Air ejector for air/vacuum circuit - of well drill rigs with annular nozzle automatically controlled by upstream air pressure

摘要

A venturi-type air ejector has an adjustable annular nozzle by which the degree of vacuum can be adjusted. The vacuum removes the cuttings from the bottom of a bore hole through a coaxial central string of pipes. The annulus formed between the latter and an outer string of pipes receives compressed air which is blown down to the borehole bottom from the same compressor which powers the air ejector. This prevents the escape of air with suspended cuttings through the packing which seals the pipe string against the borehole walls. The air is accelerated to supersonic velocity before it is mixed with the induced air flow in the ejector. The vacuum is controlled automatically as a function of the upstream air pressure.