A numerical model to predict film torque of hydro-viscous clutch was developed.The model was established with computational fluid dynamics（CFD）.The pressure distribution,velocity of flow and film torque were obtaine...A numerical model to predict film torque of hydro-viscous clutch was developed.The model was established with computational fluid dynamics（CFD）.The pressure distribution,velocity of flow and film torque were obtained based on vertical-horizontal grooved plate and radial grooved plate separately.The boundary conditions,such as the relative rotation,the fluid temperature and the oil feeding pressure,were also discussed.The results showed that the film torque of two kinds of grooved plate increased with increasing relative rotation.However,the film torque decreased with increasing fluid temperature and feeding pressure.Meanwhile,the film torque of radial grooved plate was less than vertical-horizontal grooved plate at the same condition.Our study showed that the model can efficiently calculate the film torque with complex geometry parameters and boundary conditions.展开更多
Weather conditions play a pivotal role in embryo development and parental incubation costs,potentially impacting the clutch size and incubation behavior of birds.Understanding these effects is crucial for bird conserv...Weather conditions play a pivotal role in embryo development and parental incubation costs,potentially impacting the clutch size and incubation behavior of birds.Understanding these effects is crucial for bird conservation.Reeves’ s Pheasant(Syrmaticus reevesii) is a threatened species endemic to China,which is characterized by female-only incubation.However,there is a lack of information regarding the impact of weather conditions on clutch size and incubation behavior in this species.Using satellite tracking,we tracked 27 wild female Reeves’ s Pheasants from 2020 to 2023 in Hubei Province,China.We explored their clutch size and incubation behavior,as well as their responses to ambient temperature and precipitation.Clutch size averaged 7.75 ±1.36,had an association with average ambient temperature and average daily precipitation during the egglaying period,and was potentially linked to female breeding attempts.Throughout the incubation period,females took an average of 0.73 ±0.46 recesses every 24 h,with an average recess duration of 100.80 ±73.37 min and an average nest attendance of 92.98 ±5.27%.They showed a unimodal recess pattern in which nest departures peaked primarily between 13:00 and 16:00.Furthermore,females rarely left nests when daily precipitation was high.Recess duration and nest attendance were influenced by the interaction between daily mean ambient temperature and daily precipitation,as well as day of incubation.Additionally,there was a positive correlation between clutch size and recess duration.These results contribute valuable insights into the lifehistory features of this endangered species.展开更多
The wet multi-disc clutches are extensively used in various transmission systems,withone of the most prevalent failure modes being the buckling deformation of friction components.Animproved Hilbert-Huang transform met...The wet multi-disc clutches are extensively used in various transmission systems,withone of the most prevalent failure modes being the buckling deformation of friction components.Animproved Hilbert-Huang transform method(IHHT)is proposed to address the limitations of tradi-tional time-domain vibration analyses,such as low accuracy and mode mixing.This paper first clas-sifies the buckling degree of the friction components.Next,wavelet packet transform(WPT)isapplied to the vibration signals of different buckling plates to partition them into distinct fre-quency bands.Then,the instantaneous features are extracted by empirical mode decomposition(EMD)and Hilbert transform(HT)to discarding extraneous intrinsic mode function(IMF)com-ponents.Comparative analyses of Hilbert spectral entropy and time-domain features confirm theenhanced precision of IHHT under specific classifiers,which is better than traditional methods.展开更多
The control of the clutch engagement for an automatic mechanical transmission in the process of a tracklayer getting to start is studied. The dynamic model of power transmission and automatic clutch system is develope...The control of the clutch engagement for an automatic mechanical transmission in the process of a tracklayer getting to start is studied. The dynamic model of power transmission and automatic clutch system is developed. Using tools of Simulink, the transient characteristics during the vehicle starting, including the jerk and the clutch slip time, are provided here. Based on the analyses of the simulation results and driver’s experiences, a fuzzy controller is designed to control the clutch engagement. Simulation results verify its value.展开更多
Based on the theoretical analyses, the dynamic and mathematical models of the system were developed. The models were implemented in the ambit of the Matlab/Simulink environment, and an integrated simulation model was ...Based on the theoretical analyses, the dynamic and mathematical models of the system were developed. The models were implemented in the ambit of the Matlab/Simulink environment, and an integrated simulation model was developed. The dynamic performance of the power shift clutch during engagement and disengagement was studied by using this assembly model. The sliding speed, torque transmitted through the clutch, and the rate at which energy is dissipated during the process were determined. Using this model, the calculation during simulation can be simplified. This lays a foundation for the dynamic performance research on the power train with the power shift clutch, and provides a powerful tool for developing an automatic, electronically controlled transmission.展开更多
The oil film clutch, which is superior in speed adjustment, is capable of being used in the belt conveyor to carry out soft start operation. According to running properties of both belt conveyor and oil film clutch...The oil film clutch, which is superior in speed adjustment, is capable of being used in the belt conveyor to carry out soft start operation. According to running properties of both belt conveyor and oil film clutch, equations that are used to decide the lubricating oil flow and the number of oil films (i.e. the number of rotating and stationary plates) are deduced theoretically. Also key parameters are provided for the design of the hydraulic system. All these together provide the theoretical basis for the soft start design of the belt conveyor and references for the application of the oil film clutch in similar fields.展开更多
Aim To carry out an experiment of the application of ER fluids in the clutch by reforming a fan clutch used in a truck. Methods At three different input rotating speeds,when the strength of applied electric field was ...Aim To carry out an experiment of the application of ER fluids in the clutch by reforming a fan clutch used in a truck. Methods At three different input rotating speeds,when the strength of applied electric field was changed, the output rotating speeds were recorded and analyzed. Results By comparing the results got under different experimental procedures with those measured with an electro-rheometer, it can be seen that the shearing rate has tremendous influence on the speed modulating of a fan clutch. This is because the disperse phase can't form chains (clusters)easily at high shear rate.Conclusion The result tested on the present ER fluid demonstrates that this fluid will show the properties of Newton one,i.e. its apparent viscosity is constant. as the shear rate increases.展开更多
The design of sleeve detach and reunion drive device of screw melt ex- truder equipment was optimized, based on the present installation of hygraulic drive device to achieve the mechanical opening and closing of the s...The design of sleeve detach and reunion drive device of screw melt ex- truder equipment was optimized, based on the present installation of hygraulic drive device to achieve the mechanical opening and closing of the sleeve, the dynamic model of the sleeve detach and reunion drive was theoretically measured, and it was verified that the device is simple to operate and convenient to maintain, thus it has great social values.展开更多
The Hainan Peacock Pheasant (Polyplectron katsumatae),the smallest allied species of somber forest peacock pheasants among the taxa of Polyplectron spp.,is a rare tropical forest bird endemic to China,and distributed ...The Hainan Peacock Pheasant (Polyplectron katsumatae),the smallest allied species of somber forest peacock pheasants among the taxa of Polyplectron spp.,is a rare tropical forest bird endemic to China,and distributed only in the mountainous region of central and southwestern Hainan Island dominated by evergreen broadleaf forests.By integrating references and unpublished data based on our field surveys,we presented information on species status,distribution and population,habitat and home range,breeding ecology and conservation of the Hainan Peacock Pheasant.Future investigation should focus on its life history traits in relation to vulnerability.Considering its limited distribution and small population size,it has recently been recognized as "Endangered" by the IUCN Red List to prevent loss of this island endemic.展开更多
Gives a dynamic mathematical model of a typical type of multiple discs hydroviscous drive device which has been proved to be correct through tests.Utilizing the method of root-locus analysis the dynamic performance of...Gives a dynamic mathematical model of a typical type of multiple discs hydroviscous drive device which has been proved to be correct through tests.Utilizing the method of root-locus analysis the dynamic performance of this device is studied according to the model.Theoretical analysis and test re- suits show that the dynamic performance of the object of study can be greatly improved by speed negative feedback.展开更多
Reduction of drag torque is one of important potentials to improve transmission efficiency.Existing mathematical model of drag torque was not accurate to predict the decrease after oil film shrinking because of the di...Reduction of drag torque is one of important potentials to improve transmission efficiency.Existing mathematical model of drag torque was not accurate to predict the decrease after oil film shrinking because of the difficulty in modeling the flow pattern between two plates.Flow pattern was considered as laminar flow and full oil film in the gap between two plates in traditional model.Subsequent equivalent circumferential degree model presented an improvement in oil film shrinking due to centrifugal force,but was also based on full oil film in the gap,which resulted difference between model prediction and experimental data.The objective of this paper is to develop an accurate mathematical model for the above problem by using experimental verification.An experimental apparatus was set up to test drag torque of disengaged wet clutch consisting of single friction and separate plate.A high speed camera was used to record the flow pattern through transparent quartz disk plate.The visualization of flow pattern in the clearance was investigated to evaluate the characteristics of oil film shrinking.Visual test results reveal that the oil film begins to shrink from outer radius to inner radius at the stationary plate and only flows along the rotating plate after shrinking.Meanwhile,drag torque decreases sharply due to little contact area between the stationary plate and the oil.A three-dimensional Navier-Stokes （N-S） equation based on laminar flow is presented to model the drag torque.Pressure distributions in radial and circumferential directions as well as speed distributions are deduced.The model analysis reveals that the acceleration of flow in radial direction caused by centrifugal force is the key reason for the shrinking at the constant feeding flow rate.An approach to descript flow pattern was presented on the basis of visual observation.The drag torque predicted by the model agrees well with test data for non-grooved wet clutch.The proposed model enhances the precision for predicting drag torque,and lays down a framework on which some subsequent models are developed.展开更多
Reduction of drag torque in disengaged wet clutch is one of important potentials for vehicle transmission improvement. The flow of the oil film in clutch clearance is investigated. A three-dimension Navier-Stokes(N-S)...Reduction of drag torque in disengaged wet clutch is one of important potentials for vehicle transmission improvement. The flow of the oil film in clutch clearance is investigated. A three-dimension Navier-Stokes(N-S) equation based on laminar flow is presented to model the drag torque. Pressure and speed distribution in radial and circumferential directions are deduced. The theoretical analysis reveals that oil flow acceleration in radial direction caused by centrifugal force is the key reason for the shrinking of oil film as constant feeding flow rate. The peak drag torque occurs at the beginning of oil film shrinking. A variable is introduced to describe effective oil film area and drag torque after oil film shrinking is well evaluated with the variable. Under the working condition, tests were made to obtain drag torque curves at different clutch speed and oil viscosity. The tests confirm that simulation results agree with test data. The model performs well in the prediction of drag torque and lays a theoretical foundation to reduce it.展开更多
Start-up working condition is the key to the research of optimal engagementof automatic clutch for AMT. In order to guarantee an ideal dynamic performance of the clutchengagement, an optimal controller is designed by ...Start-up working condition is the key to the research of optimal engagementof automatic clutch for AMT. In order to guarantee an ideal dynamic performance of the clutchengagement, an optimal controller is designed by considering throttle angle, engine speed, gearratio, vehicle acceleration and road condition. The minimum value principle is also introduced toachieve an optimal dynamic performance of the nonlinear system compromised in friction plate wearand vehicle drive quality. The optimal trajectory of the clutch engagement can be described in theform of explicit and analytical expressions and characterized by the deterministic and accuratecontrol strategy in stead of indeterministic and soft control techniques which need thousands ofexperiments. For validation of the controller, test work is carried out for the automated clutchengagements in a commercial car with an traditional mechanical transmission, a hydraulic actuator, agroup of sensors and a portable computer system. It is shown through experiments that dynamicbehaviors of the clutch engagement operated by the optimal control are more effective and efficientthan those by fuzzy control.展开更多
The flow field of the oil film between frictional pairs in the hydroviscous drive test rig is investigated. A three-dimensional Navier-Stokes（N-S） equation considering viscous force and inertial force rather than Re...The flow field of the oil film between frictional pairs in the hydroviscous drive test rig is investigated. A three-dimensional Navier-Stokes（N-S） equation considering viscous force and inertial force rather than Reynolds equation or modified Reynolds equation is presented to model the flow field. Pressure and temperature distribution in radial and circumferential direction under three different conditions, i.e., isothermal, that considering viscosity-temperature characteristic as well as shear thinning non-Newtonian fluid are simulated, respectively, by utilizing the commercial computational fluid dynamics（CFD） software FLUENT. The results reveal that the grooves on the driven plate make the pressure, temperature distribution present periodic variation. The oil temperature and shear rate have important effects on the flow field between frictional pairs, and the oil temperature is more important parameter. The simulation results lay a theoretical foundation for the reasonable designs ofhydroviscous drive.展开更多
基金Supported by the National Natural Science Foundation of China(51275039)
文摘A numerical model to predict film torque of hydro-viscous clutch was developed.The model was established with computational fluid dynamics（CFD）.The pressure distribution,velocity of flow and film torque were obtained based on vertical-horizontal grooved plate and radial grooved plate separately.The boundary conditions,such as the relative rotation,the fluid temperature and the oil feeding pressure,were also discussed.The results showed that the film torque of two kinds of grooved plate increased with increasing relative rotation.However,the film torque decreased with increasing fluid temperature and feeding pressure.Meanwhile,the film torque of radial grooved plate was less than vertical-horizontal grooved plate at the same condition.Our study showed that the model can efficiently calculate the film torque with complex geometry parameters and boundary conditions.
基金supported by the National Natural Science Foundation of China (grant number 31872240)。
文摘Weather conditions play a pivotal role in embryo development and parental incubation costs,potentially impacting the clutch size and incubation behavior of birds.Understanding these effects is crucial for bird conservation.Reeves’ s Pheasant(Syrmaticus reevesii) is a threatened species endemic to China,which is characterized by female-only incubation.However,there is a lack of information regarding the impact of weather conditions on clutch size and incubation behavior in this species.Using satellite tracking,we tracked 27 wild female Reeves’ s Pheasants from 2020 to 2023 in Hubei Province,China.We explored their clutch size and incubation behavior,as well as their responses to ambient temperature and precipitation.Clutch size averaged 7.75 ±1.36,had an association with average ambient temperature and average daily precipitation during the egglaying period,and was potentially linked to female breeding attempts.Throughout the incubation period,females took an average of 0.73 ±0.46 recesses every 24 h,with an average recess duration of 100.80 ±73.37 min and an average nest attendance of 92.98 ±5.27%.They showed a unimodal recess pattern in which nest departures peaked primarily between 13:00 and 16:00.Furthermore,females rarely left nests when daily precipitation was high.Recess duration and nest attendance were influenced by the interaction between daily mean ambient temperature and daily precipitation,as well as day of incubation.Additionally,there was a positive correlation between clutch size and recess duration.These results contribute valuable insights into the lifehistory features of this endangered species.
文摘The wet multi-disc clutches are extensively used in various transmission systems,withone of the most prevalent failure modes being the buckling deformation of friction components.Animproved Hilbert-Huang transform method(IHHT)is proposed to address the limitations of tradi-tional time-domain vibration analyses,such as low accuracy and mode mixing.This paper first clas-sifies the buckling degree of the friction components.Next,wavelet packet transform(WPT)isapplied to the vibration signals of different buckling plates to partition them into distinct fre-quency bands.Then,the instantaneous features are extracted by empirical mode decomposition(EMD)and Hilbert transform(HT)to discarding extraneous intrinsic mode function(IMF)com-ponents.Comparative analyses of Hilbert spectral entropy and time-domain features confirm theenhanced precision of IHHT under specific classifiers,which is better than traditional methods.
文摘The control of the clutch engagement for an automatic mechanical transmission in the process of a tracklayer getting to start is studied. The dynamic model of power transmission and automatic clutch system is developed. Using tools of Simulink, the transient characteristics during the vehicle starting, including the jerk and the clutch slip time, are provided here. Based on the analyses of the simulation results and driver’s experiences, a fuzzy controller is designed to control the clutch engagement. Simulation results verify its value.
文摘Based on the theoretical analyses, the dynamic and mathematical models of the system were developed. The models were implemented in the ambit of the Matlab/Simulink environment, and an integrated simulation model was developed. The dynamic performance of the power shift clutch during engagement and disengagement was studied by using this assembly model. The sliding speed, torque transmitted through the clutch, and the rate at which energy is dissipated during the process were determined. Using this model, the calculation during simulation can be simplified. This lays a foundation for the dynamic performance research on the power train with the power shift clutch, and provides a powerful tool for developing an automatic, electronically controlled transmission.
文摘The oil film clutch, which is superior in speed adjustment, is capable of being used in the belt conveyor to carry out soft start operation. According to running properties of both belt conveyor and oil film clutch, equations that are used to decide the lubricating oil flow and the number of oil films (i.e. the number of rotating and stationary plates) are deduced theoretically. Also key parameters are provided for the design of the hydraulic system. All these together provide the theoretical basis for the soft start design of the belt conveyor and references for the application of the oil film clutch in similar fields.
文摘Aim To carry out an experiment of the application of ER fluids in the clutch by reforming a fan clutch used in a truck. Methods At three different input rotating speeds,when the strength of applied electric field was changed, the output rotating speeds were recorded and analyzed. Results By comparing the results got under different experimental procedures with those measured with an electro-rheometer, it can be seen that the shearing rate has tremendous influence on the speed modulating of a fan clutch. This is because the disperse phase can't form chains (clusters)easily at high shear rate.Conclusion The result tested on the present ER fluid demonstrates that this fluid will show the properties of Newton one,i.e. its apparent viscosity is constant. as the shear rate increases.
文摘The design of sleeve detach and reunion drive device of screw melt ex- truder equipment was optimized, based on the present installation of hygraulic drive device to achieve the mechanical opening and closing of the sleeve, the dynamic model of the sleeve detach and reunion drive was theoretically measured, and it was verified that the device is simple to operate and convenient to maintain, thus it has great social values.
基金supported by the NationalNatural Science Foundation of China(Nos.30860044,30360015 and39830030)by Program for New Century Excellent Talents in University(NCET-10-0111)
文摘The Hainan Peacock Pheasant (Polyplectron katsumatae),the smallest allied species of somber forest peacock pheasants among the taxa of Polyplectron spp.,is a rare tropical forest bird endemic to China,and distributed only in the mountainous region of central and southwestern Hainan Island dominated by evergreen broadleaf forests.By integrating references and unpublished data based on our field surveys,we presented information on species status,distribution and population,habitat and home range,breeding ecology and conservation of the Hainan Peacock Pheasant.Future investigation should focus on its life history traits in relation to vulnerability.Considering its limited distribution and small population size,it has recently been recognized as "Endangered" by the IUCN Red List to prevent loss of this island endemic.
文摘Gives a dynamic mathematical model of a typical type of multiple discs hydroviscous drive device which has been proved to be correct through tests.Utilizing the method of root-locus analysis the dynamic performance of this device is studied according to the model.Theoretical analysis and test re- suits show that the dynamic performance of the object of study can be greatly improved by speed negative feedback.
基金supported by National Defense Arming Pre-researching Project of China(Grant No.40402060102)
文摘Reduction of drag torque is one of important potentials to improve transmission efficiency.Existing mathematical model of drag torque was not accurate to predict the decrease after oil film shrinking because of the difficulty in modeling the flow pattern between two plates.Flow pattern was considered as laminar flow and full oil film in the gap between two plates in traditional model.Subsequent equivalent circumferential degree model presented an improvement in oil film shrinking due to centrifugal force,but was also based on full oil film in the gap,which resulted difference between model prediction and experimental data.The objective of this paper is to develop an accurate mathematical model for the above problem by using experimental verification.An experimental apparatus was set up to test drag torque of disengaged wet clutch consisting of single friction and separate plate.A high speed camera was used to record the flow pattern through transparent quartz disk plate.The visualization of flow pattern in the clearance was investigated to evaluate the characteristics of oil film shrinking.Visual test results reveal that the oil film begins to shrink from outer radius to inner radius at the stationary plate and only flows along the rotating plate after shrinking.Meanwhile,drag torque decreases sharply due to little contact area between the stationary plate and the oil.A three-dimensional Navier-Stokes （N-S） equation based on laminar flow is presented to model the drag torque.Pressure distributions in radial and circumferential directions as well as speed distributions are deduced.The model analysis reveals that the acceleration of flow in radial direction caused by centrifugal force is the key reason for the shrinking at the constant feeding flow rate.An approach to descript flow pattern was presented on the basis of visual observation.The drag torque predicted by the model agrees well with test data for non-grooved wet clutch.The proposed model enhances the precision for predicting drag torque,and lays down a framework on which some subsequent models are developed.
基金supported by National Defense Arming Pre-researching Project(Grant No. 40402060102)
文摘Reduction of drag torque in disengaged wet clutch is one of important potentials for vehicle transmission improvement. The flow of the oil film in clutch clearance is investigated. A three-dimension Navier-Stokes(N-S) equation based on laminar flow is presented to model the drag torque. Pressure and speed distribution in radial and circumferential directions are deduced. The theoretical analysis reveals that oil flow acceleration in radial direction caused by centrifugal force is the key reason for the shrinking of oil film as constant feeding flow rate. The peak drag torque occurs at the beginning of oil film shrinking. A variable is introduced to describe effective oil film area and drag torque after oil film shrinking is well evaluated with the variable. Under the working condition, tests were made to obtain drag torque curves at different clutch speed and oil viscosity. The tests confirm that simulation results agree with test data. The model performs well in the prediction of drag torque and lays a theoretical foundation to reduce it.
文摘Start-up working condition is the key to the research of optimal engagementof automatic clutch for AMT. In order to guarantee an ideal dynamic performance of the clutchengagement, an optimal controller is designed by considering throttle angle, engine speed, gearratio, vehicle acceleration and road condition. The minimum value principle is also introduced toachieve an optimal dynamic performance of the nonlinear system compromised in friction plate wearand vehicle drive quality. The optimal trajectory of the clutch engagement can be described in theform of explicit and analytical expressions and characterized by the deterministic and accuratecontrol strategy in stead of indeterministic and soft control techniques which need thousands ofexperiments. For validation of the controller, test work is carried out for the automated clutchengagements in a commercial car with an traditional mechanical transmission, a hydraulic actuator, agroup of sensors and a portable computer system. It is shown through experiments that dynamicbehaviors of the clutch engagement operated by the optimal control are more effective and efficientthan those by fuzzy control.
基金National Natural Science Foundation of China(No.50475106)
文摘The flow field of the oil film between frictional pairs in the hydroviscous drive test rig is investigated. A three-dimensional Navier-Stokes（N-S） equation considering viscous force and inertial force rather than Reynolds equation or modified Reynolds equation is presented to model the flow field. Pressure and temperature distribution in radial and circumferential direction under three different conditions, i.e., isothermal, that considering viscosity-temperature characteristic as well as shear thinning non-Newtonian fluid are simulated, respectively, by utilizing the commercial computational fluid dynamics（CFD） software FLUENT. The results reveal that the grooves on the driven plate make the pressure, temperature distribution present periodic variation. The oil temperature and shear rate have important effects on the flow field between frictional pairs, and the oil temperature is more important parameter. The simulation results lay a theoretical foundation for the reasonable designs ofhydroviscous drive.
