A Self-cooling Bit with Transpiration Cooling Structures

Badger exploration is a novel drilling technology that removes the need for a fixed rig and can achieve drilling without drill strings and drilling fluid. To achieve bit cooling during badger drilling, this paper proposes a self-cooling bit that can achieve self-cooling based on transpiration cooling technology. The self-cooling bit is characterized by the coolant chambers, capillary tubes and transpiration holes, the coolant can be pumped to flow through capillary tubes and transpiration holes to absorb the cutting heat and reduce the temperature of the cutters during drilling. The transpiration cooling model of the self-cooling bit cutter is developed theoretically, liquid metal is chosen as the coolant, and numerical simulations are conducted to investigate the cooling process of the cutter. Finally, a simplified self-cooling bit is built and tested in a rock breaking experiment, and the experimental results show that the temperature of the self-cooling bit cutter can be reduced significantly and maintained at a low value during the rock-breaking process, verifying the feasibility of the self-cooling bit. Analysis of the experimental results obtained with different parameters shows that the radial transpiration holes, the small size transpiration holes and the high flow rate of coolant are conducive to cutter cooling and promote the full and rapid absorption of the cutting heat by the coolant. The above work is helpful for the improvement and application of badger exploration technology.