Research on dynamic features of hydraulic system for fully mechanized mining support and its improvement design

In the hydraulic support work of fully mechanized working face, there are often problems such as insufficient initial support force and slow moving speed of the support. Currently, most solutions are based on the steady-state operation law of the hydraulic system of the support, such as increasing the flow rate of the pump station and reducing pressure loss. There is relatively little research on the dynamic features of the hydraulic system. The dynamic equation of the hydraulic system for the fully mechanized mining support is established. The dynamic features of the hydraulic system related to the initial support force and moving speed of the support, as well as the hydraulic impact features of the emulsion pipeline system, are theoretically analyzed. It is found that the approximate no-load operation of the column or jack and the hydraulic impact of long-distance pipelines are the main reasons for the significant pressure drop and fluctuation in the hydraulic system of the support. The mechanism of hydraulic impact in the hydraulic system of the bracket is revealed to be the sudden opening and closing of the electro-hydraulic directional valve and the pressure of the column touching the top. The correctness of the theoretical analysis is verified through on-site measured data and AMESim simulation. An improvement plan for the hydraulic system of the fully mechanized mining support is proposed. It includes the installation of multiple accumulators on the support, the addition of hydraulic control one-way valves and electro-hydraulic directional valves to control the charging and discharging methods of the hydraulic system accumulators at different stages of frame movement. The method uses the instantaneous high flow features of the accumulators and the overpressure generated by the peak hydraulic impact pressure of long-distance pipelines to enhance the initial support force of the support. The simulation results show that the improved system can effectively increase the initial support force and frame moving speed of the hydraulic support.