﻿ 冲压空气涡轮叶片设计和气动性能数值模拟<sup>*</sup>
 文章快速检索 高级检索

1. 北京航空航天大学 交通科学与工程学院 北京市清洁能源与高效动力工程中心, 北京 100083;
2. 北京航空航天大学 能源与动力工程学院, 北京 100083

Blade design and aerodynamic performance numerical simulation on ram air turbine
JI Fenzhu1, ZHANG Mengjie1, WANG Rui1, WANG Yan1, DU Farong2
1. Engineering Center of Beijing Clean Energy and High Efficient Power, School of Transportation Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100083, China;
2. School of Energy and Power Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100083, China
Received: 2017-08-01; Accepted: 2017-10-13; Published online: 2018-01-09 17:13
Foundation item: National Natural Science Foundation of China (51375029)
Corresponding author. DU Farong.E-mail:dfr@buaa.edu.cn
Abstract: Ram air turbine (RAT) is a part of the emergency energy system in plane. It can extract energy from airflow through rotating turbine. Design of turbine blade and study on aerodynamic performance are the key for utilizing airflow energy efficiently. Aimed at the power needed by some type of emergency energy system, we designed turbine blade based on the momentum-blade element theory. Then aerodynamic performance of RAT is simulated by using computational fluid dynamics (CFD) method. Besides, the method of multiple rotation frame (MRF) is used to simulate 3D mixed flow field of the RAT where the pitch angle is adjustable. The performances of turbine power and rotor power coefficient are studied varying with airflow velocity and flight altitude. Distribution of pressure and velocity on blade surface are analyzed. The results show that the extracted power and rotor power coefficient of RAT vary with airflow velocity and pitch angle. RAT has different dynamic performance at different flight altitudes in the flight envelope. Constant power could be obtained by adjusting the pitch angle of RAT. Besides, flow state of the whole field is ideal, but there is still room to improve.
Key words: ram air turbine (RAT)     blade design     numerical simulation     aerodynamic performance     rotor power coefficient

1 RAT系统涡轮叶片设计

 图 1 NACA系列不同翼型升阻比随叶片迎角变化曲线 Fig. 1 Variation curves of lift drag ratio of different NACA airfoils with attack angle of blade

 (1)

 (2)
 (3)

 (4)
 (5)

 (6)
 (7)

 (8)
 (9)

 图 2 叶片弦长和扭角随径向半径变化曲线 Fig. 2 Variation curves of blade chord length and twist angle with radial radius
2 RAT系统涡轮气动性能理论分析

RAT系统中，涡轮以迎面气流作为动力源。由空气动力学理论可知，迎面气流的冲压能量与速度的三次方成线性关系，即

 (10)

RAT在迎面气流作用下旋转并把气流的冲压能量转换为涡轮功率而输出，涡轮输出功率可通过理论分析或数值模拟得到，由式(11)计算：

 (11)

RAT系统涡轮的功率提取系数，即风能利用系数为

 (12)

 (13)

3 RAT系统涡轮气动性能数值模拟 3.1 计算模型

 图 3 RAT涡轮流场网格 Fig. 3 Grid in turbine flow field of RAT

RAT旋转对周围流场产生影响，为了把RAT对流场的扰动降低到最小，理论上外边界应为无限大。实际上，在数值仿真时设置合适的外边界以提高计算效率。若外边界设置太小，气体流动受到干扰，进而影响计算精度。通常，取外边界尺寸为模型尺寸的10倍或以上。考虑到本文所研究RAT直径为353 mm，计算时取外边界(区域1)直径为4400mm，入口端长度为1000mm，出口端长度为3 600 mm；旋转域2半径为210 mm，长为160 mm；区域3为2个半径为40 mm、长为155 mm的圆柱，如图 4所示。此外，区域划分时必须满足2个要求：①2个圆柱区域在靠近轮毂的端面与叶片根部相切；②2个圆柱区域和叶片共轴线，其目的是保证每次转动区域31和32时RAT具有完整性。

 图 4 流体区域划分 Fig. 4 Division of fluid region

 (14)

3.2 边界条件

1) 进出口边界条件。RAT工作条件是大雷诺数流动，理想气体并做湍流运动。进出口边界设置为速度入口、压力出口和压力远场条件。来流速度V垂直于入口边界，涡轮转速为n

2) 壁面边界条件。壁面滑移特性与涡轮外部流动特性有关。若流体为无黏流动，则涡轮壁面具有滑移特性，视具体情况给定粗糙度和壁面滑移等。本文研究的RAT为无滑移壁面。此外，为减小边界干扰，设置静止域外围远场边界与涡轮距离为涡轮直径的10倍以上，取3 600 mm。

3.3 数值模拟

RAT处在一个可压缩有黏性的非定常流场中，采用多重旋转坐标系(MRF)模型把问题转化为稳定流动。选用CFD方法对涡轮气动性能进行数值模拟。空气设为理想气体，黏性系数随温度的变化以Sutherland公式计算，即

 (15)

4 计算结果分析

4.1 不同叶尖速比时涡轮气动性能

 图 5 涡轮风能利用系数随叶尖速比变化曲线 Fig. 5 Variation curves of rotor power coefficient of turbine with tip speed ratios
4.2 不同桨距角时涡轮气动性能

 图 6 涡轮输出功率和风能利用系数随桨距角变化曲线 Fig. 6 Variation curves of turbine output power and rotor power coefficient with pitch angles
4.3 不同入流角时涡轮气动性能

 图 7 涡轮输出功率随入流角变化曲线 Fig. 7 Variation curves of turbine output power with inflow angle
4.4 涡轮流场分析

 图 8 叶片压力面和吸力面压力云图 Fig. 8 Pressure contours of acting surface and suction surface

 图 9 不同来流速度和桨距角下流线图 Fig. 9 Streamlines at different inflow velocities and pitch angles
5 结论

1) 涡轮转速一定时，风能利用系数随叶尖速比的增加先增大后减小，每一桨距角对应一个最大风能利用系数和最佳叶尖速比，且桨距角越小，最大风能利用系数越大。

2) 针对不同来流速度，适当调整叶片桨距角不仅可以提高涡轮风能利用系数，同时还可以实现涡轮恒功率输出，满足设计要求。

3) 从整个流场来看，叶片主要做功区域位于中部靠近叶尖部分、相对叶高40%～95%的区域，吸力面叶根区域静压分布不甚合理，仍有改进空间。

4) 采用正向研究方法，基于叶素-动量理论设计的RAT叶片能够满足某型RAT需要，研究方法具有明显的先进性。

 [1] KOERNER M. Recent developments in aircraft emergency power[C]//35th Intersociety Energy Conversion Engineering Conference and Exhibit (IECEC). Reston: AIAA, 2015: 12-19. [2] MANWELL J F, MCGOWAN J G, ROGERS A L. Wind enery explained: Theory, design and application[M]. New York: John Wiley & Sons Ltd., 2002. [3] BURTON T, SHARPE D, JENKINS N, et al. Wind energy handbook[M]. New York: John Wiley & Sons Ltd., 2001. [4] BETZ A. Schraubenpropeller mit geringstem energieverlust. dissertation[R]. Gottingen: Gottingen Nachrichten, 1919. [5] WILSON R E, LISSAMAN P B S. Applied aerodynamies of wind power machines[R]. Washington, D. C. : NASA STI/Recon Technical Report N, 1974. [6] GAO X, HU J. Numerical simulation to the effect of rotation on blade boundary layer of horizontal axial wind turbine[C]//2010 World Non-Grid-Connected Wind Power and Energy Conference. Piscataway, NJ: IEEE Press, 2010: 1-4. [7] 周世刚, 刘红, 王佳莉. 冲压空气涡轮验证技术研究[J]. 测控技术, 2016, 35 (Suppl): 364–367. ZHOU S G, LIU H, WANG J L. Research on verification technology of ram air turbine[J]. Measurement and Control Technology, 2016, 35 (Suppl): 364–367. (in Chinese) [8] CHOI N J, SANG H N, JEONG J H, et al. Numerical study on the horizontal axis turbines arrangement in a wind farm:Effect of separation distance on the turbine aerodynamic power output[J]. Journal of Wind Engineering & Industrial Aerodynamics, 2013, 117 : 11–17. [9] 刘勇. 风力发电机气动性能数值模拟[D]. 哈尔滨: 哈尔滨工业大学, 2007: 33-35. LIU Y. Numerical simulation of wind turbine aerodynamic performance[D]. Harbin: Harbin Institute of Technology, 2007: 33-35(in Chinese). [10] 方祥军, 刘思永, 王屏. 可变桨距冲压空气涡轮混合型流场数值研究[J]. 北京航空航天大学学报, 2004, 30 (2): 152–155. FANG X J, LIU S Y, WANG P. Numerical study on mixed flow field of variable pitch ram air turbine[J]. Journal of Beijing University of Aeronautics and Astronautics, 2004, 30 (2): 152–155. (in Chinese) [11] 何玉林, 李海峰, 金鑫, 等. 风力机叶片翼型气动特性模型[J]. 机械科学与技术, 2010, 29 (12): 1589–1594. HE Y L, LI H F, JIN X, et al. Airfoil aerodynamic characteristics model of wind turbine blade[J]. Mechanical Science and Technology, 2010, 29 (12): 1589–1594. (in Chinese) [12] 查健锐, 杨殷创, 钱燕. 基于Fluent的多翼型低速气动特性比较[J]. 合肥师范学院学报, 2014, 32 (6): 38–42. ZHA J R, YANG Y C, QIAN Y. Comparison of aerodynamic characteristics of multi airfoils at low speed based on Fluent[J]. Journal of Hefei Normal University, 2014, 32 (6): 38–42. (in Chinese) [13] 勒古里雷斯D. 风力机的理论与设计[M]. 施鹏飞, 译. 北京: 机械工业出版社, 1987. LE GOURIERES D. Design and theory of wind turbine[M]. SHI P F, translated. Beijing: China Machine Press, 1987(in Chinese). [14] 王瑞. 冲压空气涡轮多工况动力性能研究[D]. 北京: 北京航空航天大学, 2017. WANG R. Study on dynamic performance of ram air turbine under different working conditions[D]. Beijing: Beihang University, 2017(in Chinese). [15] 王健, 卢岳良, 杨斐, 等. 两型冲压空气涡轮翼型气动特性分析[C]//第六届中国航空学会青年科技论坛, 2014: 5. WANG J, LU Y L, YANG F, et al. Aerodynamic characteristics analysis of two ram air turbine airfoil[C]//The Sixth China Aviation Society Youth Science and Technology Forum, 2014: 5(in Chinese).

#### 文章信息

JI Fenzhu, ZHANG Mengjie, WANG Rui, WANG Yan, DU Farong

Blade design and aerodynamic performance numerical simulation on ram air turbine

Journal of Beijing University of Aeronautics and Astronsutics, 2018, 44(7): 1387-1394
http://dx.doi.org/10.13700/j.bh.1001-5965.2017.0514