On the bridging mechanism in vibration controlled dispensing of pharmaceutical powders from a micro hopper
On the bridging mechanism in vibration controlled dispensing of pharmaceutical powders from a micro hopper
Accurate batch dispensing of pharmaceutical powders, on the scale of hundreds of microns, in small doses is a challenging task. A novel dispensing technique has been developed by Yang et al. using high-frequency vibration to control powder flowout of a narrow hopper. This method removes the need for mechanical valves because the powder, very quickly, forms a bridge-like structure across the passive outlet preventing outflow. Activation of the vibration has been found to destabilise the bridging structure enabling the powder to flow, when vibration stops the bridge structure quickly rebuilds and dispensing stops. In this work the Discrete Element Method (DEM) was used to simulate this novel dispensing control method in order to identify the internal mechanism that allows the flow to be controlled so precisely. A simulated conical hopper was filled with particles then oscillated vertically at high frequency (~10 kHz), amplitude and frequency were scaled from the experimental system. Two orifice sizes, a variety of DEM parameters and two vibration modes were simulated. The parametric study of DEM parameters was based around a case that provided flow rates within a factor of 2 of the experimental flow rates. Dispensing after vibration was found to stop very quickly as in experiments. Visualisation of internal structures during fill, vibration and immediately after vibration revealed a central mass of slow moving particles floating above the nozzle outlet. When the vibration stops the central mass of particles drops into contact with the walls and quickly plugs the flow.
24-37
Jasion, G.T.
16cfff1d-d178-41d1-a092-56e6239726b8
Shrimpton, J.S.
9cf82d2e-2f00-4ddf-bd19-9aff443784af
Li, Z.
b760ad9c-e89c-407f-bbdf-bf5f95496555
Yang, S.
e0018adf-8123-4a54-b8dd-306c10ca48f1
November 2013
Jasion, G.T.
16cfff1d-d178-41d1-a092-56e6239726b8
Shrimpton, J.S.
9cf82d2e-2f00-4ddf-bd19-9aff443784af
Li, Z.
b760ad9c-e89c-407f-bbdf-bf5f95496555
Yang, S.
e0018adf-8123-4a54-b8dd-306c10ca48f1
Jasion, G.T., Shrimpton, J.S., Li, Z. and Yang, S.
(2013)
On the bridging mechanism in vibration controlled dispensing of pharmaceutical powders from a micro hopper.
Powder Technology, 249, .
(doi:10.1016/j.powtec.2013.07.027).
Abstract
Accurate batch dispensing of pharmaceutical powders, on the scale of hundreds of microns, in small doses is a challenging task. A novel dispensing technique has been developed by Yang et al. using high-frequency vibration to control powder flowout of a narrow hopper. This method removes the need for mechanical valves because the powder, very quickly, forms a bridge-like structure across the passive outlet preventing outflow. Activation of the vibration has been found to destabilise the bridging structure enabling the powder to flow, when vibration stops the bridge structure quickly rebuilds and dispensing stops. In this work the Discrete Element Method (DEM) was used to simulate this novel dispensing control method in order to identify the internal mechanism that allows the flow to be controlled so precisely. A simulated conical hopper was filled with particles then oscillated vertically at high frequency (~10 kHz), amplitude and frequency were scaled from the experimental system. Two orifice sizes, a variety of DEM parameters and two vibration modes were simulated. The parametric study of DEM parameters was based around a case that provided flow rates within a factor of 2 of the experimental flow rates. Dispensing after vibration was found to stop very quickly as in experiments. Visualisation of internal structures during fill, vibration and immediately after vibration revealed a central mass of slow moving particles floating above the nozzle outlet. When the vibration stops the central mass of particles drops into contact with the walls and quickly plugs the flow.
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Accepted/In Press date: 26 July 2013
e-pub ahead of print date: 3 August 2013
Published date: November 2013
Organisations:
Optoelectronics Research Centre, Aeronautics, Astronautics & Comp. Eng
Identifiers
Local EPrints ID: 361674
URI: http://eprints.soton.ac.uk/id/eprint/361674
ISSN: 0032-5910
PURE UUID: c852ad76-63a7-48d3-a2f3-786eb1ed05f5
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Date deposited: 29 Jan 2014 15:30
Last modified: 15 Mar 2024 03:29
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Author:
Z. Li
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