Design of Turbine-powered Pulse Generator for Large-displacement Working Condition

Turbine-powered pulse generators have problems such as insufficient erosion resistance and severe generator RPM overload during drilling ultra-large boreholes exceeding ø444.5 mm. In order to improve the erosion resistance and stability of the tool and prolong the tool’s service life, the following measures are taken:①design optimization of the turbine and guide vane structure; ②design optimization of the mechanical structure and material of the pulse generator. The results of indoor tests and field tests show that, the ratio of turbine RPM and displacement under the same displacement decreases from 84~87 before optimization to 62~64 after optimization. The optimal range of turbine RPM is 3 500~5 000 r/min. When the displacement is 70 L/s, the turbine RPM before optimization is 6 070 r/min, which is beyond the adaptable RPM of the power supply circuit board. The optimized turbine RPM is about 4 500 r/min, which is within the optimal speed range. The improved cross-sectional area of the flow path is 1.62 times larger than that of the previous flow path, leading to a 38% reduced over-current velocity. The optimized turbine-powered pulse generator operates normally under large displacement. The actual turbine RPM is in line with the laboratory prediction data, providing a stable guarantee for the service life.