Abstract
The extrusion processes of ceramic pastes, including 3D printing, are used for the production of high-value products. Ceramic paste extrusion is a complex process which depends on the paste rheological properties, die and extruder geometries, and operational parameters. Modeling and quantitative analysis of paste molding are important to design proper extrusion process for the production of high-value extrudates of desired strength, shape, and morphology. In this paper, the mathematical model of ram extrusion of ceramic materials is established, and the paste continuity and momentum equations for non-Newtonian fluid based on the modified Herschel-Bulkley viscous model were solved numerically. The effects of die geometry and paste feed rate on the distributions of paste velocity and pressure in the extruder and die were investigated numerically. As a result, the steeper radial profile of longitudinal velocity and higher value of longitudinal velocity were obtained in the narrow die. The pressure significantly increases in the die at a high feed rate, and the pressure profile is almost flat in the barrel. The rate of increase of the maximum pressure decreases with an increase of paste feed rate. The pressure steeply increases in the die of small diameter. The maximum pressure linearly increases with the ratio of die length to diameter.
Highlights
The extrusion process of ceramic pastes is commonly used for the production of high-value products, e.g., catalyst pellets for the chemical reactor (Devyatkov et al, 2016), honeycomb catalyst for purifying gas exhausted from an automobile (Govender and Friedrich, 2017), and ceramic packings for adsorption and direct heat transfer (Darakchiev et al, 2016)
The pressure significantly increases in the die at a high feed rate and the pressure profile is almost flat in the barrel
The extrusion of ceramic materials for the production of high-value materials was studied in the present research
Summary
The extrusion process of ceramic pastes is commonly used for the production of high-value products, e.g., catalyst pellets for the chemical reactor (Devyatkov et al, 2016), honeycomb catalyst for purifying gas exhausted from an automobile (Govender and Friedrich, 2017), and ceramic packings for adsorption and direct heat transfer (Darakchiev et al, 2016). Ceramic paste extrusion is a complex process which depends on the paste rheological properties, die and extruder geometries, and operational parameters (Benbow and Bridgwater, 1993). The paste rheological properties are controlled by several factors including volume fraction of particles and their size distribution and shape, packing density and surface characteristics, as well as amount and properties of binder and other additives (Powell et al, 2013). Modeling and quantitative analysis of paste extrusion are important to design properly the extrusion process for the production of high-value extrudates of desired strength, shape, and morphology. The effects of die geometry and paste feed rate on the distributions of paste velocity and pressure in the extruder and die will be investigated numerically
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