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An investigation is presented on the unsteady flow behaviour near the tongue region of a single-suction volute-type centrifugal pump with a specific speed of 0.47. For this study, the flow through the test pump, which was available at laboratory, was simulated by means of a commercial CFD software that solved the Navier-Stokes equations for three-dimensional unsteady flow (3D-URANS). A sensitivity analysis of the numerical model was performed in order to impose appropriate parameters regarding grid size, time step size and turbulence model. The predictions of the numerical model were contrasted with experimental results of both global (flow-head curve and static pressure distribution at volute front side) and unsteady variables (unsteady pressure distribution at the volute front side filtered at the blade-passing frequency). Once validated, the model was used to study the flow pulsations associated to the interaction between the impeller blades and the volute tongue as a function of the flow rate, for several flow rates ranging from 20% to 160% of the nominal flow rate. The study allowed relating the blade passage with the pulsations of pressure and tangential and radial velocity at a number of reference locations in the near-tongue region. The numerical model was also used to evaluate the evolution of the leakage flow between the impeller-tongue gap and of the flow exiting the impeller through some specific angular intervals, during one single-blade passage.  相似文献
四旋翼微型飞行器控制系统设计   总被引:6,自引:1,他引:5  
四旋翼微型飞行器是一种以4个电机作为动力装置,通过调节电机转速来控制飞行的欠驱动系统;为了实现四旋翼微型飞行器的自主飞行控制,对飞行控制系统进行了初步设计,并且以C8051F020单片机为计算控制单元,给出了飞行控制系统的硬件设计,研究了设计中的关键技术;由于采用贴片封装和低功耗的元器件,使飞行器具有重量轻、体积小、功耗低的优点;经过多次室内试验,该硬件设计性能可靠,能满足飞行器起飞、悬停、降落等飞行模态的控制要求。  相似文献
解耦变结构交流速度控制系统的研究   总被引:5,自引:1,他引:4  
本文提出了一种新型的AC速度控制系统——解耦变结构控制系统。它利用解耦原理简化感应电动机的数学模型,然后采用变结构控制原理克服转子电阻随温度变化带来的不良影响,保证了系统的动态和静态性能。文中推导出解耦变结构速度控制系统的数学模型、滑模控制器结构,并给出仿真结果。  相似文献
航空发动机试车中转子故障诊断   总被引:5,自引:3,他引:2  
航空发动机成本高,寿命低,难维护;发动机故障造成飞机失事的例子时有发生,倍受人们的重视;据统计,该类故障中的80%来自于结构复杂、高速旋转的转子部件;讨论生产试车中转子振动故障的早期诊断技术,首先分析转子、叶片、轴承、齿轮故障的特征;而后通过实时的功率谱、倒频谱分析技术识别与此特征对应的故障位置、类型及程度;最后以某型发动机转子振动的实例说明该项技术的实际应用。  相似文献
滚动轴承-转子系统支承松动时的复杂运动研究   总被引:4,自引:1,他引:3       下载免费PDF全文
基于转子动力学、Hertz理论和非线性动力学理论,针对一端支座松动的滚动轴承-转子系统的运动特征,考虑了松动间隙的非线性情况,建立了系统的动力学方程.在对转子系统动力学方程进行数值积分之后,通过分叉图、庞加莱图、相图和关联维数等显示了转子系统随转速变化和松动间隙的扩展会出现复杂动力学现象,并且研究了滚动轴承-转子系统在支承松动时的分岔和混沌运动及其变化规律,得出了有工程价值的结论,这些结论可为该类故障的诊断提供参考.  相似文献
This work deals with the stabilization and collision avoidance control of a riderless bicycle (see Figure 1). It is assumed here that the bicycle is controlled by a pedalling torque, a directional torque, and by a rotor mounted on the crossbar that generates a tilting torque.Given two points rA, rB, and a circular obstacle in the horizontal plane. Also, given a time interval [0, tf], where 0 < tf < ∞. It is shown here that by applying a kind of inverse dynamics control, the motion of the bicycle is stabilized while simultaneously controlling its speed and direction in such a manner that the point of contact between the bicycle's rear wheel and the horizontal plane will be able, during [0, tf], to move from rA to rB without hitting the obstacle.  相似文献
Flexible rotor is a crucial mechanical component of a diverse range of rotating machineries and its condition monitoring and fault diagnosis are of particular importance to the modern industry. In this paper, Bayesian belief network (BBN) is applied to the fault inference for rotating flexible rotors with attempt to enhance the reasoning capacity under conditions of uncertainty. A generalized three-layer configuration of BBN for the fault inference of rotating machinery is developed by fully incorporating human experts’ knowledge, machine faults and fault symptoms as well as machine running conditions. Compared with the Naive diagnosis network, the proposed topological structure of causalities takes account of more practical and complete diagnostic information in fault diagnosis. The network tallies well with the practical thinking of field experts in the whole processes of machine fault diagnosis. The applications of the proposed BBN network in the uncertainty inference of rotating flexible rotors show good agreements with our knowledge and practical experience of diagnosis.  相似文献
Rigid coupling and flexible connection made up of elastic coupling units are widely applied to rotor-bearing system with multi-branched shafting system. This paper proposes a modal synthesis method of lateral vibration analysis for such kind of rotor-bearing system. When the proposed approach is developed, the elastic coupling unit is defined as “flexible substructure” which is treated individually and the other parts are partitioned into some substructures which are analyzed by finite element method. The lower-frequency normal modes of the substructures are retained; whereas the higher-frequency normal modes are neglected by a frequency truncation criterion and the residual flexibility of those omitted modes is considered. The lower-frequency normal modes and residual flexibility are considered to be the assumed modes of Rayleigh–Ritz analysis of whole structure. The approach to the treatment of higher-frequency modes leads to a great reduction in the calculation time and a significant improvement in the efficiency of modal synthesis. Examples show that the proposed approach is very effective for the vibration analysis of rotor-bearing system with multi-branched shafting system and the results derived from this approach are in a good agreement with those from transfer matrix method.  相似文献
三相感应电动机的在线故障检测与诊断问题研究   总被引:2,自引:0,他引:2  
本文建立了三相感应电动机的通用故障模型,提出了一种检测、分离、并估计出其转子与定子故障的新方法.最后,应用一个4470千瓦的大型电动机的实际参数作了仿真研究,验证了本文方法的有效性.  相似文献
开关磁阻电动机新型非直接位置传感器技术研究   总被引:2,自引:1,他引:1  
开关磁阻电动机(SRD)的非直接位置传感器技术是开关磁阻研究领域的热门课题之一。本文详细地介绍了一种新型的开关磁阻电机非直接位置传感器方案,这种方案通过测量测试线图的电感来获得实时转子位置信息,并使用了线圈反串技术和串联谐振技术来消除开关磁阻电机内部电磁场对于测试电路的干扰。详细地阐述了方案的工作机理,并给出了如何使用该方案进行开关磁阻电机的正常启动和运行控制的具体实施方法。  相似文献
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