"Axial Fan" airfoil cross-section of the blade airfoil is called, it has a certain geometric lines, and some aerodynamic properties. Equidistant arrangement of the same airfoil airfoil series called cascades. This plane is called the cascade line cascade. Since the flow axial flow impeller can be simplified to a similar line in a plane leaves the gate in the flow airfoil, and in-line flow around a cascade of the same situation of each wing, so long as the study of the flow around an airfoil case on it. Here we note that the definition of several parameters: blade mounting angle βα: the angle (in cascade connection each airfoil corresponding points) chord and the column line. Flow angle β1, β2: the angle between the cascade inlet and outlet of the relative speed and the circumferential speed in the opposite direction between.