"24V DC Cooling Fan" in a certain range, the greater the curvature of the blade, at the same rotational speed, the greater the kinetic energy of the gas, i.e., the larger the air volume and pressure; same time, the greater the drag on the blade, the motor torque requirements greater. When the ratio is high arc / chord length in excess of 0.1, "24V DC Cooling Fan" will no longer lift coefficient increases linearly, the "range" that 0.05 <arc height / chord length <0.1. Blade Angle: dip the greater the pressure difference between the upper and lower leaf surface, the greater the pressure at the same speed; but "24V DC Cooling Fan" surface pressure, may have reflux phenomenon, but lower fan performance. Therefore, the blades should also enhance the inclination within certain limits.