A jet blower is an ejector operating at, or near, atmospheric pressure with a very low compression ratio,
generally less than 1:2. It is designed to move a large amount of gas across a small pressure differential.
Whereas pressure differentials of standard steam jet ejectors are usually measured in inches of Hg, pressure
differentials of jet blowers are measured in inches of H2O ("in. w.c."). Jet blowers are either steam or
air operated.
Stainless steel jet blowers are found in pulp and paper mills in "NCG scavenging systems", and are used
instead of mechanical fans. They are used to collect "noxious" gases from various sources at slightly below
atmospheric pressure and boost them through a flame arrestor to an incinerator at slightly above atmospheric
pressure. Steel jet blowers find their greatest application in the power industry as turbine gland ejectors.
Because the pressure differentials are so comparatively small, it is possible to use low pressure motive
steam (e.g. 50 psig or less). Since we custom design our "BL" series ejectors, it is still possible to
achieve high efficiencies (low motive to suction ratios). Jet blowers are "subcritial flow devices". It is possible
to maintain suction and discharge pressures, and to vary the suction capacity by throttling the motive steam
pressure (and consequently the motive steam flowrate). Suction capacity decreases roughly as the square of
the motive steam flowrate decreases. However, it has been found that increasing the motive steam flowrate
above design does not increase the suction flowrate substantially.
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