Abstract: A method to improve the mechanical smoke exhaust effect of a vehicle base with a cover by setting up a top branch pipe was proposed. CFD fluid dynamics numerical simulation software was used to study the smoke exhaust effect of the top branch pipe. Four openings embodiment, three kinds of top air duct openings and different amount of smoke were provided, the comparative analysis was conducted through measuring the height of smoke layer, temperature under the cover, visibility and CO concentration of vehicle base with upper cover. The results showed that the smoke exhaust effect of the four kinds of openings is in the order of good to poor as top branch pipe, top opening, side opening, bottom opening.The reduction of the number of openings in the top branch pipe has no significant effect on the smoke exhaust effect, but it will increase the air velocity at the smoke vent. The mechanical smoke exhaust volume of the vehicle base with the upper cover will be increased by setting the top branch pipe, which can improve the smoke exhaust effect significantly.

Key words: covered vehicle base, top branch pipe, smoke vent;smoke exhaust effect