离心泵扭矩和转速的非定常特性研究

发布时间：2018-08-06 12:41

【摘要】：扭矩和转速是离心泵最重要的两个运行参数,它们是相互联系相互影响的整体,共同反映着离心泵内部流动状态。离心泵—电机作为一个整体系统,在实际运行过程中,由电机产生的扭矩通过转子轴系带动离心泵叶轮旋转对流体做功并将能量传递给流体,是一个水—机—电三物理场耦合的过程,因此研究离心泵扭矩和转速的非定常特性对于掌握离心泵—电机系统的能量转换机理具有十分重要的意义。目前迅速发展的无传感器监测技术,即是通过电机电信号对离心泵的扭矩和转速进行提取,结合不同流态下扭矩和转速的特征,实现离心泵的流态诊断。因此,对离心泵扭矩和转速非定常特性的研究也将为无传感器监测方法提供理论支持。考虑到在离心泵实际运行中水—机—电的耦合作用,对离心泵扭矩和转速的仿真,必须建立水机电三物理场耦合的联合仿真方法,该方法更加贴合物理实际,也将为离心泵非定常特性研究提供新的思路。基于此,本文提出了一种能够实现水—机—电联合仿真的方法,采用试验研究和数值仿真相结合的方式,对离心泵扭矩和转速的非定常特性进行了研究。本研究的主要工作和创新点有:1、建立了简单可行的离心泵水—机—电联合仿真方法,使离心泵扭矩和转速的非定常仿真成为可能,为离心泵内部非定常流动特性的研究提供了新的思路。充分考虑了电机电磁力矩、转子轴系的响应特征、离心泵内部流场的非定常特性三者间的综合作用,最终建立了Fluent—MATLAB/Simulink联合仿真平台。2、搭建了基于虚拟仪器的试验采集平台,利用轴编码器基于变M/T法对转速的瞬态数据进行了高精度的测量。通过Labview编写程序对试验数据进行监测与采集,利用轴编码器基于变M/T法编写的转速采集程序,能够准确地捕捉到转速的动态变化,动态性能良好,数据精确度高。3、基于试验数据,对离心泵扭矩的非定常特性进行了系统的分析,建立了扭矩的时频特征谱。在时域上,离心泵的扭矩随着流量的增大近似线性增加,而扭矩波动程度则随着流量的增大而趋于平稳;在频域上,建立了不同流量及空化程度下扭矩的频率特征谱。在空化条件下,离心泵的扭矩具有明显的特征,本文建立了不同流量下离心泵扭矩的空化特性曲线。在不同流量及空化条件下,扭矩的主频均为轴频,波动程度与流量和空化状态无关,泵内部流动状态对扭矩主频作用不明显。4、基于试验数据,对离心泵转速的非定常特性进行了系统的分析,分别在时域、频域和时频联合域对离心泵的转速进行了研究,建立了转速的时频特征谱。在时域上,转速随流量的增大而降低,空化初生时转速波动程度最大;在频域上,获得了不同流量及不同空化程度下频域特征谱;在时频联合域上,转速信号的主要能量集中在39Hz-46.9Hz,该部分能量占整个转速信号能量的50%以上。
[Abstract]:Torque and rotational speed are the two most important operating parameters of centrifugal pump. They are the whole of interrelation and mutual influence and reflect the flow state of centrifugal pump together. Centrifugal pump-motor as a whole system, in the actual operation process, the torque generated by the motor through the rotor shaft to drive the centrifugal pump impeller rotation work on the fluid and transfer the energy to the fluid, The study of the unsteady characteristics of torque and rotational speed of centrifugal pump is very important for mastering the energy conversion mechanism of centrifugal pump motor system. At present, sensorless monitoring technology is developed rapidly, that is, the torque and speed of centrifugal pump are extracted by electrical signal of motor, and the characteristics of torque and speed under different flow state are combined to realize the diagnosis of flow state of centrifugal pump. Therefore, the research on the unsteady characteristics of torque and speed of centrifugal pump will also provide theoretical support for sensorless monitoring. Considering the coupling effect of water, machine and electricity in the actual operation of centrifugal pump, the simulation of torque and rotational speed of centrifugal pump must be carried out by establishing a joint simulation method of coupling of three physical fields of water electromechanical, which is more in line with physical reality, It will also provide new ideas for the study of the unsteady characteristics of centrifugal pumps. Based on this, this paper presents a method to realize the combined simulation of water, machine and electricity. The unsteady characteristics of torque and rotational speed of centrifugal pump are studied by the combination of experimental research and numerical simulation. The main work and innovation of this study are as follows: 1. A simple and feasible simulation method of centrifugal pump with water, machine and electricity is established, which makes it possible to simulate the torque and rotational speed of centrifugal pump unsteady. It provides a new idea for the study of unsteady flow characteristics in centrifugal pump. Considering the electromagnetic torque of the motor, the response characteristics of rotor shafting and the unsteady characteristics of the flow field in the centrifugal pump, the combined simulation platform of Fluent-MATLAB/Simulink. 2 is established, and the experimental acquisition platform based on virtual instrument is built. Based on the variable M / T method, the shaft encoder is used to measure the rotational speed with high accuracy. The Labview program is used to monitor and collect the test data, and the rotational speed acquisition program based on the variable M / T method is used to capture the dynamic change of the rotational speed accurately, and the dynamic performance is good. Based on the experimental data, the unsteady characteristic of torque of centrifugal pump is analyzed systematically, and the time-frequency characteristic spectrum of torque is established. In time domain, the torque of centrifugal pump increases linearly with the increase of flow rate, while the fluctuation degree of torque tends to be stable with the increase of flow rate. In frequency domain, the frequency characteristic spectrum of torque with different flow rate and cavitation degree is established. Under cavitation conditions, the torque of centrifugal pump has obvious characteristics. In this paper, the cavitation characteristic curve of centrifugal pump torque with different flow rate is established. Under different flow and cavitation conditions, the main frequency of torque is axial frequency, and the fluctuation degree is independent of flow rate and cavitation state. The unsteady characteristics of centrifugal pump speed are systematically analyzed. The rotational speed of centrifugal pump is studied in time domain, frequency domain and time-frequency combined domain, respectively, and the time-frequency characteristic spectrum of speed is established. In time domain, the rotational speed decreases with the increase of flow rate, and the fluctuation degree of rotational speed is the greatest at the beginning of cavitation. In frequency domain, the characteristic spectrum of frequency domain is obtained under different flow rate and different cavitation degree; in time-frequency joint domain, the characteristic spectrum of frequency domain is obtained. The main energy of the rotational speed signal is 39Hz-46.9 Hz, which accounts for more than 50% of the total rotational speed signal energy.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH311

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