Performance Analysis And Dynamic Characteristics Study Of Mechanical Seals For High-speed And High-pressure Pumps

The mechanical seal of high-speed and high-pressure pump is an important part of marine pumps,and its stable operation is related to the safe operation of ships.Particulate impurities,vibration and shock in seawater and fresh water seriously affect the performance of the mechanical seal of high-speed and high-pressure pumps.In this paper,numerical simulation and experimental research methods are used to carry out in-depth research on the sealing performance and vibration characteristics of high speed and high pressure,in order to improve the sealing performance and vibration resistance.Considering the influence of frictional heat on sealing performance,the boundary conditions for calculating the finite element of thermo-solid interaction were determined,and the temperature and deformation field analysis model of thermo-solid interaction of mechanical seal of high-speed and high-pressure pump was established.The temperature and deformation distribution of the mechanical seal of the high-speed and high-pressure pump were calculated,and the large amount of frictional heat generated by the high speed caused the deformation to change from radial distribution to axial distribution,and the deformation caused by thermal stress far exceeded the mechanical stress.Based on fractal theory,fractal parameters are used to characterize the surface topography of the sealing end,and the calculation formula for the leakage amount and friction rate of the mechanical seal of high-speed and high-pressure pump is derived.The results show that the fractal dimension of the mechanical seal face of high-speed and high-pressure pump is in the range of 1.5～1.6,and the characteristic scale coefficient is in the range of 1×10^-8～1×10^-7,which can maintain a low wear rate and leakage amount in seawater and freshwater environments,which provides guidance for the actual processing and manufacturing of sealing rings.The performance evaluation parameters of mechanical seals of high-speed and high-pressure pumps were defined,and the changes of sealing performance under different operating parameters,structural parameters and material parameters were compared and analyzed.The results show that the speed and thermal expansion coefficient have the most obvious influence on the sealing performance,and the high speed and large thermal expansion coefficient will lead to large thermal deformation and failure of the end face.When the sealing structure parameters are maintained:end face width4～4.5mm,moving ring width 15～15mm,static ring convex thickness（ratio）within the range of 0.12～0.14,the running performance of the mechanical seal of high-speed and high-pressure pump is better.Based on the response surface method,the multi-objective optimization of the sealing structure parameters is carried out,the structure of the obtained optimal parameters combination.Aiming at the vibration condition of the mechanical seal of high-speed and high-pressure pump,the vibration analysis model of the mechanical seal of high-speed and high-pressure pump is established,and the vibration characteristics of the mechanical seal of high-speed and high-pressure pump are analyzed by using MALTAB software,and the results show that the vibration has obvious effects on the contact force of the end face and the pressure of the liquid film,and excessive vibration will lead to uneven distribution of the liquid film at the sealing end or even in the state of dry friction to accelerate the seal failure.The vibration characteristics and sealing performance of seals under different spring rates and static ring masses were compared and analyzed,and the optimal value range of anti-vibration parameters was obtained,and the spring rate had the greatest influence on seal vibration.Under the premise of meeting the requirements of seal leakage,reducing the spring rate and static ring quality can improve the vibration resistance of the mechanical seal of the high-speed and high-pressure pump.Aiming at the application of different sealing ring materials in seawater and freshwater environments,the friction and wear test of high-speed and high-pressure pump mechanical seal ring material pairing was carried out,and the end morphology,friction coefficient and wear rate changes of three different moving ring materials（silicon carbide,cemented carbide,cemented carbide spraying）and silicon carbide static ring paired in seawater and freshwater environments were explored,and the wear mechanism of different sealing ring materials was obtained.The results show that the silicon carbide moving ring shows better friction characteristics due to its stable chemical properties and wear resistance,while the moving ring is a combination of cemented carbide and cemented carbide spraying material,which is easy to cause end face oxidation due to high temperature in seawater and fresh water environment,which aggravates wear.Independently developed and built a high-speed and high-pressure pump mechanical seal performance test bench,carried out variable pressure and variable speed seal performance tests,and verified the accuracy and reliability of the high-speed and high-pressure pump mechanical seal performance analysis model.By analyzing the performance and vibrating characteristics of high pressure high-speed pumps,this article obtained high speed mechanical compaction of thermal liters,as well as laws of transformation of high pressure high-speed pumps,investigating the mechanism of wear and tear of friction between ring materials and opening the properties of sealed vibrations.Providing the foundation for optimizing the design,selecting leakproof materials,leakproof performance and increasing vibration resistance of high pressure high-speed pumps.