Vane pumps and "Axial Fan" basic equation is established when obtaining energy fluid by rotating an impeller quantitative relationship. The Euler equation is first pushed out in 1756, the so called Euler equation, also called the energy equation. Wherein there are two assumptions: (1) over the impeller: infinite number of blades, blade thickness infinitely thin, namely: strict fluid particles flow along the blade profile, which coincides with the trace of the blade profile; (2) the fluid is ideal, incompressible fluid, namely: the flow process without energy loss, fluid density is constant. By: Moment of Momentum's Law: that steady flow, the fluid per unit time effluent flowing into the control volume change moment of momentum given axis is equal to the role of all external forces on the same axis moment algebra in the fluid of the control body and.