Influence Micro Cooling Fan number of blade performance

1 "Micro Cooling Fan" number of blades is too small, the expansion angle increases, resulting in a pressure gradient is high, side boundary layer thickness, so that the cooling fan to efficiency.
Increasing the number of blades 2, a single blade load drop, reducing the impeller exit flow angle of deflection, the other conditions increase the slip coefficient, the first coefficient corresponding increase in energy.
The number of blades 3 "Micro Cooling Fan" excessive flow friction loss increases airflow, resulting in the flow channel inlet blockage, so cooling fan efficiency. That optimal blade number is how much? Xin Jian Electronics Co., Ltd. of technology to do a series of experiments, a fan of the original model five blades rotating at 3000rpm, for example, by changing the number of blades to analyze the impact of the number of leaves on the fan performance. Compare the fan when the impact 4,5,6,7, through experiments, we see that, for each fan, all with the increase in traffic efficiency are first increased then decreased. When the flow is less than 0.006 cubic meters per second, "Micro Cooling Fan" blade 5 and 6. Both cooling fans than the other two models is high, this is because the small number of blades, the gas flows through the small, low fan total pressure, thus resulting in lower efficiency: When an increase in the number of blades, the increased generation of eddy currents. Causing the blade lift coefficient decreased, so that the flow path within the flow losses rise rapidly decreased efficiency.