Research On Sealing Performance Of Flared Coupling In Special Vehicles

Due to its compact structure and convenient assembly and disassembly,the flared coupling is widely used in the pipeline system in the fields of aviation,spaceflight,vehicle,ship,etc.,playing the role of pipeline connection and sealing.In practical engineering application,flared coupling usually carry oil pressure,temperature,and vibration load,resulting in flared coupling prone to leakage and bring security risks and economic losses in the use of the process.This paper in view of the special vehicle common flared coupling,combined with theoretical analysis,numerical simulation and experimental verification method,we studied the axial fastening force effect on the seal performance,relationship between preload and tightening torque,and axial tightening force decline law on vibration conditions,providing theory foundation and realization technology to improve the sealing performance of the flared coupling.The detailed research work is as follows:(1)The research status at home and abroad was analyzed,and the problems and shortages of the existing research were pointed out,and the research contents and significance of the thesis were presented.(2)A method for determining the axial force of the sealing performance of the flared coupling was presented.First,the establishment of a flared coupling sealing contact model of the interface,to explore the seal contact area parameter variation under the action of axial tightening force;on this basis,according to the flared coupling sealing performance of the sealing criterion and an axial tightening force is determined,to realize the maximum guarantee the sealing performance.The axial fastening force method for determining other conical surface sealing structure is also applicable.(3)The formula of the relationship between preload and tightening torque of the flared coupling was verified.The contact surfaces of the flared couplings were analyzed,and the contact states of each component were obtained.On the basis of this,a three-dimensional finite element analysis model is established,and the accuracy of the theoretical formula is verified by the three-dimensional finite element analysis model.(4)The research method of the axial tightening force decline law of the flared coupling under the vibration condition was established.The method introduced pretension 179 element into 3D model,for flared tube end transverse displacement load was applied.Based on this method,the thesis explored the nut loosening mechanism and an axial tightening force decline,and by adjusting the model parameters on the amplitude,friction coefficient,fitting clearance on vibration condition flared coupling to study the influence of fastening axial force decline.(5)The experimental research methods of sealing performance of two kinds of flared coupling was presented: the method of comprehensive verification of flared couplings of sealing performance;the lateral vibration test method of flared couplings.In the comprehensive verification of flared couplings of sealing performance,the actual working conditions is simulated under laboratory conditions,explores the influence of the oil pressure,oil temperature,vibration frequency,amplitude,and pre tightening torque.Flared coupling lateral vibration experiment applied cyclic lateral displacement in the end of flaring tubing,and study the loosening of nuts.Flared coupling lateral vibration experiment could be used to track and measure the lateral thrust and nut loosening angle,which was used for the experimental analysis and the verification simulation results.