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A gravity settling chamber plays an important role in improving the effect of the dust removal when it is selected as a dust collector in a pneumatic cleaning system for cleaning a subway tunnel. The settling rate and the indexes evaluating the secondary blowing are studied to assess the effect of the dust removal in this paper. Regarding the length of the settling chamber, the height of the inlet duct, and the diameter and height of the outlet duct as the variables of the key structures, a flow field simulation analysis of the gravity settling chamber with different heights of the dust accumulation is carried out, then the key structure parameters are optimized by means of the experimental method of uniform design. Finally, the settling chamber with an excellent dust removal effect is obtained. Major conclusions can be drawn as follows. (1) The maximum velocity and the mean velocity ratio of the airflow near a dust accumulation surface are important evaluation indexes for judging the secondary blowing. (2) The maximum velocity near a dust accumulation surface usually doesn't appear on the vertical plane through the axis of the inlet duct or the outlet duct. (3) An excellent settling effect can be ensured during the whole cleaning process only when the maximum design height of the dust-accumulation surface is considered as a key working condition. (4) An excellent settling effect can be realized if the settling chamber without any filtering device and affiliated baffle structure are long enough. (5) The secondary blowing can be avoided if the inlet and outlet of the setting chamber are far away from the dust-accumulation surface. This study has a good guiding significance for the design of gravity settling chamber.

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