| As one of the key components in the emulsion pump station,unloading valve plays an important role in the system to maintain the pressure balance and stabilize the system.However,when the unloading valve continues to work for more than 1500 hours,it is easy to have problems such as unstable response and gas erosion,which seriously affect the system safety and reliability.Taking WXF6 unloading valve as the research object,the dynamic characteristics and anti-cavitation performance are studied.The solution to improve the stability of the system and reduce cavitation damage is put forward,which greatly increases the service life of unloading valve,and provides theoretical basis and data reference for the development of safe,stable and highly stable unloading valve in coal mine.The main research work and conclusions of this paper are as follows:1)Established the unloading valve mathematical model and AMESim dynamic simulation model,analyzed the key structural parameters affecting the response of the system.The influence of the structural parameters of the main valve and the pilot valve on the dynamic performance of the system is studied,and the inlet pressure,outlet pressure,inlet flow rate and displacement curve of the main valve core are obtained.The results show that the system stability and energy consumption can be improved by appropriately increasing the taper of the main valve core opening,outlet back pressure,opening of the pilot valve core,seat diameter and damping hole diameter,or reducing the spring stiffness of the main valve and the pilot valve.2)A THREE-DIMENSIONAL model of the internal flow passage of the unloading valve was established to study the cavitation mechanism and the main cavitation locations.The cavitation resistance characteristics of the main spool at the opening degree of 0.5,0.75 and 1.25mm were analyzed.Through Fluent flow field simulation calculation,the pressure,velocity and gas phase distribution cloud map of section A and B were obtained.The results show that the high speed jet produces pressure difference,and then forms a low pressure area in the valve cavity and cavitation occurs.The bubble under cavitation enters into the valve sleeve along with the emulsion medium,and suddenly collapses near the high pressure area at the outlet of the valve sleeve,causing cavitation damage.The location of the damage is consistent with the actual location.In addition,the results show that the cavitation degree of unloading valve is different with different opening degrees.The smaller opening degree is,the more serious cavitation is.3)According to the main factors affecting cavitation damage,the corresponding optimization structure is carried out.L9(32×22)orthogonal table is adopted on the basis of simulation calculation and verification.The mixed orthogonal tests of two-factor,three-level and two-factor,two-level were established,and the cloud map of valve breath phase distribution and the mean gas phase fraction were taken as the optimization objectives.The simulation results show that the influence degree of each factor on unloading valve is A(R=7.49%)>C(R=3.50%)>B(R=2.54%)>D(R=1.04%),and K3>K2>K1 in factor A;K2>K3>K1 in factor B;K2>K1 in factor C;K2>K1 in factor D.Finally,the optimal structure scheme is A3B2C2D2,which is verified by calculation and is consistent with the predicted results.Fig[43]table[6]reference[85]... |
