Axial flow fan in super long tunnel construction on plateau

An axial flow fan in the super long tunnel construction on a plateau aims to realize the purposes of long air distance, low noise, high efficiency, and large air quantity. The axial flow fan comprises an air inlet muffler, a primary host machine, a secondary host machine, a third host machine, a fourth host machine, a primary impeller, a secondary impeller, a third impeller, a fourth impeller, an air outlet muffler, a blast pipe connector and a sound-absorbing panel; the blade molded line of the impeller blade adopts a airfoil twisted type; each impeller of the host machine is driven by the electric motor with same power; the impeller adopts the type of direct connection with the motor; the rotation directions of adjacent impellers are reverse; the primary impeller and a secondary impeller, and the third impeller and the fourth impeller rotate mutually; the sound-absorbing panel is respectively arranged on two sides of the casing of the host machine; and each connection component is connected by the galvanize