This study aims to complete and validate a recently developed reduced-order model for the fast prediction of aerodynamic performance (P -Q) curve of electronics cooling fans, taking into account the real fan geometry and the tip clearance effect. The effect of tip clearance on tip vortex generation and fan performance was revealed by an experimentally validated 3D computational fluid dynamics (CFD) method. Six different tip clearance ratios ranging from 0% to 12.7% were investigated. The tip clearance was found to have a strong effect on tip vortex generation, which significantly affects the aerodynamic performance of the fan. Fan efficiency increased by up to 7% by reducing the tip clearance ratio by 2.5%. The tip clearance effect was successfully included by the analytical method combined with a correlation equation developed based on the CFD study. The results show that the combined reduced-order model can produce reasonably accurate predictions for fan P -Q curve with errors less than 7.1% compared to CFD results, while having a wide valid range of tip clearance ratio up to 10%. The precision of this model was further validated against experimental results for eight commercial fans. The computational speed of this model is more than three orders of magnitude faster than a steady-state CFD study, making it highly appropriate for fast analysis of fan performance and thermal-flow co-design.

The development of high-performance aero engines put forward higher performance requirements for compressor components, and the improvement of aerodynamic performance of compressors has important engineering application value. The blade tip recess has great potential and advantages in improving the aerodynamic performance of compressors. In order to better understand the effect of the blade tip recess on the compressor aerodynamic performance, in this paper, the influence mechanism of the blade tip recess on the aerodynamic performance of the isolated rotor of a transonic axial compressor stage is discussed. Under the premise that the numerical method's results are almost consistent with the experimental test results, the full three-dimensional unsteady numerical results show that the main reason for the original blade rotor stall is the leading edge of the blade tip blockage, which is caused by blade tip clearance leakage vortex breakage. After adopting the measures of the blade tip recess, the study shows that the blade tip recess can increase the rotor stall margin by 2.10% without reducing the rotor efficiency and the total pressure ratio. A detailed analysis of the blade tip flow field shows that the blade tip recess can reduce the intensity of the tip clearance leakage flow by increasing the turbulence intensity of the blade tip near the casing wall, and reduces the leading edge of blade tip blockage, improves the rotor blade tip flow field, thereby achieving the purpose of enhancing rotor stability.