Specific speed and overall dimensions in calculation and selection of transverse fans

Abstract

When calculating, designing and selecting the fans, along with the similarity theory and dimensional analysis, the criteria of specific speed and overall dimensions are used, which allow to study a great number of aerodynamic configurations and characteristics of highly efficient fan prototypes and at the same time to choose the configuration which meets technical requirements most completely. The criteria of specific speed and overall dimensions are properly elaborated and used when designing and calculating radial and axial fans, but not suitable for the transverse fans, because in their flowing part the air flow is not three-dimensional but two-dimensional, and consequently there is an additional independent parameter in calculation, namely the usable width. Based on the main correlations of transverse fans’ parameters (the propeller diameter and its rotation frequency, the usable width of flowing part) and moving air density, dimensionless and dimensional criteria of specific speed and overall dimensions for these air flow generators are derived. On the basis of theoretical and experimental studies, the cause-and-effect laws allowing to determine the criteria of specific speed and overall dimensions for transverse fans are revealed. Graphical interpretation of rational values areas of these criteria is shown, and calculations are performed. According to the known values of criteria of specific speed and overall dimensions, the examples of calculations for transverse fans using the dimensionless aerodynamic configurations and characteristics of highly efficient fan prototypes are given. The calculations are supplied with graphical interpretation.