Study on effect of ridge arrangement on surface flow field of an impregnated bit

Abstract:

The crown structure of an impregnated diamond bit is a critical factor affecting its rock-breaking efficiency and drilling performance. The ridge arrangement of a ridged impregnated diamond bit directly determines the cooling and cleaning performance of drilling fluid acting on the bit crown at the bottom hole. To investigate how ridge arrangement affects the flow characteristics of fluid over the bit surface， three ridge layouts （forward， reverse and symmetric） are designed for bit crowns of ridged impregnated diamond bits with an outer diameter of 78 mm and an inner diameter of 48 mm. Using clean water as the working medium， ANSYS Fluent is adopted to conduct hydrodynamic simulations of fluid flow on the bit surface. Under a bit rotational speed of 62.83 rad/s， the flow characteristics and velocity distribution of surface fluid with different ridge layouts are compared， and the influence of structural parameters on fluid flow behavior is clarified. The simulation results show that the maximum fluid velocity for all three layouts occurs near the water ports， ranging from 7.92 to 9.15 m/s. High-velocity zones between ridges concentrate at the front edge of ridges facing the rotation direction. The forward layout imposes the weakest disturbance on inter-ridge fluid velocity. The flow velocity at ridge fronts reaches 5.60 m/s， approximately 17.89% and 2.04% higher than those of the reverse and symmetric layouts， respectively， and the high-velocity zone can cover the high-temperature regions at the front of the three ridges. The inter-ridge velocity of the forward layout reaches 3.20 m/s， which is about 102.50% and 247.80% higher than the reverse and symmetric layouts， respectively. Meanwhile， the ridges in the forward layout exert the least influence on fluid streamlines. Comprehensive analysis demonstrates that the forward ridge arrangement is optimal for preserving surface flow velocity， improving ridge cooling conditions and enhancing the removal of cuttings between ridges and at the bottom hole.