# Simulation of the Influence of Wing Angle Blades on the Performance of Counter-Rotating Axial Fan
## 1 Introduction  
The blade is the main working component of the counter-rotating axial fan for mining, and its shape and structure will directly affect the overall performance of the fan. However, the traditional counter-rotating fan has the problems of low efficiency and high aerodynamic noise. Therefore, studying the shape of the blade has important reference value for improving the performance of the counter-rotating axial flow fan. [PERSON] et al. [1] used response surface method and three-dimensional flow field analysis method to optimize the swept parameters of the two-stage blades of the contra-rotating axial flow fan for mines, which increased the fan efficiency by 1.64% and improved the flow of internal fluid. [PERSON] et al. [2, 3] perforated the trailing edge of the primary blade and the leading edge of the secondary blade of a small counter-rotating axial fan, and found that the blade perforation reduced the overall noise of the fan by 6-7 dB (A). [PERSON] et al. [4] used numerical calculation software to simulate three types of counter-rotating fans with a primary impeller hub ratio of 0.72 and a secondary impeller hub ratio of 0.72, 0.67, and 0.62. The highest efficiency was observed when the secondary impeller hub ratio was 0.62. [PERSON] et al. [5] studied the effect of two-stage impeller spacing on the axial flow fan, and pointed out that when the impeller spacing is 0.9 times the chord length, the performance of the fan is optimal. In recent years, with the development of biomimetic technology, living organisms with excellent flow field characteristics in nature have attracted more and more attention. Since the blade is the main working component of the fan, the bionic research is mostly carried out around the blade. [PERSON] et al. [6] improved the NACA4412 airfoil based on their study of the wing structure of swallows, and the lift coefficient and lift-drag ratio of the bionic blade were improved compared to the original blade. Inspired by the non-smooth leading edge of the long-eared ow's wings, [PERSON] et al. [7] designed a bionic blade with such a leading edge and introduced this type of blade into an axial fan. The noise of the fan was significantly reduced to the range of 500-2000 Hz, and the maximum noise reduction was about 2.52%. [PERSON] et al. [8] improved the performance of the fan by applying a sawtooth structure on the edge of the fan blade based on the silent principle of bird flight. Under ideal conditions, the bionic blade reduced the noise by 2.2 dB (A). The noise reduction rate was about 2.5%, and the fan efficiency was increased by 5.3%. [PERSON] et al. [9, 10], based on the low-noise feature of the ow's flight, installed a bionic serrated structure on the trailing edge of the SD 2030 airfoil blade, and explored the aerodynamics of the blade at different angles of attack and with different sizes of the serrated structures. The analysis showed that the blade trail expansion speed increases with the increase of the size of the saw tooth structure. Studies have shown that the use of bionic methods to optimize the blades can effectively improve the aerodynamic performance of the blades, thereby improving the internal flow field of the fan. However, in the past, the optimal design of counter-rotating fans was mostly the application of conventional methods, while the bionic methods were mostly concentrated on single blade or single-stage axial flow fans, and there were few bionic researches on blades of counter-rotating axial flow fans for mining. Therefore, this paper takes the FBD No.8.0 mine counter-rotating fan as the research object. Inspired by the wing angle structure of migratory birds that will improve the external flow field of the wings during the long-term evolution of migratory birds, the wing angle bionic design of the fan blade was carried out. At the same time, orthogonal experiments and numerical calculations were used to simulate the performance and noise of the modified fan, and a static analysis was carried out.