Formation of automobile emission plume and air exhaust mode of underground parking garages

Points out that the automobile emission is actually a form of thermal plume. Makes flow visualized experiments separately for three exhaust modes, i.e. exhaust from upper part, lower part and simultaneously from upper and lower part of a garage, and analyses the formation and development process of the plume based on the obtained pictures. Measures exhaust air rate for the first two modes. The results show that the formation process of the plume is basically the same for the three modes and that exhaust air rate for the first exhaust mode is larger than that of the second in the case of the same air outlet area. Points out inappropriateness in adopting the mode of exhaust mainly from lower part of an underground parking garage, and recommends the mode of exhaust from upper openings.