- Title
- Development of design models for air-gravity fine powder transport
- Creator
- Ding, Hongliang
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2017
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Air-gravity conveyors are widely used in industry to convey bulk materials with the advantages of low particle velocities, low levels of particle attrition, potentially high conveying rates and low power consumption. Most current designs are based on empirical design charts and past experience as there have been relatively few investigations attempting to model the flow of air-gravity conveyor systems. Instead of empirically based methods, this thesis adopted a new continuum approach based on fluid rheology to assess the flow performance of fine powders within air-gravity conveyors. Meanwhile, this thesis also conducted computational fluid dynamic (CFD) numerical simulations of an air-gravity conveying system with fluidised materials. Therefore, the objective of this research focused on the following specific aspects: design of the air-gravity conveyor; experimental determinations of the flow behaviour of aerated materials; theoretical modelling of the fluidised flow conveying models based on the rheology; validation of the proposed conveying models; and CFD simulation of the air-gravity fluidised conveying system. Initially, experimental investigations on the basic parameters including density parameters, particle size distribution and air-particle parameters were conducted on sand and flyash. Essentially, a combination of a fluidisation chamber and a rotary viscometer was applied for testing the shear stress and shear rate of fluidised materials, and then the rheology parameters could be determined accordingly. Secondly, the air-gravity conveyor was designed to form a circulation system for future experimental research. Detailed drawings are presented in this thesis. Essentially, the conveying system consists of four sections: hopper feed section, material conveying section, material receive section and material return section. Instrumentation for measuring pressure and mass flow rates was designed and installed in an experimental area. Thirdly, air-gravity conveying tests were conducted on sand and flyash. The material bed height, material mass flow rate and pressure drop were measured and analysed under vent and non-vent condition. Based on the experimental test procedure and test programme, the effect of air flow rate and channel inclination on the depth of flowing beds, material mass flow rate and pressure drop along the channel were investigated and discussed. Fourthly, a fundamental conveying model for air-gravity conveyor flows in inclined channels, with an emphasis on the conservation of momentum taking into account the rheology of the gas-solid mixture, was developed to predict the flow behaviour of material in air-gravity conveyors. By inputting the rheological parameters and conveying design data, the steady flow bed height of this air-gravity conveying system could be predicted. After that, rheology based conveying models were evaluated and validated by comparing the steady flow bed height produced from the conveying models with the experimental measurements. Results showed good agreements between the model predictions and experimental observations for sand and flyash with the overall error under 30%. Lastly, CFD has been used to simulate the air-gravity flow, where a steady, three-dimensional fluidised granular flow is considered in a rectangular channel having frictional side walls for different flow conditions. The results of simulated bed heights along the air-gravity channel are discussed. The developed CFD model predicted the flow bed heights along the conveying channel for sand and flyash quite well. Moreover, centreline volume fraction and velocity along the channel, and velocity distribution at the cross section of the channel were also investigated, and results showed that the CFD simulation enables the system to prediction of the fine powder flow behaviour in an air-gravity conveying system.
- Subject
- air-gravity conveyor; mathematical model; CFD simulation; fluidised flow; rheology
- Identifier
- http://hdl.handle.net/1959.13/1354663
- Identifier
- uon:31323
- Rights
- Copyright 2017 Hongliang Ding
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 5 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 235 KB | Adobe Acrobat PDF | View Details Download |