Silos are widely used structures designed with hoppers or as flat bottoms to store different types of particulate materials (pellets, grains, powders, etc.). Although they have been used in industry for a long-time, further research is needed. This article provides design recommendations that prevent structural failures and ensure efficient discharge. The discrete element method (DEM) has been commonly used in recent decades in silo/bin research to simulate the behavior of stored materials. In this study, DEM was used to investigate the relationship between the slot width and particle size on the discharge behavior in a flat-bottom silo using particle shape configurations with different elongations and aspect ratios. Sixteen DEM models were developed using the multi-sphere approach to obtain the particle configurations, ranging from single spheres to 4×4×4 clusters of spheres arranged along orthogonal axes (x, y, and z). The simulations involved between 459 and 29,383 particles with a total mass of 40 kg in each model. The established comparisons include information on the bulk density, velocity profiles, residual masses, and discharge rates.

Aluminum powder is an attractive fuel, especially for micropropulsion, due to its wide availability, high volumetric and gravimetric energy densities, and environmental friendliness. For safety reasons, the powder is preferably stored and supplied to a combustion chamber separately from the oxidizer. However, powder supply systems for micropropulsion applications are technologically immature. To improve this situation, a powder supply system was developed, and the impacts of important design factors on the supply characteristics were studied. This included operating modes, carrier gas pressures, gas line conductances, and powder line lengths. The results showed that, when compared to continuous operation, pulsed operation achieved 1) significantly higher powder flow rates and 2) significantly higher ratios of powder to carrier gas mass flow rates, ϕ. Furthermore, higher carrier gas pressures can increase the powder mass flow rates, but this reduces ϕ. The gas line conductance had a lesser impact on the powder flow rates than the pressure, but increasing the former also increased the powder flow rates without significant impact on ϕ. The powder line length had a negative impact on the powder flow rate, but no significant impact on ϕ. These results will help the future development of micropropulsion systems that use powder fuels.

Dry powder coating, characterised by the blending of poorly flowing powders with finer coating powders to optimise flowability, represents a sophisticated and evolving approach to powder processing. The optimisation of this method involves precise formulation, carefully combining powders with different particle properties to achieve a desirable blend aimed at enhancing the flow characteristics during the application process. Over the last decade, this field has witnessed increasing activity, focusing on key mixing parameters, such as mixer type and mixing power, as well as understanding the influence of constituent powder characteristics, including size ratio, density, and cohesion. Various techniques have been used to assess the flowability improvement or quantify the degree of coating. This review aims to provide a comprehensive exploration of the literature on powder coating research, highlighting its significance in both academic research and industrial applications. This paper discusses current coating analysis techniques using state-of-the-art equipment and reviews recent findings, particularly the nascent attempts to establish regime maps for dry powder coating.

Particle motion affects microscopic momentum, heat/mass transfers, and macroscopic mixing/separation performances in engineering processes ranging from those involving granular flows to multiphase systems. The primary interests of researchers seeking to improve the performances of such processes are finding the best ways to understand particle motion. Several methods have been developed to understand particle motion, among which radiation-based techniques have shown particular advantages because they can non-invasively investigate dynamic particle motion. This article reviews four prominent radiation-based techniques for studying particle motion, including Radioactive Particle Tracking (RPT), Positron Emission Particle Tracking (PEPT), X-ray-based methods and Magnetic Resonance Imaging (MRI). The principles and characteristics of these techniques are explained, and recent advances and applications are reviewed.

In powder-based Additive Manufacturing (AM) the precise control of process parameters plays a significant role in the quality and efficiency of the printing process. Among these, the effect of temperature has received less attention in the literature, although it is a significant factor that influences the inter-particle forces and, consequently the powder flow and spreading behaviour of powders. In selective laser sintering (SLS) or selective laser melting (SLM), pre-heating the chamber and powder bed is a required step prior to sintering, hence, the temperature can significantly influence the layer adhesion and spread quality. In this context, the present study explores the effect of elevated temperature on the flow and spreading behaviours of AlSi10Mg powders. The flow properties of two different grades of aluminium alloy powders are characterised using the Carney and Hall flow tests, angle of repose and shear test techniques at different temperatures and correlated with the spreading behaviour at elevated temperatures, measured using the spreading rig with a heated bed developed at the University of Leeds. This study revealed that at elevated temperatures the spreadability of AlSi10Mg powders worsens because of changes in interparticle forces and particle surface interactions.