Research on structural parameter optimization of self-propelled radial water jet drill bits based on FLUENT numerical simulation

Self-propelled multi-hole jet drill bits are key components of water jet radial drilling technology, and their self-propelled force is the main factor affecting the efficiency of the water jet drilling system. To address the inadequacy of existing studies that analyze the influence of single structural parameters on the self-propelled force, a self-propelled model of the multi-hole jet drill bit is constructed. The effects of the number, diameter, and angle of orifices on the self-propelled force are numerically investigated using FLUENT software. The jet velocity, jet pressure, and turbulence intensity are calculated to optimize the structural parameters of the drill bit. The results show that an increase in the number of orifices leads to a reduction in the jet velocity of the lateral orifices. The number of forward orifices mainly affects the rock-breaking effect and hole diameter, while the number of backward orifices primarily influences the magnitude of the self-propelled force. The optimal number of forward orifices is 3, and that of backward orifices is 6. Furthermore, the orifice diameters directly affect the rock-breaking efficiency. Increasing the diameters of the forward and central orifices weakens the self-propelled capacity of the jet bit, whereas the diameter of the backward orifice directly affects the overall performance. The optimal overall performance is achieved with center, forward, and backward orifice diameters of 0.8 mm, 0.6 mm, and 1.0 mm, respectively. The orifice angle affects the hole-enlargement capability and the self-propelled effect, and increasing the forward or backward orifice angle reduces the jet velocity. Considering the jet stability, jet velocity, and jet pressure comprehensively, the preferred forward orifice angle and backward orifice angle are 25° and 35°, respectively.