Abstract: An inlet duct for use with an engine is presented. The invention includes a duct structure, at least one spike disposed along an interior surface of the duct structure, and an inlet throat formed by one or more apexes disposed along an equal number of spikes. The inlet throat corresponds to the minimum cross-sectional area through which airflow passes as otherwise allowed by the maximal obstruction formed by the apex(es) within the duct structure. Each spike is bounded by a longitudinal ridge and a lateral ridge along an upper end and a base. The ridges intersect at the apex. A portion of each spike upstream of the inlet throat functions primarily as a supersonic diffuser and downstream as a subsonic diffuser. Airflow is isentropically compressed and then expanded within the inlet duct so that greater-than-subsonic flow at an input end is reduced to subsonic flow at an output end.

Abstract: Apparatus for transferring powdered ore from a storage tank to a bin associated with an electrolytic cell. The cell defines a chamber containing an electrolyte and includes means for transferring ore from the bin to the chamber. The apparatus comprises a fluidizing conveyor for conveying powdered ore from a storage tank to the bin, a first vent interconnecting the conveyor and bin and a second vent interconnecting the bin and chamber. In a preferred embodiment, a source of pressurized gas causes ore to flow through the conveyor, and the apparatus further comprises a pressure switch for closing the source in response to a buildup of fluid pressure in the conveyor. Another preferred feature is a fluidizing pad inside a conduit connecting the storage tank to the conveyor.