Abstract
The pneumatic conveying experiments of hulls as to specified tube were carried out in our previous report. Energy efficiency at the ejector part was searched from the results and fig. 2 as to flying velocities of the materials.
The mechanism of pneumatic conveying with ejector feeder was investigated in this report. The results were as follows.
(1) The experiment was performed at the condition lbest of which conveying weight became maximum under various distances l between nozzle and ejector. Effective conveying energy Ps was in direct proportion to W and the value of W/Ps were constant at any conditions beyond the ejector (fig. 3). The values of W/Ps were small at the conditions except lbest.
(2) Energy efficiency η was defined as a ratio of supplied energy Pf to energy Ps for conveying. The value of η became maximum at the opening ratio (Dd/Dn)best that the value of W was maximum.
The values ranged from 0.30 to 0.40 at conveying nothing but air, and ranged from 0.19 to 0.30 at conveying air and materials.
It was recognized that the value of η became larger according to decrease of static pressure hf. The relation was clearer at conveying air and materials (fig. 4 & 5).
(3) Air flow Qa for conveying was maximum near the (Dd/Dn)best η was, The Qs had positive correlation to hf and diameter of nozzle Dn. Balances of Qa and supplied air flow Qf were almost positive at conveying nothing but air, while were almost negative at conveying air and materials (fig. 4 & 5).
(4) Although effective static pressure h2 beyond the ejector showed larger fluctuation at conveying air and materials than at conveying nothing but air, they were seemed equal at the practical conditions that Dn was large. Effective static pressure h2 was maximum near the (Dd/Dn)best as W, η and Qa were, and it had positive correlation to hf and Dn (fig. 4 & 5).
(5) Effective static pressure h2 was equal to the flow resistance between Qa and W. In the case of conveying nothing but air, it was recognized that h2 was in direct proportion to square of Qa (fig. 6). The h2 had cross-correlation to Qa and m as fig. 7 showed, and the relation was represented by equation (5). But in the case of conveying air and materials, a large fructuation was observed in the tendency. This means the eq. (6) which represents pressure drop β can be transformed into eq. (7).
