Abstract
Reverse circulation down-the-hole (RC-DTH) air hammers have been widely used in construction and mining activities owing to their high drilling efficiency and good dust control performance. This paper presents a computational fluid dynamics (CFD) approach with the dynamic mesh method for evaluating the performance of RC-DTH air hammers. Nine stages of operating conditions of the RC-DTH air hammer are described herein to better understand the operating mechanism of the RC-DTH air hammer. Dynamic layering, sliding interfaces, as well as user-defined functions were employed to update the mesh in dynamic mesh modelling. The influences of rebound coefficient, input air pressure, and piston mass on the performance of RC-DTH air hammers were studied. It was found that increasing the rebound coefficient and input air pressure can improve the impact performance of RC-DTH air hammers, whereas increasing input air pressure can reduce energy efficiency and increase energy consumption. In addition, simulation results indicate that increasing the input air pressure may increase the stroke of the piston; the piston mass should be optimally selected to match the designed geometric parameters to avoid a significant drop in performance. The CFD approach with the dynamic mesh method shows superiority in evaluating the performance of RC-DTH air hammers.