Abstract
Pneumatic conveyance is coming into increasing use in industry. The investigation described was intended to explore general principles.
Tests were made with an experimental horizontal conveyer, using sand and linseed respectively as the materials conveyed. The air stream was maintained by an injector with an annular high-pressure nozzle surrounding the conveyer pipe. The grains were allowed to fall into the air stream at the inlet, and were collected in separators at the outlet.
The test results showed that there is a definite optimum position for the injector in the pipe line, and that it is an advantage to use a divergent diffuser at the outlet end. Definite relations were also found to exist betweeen (a) the air velocity and the rate of conveyance of solids, (b) the pressure gradient in the pipe and the injector pressure, and (c) the additional pressure drop due to the grain and the rate of grain conveyance. There are indications that the effective coefficient of friction between the grain and the pipe falls as the grain velocity increases; this conclusion is borne out by visual observation, which shows that the path of a grain consists of a series of leaps, whose length increases with the grain speed.
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