| 摘要 |
A chimney comprises a central column through which the combustion gases or the like are forced, this column terminating at its upper end in a nozzle of smaller cross-section, and an outer wall which surrounds the column while leaving an annular intermediate space into which air is forced under a pressure slightly above the pressure of the combustion gases within the central column, this outer wall joining the periphery of the column in the zone of the upper nozzle. Apertures are provided in the wall of the column just below the nozzle to connect the annular space and the inside of the column. Air is thus introduced centripetally into the stream of combustion gases, a part of this air becoming progressively mixed with the said gases while another part forms a protective thermally insulating sleeve around the jet of these gases which issues from the nozzle, thus delaying the condensation of water droplets and the formation of a white cloud, which therefore only appears at a substantial height above the top of the chimney. |
