Passive hydraulic intensifier for while-drilling operations in underground coal mines and its performance analysis
TIAN Hongjie
Abstract：To address the problems of existing hydraulic intensifiers used in underground coal mines-such as large size,inability to achieve pressure boosting while drilling,and the need for auxiliary driving devices-a passive hydraulic intensifier for while-drilling operations was developed based on the piston differential pressurization principle,employing a multi-stage multi-chamber modular design and a coordinated control technique using directional valves.This intensifier did not rely on an external high-pressure pump and converted low-pressure underground mine water into high-pressure water autonomously,enabling high-pressure permeability-enhancement operations.It achieved a pressurization ratio of 1∶10 with a minimum pressurization pressure of 20 MPa.The influences of high-pressure outlet diameter,effective piston acting area ratio,and input pressure on the performance of the intensifier were analyzed:the larger the high-pressure outlet diameter,effective piston acting area ratio,and input pressure,the faster the flow velocity of the high-pressure liquid,but the longer the time required for the high-pressure liquid to reach a steady-state velocity.Field industrial test results showed that,during hydraulic punching and cavity creation in a soft coal seam with a firmness coefficient of 0.15,the average coal output per meter of borehole reached 1.5 t/m,and the intensifier exhibited stable performance,achieving pump-free high-pressure hydraulic permeability enhancement.
Keywords：pressure-relief permeability enhancementpassive hydraulic intensifier for while-drilling operationspiston differential pressurizationhydraulic punchingcoordinated control using directional valves
Publication Date：2025-11-30
Online Publishing Date：2025-12-25(First online date of this platform, not the publication date of the document)
Pages：7( 40-45,156 )