During the production of natural gas hydrates,micron-sized sand particles coexist with hydrate within the transportation pipeline,posing a significant threat to the safety of pipeline flow.However,the influence of san...During the production of natural gas hydrates,micron-sized sand particles coexist with hydrate within the transportation pipeline,posing a significant threat to the safety of pipeline flow.However,the influence of sand particles on hydrate formation mechanisms and rheological properties remains poorly understood.Consequently,using a high-pressure reactor system,the phase equilibrium conditions,hydrate formation characteristics,hydrate concentration,and the slurry viscosity in micron-sized sand system are investigated in this work.Furthermore,the effects of sand particle size,sand concentration,and initial pressure on these properties are analyzed.The results indicate that a high concentration of micron-sized sand particles enhances the formation of methane hydrates.When the volume fraction of sand particles exceeds or equals 3%,the phase equilibrium conditions of the methane hydrate shift to the left relative to that of the pure water system(lower temperature,higher pressure).This shift becomes more pronounced with smaller particle sizes.Besides,under these sand concentration conditions,methane hydrates exhibit secondary or even multiple formation events,though the formation rate decreases.Additionally,the torque increases significantly and fluctuates considerably.The Roscoe-Brinkman model yields the most accurate slurry viscosity calculations,and as sand concentration increases,both hydrate concentration and slurry viscosity also increase.展开更多
In the traditional reliability evaluation based on the Bayesian method,the failure probability of nodes is usually expressed by the average failure rate within a period of time.Aiming at the shortcomings of traditiona...In the traditional reliability evaluation based on the Bayesian method,the failure probability of nodes is usually expressed by the average failure rate within a period of time.Aiming at the shortcomings of traditional Bayesian network reliability evaluation methods,this paper proposes a Bayesian network reliability evaluation method considering dynamics and fuzziness.The fuzzy theory and the dynamic of component failure probability are introduced to construct the dynamic fuzzy set function.Based on the solving characteristics of the dynamic fuzzy set and Bayesian network,the fuzzy dynamic probability and fuzzy dynamic importance degree of the fault state of leaf nodes are solved.Finally,through the dynamic fuzzy reliability analysis of CNC machine tool hydraulic system balance circuit,the application of this method in system reliability evaluation is verified,which provides support for fault diagnosis of CNC machine tools.展开更多
基金supported by the Natural Science Starting Project of Sichuan Provincial Youth Foundation Project(2025ZNSFSC1356)Southwest Petroleum University,China(2023QHZ019)+1 种基金General Project of the Sichuan Provincial Natural Science Foundation,China(24NSFSC1295)Open fund of Dazhou Industrial Technology Institute of Intelligent Manufacturing,China(ZNZZ2215).
文摘During the production of natural gas hydrates,micron-sized sand particles coexist with hydrate within the transportation pipeline,posing a significant threat to the safety of pipeline flow.However,the influence of sand particles on hydrate formation mechanisms and rheological properties remains poorly understood.Consequently,using a high-pressure reactor system,the phase equilibrium conditions,hydrate formation characteristics,hydrate concentration,and the slurry viscosity in micron-sized sand system are investigated in this work.Furthermore,the effects of sand particle size,sand concentration,and initial pressure on these properties are analyzed.The results indicate that a high concentration of micron-sized sand particles enhances the formation of methane hydrates.When the volume fraction of sand particles exceeds or equals 3%,the phase equilibrium conditions of the methane hydrate shift to the left relative to that of the pure water system(lower temperature,higher pressure).This shift becomes more pronounced with smaller particle sizes.Besides,under these sand concentration conditions,methane hydrates exhibit secondary or even multiple formation events,though the formation rate decreases.Additionally,the torque increases significantly and fluctuates considerably.The Roscoe-Brinkman model yields the most accurate slurry viscosity calculations,and as sand concentration increases,both hydrate concentration and slurry viscosity also increase.
基金This research was supported by the Sichuan Science and Technology Depart-ment under Contract Nos.2019YJ0396 and 2018JY0516the National Natural Science Foundation of China under the Contract No.51705041.
文摘In the traditional reliability evaluation based on the Bayesian method,the failure probability of nodes is usually expressed by the average failure rate within a period of time.Aiming at the shortcomings of traditional Bayesian network reliability evaluation methods,this paper proposes a Bayesian network reliability evaluation method considering dynamics and fuzziness.The fuzzy theory and the dynamic of component failure probability are introduced to construct the dynamic fuzzy set function.Based on the solving characteristics of the dynamic fuzzy set and Bayesian network,the fuzzy dynamic probability and fuzzy dynamic importance degree of the fault state of leaf nodes are solved.Finally,through the dynamic fuzzy reliability analysis of CNC machine tool hydraulic system balance circuit,the application of this method in system reliability evaluation is verified,which provides support for fault diagnosis of CNC machine tools.
