enginehistory.org

[jjuutinen]

Was there some specific reason why Bristol and Junkers used fully shrouded impellers in their blowers?

[jrussell]

Shrouded impellers were used on turbochargers in general because of the very high adiabatic effiency because of minimal recirculation from impeller back to the inducer. The extra weight and dramatically increased inertia, coupled with a tendency to collect dirt, and higher cost of production pretty much doomed using this design as newer designs can achieve better effiency without the drawbacks. As far as I know, none like this are in production at this time ( can't wait to here how many are ). The basic principle is still valid though, and for an engine that runs at a constant speed they still might be the best from an effiency standpoint