"220V Cooling Fan" dimensionless parameters are dimensionless combination of several performance parameters, the same dimensionless parameters can be made from various combinations of these performance parameters. Therefore, similar to the corresponding series of fan operating point though "220V Cooling Fan" has the same dimensionless parameter, however, the performance parameters of these points are not the same. The use of non-dimensional performance curves select fans and fan performance parameters for checking, according to the dimensionless parameters are required and the fan speed n, impeller diameter D2, calculate the amount of wind "220V Cooling Fan" fan, total pressure and power. Still using dimensionless parameter expressions, and consider the relationship between the impeller and the impeller disc area A2 exit velocity u2 are implicated.