1. Overview: The FBD series mine-use explosion-proof axial flow local ventil (hereinafter referred to as the ventilator) complies with MT222-2007 "Technical Conditions for Axial Flow Local Ventilators Opposite Rotation" and Q/YAF001-2011 "FBD Series Mine-use Explosion-proof Axial Flow Local Ventilators standards. It is suitable for local ventilation in coal mines below the ground that contain gas or coal dust and other environments with explosive hazards. It is used with positive pressure air ducts It can also be used as ventilation equipment for tunnel construction. Specific introduction is as follows: (1) The ventilator adopts computational fluid dynamics to optimize the-objective design of the fan as a whole, and the blades are made of aviation engine FMIA airfoil, which makes the fan have a large area of efficient working conditions and the ventilator has the characteristics of compact structure, large air volume, high wind pressure, long air delivery distance, high efficiency, energy saving, low noise, etc. (2) The ventilator is directly driven by two YBF2 series fan special explosion-proof electric motors, and in order to extend the service life of the fan SKF series bearings from Sweden are selected for the motor bearings. (Add bearing photos) (3) According to the different needs of users, there are 3 types silencers to choose from; a) ordinary outlet silencer; (add photos) b) inlet and outlet combined silencer; (add photos) c) side inlet, and outlet combined silencer. (add photos) The third type (c) of combined silencer adds a side inlet component, which changes the direction of the airflow at the without affecting the air intake volume, so that the noise is refracted, and in combination with the inlet and outlet silencers, the noise is greatly reduced. After testing by national mine equipment testing center, its noise value is 20-30 decibels lower than that of ordinary ventilators. (4) The explosion- type of the ventilator and the electric motor is: explosion-proof type, explosion-proof mark is: ExdbI. (5) The working voltage is 80V/660V, 660V/1140V, and it should not exceed ±5% of the rated value. The voltage is 50HZ. The ventilator used underground should have a greater air supply volume than the working air volume of the ventilator. The foundation for the installation the ventilator should be solid and free of water spray. The height of the ventilator's inlet edge from the ground or top wall should not be less than .3m. The air duct used should be able to withstand the pressure of the ventilator, and the diameter of the air duct should not be less than the diameter of impeller. (6) Service life The service life is not less than ***, and the safe operation time before the first major overhaul is not less than 1300h. 2. Structural characteristics, working principle, and technical parameters (1) The ventilator consists of a collector, electric motor, fan, secondary fan, electric motor, silencer, etc. (Figure 1 with a regular silencer; Figure 2 with an inlet and outlet silencer; Figure  with a side inlet combined silencer). The ventilator shell structure is made of welded steel plates, the inner cylinder is made of perforated steel plates welded, lined with sound-absorbing materials, and the electric motor is connected to the air duct by bolts through a flange stop, with the motor shell and perforated steel as the inner air duct, and the two-stage impellers rotate at the same speed in opposite directions. (2) Working principle The ventilator is *** and two impellers, which are driven by two identical capacity and model explosion-proof special electric motors, and the two impellers rotate in opposite directions. Air enters the first-stageeller and exits through the second-stage impeller after obtaining energy. The second-stage impeller also has the function of the static vane fence in the ordinary axial flow ventator, and the straightened circumference