Nonbonded flexible pipes consist of polymer materials that experience stress relaxation at high temperatures,which ultimately affects the sealing performance of end sealing systems.To assess stress relaxation curves u...Nonbonded flexible pipes consist of polymer materials that experience stress relaxation at high temperatures,which ultimately affects the sealing performance of end sealing systems.To assess stress relaxation curves under varying temperatures and pre-strains,this paper conducts both tensile and stress relaxation tests on PVDF materials.To describe the stress relaxation characteristics of these materials,the Prony series is utilized.In order to identify the parameters of the series,the paper employs the Levenberg-Marquardt method of nonlinear regression.A finite element model is established to verify the accuracy of the parameter identification method.Subsequently,the paper establishes a two-dimensional axisymmetric finite element model of the sealing system in the end fitting,while taking into account fluid pressure inside the pipeline using a pressure penetration method.The impact of stress relaxation on the sealing performance is then discussed.Finally,the paper alters the coefficients of the Prony series to explore their significance on the sealing performance of the sealing system.展开更多
Elbows in pneumatic conveying systems are normally prone to the erosive effects of conveyed particles.There are a number of solutions available to reduce such damage.A widely used geometric alternative for replacing t...Elbows in pneumatic conveying systems are normally prone to the erosive effects of conveyed particles.There are a number of solutions available to reduce such damage.A widely used geometric alternative for replacing the 90°elbow and reducing erosive wear is the plugged tee.Another option,although less commonly used,is the vortex-chamber elbow.In both cases,the effective reduction in erosion brought about is unclear,as it strongly depends on the operating conditions.The present study assesses relative erosion among the plugged tee,vortex-chamber elbow,and standard elbow for a dilute gas-solid multiphase flow.A numerical model is employed to predict the penetration ratio and validated using experimental data for the plugged tee.Simulations are run for the standard and vortex-chamber elbows and plugged tee under the same conditions to compare the mechanics involved and the relative erosion reduction.The analysis uses variables relating to particle-wall interactions(impact angle,impact velocity,impact frequency)to illustrate the nature of the erosive process in each pipe fitting.In general,the geometric configurations of both the plugged tee and vortex-chamber elbow promote changes in particle dynamics that reduce the rate of erosion.On the basis of the relative erosion of the standard elbow,the plugged tee proves to be an interesting option in cases of a low mass loading,while the vortex-chamber elbow demonstrates its erosion reduction potential for higher mass loading conditions.Furthermore,the advantages and disadvantages of each fitting are highlighted.展开更多
基金the National Natural Science Foundation of China[Grant No.52088102,52001208,52111530135]Joint Funds of the National Natural Science Foundation of China[Grant No.U19B2013]+2 种基金Young Elite Scientists Sponsorship Program by CAST[Grant No.2020QNRC001]Chenguang Program of Shanghai Education Development Foundation and Shanghai Municipal Education Commission[Grant No.21CGA15,19CG10]Natural Science Foundation of Shanghai[Grant No.21ZR1434500,22ZR1434100].
文摘Nonbonded flexible pipes consist of polymer materials that experience stress relaxation at high temperatures,which ultimately affects the sealing performance of end sealing systems.To assess stress relaxation curves under varying temperatures and pre-strains,this paper conducts both tensile and stress relaxation tests on PVDF materials.To describe the stress relaxation characteristics of these materials,the Prony series is utilized.In order to identify the parameters of the series,the paper employs the Levenberg-Marquardt method of nonlinear regression.A finite element model is established to verify the accuracy of the parameter identification method.Subsequently,the paper establishes a two-dimensional axisymmetric finite element model of the sealing system in the end fitting,while taking into account fluid pressure inside the pipeline using a pressure penetration method.The impact of stress relaxation on the sealing performance is then discussed.Finally,the paper alters the coefficients of the Prony series to explore their significance on the sealing performance of the sealing system.
文摘Elbows in pneumatic conveying systems are normally prone to the erosive effects of conveyed particles.There are a number of solutions available to reduce such damage.A widely used geometric alternative for replacing the 90°elbow and reducing erosive wear is the plugged tee.Another option,although less commonly used,is the vortex-chamber elbow.In both cases,the effective reduction in erosion brought about is unclear,as it strongly depends on the operating conditions.The present study assesses relative erosion among the plugged tee,vortex-chamber elbow,and standard elbow for a dilute gas-solid multiphase flow.A numerical model is employed to predict the penetration ratio and validated using experimental data for the plugged tee.Simulations are run for the standard and vortex-chamber elbows and plugged tee under the same conditions to compare the mechanics involved and the relative erosion reduction.The analysis uses variables relating to particle-wall interactions(impact angle,impact velocity,impact frequency)to illustrate the nature of the erosive process in each pipe fitting.In general,the geometric configurations of both the plugged tee and vortex-chamber elbow promote changes in particle dynamics that reduce the rate of erosion.On the basis of the relative erosion of the standard elbow,the plugged tee proves to be an interesting option in cases of a low mass loading,while the vortex-chamber elbow demonstrates its erosion reduction potential for higher mass loading conditions.Furthermore,the advantages and disadvantages of each fitting are highlighted.
