An ejector system comprises a lobed, supersonic primary nozzle and a
convergent/divergent ejector shroud. The lobed nozzle is just upstream
from the ejector shroud, such that there is an annular space between the
nozzle and shroud for admitting a secondary flow. In operation, a primary
flow of high-pressure steam or air is directed through the primary nozzle,
where it is accelerated to supersonic speed. The primary flow then exits
the primary nozzle, where it entrains and is mixed with the secondary
flow, creating a low pressure region or vacuum. The ejector shroud
subsequently decelerates the combined flow while increasing the flow
pressure, which increases suction performance and reduces energy loss.
Because the primary nozzle mixes the two flows, the ejector shroud is able
to have a length-to-entrance-diameter ratio significantly smaller than
typical shrouds/diffusers, which decreases the system's size and increases
performance.
