论文总字数：30800字

摘 要

在现代工业中，泵是经常使用的输送流体的机器，它的类型多种多样。本文的研究对象是低温泵，它是一种用来输送低温介质的离心泵。本文采用数值模拟的方法，研究分析了低温泵在输送相变介质时内部流场的流动情况，并对其进行了扬程和水力效率的性能预测。研究结果对低温泵的优化设计和泵性能的提高具有一定的参考意义，本文主要研究内容及结论如下：

（1）建立了低温泵模型，通过ICEM对叶轮和蜗壳分别进行网格划分，并将其进行组装。简要介绍了Fluent软件中低温泵内流动模拟时的边界条件的设置以及数值计算方法中的控制方程和湍流模型的选择。

（2）研究了量纲分析法中的白金汉姆法，根据白金汉姆法的基本定理推算出低温泵无量纲数的表达式，推导输送不同物性介质模型泵和原型泵的相似准则。制定模型泵与原型泵的模化方案，对上面筛选出的最佳方案一一进行模拟。通过分析，得出根据相似理论设计的泵的无量纲性能曲线同样可以用一样的无量纲性能曲线来表示，模型泵的性能可以转换成原型泵的性能的结论。

（3）使用了Fluent计算软件来对低温泵内部流场的流动情况进行定常模拟，进行了边界、壁面条件等的设置。

（4）研究了低温泵内输送单相介质时的压力云图，结果表明，压力总体分布较为平均，叶轮入口处压力最小并且随着叶轮方向压力渐渐增大。随着流量的增大，蜗壳进口出压力最小，出口处的压力逐渐增大。在不同工况时，进口流量的增大对叶轮处压力影响不大。它的速度矢量图的研究结果表明：随着流量增大，泵内流速增大，蜗壳出口处速度最小，叶轮处速度随着叶轮方向逐渐增大。在不同工况时泵速度变化趋势一致，泵的性能稳定。

（5）研究了低温泵在输送单相介质时的外特性，结果表明，在转速一定的条件下，当流量小的时候扬程基本变化不大，当泵内流量达到某一数值时，扬程开始下降。水力效率先增大后减小，当流量为某一固定值时此时水力效率最大。

（6）研究了低温泵内输送气液两相介质时的压力云图，结果表明，在叶轮中心处压力为负值，压力随着叶轮方向渐渐增大且在叶轮进口处最小，从叶轮以及蜗壳的进口一直到出口，其压力都呈现逐步升高的趋势。速度矢量图的研究结果表明：在不同流量的条件下，速度矢量图的趋势大致相似，泵的性能较为稳定。它的气相体积分布图表明：随着流量增大，各工况下气相分布情况几乎一致，说明泵性能稳定。

（7）研究了低温泵在输送气液两相介质时的外特性，结果表明，随着流量的增大，扬程逐渐减小，水力效率逐渐增大，当达到某一特定的值时，水力效率逐渐降低。

关键词：低温泵、相变介质、相似准则、数值模拟、性能预测

Modeling test method and performance prediction of phase change medium delivered by cryogenic pump

Abstract

In modern industry, pumps are often used for conveying fluids and their types are varied. The research object of this dissertation is cryogenic pump, which is a kind of centrifugal pump used to transport cryogenic medium.In this dissertation, the numerical simulation method is used to study and analyze the flow situation of the internal flow field of the low-temperature pump in the transportation of phase change medium.The performance prediction of head and hydraulic efficiency is also made. The research results have certain reference significance for the optimal design of low temperature pump and the improvement of pump performance.The main research contents and conclusions are as follows:

1. The flow field modeling inside the cryogenic pump was studied. The internal flow fields of the impeller and the volute were meshed and assembled by ICEM. The internal flow fields of impeller and volute were meshed and assembled by ICEM. This dissertation briefly introduced the setting of boundary conditions, the selection of control equation and turbulence model in the numerical calculation method in the flow simulation of low temperature pump in fluent software.
2. Based on the basic theorem of Buckingham method, the expression of dimensionless number of cryogenic pump and the similarity criterion of model pump ,prototype pump conveying different physical medium was deduced. The modeling scheme of the model pump and the prototype pump for transporting clean water and phase change medium was formulated. The best scheme selected above was simulated one by one. Based on the analysis of the simulation results.It is concluded that the dimensionless performance curve of the pump designed according to the similarity theory can also be represented by the same dimensionless performance curve, and the performance of the model pump can be transformed into that of the prototype pump.
3. In this dissertation, the specific steps and the setting of boundary and wall conditions for the flow simulation of the internal flow field of cryogenic pump using Fluent time-invariant numerical simulation were described in detail.
4. The pressure cloud charts of single-phase medium in low-temperature pump was studied. The results show that the overall pressure distribution is relatively average, and the pressure at the inlet of impeller is the smallest and gradually increases with the pressure in the direction of impeller. With the increase of the flow, the inlet pressure of the volute is the smallest, and the pressure at the outlet is increasing gradually. Under different working conditions, the increase of inlet flow has little effect on the pressure at the impeller. The results of the velocity vector diagram show that the velocity in the pump increases with the increase of the flow. The velocity at the outlet of the volute is the smallest, and the velocity at the impeller increases with the direction of the impeller. The variation trend of pump speed in different working conditions is consistent and the performance of the pump is stable.
5. The external characteristics of the low-temperature pump in the transmission of single-phase medium were studied. The results show that under the condition of a certain speed, when the flow rate is small, the head basically changes little, when the flow rate in the pump reaches a certain value, the head begins to decline. The hydraulic efficiency increases first and then decreases. When the flow rate is a fixed value, the hydraulic efficiency is the largest.

（6）The results show that the pressure at the center of impeller is negative, and the pressure increases gradually with the direction of impeller and is the smallest at the inlet of impeller. The pressure increases gradually from the inlet of impeller and volute to the outlet. The research results of velocity vector graph show that, Under the condition of different flow rate, the trend of velocity vector graph is similar, and the performance of pump is stable. Its gas volume distribution diagram shows that: with the increase of flow rate, the gas distribution is almost the same under all working conditions, indicating that the pump performance is stable.

1. In this dissertation, the external characteristics of low temperature pump in the transportation of gas-liquid two-phase medium were analyzed. It is found that with the increase of flow, the head decreases gradually. The hydraulic efficiency increases gradually. When reaching a certain value, the hydraulic efficiency decreases gradually.

Keywords: Cryogenic pump; Similarity criterion; Numerical simulation; Performance prediction

目 录

摘 要 I

Abstract III

第一章 绪论 1

1.1 课题背景 1

1.2 低温泵相关理论 1

1.2.1 低温泵的结构和组成 1

1.2.2 现代低温泵设计 2

1.2.3 低温泵的输送介质 2

1.3 国内外研究现状及发展方向 3

1.3.1 国内研究现状 3

1.3.2 国外研究现状 3

1.3.3 未来发展方向 4

第二章 低温泵的实体建模与网格划分 5

2.1 低温泵的三维建模 5

2.1.1 叶轮的三维建模 5

2.1.2 蜗壳的实体建模 7

2.1.3 建立整体三维实体模型 8

2.2 网格划分 8

2.2.1 网格的类型 8

2.2.2 三维实体模型的网格划分 9

2.2.3 网格质量检查 9

2.3 边界条件设置 9

2.3.1 流场的耦合模型 9

2.3.2 边界条件的介绍 9

2.3.3 边界条件设定 10

2.4 Fluent介绍 10

2.5 数值计算方法 10

2.5.1 控制方程 10

2.5.2 三维湍流模型 11

2.6 本章小结 12

第三章 低温泵输送相变介质的模化试验方法及其方案 13

3.1 量纲分析法 13

3.2 低温泵输送单相介质的模化试验方法 13

3.2.1 无量纲特性分析 13

3.2.2 模化方案设计 15

3.3 低温泵输送气液两相介质的模化试验方法 16

3.3.1 无量纲特性分析 16

3.3.2 模化方案设计 17

3.4 各方案下的模化设计结果及分析 18

3.6 本章小结 21

第四章 低温泵内定常数值模拟分析 23

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