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Finite element analysis of flow field and temperature field of electro-hydraulic pump by Fluent
FU Yongling, YANG Jiayuan, ZHU Deming
School of Mechanical Engineering and Automation, Beijing University of Aeronautics and Astronautics, Beijing 100083, China
Received: 2016-07-19; Accepted: 2016-08-26; Published online: 2016-08-26 10:56
Corresponding author. FU Y L, E-mail: 13901397185@126.com
Abstract: The integrated structure and working principle of three phase induction motor-axial piston electro-hydraulic pump (EHP) were introduced. The mechanical losses were calculated. A model of EHP was established in Ansoft software, and then the electromagnetic losses were analyzed. Finite element coupling model was established. The flow and temperature distribution of hydraulic oil as well as the temperature field distribution of the key parts were analyzed by Fluent software. The analysis results depict that hydraulic oil can fully flow in internal flow road. The maximum temperature of stator is not more than 58℃, and the maximum temperature of rotor is not more than 40℃ under rated condition when the inlet oil temperature is 35℃. Cooling effect is better than motor-pump sets. The results also show that stator oil hole can obviously improve cooling effect. The maximum temperature of stator is reduced by 0.6℃, and local region temperature is reduced by more than 3℃ when four oil holes with a diameter of 10 mm are made.
Key words: electro-hydraulic pump (EHP)     flow field     temperature field     finite element     loss

1 电液泵结构模型

 图 1 轴向柱塞式电液泵结构示意图 Fig. 1 Schematic diagram of axial piston EHP

2 电液泵损耗

2.1 电磁损耗

 参数 数值 定子外径/mm 290 定子内径/mm 187 转子内径/mm 90 铁芯长度/mm 190 气隙长度/mm 0.6 极对数 2 输出功率/kW 22

 图 2 Ansoft电机模型 Fig. 2 Ansoft motor model

 W 损耗类型 数值 定子铜耗 892.93 定子铁耗 432.04 转子铝耗 482.53 摩擦损耗 293.65 杂散损耗 110.00

2.2 机械损耗

2.2.1 黏性摩擦损耗

1) 配流副黏性摩擦损耗

 (1)

2) 滑靴副黏性摩擦损耗

 (2)

3) 柱塞副黏性摩擦损耗

 (3)

2.2.2 滑动摩擦损耗

1) 配流副滑动摩擦损耗

 (4)

2) 滑靴副滑动摩擦损耗

 (5)

3) 滑靴球绞间摩擦损耗

 (6)

4) 柱塞副间摩擦损耗

 (7)

2.2.3 油隙摩擦损耗

 (8)

2.2.4 轴承摩擦损耗
 (9)

2.2.5 机械损耗计算

 参数 数值 Z 9 dz/mm 14.2 μ/(Pa·s) 0.04 Rf/mm 50 Δp/MPa 28 R/mm 92.9 β/(°) 20 ω/(rad·s-1) 1 460 fc1 0.1 fc2 0.1 fc3 0.08 fb 0.002 注：dz—柱塞直径；Rf—分度圆直径。

 W 损耗类型 数值 黏性摩擦损耗 配流副 335.34 柱塞副 300.84 滑靴副 17.67 滑动摩擦损耗 配流副 46.48 柱塞副 2.10 滑靴副 38.30 滑靴球绞 21.06 油隙摩擦损耗 1 491.60 轴承摩擦损耗 5.73

3 Fluent建模 3.1 几何建模

1) 电液泵缸体、滑靴、柱塞、压紧螺塞等内部零件对吸油和散热影响很小，予以忽略。

2) 去除零件中倒角、圆角等对仿真结果影响不大但影响网格划分的部分。

3) 将壳体翅片去除，但是在设置壳体与空气间热对流系数边界条件时进行等效修正。

 图 3 电液泵三维简化模型 Fig. 3 3D simplified model of EHP

 图 4 内部流体剖面图 Fig. 4 Sectional view of internal fluid
3.2 网格划分

 图 5 电液泵网格划分模型 Fig. 5 EHP meshing model
3.3 材料属性与边界条件

3.3.1 材料属性

 材料 密度/(kg·m-3) 比热容/(J·kg-1·K-1) 热导率/(W·m-1·K-1) 运动黏度/(Pa·s) 46#液压油 872 1 800 0.13 0.04 硅钢片 7 850 502.4 58.2 铸铝 2 719 871 202.4 碳钢 8 030 502.48 16.27

3.3.2 边界条件

1) 进口边界

2) 出口边界

3) 壁面边界

4) 热源

2.1节和2.2节计算得到的电磁损耗和机械损耗以热源的形式添加到模型中。其中热源又分为面热源与体热源。定子铜耗和定子铁耗统一加载在定子体上，转子铝耗、摩擦损耗、杂散损耗和油隙摩擦损耗加载在转子体上，这两部分是体热源；斜盘副和配流副的黏性摩擦损耗和滑动摩擦损耗分别加载在斜盘面和配流盘面，轴承摩擦损耗加载在转子轴承面，这三部分是面热源。经过计算，得到了表 6所示的热源参数表。

 参数 体热源 面热源 定子产热率/(W·m-3) 转子产热率/(W·m-3) 转子轴承面产热率/(W·m-2) 斜盘面产热率/(W·m-2) 配流盘面产热率/(W·m-2) 数值 169 445.80 281 531.60 64.85 11 134.87 67 630.48

4 仿真与分析 4.1 额定工况下的流场与温度场分析

 图 6 额定工况下液压油流动速度迹线 Fig. 6 Speed streamline of hydraulic oil under rated condition

 图 7 额定工况下的温度分布剖面图 Fig. 7 Sectional view of temperature distribution under rated condition

4.2 定子通油孔对散热性能的影响分析

 图 8 打孔前后电液泵温度分布 Fig. 8 Temperature distribution of EHP before and after hole drilling

 图 9 打孔前后电机定子轴向最高温度分布曲线 Fig. 9 Motor stator's axial maximum temperature distribution curves before and after hole drilling
5 结论

1) 对电液泵的流场和温度场仿真分析结果显示，额定工况下，电液泵内部流动的液压油可以起到冷却电机定转子的作用，其中，定子最高温度不超过58 ℃，转子最高温度不超过40 ℃。对比传统的三相异步电机，液压油冷却的效果要优于传统风冷。

2) 电液泵中温度最高的区域集中在定子内部，原因在于定子固定不动，与液压油接触的有效散热面积小，散热效果较差；电机转子由于自身的旋转运动，与四周的液压油接触比较充分，因而散热效果较好。

3) 对比打孔前后电液泵的散热效果，电机定子上4个ϕ10 mm的通油孔可以明显改善散热效果。其中最高温度下降0.6 ℃，且最高温度分布区域减小很多，整体散热效果比打孔前要好得多。

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#### 文章信息

FU Yongling, YANG Jiayuan, ZHU Deming

Finite element analysis of flow field and temperature field of electro-hydraulic pump by Fluent

Journal of Beijing University of Aeronautics and Astronsutics, 2017, 43(8): 1647-1653
http://dx.doi.org/10.13700/j.bh.1001-5965.2016.0605