﻿ 对旋风机转速改变对其气动特性的影响<sup>*</sup>
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Influence of rotating speed variation on aerodynamic characteristics for counter rotating fan
SUN Wenlong, FANG Xiangjun
School of Energy and Power Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100083, China
Received: 2017-03-21; Accepted: 2017-05-12; Published online: 2017-06-19 11:55
Corresponding author. FANG Xiangjun, E-mail: 185352895@qq.com
Abstract: The aerodynamic characteristics of counter rotating fan was effected by rotating speed ratio of first and second stages, appropriate speed ratio could improve aerodynamic characteristics of counter rotating fan. The influence of rotating speed variation of first and second stages on the aerodynamic characteristics of counter rotating fan was studied by numeral calculation and experiments. First, the influence of changes in rotating speed on powers and internal flow parameters was quantitatively analyzed by velocity triangle. Then, the results of calculation were compared with the results of experiment to analyze the performance of fan under the standard rotating speed. Finally, air flows in the fan were analyzed with the results of calculation. It is found that the flow parameters and performance of fan change more efficiently by changing the rotating speed of the first stage under the same rotating speed changing percentage of first and second stages when the conditions of inlet keep invariant. Combined with the performance of fan and the demand of reality, the most optimal rotating speed ratio is 1.1:1. The efficiency of counter rotating fan is 75% under this rotating speed ratio and transmission efficiency of 88.4%.
Key words: counter rotating fan     CFD     rotating speed ratio     performance     velocity triangle     aerodynamic characteristics

1 对旋风机物理模型和数学模型 1.1 物理模型

 图 1 对旋风机的基本结构及测点分布 Fig. 1 Fundamental structure of counter rotating fan and distribution of measuring points
 图 2 对旋风机的叶片几何 Fig. 2 Blade geometry of counter rotating fan
1.2 数值方法

1.3 网格模型

 图 3 计算网格 Fig. 3 Computational grid
1.4 边界条件

2 速度三角形分析

 图 4 对旋式轴流风机基元级速度三角形变化示意图 Fig. 4 Sketch map of velocity triangle in elementary stage for counter rotating axial flow fan

2.1 轮缘功变化分析

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2.2 气流角变化分析

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3 数值计算与实验数据比较和分析 3.1 数值计算与实验数据比较

 图 5 转速3 000-3 000计算总压升和总功率与实验对比 Fig. 5 Comparison of calculated and measured total pressurerise and total power under rotating speed 3 000-3 000
3.2 数值计算结果流场分析

 图 6 不同转速下50%叶高处静压云图 Fig. 6 Contours of static pressure on middle section under different rotating speeds

 图 7 不同转速下50%叶高处流线图 Fig. 7 Streamlines on middle section under different rotating speeds

3.3 数值计算结果气动特性分析

 图 8 风机质量流量、总压升随转速变化曲线 Fig. 8 Curves of mass flow rate and total pressure rise of fan with change of rotating speed

 图 9 风机第1、2级总压升随转速变化曲线 Fig. 9 Curves of total pressure rise of first and second stages of fan with change of rotating speed

 图 10 风机总功率随转速变化曲线 Fig. 10 Curves of total power of fan with change of rotating speed

 图 11 风机第1、2级轴功率随转速变化曲线 Fig. 11 Curves of shaft power of first and second stages with change of rotating speed

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 图 12 风机效率随转速变化曲线 Fig. 12 Curves of fan efficiency with change of rotating speed
4 结论

1) 通过对速度三角形的分析与数值计算可知，保持第2级叶轮转速不变，增大第1级叶轮转速，两级叶轮的功率以及气流迎角和落后角都会增大；保持第1级叶轮转速不变，增大第2级叶轮转速，第1级叶轮的参数保持不变，第2级叶轮的功率和相应气流角会增大。

2) 根据数值计算结果可知在保持第2级叶轮转速不变的情况下，提高第1级叶轮的旋转速度，气流进口角减小，滞止点向压力面移动，第2级变化与之相反；保持第1级叶轮转速不变，提高第2级叶轮转速，第1级变化较小，第2级的滞止点向压力面移动。

3) 改变相同百分比下，第1级叶轮转速改变对风机的流量和总压升的影响比改变第2级叶轮的影响大。

4) 结合实际使用以及轴功率随前后两级叶轮转速改变曲线图，确定了风机的最佳转速比为1.1：1，传动效率为88.4%下对旋风机效率为75%。

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#### 文章信息

SUN Wenlong, FANG Xiangjun

Influence of rotating speed variation on aerodynamic characteristics for counter rotating fan

Journal of Beijing University of Aeronautics and Astronsutics, 2017, 43(12): 2480-2487
http://dx.doi.org/10.13700/j.bh.1001-5965.2017.0169