| Among the various energy sources in China,coal has always been the most important one.In order to achieve "efficient and safe" coal mining operations,the performance requirements of the hydraulic support,which is the main support and safety guarantee for coal mining under the mine,have been increasing.The safety valve is the most important basic component of the hydraulic support system,mainly to control the flow and protection in case of overload;its operating characteristics have a great impact on the overall hydraulic support system power stability and reliability,through literature research,in the use of pilot operated safety valve,there are certain index requirements for its sensitivity and dynamic characteristics.For this reason,an in-depth study of the dynamic characteristics involved in the pilot operated safety valve is required.The main research focus of this paper is as follows:(1)Introduce the background and significance of this paper,explain the current importance of hydraulic supports in coal mining and the critical role of safety valves in hydraulic supports,the advantages and disadvantages of pilot operated safety valves compared with other safety valves,select pilot operated safety valves as the research object,and introduce the development status of pilot operated safety valves at home and abroad.The working principle of the pilot operated safety valve and the calculation of the basic structure dimensions are analyzed,and the performance indexes and dynamic characteristics of the pilot operated safety valve are listed,and its static equilibrium equation is given to lay a certain theoretical foundation for the next step of the state characteristics study.(2)Using AMEsim dynamic analysis software,a simulation model of the pilot safety valve in the overall circuit in AMEsim is constructed,and the dynamic characteristics of the pilot safety valve under five different structural parameters(mass of main spool,mass of pilot spool,shear modulus of pilot spring,inlet cavity volume,and damping hole diameter parameters)are analyzed in detail.The results show that the dynamic characteristics of the pilot operated safety valve can be optimized by reducing the valve cavity volume,increasing the damping hole diameter,reducing the shear modulus of the pilot spring,and reducing the spool mass.(3)Using Fluent fluid simulation software,four pilot-operated safety valves with different spool openings were studied in detail,using localization as the study object.Under the same boundary conditions,different opening degrees,the same opening degree,different inlet pressure and outlet pressure,the flow field total pressure cloud diagram change law,flow field velocity diagram change law and turbulent kinetic energy distribution diagram change law of the flow channel near the safety valve spool.(4)The response surface optimization design method is selected,and the fitting equations for the pressure drop and the three structural parameters of the main valve are obtained by quadratic polynomial fitting,and the design variables are taken as A=130.593 mm,seat diameter B=104.82 mm,and seat edge angle C=21.9947°.The optimized model reduces the pressure drop by 92,330 Pa compared to the base safety valve. |
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