Research On Sealing Charateristics Of Typical Flanged Casing Structure

Aeroengine parts of the casing commonly used bolted flanged connection structure.Because of the high temperature difference and pressure difference inside and outside the casing,it is easy to cause gas leakage on the joint surface of the installation side,which will inevitably reduce the working efficiency of the engine and even cause accidents.Therefore,it is of great significance to study the sealing characteristics of the bolted flanged connection structure of the aeroengine casing.In this paper,the contact condition between the casing flanges is taken as a key research object,and the bolted flanged connection structure in a segment casing is simplified,and use Ansys Workbench software to build three-dimensional model,the contact analysis method is used to calculate the contact pressure and contact gap of the contact surface,and the influence of the structural parameters,such as number of bolts,diameter of bolts,thickness of the flange and the axial force,internal pressure and bending moment on the sealing performance of the bolted flanged connection;the effects of the same bolt pretension in different loading method and the different bolt pretension in same loading method on the sealing characteristics of flange are also studied;finally,the influence of temperature on the sealing characteristics of the bolted flanged connection is studied.The research shows that with the decrease of the number of bolts,the bolt spacing is increased,the contact gap between the contact surface increases at first and then decreases and then increases;increasing the bolt diameter,average contact pressure increases,the average contact gap corresponding to gradually reduce.The larger the bolt diameter,the larger the area of action,and the constant number of bolts,so that the middle of the two bolt holes subjected to a preload will be larger,and then the sealing performance is better;the average contact pressure increases with the increase of the thickness of the flange,and the contact gap decreases with the thickness of the flange.Increasing the axial force and bending moment,the average value of the contact gap increases,which has a negative impact on the sealing performance of the bolted flanged connection,which leads to serious leakage.With the increase of the internal pressure,the average value of the contact gap becomes smaller and then increases gradually.Therefore,the internal pressure,as a whole,has a negative effect on the sealing performance of the bolted flanged connectionIn the ASME PCC-1-2010 traditional method,its alternatives and JIS B 2251-2008 and other 7 methods,the alternative third is the best solution,because this method can not only guarantee the sealing of lange,the tightening steps are relatively little;the star loading method2 A is better than the sequential loading method 2B by comparing the alternatives 2A and the alternative 2B;when the preload is 3750 N,the sealing characteristics of the bolted flangedconnection are best,not the maximum 5000 N.So it is not the preload is greater,that the sealing performance of the bolted flanged connection is better.Due to the different axial and radial temperature distributions at the bolted flanged connections,the amount of expansion is different during the operation stage,which makes the lower end of the flange separated more and the contact gap larger than the assembly stage of only the bolt preload.Further,the sealing performance is deteriorated and the amount of leakage is increased.The research in this paper can provide a guideline for comprehensive optimization design of anti-leakage for the flange of aeroengine casing.