Use an axial fan to ventilate the outside, but also have to make up the wind, it is ventilation. If the room is well sealed, there is not much air to be discharged from an axial fan. If an axial flow fan is used to exhaust the outside air, the natural air flow is used to replenish fresh air into the room, which is negative pressure ventilation.
The front deflector + impeller stage ventilator has a vane mounting angle adjustable and fixed front deflector at the front end of the impeller. In order to produce a negative winding speed before the impeller inlet, the winding speed of the air flow at the impeller exit is zero. Since the front deflector deteriorates the velocity field and pressure field of the impeller inlet airflow, and increases the average relative velocity of the impeller, the ventilator loss increases and the efficiency decreases. In addition, the noise of this type of explosion-proof axial fan has also increased.