Modelling of velocity and porosity within horizontal dense phase pneumatic conveying using an in-situ inertial measurement unit and CFD-DEM

Dense phase conveying is an attractive mode of flow within pneumatic conveying as it has the benefits of high material throughputs as well as reduced pipe wear. It has seen limited implementation, mainly due to the complexity of the flow that results in unreliable design procedures. The difficulty of studying this mode of flow also manifests in the tendency of researchers to isolate parameters that govern the flow, despite the fact that it is well understood that these parameters are interlinked heavily. Many of the crucial parameters are difficult to obtain experimentally, causing significant assumptions to be made when measuring them. This thesis is an attempt to solve this problem by using an in-situ measurement method – an inertial measurement unit (IMU). An IMU is a sensor that can measure rotations, accelerations and pressures; but what is more important it is small enough to be placed into the flow to be carried together with particles. Post-processed IMU results proved to accurately estimate velocities and displacements and were subsequently used for making various observations relevant to slug flow. For example, it was confirmed that there is no relative axial movement between particles in a slug and that pressure drop over even a relatively short slug can be non-linear. What is more, the IMU allowed the accurate measurements of parameters like particle time spent in slug, distance travelled and propagation velocity. The ability to measure all of these parameters lead towards developing a kinematic velocity model based on conservation of mass and an empirical relationship between particle and slug velocities. The model was found to accurately predict such transport boundaries like minimum stationary layer fraction and maximum particle velocity. It was also shown that the model can be used to estimate the time it takes for a slug to reach its steady state length. The model was validated using author’s experimental data, other researchers’ experimental data, IMU measurements and CFD-DEM simulations. The IMU has greatly enhanced the understanding of dense phase pneumatic conveying due to the ability to measure particle velocities and pressures in-situ and track their changes as a slug moves along the pipeline.