Inline axial flow fan

An inline axial flow fan having at least first and second axial flow fans arranged in an inline manner along an axial direction of a rotational shaft of a rotational driving apparatus, comprising:

• a first rotor blade and a first stator blade that are included in the first axial flow fan;
• a second rotor blade and a second stator blade that are included in the second axial flow fan;
• a first flow control grid arranged in a gas discharge side of the first axial flow fan;
• and
• a second flow control grid arranged in a gas discharge side of the second axial flow fan, an axial length of the second flow control grid being shorter than an axial length of the first flow control grid, wherein:
• the first flow control grid has a stator blade having a smooth circular arc leading edge shape matching a circular arc shape of the first stator blade of the first axial flow fan, and a trailing edge shape extending in parallel with an airflow direction, and
• the second flow control grid has a stator blade having a smooth circular arc shape matching a circular arc shape of the second stator blade of the second axial flow fan.