No abstract

No abstract

No abstract

The flow behavior of sand particles during the core shooting process has been studied by combination of computational fluid dynamics (CFD) simulations and experiments. In the CFD simulations, a two-fluid model (TFM), in which a kinetic-frictional constitutive correlation is incorporated, has been applied to describe the flow dynamics of core shooting process. The influences of turbulence model and boundary conditions on the modeling of core shooting process are further investigated. The simulation results indicate that there are certain sensitivities to the wall boundary condition in the sand flow behavior while no significant difference is observed between the results of the laminar and turbulence models. Using high-speed photography system and pressure measuring system, systematic experiments have been carried out to fully validate the model and good agreement is obtained between simulations and experiments. Based on the simulation and experimental results, the flow behavior of sand particles in the core box is analyzed, and the effects of nozzle dimension (D=6, 8, 10, 15mm) and shooting pressure (P in =0.3, 0.4, 0.5MPa) on the hydrodynamic properties such as sand particle mass flux, sand volume fraction at the nozzle and distribution of sand velocity are discussed.

Core shooting process is the most widely used technique to make sand cores and it plays an important role in the quality of sand cores as well as the manufacture of complicated castings in metal casting industry. In this paper, the flow behavior of sand particles in the core box was investigated synchronously with transparent core box, high-speed camera, and pressure measuring system. The flow pattern of sand particles in the shooting head of the core shooting machine was reproduced with various colored core sand layers. Taking both kinetic and frictional stress into account, a kinetic-frictional constitutive correlation was established to describe the internal momentum transfer in the solid phase. Two-fluid model (TFM) simulations with turbulence model were then performed and good agreement was achieved between the experimental and simulation results on the flow behavior of sand particles in both the shooting head and the core box. Based on the experimental and simulation results, the flow behavior of sand particles in the core box, the formation of “dead zone” in the shooting head, and the effect of drag force were analyzed in terms of sand volume fraction (αs), sand velocity (Vs), and pressure variation (P).