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Attachments: Jenike design charts for conical hopper w 40 30 8 = 30° 8 = 40° 10 30° 20° Φw Φw 20 200 10° 125 1-30 18 13 40 10° 0 O 10 20° 30 40° 50° 60° ө 25 20 8.30 0 10 20 30+ 400 50 40 8-608-50 Wall Friction Curves 43 8 = 50° Ow ow Flow Factor Curves + 1.3 30 8-40 8=30 30 8-30 1.7 8=35 25 30 1.0 10 20 1.5 Wall Friction, degrees Hopper Flow Factor (ff) 10 20 30 40 ө 50 8-40 - -8 = 60° TES ...... 1.3 10 8=30 3=50 8-40 12 - w 0-60 20 10 + 1.1 8=50 5-60 LED 10 1 0 5 35 40 45 10 15 20 25 30 Semi-included angle, degrees o Ꮎ 0 40 SO ө
1.1 Shear-cell tests were carried out on a powder for which an aluminium conical hopper is to be designed. The results of the tests are summarised in Table 1. In addition, the angle of wall friction between the powder and aluminium is 22°, and the bulk density of the powder is 920kg/m². Typical Jenike design charts for conical hoppers for some angles of internal friction are attached. Determine the following: a) The effective angle of internal friction of the powder (C). b) The Powder Flow Function (PFF) for the powder. c) The semi-included hopper angle to safely achieve mass flow () and the Hopper Flow Factor (ff). d) The critical unconfined yield stress (Ocrit), and the minimum outlet diameter (B) to ensure mass flow when required. e) The maximum discharge rate of the powder from the hopper. f) The pressures at the base of a 20-m high silo having diameter of 3.2 m. How do these values compare with the maximum pressures for a very tall silo? Table 1: Shear-cell test data Yield locus #1 Yield locus #2 Yield locus #3 Normal Stress Oc (kPa) Shear Stress t (kPa) 0.8 Normal Stress Oc (kPa) Shear Stress t (kPa) Normal Stress Oc (kPa) 1.0 Shear Stress t (kPa) 0.3 0.6 1.0 1.5 1.5 1.3 2.3 1.8 2.6 2.3 3.1 2.0 4.0 2.6 5.8 3.8