A combine harvester has a threshing mechanism for threshing grain and cleaning apparatus for removing chaff from the threshed grain. The threshing mechanism includes a plurality of concaves and the cleaning apparatus includes and upper chaffer and a lower sieve. The combine harvester also has a blower having a rotating impeller and a blower housing. The blower housing has a first duct that directs a first airstream onto the upper chaffer and lower sieve, and a second duct that directs a second airstream along the underside of the concaves. An inlet to the second duct has a cross-sectional area that is larger than the cross-sectional area of an outlet of the second duct. The blower has a divider plate that separates high-velocity air from the impeller and directs the high-velocity air to either the first duct or the second duct.
