Research on key components of pump-suction coring drillwith local reverse circulation

To solve the problem of low core recovery percentage when drilling in loose broken stratum using the existing coring drills, the locally reversely cycling performance of pump-suction coring drill with local reverse circulation is investigated. By means of CFD analyses, the effects of three key parameters of the vital component, negative suction part, which are enlarged radius (Ry), center distance (D), and rotational speed (N) on the locally reversely cycling performance were simulated numerically. These simulated effects were examined by experiments. The results show that the pressure difference P which manifests the effect of negative suction is affected significantly by the above three parameters. For the P91 coring drill with local reverse circulation at the hole bottom, the combination of parameters Ry=18 mm, D=27.3 mm, and N=300 r/min leads to an ideal effect. According to the optimized structural parameters, the negative suction parts were manufactured and tested in terms of locally reversely cycling performance. The tests show that with the same pump volume, the local reverse circulation efficiency of the present coring drill is 30% higher than that of fluidic drilling tool with local reverse circulation at the borehole bottom.