Numerical analysis for propulsion characteristics of ducted fans in different shapes
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摘要:
以分布式涵道风扇推进为背景,使用多重参考系(MRF)和给定力分布的动量源方法(MSM)求解雷诺平均N-S(RANS)方程,对不同形状涵道风扇推进特性进行了数值模拟分析。对桨盘与不同形状涵道壁面之间的相互作用原理进行了研究,进而对不同外形分布式涵道风扇进行了分析。结果表明:纯圆形机匣推进特性最佳,纯方形最差,由方转圆的机匣推进特性居中;非圆机匣圆角的存在会诱使机匣内壁出现分离,产生干扰阻力,且圆角半径越小,影响越显著;非圆机匣影响风扇进口面积和桨尖涡的大小,从而从桨盘效率和唇口吸力两方面影响涵道推进效率。
Abstract:With distributed ducted fans propulsion as the background, the Reynolds-averaged Navier-Stokes (RANS) equation was solved by using multiple reference frame (MRF) and momentum source method (MSM) with given force distribution, and numerical simulation analysis of ducted fans with different shapes was carried out. The interaction between the fan panel and the duct wall with different shapes was analyzed and compared. Then numerical calculation of distributed ducted fans with different shapes was carried out. It showed that the circle ducted fan had the best propulsion characteristics, while the square ducted fan had the worst. The propulsion characteristics of the rectangular to circular ducted fan was between them. The existence of corners in non-circular ducted fan could induce separation of the inner flow and generate interference resistance, and the smaller radius of the corner indicated the more significant influence. The non-circular duct wall affected the fan inlet area and the size of the blade tip vortex. Therefore, the ducted fan propulsion efficiency was affected via the fan panel efficiency and lip suction.
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表 1 涵道风扇静拉力CFD计算与实验测量结果
Table 1. CFD calculation and experimental measurement results of static tension of ducted fan
参数 CFD 天平测力实验 拉力/N 34.8 33.6 误差/% 3.6 表 2 MRF、MSM、UNST方法计算结果
Table 2. Calculation results of MRF,MSM,UNST methods
参数 MRF MSM UNST 总拉力/N 16.438 14.152 15.592 桨盘拉力/N 13.753 15.011 15.861 计算时长/h 16 12 96 表 3 不同数量网格计算结果
Table 3. Results of different numbers of mesh
参数 网格量/万 660 720 790 850 930 总拉力/N 13.54 13.71 13.53 13.93 14.05 桨盘拉力/N 17.27 17.44 17.08 17.39 17.41 总扭矩/(N·m) 0.876 0.861 0.863 0.859 0.861 表 4 不同形状涵道壁阻力计算结果
Table 4. Calculation results of drag of duct walls in different shapes
外形 阻力/N r=0(方) 0.57 r=0.2 0.50 r=0.4 0.46 r=0.6 0.39 r=0.8 0.39 r=1(圆) 0.36 方转圆 0.85 表 5 不同速度下各形状涵道风扇效率
Table 5. Efficiency of ducted fans with different shapes and different speeds
外形 η0(V=0 m/s) η V=15 m/s V=30 m/s r=0(方) 0.565 0.174 0.236 r=0.2 0.594 0.175 0.265 r=0.4 0.612 0.215 0.264 r=0.6 0.659 0.214 0.254 r=0.8 0.743 0.254 0.251 r=1(圆) 0.880 0.300 0.281 方转圆 0.738 0.232 0.160 单独转子 0.400 0.198 0.290 表 6 各形状涵道阵列壁面阻力计算结果
Table 6. Calculation results of drag of duct arrays in different shapes
外形 阻力/N 方涵道 1.735 圆涵道 1.877 方转圆涵道 2.659 表 7 V=0 m/s各外形涵道风扇阵列推进特性计算结果
Table 7. Calculation results of the propulsion characteristic of ducted fan arrays with various shapes at V=0 m/s
参数 方涵道 圆涵道 方转圆涵道 T/N 68.634 90.596 82.935 Tp1/N 17.312 13.155 14.941 Tp2/N 17.245 13.116 15.066 Tp3/N 16.801 13.149 14.877 Ts/N 17.272 51.289 38.049 M/(N·m) 2.927 2.566 2.712 η0 0.560 0.843 0.730 表 8 V=15 m/s各外形涵道风扇阵列推进特性计算结果
Table 8. Calculation results of the propulsion characteristic of ducted fan arrays with various shapes at V=15 m/s
参数 方涵道 圆涵道 方转圆涵道 T/N 40.071 55.694 46.795 Tp1/N 17.451 11.882 13.968 Tp2/N 17.064 11.965 14.024 Tp3/N 17.423 11.972 13.949 Ts/N −11.867 19.874 4.853 M/(N·m) 2.892 2.492 2.652 η 0.180 0.291 0.229 -
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