As a fundamental component of an automobile engine’s timing chain drive system, the hydraulic automatic tensioner signifcantly enhances fuel economy while minimizing system vibrations and noise. However, there is a n...As a fundamental component of an automobile engine’s timing chain drive system, the hydraulic automatic tensioner signifcantly enhances fuel economy while minimizing system vibrations and noise. However, there is a noticeable lack of research on automatic hydraulic tensioners. This study presents a comprehensive calculation approach for the principal parameters of a hydraulic automatic tensioner. An efective method, grounded in hydraulics and multibody dynamics, was introduced for estimating the dynamic response of such a tensioner. The simulation model developed for the hydraulic tensioner is characterized by its rapid dynamic response, consistent operation, and high accuracy. The dynamic behavior of the tensioner was analyzed under varying boundary conditions, using sinusoidal signal excitation. It was observed that the maximum damping force increases with a decreasing leakage gap. Conversely, an increase in oil temperature or air content leads to a decrease in the maximum damping force. The reaction forces derived from these calculations align well with experimental results. This calculation and simulation approach ofers considerable value for the design of innovative hydraulic tensioners. It not only streamlines the design phase, minimizes the number of trials, and reduces product costs, but also provides robust insights for evaluating the performance of hydraulic tensioners.展开更多
Tension Leg Platform(TLP)in deepwater oil and gas field development usually consists of a hull,tendons,and top tension risers(TTRs).To maintain its top tension,each TTR is connected with a tensioner system to the hull...Tension Leg Platform(TLP)in deepwater oil and gas field development usually consists of a hull,tendons,and top tension risers(TTRs).To maintain its top tension,each TTR is connected with a tensioner system to the hull.Owing to the complicated configuration of the tensioners,the hull and TTRs form a strong coupled system.Traditionally,some simplified tensioner models are applied to analyze the TLP structures.There is a large discrepancy between their analysis results and the actual mechanism behaviors of a tensioner.It is very necessary to develop a more detailed tensioner model to consider the coupling effects between TLP and TTRs.In the present study,a fully coupled TLP hull-TTR system for hydrodynamic numerical simulation is established.A specific hydraulic pneumatic tensioner is modeled by considering 4 cylinders.The production TTR model is stacked up by specific riser joints.The simulation is also extended to analyze an array of TTRs.Different regular and irregular waves are considered.The behaviors of different cylinders are presented.The results show that it is important to consider the specific configurations of the tensioner and TTRs,which may lead to obviously different response behaviors,compared with those from a simplified model.展开更多
Different land use,and associated variations in agricultural or silvicultural practices,can cause substantial variations in soils’hydraulic properties.Thus,the optimal method for measuring these properties may vary,e...Different land use,and associated variations in agricultural or silvicultural practices,can cause substantial variations in soils’hydraulic properties.Thus,the optimal method for measuring these properties may vary,even among neighboring sites.In this study these variations were examined by comparing measurements of hydraulic properties of soil in fields used for poplar,alfalfa and wheat cultivation obtained with two steady flow methods(the White and Sully,and single disc with multiple tension methods)and two transient flow methods(the single disc with single tension,and multiple tensions with multiple disc radius methods).The fields were all located in Changwu municipality,a major grain-producing area in Shaanxi Province,China.Disc tension infiltrometers were used to measure unconfined,unsaturated infiltration over a range of supply pressure heads(h=−9 cm,−6 cm,−3 cm and 0)at the soil surface.Intact soil cores were sampled near the surface to determine bulk density and soil water retention curves at potentials ranging from−0.15 kPa to−100 kPa.Unsaturated hydraulic conductivity values over the range of supply pressure heads were estimated using Wooding’s equation for steady-state flow from a disc source.The van Genuchten water retention model was fitted to experimental data to estimate the parameter values.The results indicated that land use affects soils’saturated and unsaturated hydraulic conductivity.Further,steady state flow methods are most appropriate for measuring hydraulic properties of soils under poplar and wheat,due to their high organic contents and saturated hydraulic conductivity.However,for soils supporting alfalfa(which are more homogeneous),instant methods provide better results,in addition to substantial time and labor savings.展开更多
文摘As a fundamental component of an automobile engine’s timing chain drive system, the hydraulic automatic tensioner signifcantly enhances fuel economy while minimizing system vibrations and noise. However, there is a noticeable lack of research on automatic hydraulic tensioners. This study presents a comprehensive calculation approach for the principal parameters of a hydraulic automatic tensioner. An efective method, grounded in hydraulics and multibody dynamics, was introduced for estimating the dynamic response of such a tensioner. The simulation model developed for the hydraulic tensioner is characterized by its rapid dynamic response, consistent operation, and high accuracy. The dynamic behavior of the tensioner was analyzed under varying boundary conditions, using sinusoidal signal excitation. It was observed that the maximum damping force increases with a decreasing leakage gap. Conversely, an increase in oil temperature or air content leads to a decrease in the maximum damping force. The reaction forces derived from these calculations align well with experimental results. This calculation and simulation approach ofers considerable value for the design of innovative hydraulic tensioners. It not only streamlines the design phase, minimizes the number of trials, and reduces product costs, but also provides robust insights for evaluating the performance of hydraulic tensioners.
基金The research was financially supported by the National Natural Science Foundation of China for Youth(Grant No.51609169)Guangxi Science and Technology Major Project(Grant No.Guike AA17292007)+2 种基金the National Key R&D Program of China(Grant No.2018YFC0310502)National Natural Science Foundation of China(Grant No.51779173)China Scholarship Council(CSC).
文摘Tension Leg Platform(TLP)in deepwater oil and gas field development usually consists of a hull,tendons,and top tension risers(TTRs).To maintain its top tension,each TTR is connected with a tensioner system to the hull.Owing to the complicated configuration of the tensioners,the hull and TTRs form a strong coupled system.Traditionally,some simplified tensioner models are applied to analyze the TLP structures.There is a large discrepancy between their analysis results and the actual mechanism behaviors of a tensioner.It is very necessary to develop a more detailed tensioner model to consider the coupling effects between TLP and TTRs.In the present study,a fully coupled TLP hull-TTR system for hydrodynamic numerical simulation is established.A specific hydraulic pneumatic tensioner is modeled by considering 4 cylinders.The production TTR model is stacked up by specific riser joints.The simulation is also extended to analyze an array of TTRs.Different regular and irregular waves are considered.The behaviors of different cylinders are presented.The results show that it is important to consider the specific configurations of the tensioner and TTRs,which may lead to obviously different response behaviors,compared with those from a simplified model.
基金the National Natural Science Foundation of China(grant nos.51239009,41371239)Science and Technology Planning Project of Shaanxi Province(2013kjxx-38)Natural Science of Shaanxi Province(2015JQ5161).
文摘Different land use,and associated variations in agricultural or silvicultural practices,can cause substantial variations in soils’hydraulic properties.Thus,the optimal method for measuring these properties may vary,even among neighboring sites.In this study these variations were examined by comparing measurements of hydraulic properties of soil in fields used for poplar,alfalfa and wheat cultivation obtained with two steady flow methods(the White and Sully,and single disc with multiple tension methods)and two transient flow methods(the single disc with single tension,and multiple tensions with multiple disc radius methods).The fields were all located in Changwu municipality,a major grain-producing area in Shaanxi Province,China.Disc tension infiltrometers were used to measure unconfined,unsaturated infiltration over a range of supply pressure heads(h=−9 cm,−6 cm,−3 cm and 0)at the soil surface.Intact soil cores were sampled near the surface to determine bulk density and soil water retention curves at potentials ranging from−0.15 kPa to−100 kPa.Unsaturated hydraulic conductivity values over the range of supply pressure heads were estimated using Wooding’s equation for steady-state flow from a disc source.The van Genuchten water retention model was fitted to experimental data to estimate the parameter values.The results indicated that land use affects soils’saturated and unsaturated hydraulic conductivity.Further,steady state flow methods are most appropriate for measuring hydraulic properties of soils under poplar and wheat,due to their high organic contents and saturated hydraulic conductivity.However,for soils supporting alfalfa(which are more homogeneous),instant methods provide better results,in addition to substantial time and labor savings.
