing helix rib design.     

Experimental pure fluid and binary mixture performance in a heat pump equipped with a distillation column

An experimental heat pump system that included a distillation column, accumulator/sump, and heater was experimentally investigated using two different working fluids, R32 and a mixture of R32/134a. Performance variations with changes in sump heater power, condenser and evaporator heat transfer fluid flow, and compressor speed were examined. Heating capacity generally increased with increases in the factors tested. Heating capacity increases were generally smaller with the R32/134a tests than with the R32 tests, except with variations in sump heater power. An increase in sump heater power caused a pronounced increase in the circulating R32 concentration during the mixture tests, and the heating capacity increased markedly. The increase in heating capacity with sump heater power during the R32/134a tests was on par with the increase with compressor power during these same tests. The increase in capacity with sump heater power during the R32/134a tests also was substantial even when compared with the capacity increase with compressor speed during the R32 tests.     

Numerical study on the lubrication oil distribution in a refrigeration rotary compressor

For a rolling piston rotary compressor, oil supply into various lubrication elements has been analytically studied. The lubrication system, consisting of centrifugal shaft pump, radial oil feeding holes, bearings with grooves and some other sliding surfaces has been modeled by employing equivalent electric circuit network. A computer simulation program has been developed to solve the network model of the lubrication system. Its numerical solutions include total oil flow rate into the shaft inlet, oil flow rates in the main and sub journal bearings and in the eccentric bearing, and oil leakages through roller end clearances into suction and compression chambers. Validation of the numerical simulation has been made by the measurement of the total oil flow rate into the shaft. With the aid of computer simulation, parametric studies have also been carried to investigate the effects of the bearing groove shape and groove inclination angle on the bearing oil flow rates.     

Experimental transient performance of a heat pump equipped with a distillation column

A series of experiments were conducted on a heat pump equipped with a distillation column. The system was operated with R32 and with a 30/70% by mass mixture of R32/134a to examine the difference between the transient performance trends with a pure fluid (R32), and those with a zeotropic mixture (R32/134a). Additionally, the effects of varying heat transfer fluid mass flow, compressor speed, and accumulator sump heat input were examined. Each test was 1 h in duration. The heat pump capacities did not generally achieve steady state during the R32/134a tests. Steady state was generally achieved during the R32 tests. As a percentage of the final (end-of-test) capacity, the rate of capacity increase was greater during the R32/134a tests than during those conducted with the pure fluid. The R32/134a tests exhibited capacity oscillations early in each transient that were not present during the R32 tests. The results show that circulating refrigerant mass and composition are the primary controlling factors with regard to transient capacity.     

Nonisothermal flow of a non-Newtonian fluid in the slowly converging channel of a belt worm-conveyor pump under conditions of complex shear

The flow of an anomalously viscous fluid with an exponential rheological equation in the converging channel of the screw of a belt worm-conveyor pump is examined taking into account the circulatory flow of the fluid, the dissipation of mechanical energy, and the exchange of heat with the environment.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 30, No. 6, pp. 1040–1046, June, 1976.     

基于线性回归的单柱塞泵单向阀参数优化

针对单柱塞泵系统中配流单向阀参数不合理所导致的吸油不充分、系统响应慢等问题,提出了一种基于线性回归的多参数优化方法。首先,通过AMESim软件进行单柱塞泵系统仿真分析,并利用MATLAB拟合工具箱分别探讨了不同单向阀参数（弹簧预紧力、弹簧刚度和阀芯质量）与进油口流量的关系。然后,在利用主成分分析法消除各参数之间相关性的基础上,以进油口流量为因变量,弹簧预紧力、弹簧刚度和阀芯质量为自变量,各参数的取值范围为约束条件,建立了基于线性回归的单向阀参数优化模型,并采用遗传算法进行优化求解。最后,根据优化前后的单向阀参数,对单柱塞泵系统进行仿真分析和实验验证。仿真结果表明,优化后进油口流量提高了21.3%;实验结果表明,优化后进油口的实际流量提高了16.8%。研究表明,所提出的多参数优化方法是一种有效的方法,可为单柱塞泵系统中配流单向阀的参数优化提供参考。     

Twin screw oil-free wet compressor for compression–absorption cycle

The performance of a twin screw compressor operating under wet (two-phase) compression conditions in an ammonia–water compression absorption heat pump cycle is investigated both theoretically and experimentally. The paper reports on the influence of the location of liquid intake or, depending what applies, injection angle and mass flow rate of the injected liquid on compressor performance. Labyrinth seals separate the oil-free process side from oil lubricated bearing housing. Labyrinth seals leakage is modelled and its impact on performance is theoretically and experimentally investigated. The need for liquid injection from the discharge side to obtain acceptable performance is discussed based on experimental results.     

离心泵转子动力学模型中流体力的简化

采用叶轮流体力的简化方式可以提高离心泵流体激励诱发振动的计算的准确程度。根据达朗伯原理对试验台架建立了包含离心泵基座的四圆盘三轴段转子动力学模型;将流体力分别简化为叶轮内20 %流体质量、40 %流体质量、CFD集中力与力矩,采用Newmark-隐式算法对转子动力学模型进行瞬态响应分析。结果表明,将叶轮上流体力简化为CFD;所得集中力与力矩时;可有效得出离心泵运转过程中流体激励所诱发的基座振动。而所获得的基座振动位移与加速度幅值均远大于将流体力简化为叶轮内20 %或40 %流体质量所获得的基座振动数值。另一方面,将流体力简化为叶轮内40 %流体质量所获得的基座振动大于简化为叶轮内20 %流体质量所获得的基座振动。     

Failure Analysis of a Locomotive Engine Oil Pump Shaft

In this study, the fracture of a locomotive engine oil pump shaft is investigated. According to the reports, all oil pump shafts of this type fail in short periods of time due to the fracture at a location on the shaft which is in contact with a pinion. Stress analysis showed that the shaft bears torsion and cyclic bending stresses in the fracture site. The fracture surface observations revealed that the cracks are generated from the surface, and fatigue fracture occurs due to the cyclic bending stresses. According to the laboratorial analysis, the shaft is a surface-hardened low alloy steel. The lack of suitable pre-heat treatment and surface hardening and the roughness created by the slippage between the shaft and the pinion are concluded to be responsible for the failure of the oil pump shaft.     

螺杆式制冷压缩机机械密封温度测试与分析

通过轴封测温试验,分析喷油量和轴封腔挡油结构对轴封温度的影响.试验结果表明,增加轴封腔喷油量可以有效降低轴封温度,增加挡油结构可使轴封各处升温均匀,这两项措施都有利于提高螺杆式制冷压缩机运行的可靠性.     

40Cr钢机油泵轴断裂分析

采用化学成分分析、断口分析、硬度测试及金相检验等方法,对某汽车机油泵轴的断裂原因进行了分析。结果表明:该泵轴的断裂为早期疲劳断裂,造成疲劳断裂的主要原因是未按要求对泵轴进行调质处理,致使材料的力学性能未达到设计要求,疲劳强度降低。     

螺旋离心泵转子系统动态响应数值分析

为研究螺旋离心泵转子对流固耦合作用的动态响应信息,以ZJ200-25型双叶片螺旋离心泵为研究对象,利用CFD软件CFX12.1和有限元软件ANSYS Workbench对其进行了考虑流场变载荷和结构相互作用的两场交替联合求解。得到转子受到的激励力以及位移响应频谱特点,结果表明：叶轮受到流场变载荷激励,发生了弯曲及拉伸振动;叶轮径向位移随流量增大而减小,其主频率与径向力主频率同为48.3Hz,轴向力以低频随机波动为主,但轴向位移仅在200Hz以内有较明显的响应,且振幅随频率增加而减小;叶轮质心位移在低阶频率处的振幅不高,高阶频率的振幅逐渐减小,轴向及径向位移均没有振幅过大的情况出现,说明螺旋离心泵转子正常工作时未发生共振,稳定性良好。本文研究结果对螺旋离心泵转子系统的设计改良及振动分析具有一定的参考意义。     

涡轮流量计时间常数校准技术研究

为了校准涡轮流量计的时间常数,建立液体阶跃流量试验装置,该装置利用螺杆泵输送流体形成平台流量,采用内啮合齿轮泵输送流体形成阶跃流量分量,通过控制高速电磁阀的开启与关闭实现阶跃流量分量与平台流量的叠加,最终产生阶跃流量。利用皮托管对阶跃流量产生时间进行评估,结果表明阶跃流量上升时间小于9 ms。在不同阶跃工况下对涡轮流量计开展时间常数校准试验,结果表明：涡轮流量计时间常数并非固定值,且受平台流量影响较大,具有随前平台流量增大而减小的趋势,受阶跃流量幅度影响较小;在小流量范围内,实际测量得到的动态流量系数与理论模型推导得到的动态流量系数偏差较大,而在大流量范围内二者较为吻合。最后对时间常数校准结果进行了不确定度评估,最大扩展不确定度约为10 ms(k=2)。研究成果有助于评估流量计动态特性,有望提高非稳态流量测量的准确度。     

江水源热泵系统取水最佳温差设计研究

在水源热泵系统的应用中,取水温差设计的合理性直接影响输配系统能耗,一般地理位置决定了取水扬程的大小,但对取水量可在满足系统冷热量的前提下,通过优化设计取水温差,同时与机组性能相匹配,最终实现系统高效运行。通过研究水源热泵机组在不同进水温度与不同流量大小下的机组EER值,结合不同流量大小下的输送水泵轴功率变化情况,以制冷系统能效比EERr作为最佳温差的判定依据。     

基于粒子群算法的高黏度大比重物料无轴螺旋输送机构优化设计

 为解决高黏度大比重物料无轴螺旋输送机的螺旋叶片变形问题,利用粒子群优化算法,以无轴螺旋叶片刚度变形最小为优化设计目标,构建了基于粒子群算法的无轴螺旋叶片优化设计模型.应用构建的理论模型,进行了实例设计,并通过实验研究进一步证实该设计方法具有先进性和实用性．将智能算法应用于机械优化设计,为该领域研究提供新思路．     

干式螺杆真空泵振动监测与故障诊断技术的研究

针对干式螺杆真空泵的运行故障,采用振动监测的方法,利用时域波形和频谱分析技术进行故障诊断.阐述了振动测试点和测量信号类型的选择方法,给出诸如转子不平衡、轴弯曲变形、转子不对中、部件松动、流体诱发振动及滚动轴承、齿轮损伤等常见故障的诊断方法.通过工程实例证明,该方法能够有效地判断出故障产生的原因和部位,为故障的早期诊断提供有力监控.     

Einstein制冷系统气泡泵理论模型修正验证研究

基于漂移流模型理论建立了气泡泵理论模型,对Einstein制冷系统中气泡泵在绝热弹状流下的提升特性进行理论分析,并以饱和纯水为工质对气泡泵稳态性能进行实验研究。根据气泡泵性能参数的实验值和理论计算值,采用最小二乘法对气泡泵阻力损失系数进行拟合,对气泡泵理论模型进行修正并得到相应的实验关联式,并对该关联式的可信度进行验证。结果表明：实验结果与理论修正结果吻合性较好,误差在5.3%以内,修正结果具有较强准确性和可行性,完善了气泡泵理论模型。为气泡泵的优化设计提供理论指导,对进一步研究Einstein制冷系统气泡泵性能具有重要参考价值。     

卡环式扭矩测试系统在抽油机上的应用

由于抽油机输出轴的不可拆卸性,目前对于其功率的测试还没有合适手段,本文介绍的方法是采用卡环式扭矩测试系统来实现对抽油机功率的测试,介绍了抽油机的工作原理、卡环式传感器的结构、测试系统的软硬件结构以及此方法的应用领域.     

Simulation model for complex refrigeration systems based on two-phase fluid network – Part II: Model application

A simulation model of complex refrigeration system based on two-phase fluid network is developed in part I of the paper [Shao, S.Q., Shi, W.X., Li, X.T., Yan, Q.S., 2008. Simulation model for complex heat pump systems based on two-phase fluid network – part I: model development. International Journal of Refrigeration 31 (3), 490–499.]. One same fluid network is used in the model to describe the refrigeration system in different operating modes with the method of the factual and fictitious branches. When there are many heat exchangers with concurrent cooling and heating, the traditional models are not able to define the flowing directions. The developed model, however, whether the initial flowing direction of the connecting branches is right or not, is able to predict the flow and heat transfer. Three typical complex refrigeration systems such as the multi-unit inverter air conditioner, heat pump with domestic hot water and multi-unit heat pump dehumidifier are simulated with the developed model as demonstrations on how to use it. The model can evaluate the influences of one or more parameters on the system performance, which can be used for the optimization of the system by all-condition performance analysis. It is shown that the two-phase fluid network model is effective and convenient for the simulation of different complex refrigeration system, especially for performance analysis, system evaluation, and optimization based on the performance prediction.