超低比转速高速离心泵水力设计与数值模拟

发布时间：2018-03-07 02:10

本文选题：高速泵　切入点：复合叶轮　出处：《扬州大学》2017年硕士论文　论文类型：学位论文

【摘要】：低比转速高速离心泵具有小流量、高扬程、结构紧凑等特点,被广泛应用于石油化工、航空航天等领域。但因其转速高,所以其内部流动与常见离心泵存在较大差异,如:在叶片吸力面易产生尾迹流,而压力面易出现射流等。高速泵的内外特性研究—直是流体机械领域重点研究课题。本文结合流量Qd=10m3/h、扬程H=410m、转速n = 8500r/min,比转速ns=18的高速泵的复合叶轮、蜗壳、诱导轮水力设计,利用三维湍流数值模拟方法,基于ANSYS CFX软件平台,对设计的高速离心泵进行全流道三维定常和非定常仿真计算,探索了高速离心泵内外特性的规律。研究得出了叶轮、蜗壳和诱导轮内的速度、压力分布特征,数值模拟预测水泵的外特性以及隔舌处的压力脉动特性。主要工作如下:(1)利用速度系数法和加大流量法,设计了流量Qd=10m3/h、扬程H = 410m、转速n = 8500r/min,比转速ns=18的高速泵的复合叶轮、蜗壳和等螺距诱导轮。(2)利用PRO/E和GAMBIT软件对离心泵的进水管、复合叶轮、蜗壳及等螺距诱导轮等过流部件进行三维建模,运用非结构化网格离散过流部件计算域。(3)为探求转速变化对离心泵内部流动影响,基于雷诺时均N-S控制方程和标准的k-ε湍流模型,利用ANSYSCFX软件,数值模拟了设计流量下6种不同转速的水泵内部流动,比较分析了转速对叶轮内静压和相对速度分布规律的影响。(4)针对设计转速n = 8500r/min,数值模拟离心泵高速运行在小流量0.4Qd、设计流量1.0Qd和大流量1.3Qd三种工况下的内外特性,研究得到了不同流量下复合叶轮内部压力场、速度场及蜗壳隔舌处的静压力场分布,数模预测高速泵的能量特性。(5)对带前置诱导轮的高速离心泵进行了三维定常数湍流值模拟,得出了小流量0.4Qd、设计流量1.0Qd和大流量1.3Qd三种工况的内外特性,对比了不同流量下诱导轮、叶轮的静压场和相对速度场分布;分析了前置诱导对水泵能量特性的影响。(6)数值模拟了带前置诱导轮的高速离心泵蜗壳与叶轮耦合非定常流动,得到了蜗壳隔舌处3个不同监测点,在小流量0.4Qd、设计流量1.0Qd和大流量1.3Qd三种工况下的压力脉动规律,对比分析了它们的时域特性和频域特性。(7)数值模拟了带前置诱导轮的高速离心泵叶轮叶栅及子午面上的空化情况,并就偏离设计点工况下诱导轮对泵汽蚀余量的影响进行了预测。
[Abstract]:Low specific speed and high speed centrifugal pump is widely used in petrochemical, aerospace and other fields because of its small flow rate, high head and compact structure. However, because of its high speed, its internal flow is quite different from that of common centrifugal pump. For example, wake flow is easily produced on the suction surface of the blade, The internal and external characteristics of high speed pump is a key research topic in fluid machinery field. In this paper, the hydraulic design of compound impeller, volute and induction wheel of high speed pump with flow rate QD 10m / h, head H = 410m, rotational speed n = 8500rr / min, specific speed ns=18, is introduced. Based on the ANSYS CFX software platform, the three-dimensional steady and unsteady simulation of the designed high-speed centrifugal pump is carried out by using the three-dimensional turbulent numerical simulation method, and the internal and external characteristics of the high-speed centrifugal pump are explored, and the impeller is obtained. The velocity, pressure distribution, numerical simulation and prediction of the external characteristics of the pump and the pressure pulsation of the tongue in the volute and the inducer wheel. The main work is as follows: 1) using the velocity coefficient method and the method of increasing the flow rate, The compound impeller of high speed pump with specific speed ns=18, volute and equal pitch inducer are designed by using PRO/E and GAMBIT software. The inlet pipe and compound impeller of centrifugal pump are designed by using PRO/E and GAMBIT software, the flow rate is 10m3 / h, the head H = 410m, the rotational speed n = 8500rr / min, the compound impeller of high speed pump with specific speed ns=18. The three-dimensional model of volute and equal pitch inducer is used to study the effect of speed change on the flow in centrifugal pump by using unstructured grid discrete flow unit. Based on the Reynolds time-averaged N-S governing equation and the standard k- 蔚 turbulence model, the internal flow of the pump with six different rotational speeds under the designed flow rate is numerically simulated by using ANSYSCFX software. This paper compares and analyzes the influence of rotating speed on the static pressure and relative velocity distribution of impeller. According to the design speed n = 8500 r / min, the numerical simulation of the internal and external characteristics of centrifugal pump under three working conditions: small flow rate 0.4Qd, design flow rate 1.0Qd and large flow rate 1.3Qd, is carried out. The internal pressure field, velocity field and static pressure field distribution at the tongue of the volute are obtained at different flow rates. The numerical model is used to predict the energy characteristics of the high speed pump. (5) the three dimensional constant turbulence value of the high speed centrifugal pump with the leading inducer is simulated. The internal and external characteristics of small flow rate 0.4Qd, design flow rate 1.0Qd and large flow rate 1.3Qd are obtained, and the distribution of static pressure field and relative velocity field of induction wheel and impeller under different flow rates are compared. The influence of leading inducement on pump energy characteristics is analyzed. Numerical simulation of the coupling unsteady flow between volute and impeller of high speed centrifugal pump with leading inductor wheel is carried out, and three different monitoring points at the tongue of volute are obtained. When the flow rate is 0.4Qd, the pressure fluctuation law is obtained under three working conditions, namely, the design flow rate of 1.0Qd and the large flow rate of 1.3Qd. The numerical simulation of cavitation on the cascade and meridian of high speed centrifugal pump impeller with leading inducer is carried out by comparing their time-domain and frequency-domain characteristics. The influence of the inducer on the cavitation margin of the pump is forecasted when it deviates from the design point.
【学位授予单位】：扬州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH311

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