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Abstract

For low-speed axial-flow fans, the arbitrary vortex design method is widely used in high total pressure rise design requirement or small hub-to-tip ratio design applications. In the conventional arbitrary vortex design method, the total pressure rise of the fan blade commonly increases from hub to tip due to greater work potential near the tip. However, the high aerodynamic load in the blade tip region will inevitably result in an intensification of the tip leakage flow which limits the improvement of fan aerodynamic efficiency, especially for fans with a high total pressure rise design requirement. To solve this problem, this paper has developed a load-oriented aerodynamic design approach to take into account the spanwise work distribution of the fan in the preliminary design stage so as to reduce the potential loss caused by overloading of blade airfoil sections in local spanwise fractions and enhance the fan aerodynamic performances. In specific, the spanwise work distribution is firstly parameterized to control the blade load along the spanwise direction. Then, the diffusion factor is correlated to the total pressure loss coefficient to achieve a rapid evaluation of blade aerodynamic performance. In the meanwhile, the spanwise work of the blade airfoil sections can be automatically optimized to achieve an optimal load distribution. Finally, two axial-flow fans are designed based on the conventional arbitrary vortex design method and the load-oriented aerodynamic design approach respectively. The computational results show that the load-oriented designed fan has achieved a lower aerodynamic loss near the blade tip compared with the conventional arbitrary vortex designed fan. At the design point, an approximately 1.5% increment of adiabatic efficiency is also obtained. Moreover, over the entire operating range, the load-oriented designed fan shows higher adiabatic efficiency than the conventional arbitrary vortex designed fan, without sacrificing the total pressure rise. The motivation of this work is to offer useful guidelines for high-performance low-speed axial fan design under the requirements of high total pressure rise and small hub-to-tip ratio applications.

Keywords

spanwise work distribution aerodynamic design approach low-speed axial fan

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Load-oriented aerodynamic design approach of low-speed axial fans in the preliminary design stage

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