| Abstract: | A computational fluid dynamics (CFD) study was conducted to investigate the effect of several important factors on the dust control performance of a down-the-hole (DTH) air hammer drill bit for reverse circulation drilling in mines. It was shown that an increasing number of suction nozzles or inclination angles of suction nozzles was advantageous to improve dust control performance of the drill bit. Lowering the location of suction nozzles in the drill bit body is another way to increase its ability to control dust. There exists a critical diameter of suction nozzles for dust control performance. A series of experimental tests in the laboratory were carried out to validate the results of CFD modelling. It was shown that the CFD simulation results were in good agreement with experimental data. A prototype of the drill bit was built for testing in laboratory experiments. The same prototype was field-tested by drilling vertically downward exploration boreholes in one of the largest Molybdenum Ore Districts in Luanchuan of Henan Province, China. Field test results indicate that the modified drill bit could control drilling dust effectively. No cuttings escaped from the borehole when it was used for downward drilling. The DTH air hammer drill bit has not been tested for drilling a vertically upward hole, and therefore, future studies are required to improve the suction capacity of the drill bit for drilling vertically upward holes. |
