The air flow characteristics in the whirl-type inlet system of a domestic heavy commercial vehicle were studied and its visualization was made. Through the simulation of rear side flow field of a moving vehicle cab

it is discovered that there is a stable pressure region outside the vehicle body， in which the inner pressure is lower than the outer pressure， and the air flow has a tendency to flow inward. A right angle design at the top of the main duct of lateral inlet pipe can cause whirl flow in this area， which makes the flowability of air flow worse， while the fillet transition design can make the flow of airflow smoothly without whirl flow. Compared with the four-blade cyclone， the central low-pressure area of six-blade cyclone is relatively large， and the movement trend of internal particles is basically consistent with that of the in-pipe pressure distribution， and there is no particle area at the center while the particle-rotation area is relatively thin and closer to the wall. The shutter can provide the best particle-obstructing performance in the fully closed state of front projection.