The contact characteristics between cycloidal gear teeth and pinwheel teeth significantly impact the operational performance of cycloidal pinwheel mechanisms.Current research methods tend to rely primarily on theoreti...The contact characteristics between cycloidal gear teeth and pinwheel teeth significantly impact the operational performance of cycloidal pinwheel mechanisms.Current research methods tend to rely primarily on theoretical calculations,with limited use of experimental methods for detecting dynamic contact properties.We propose a novel method for testing the dynamic contact characteristics of cycloidal pinwheel mechanisms.By combining Hertzian contact theory and contact strength theory,we establish a force and meshing stiffness model for the cycloidal and pinwheel gears,and determine the maximum contact stress and variations in pinwheel gear force and meshing stiffness.Based on the principle of photoelasticity,we built a testing platform for the cycloidal pinwheel mechanism to assess its contact characteristics.This platform provides the stress distribution of the cycloidal pinwheel mechanism and allows us to deduce key parameters such as the number of meshing teeth and the meshing interval.This study provides an experimental method for investigating the contact characteristics of cycloidal pinwheel mechanisms.展开更多
Based on the analysis of the pin-hole-output mechanism in the cycloid drive,a more accurate force analysis method is provided, in which the manufacture error is considered, bywhich the contact force between pin and pi...Based on the analysis of the pin-hole-output mechanism in the cycloid drive,a more accurate force analysis method is provided, in which the manufacture error is considered, bywhich the contact force between pin and pin-hole can be calculated more accurately in the wholedriving process.展开更多
In recent years, a lot of research work has been carried out on the cycloidal rotors. However, it lacks thorough understanding about the effects of the blade platform shape on the hover efficiency of the cycloidal rot...In recent years, a lot of research work has been carried out on the cycloidal rotors. However, it lacks thorough understanding about the effects of the blade platform shape on the hover efficiency of the cycloidal rotor, and the knowledge of how to design the platform shape of the blades. This paper presents a numerical simulation model based on Unsteady ReynoldsAveraged Navier–Stokes equations(URANSs), which is further validated by the experimental results. The effects of blade aspect ratio and taper ratio are analyzed, which shows that the cycloidal rotors with the same chord length have quite similar performance even though the blade aspect ratio varies from a very small value to a large one. By comparing the cycloidal rotors with different taper ratios, it is found that the rotors with large blade taper ratio outperform those with small taper ratio. This is due to the fact that the blade with larger taper ratio has longer chord and hence better efficiency. The analysis results show that the unsteady aerodynamic effects due to blade pitching motion play a more important role in the efficiency than the blade platform shape. Therefore we should pay more attention to the blade airfoil and pitching motion than the blade platform shape.The main contributions of this paper include: the analysis of the effects of aspect ratio and taper ratio on the hover efficiency of cycloidal rotor based on both the experimental and numerical simulation results; the finding of the main influencing factors on the hover efficiency; the qualitative guidance on how to design the blade platform shape for cycloidal rotors.展开更多
Cycloid speed reducers are widely used in many industrial areas due to the advantages of compact size, high reduction ratio and high stiffness. However, currently, there are not many analytical models for the mesh sti...Cycloid speed reducers are widely used in many industrial areas due to the advantages of compact size, high reduction ratio and high stiffness. However, currently, there are not many analytical models for the mesh stiffness calculation, which is a crucial parameter for the high-fidelity gear dynamic model. This is partially due to the difficulty of backlash determination and the complexity of multi-tooth contact deformation during the meshing process. In this paper, a new method to calculate the mesh stiffness is proposed including the effects of tooth profile modification and eccentricity error. The time-varying mesh parameters and load distribution of cycloid-pin gear pair are determined based on the unloaded tooth contact analysis （TCA） and the nonlinear Hertzian contact theory, allowing accurate calculations of the contact stiffness of single tooth pair and the torsional stiffness of multi-tooth pairs. A detailed parametric study is presented to demonstrate the influences of tooth profile modification, applied torque and eccentricity error on the torsional mesh stiffness, loaded transmission error, Hertzian contact stiffness and load sharing factor. This model can be applied to further study the lost motion and dynamic characteristics of cycloid speed reducer and assist the optimization of its precision, vibration and noise levels.展开更多
The most conventional vehicle pretensioner system consists of an internal gear pair with involute teeth. However, it has been well known that the corresponding gear pairs are relatively weak under the situation of imp...The most conventional vehicle pretensioner system consists of an internal gear pair with involute teeth. However, it has been well known that the corresponding gear pairs are relatively weak under the situation of impact loadings. To improve this phenomenon, a new pretensioning gear system with cycloid teeth rather than the involute ones was proposed, and dual cycloidal gear mechanisms were designed for satisfying geometric constraints and dynamic loading conditions. The simulations of the prototypes were conducted by LS-DYNA program and the experiments for a prototype were performed for a dynamic model with impact loading devices. The results show that the better operation and the smoother motion are confirmed in the proposed cycloidal gear system rather than the conventional one without interferences between gear teeth under the impact of a crash.展开更多
From the general formula for calculating the efficiency of planetary geartrains, the efficiency of the double crank ring-plate-type pin-cycloidal gear planetary drive isderived. To prove the theory, an experimental st...From the general formula for calculating the efficiency of planetary geartrains, the efficiency of the double crank ring-plate-type pin-cycloidal gear planetary drive isderived. To prove the theory, an experimental study has been conducted. The tested value of theefficiency of a sample set of the new-type drive in the experiment agrees with the calculated one.It shows that the new-type drive is of not merely high bearing capacity, but also quite highefficiency.展开更多
In order to analyze the lubricating characteristics at different meshing points in the cycloid pin wheel transmission process,the cycloid gear teeth were discretized,combined with the kinematic analysis of the cycloid...In order to analyze the lubricating characteristics at different meshing points in the cycloid pin wheel transmission process,the cycloid gear teeth were discretized,combined with the kinematic analysis of the cycloid pin gear transmission and the contact analysis of the gear teeth.The progressive mesh densification method(PMD)was used to numerically solve the film thickness.The influence of the design parameters and process parameters on the lubrication characteristics was analyzed.The elastohydrodynamic lubrication and mixed lubrication characteristics at different contact points were obtained.The optimal meshing area of the cycloid gear tooth was determined,and the film thickness ratio,contact load ratio,maximum contact pressure at different points,average film thickness and roughness after contact deformation were analyzed.The conclusion of this study provides effective guidance for the research on the modification of cycloid gear teeth.展开更多
A cycloidal speed reducer employing gears with permanent magnets acting as teeth is described. The magnets, which have their axes radially oriented in both the orbiting gear and the fixed internal gear, are inserted i...A cycloidal speed reducer employing gears with permanent magnets acting as teeth is described. The magnets, which have their axes radially oriented in both the orbiting gear and the fixed internal gear, are inserted in holes drilled in nonmagnetic rims without protruding from the cylindrical exposed surfaces. Because the orbiting gear is not restrained radially, it contacts the fixed gear and rolls on its inner surface. A normal force is developed at the contact point between the gears to balance the magnetic attraction and the centrifugal force of the orbiting gear. The friction available due to this normal force increases the transmission’s torque capacity, which is further increased by elimination of the gap between the gears. Also, the radial load on the supporting orbiting gear bearing is eliminated. A prototype with a reduction ratio of 26 is being tested.展开更多
The paper considers the modification or the manufacture error of cycloidal gear, then analyzes the relationship of pin circle meshed with the modified cycloidal gear, discuases the amount of error that leads to destro...The paper considers the modification or the manufacture error of cycloidal gear, then analyzes the relationship of pin circle meshed with the modified cycloidal gear, discuases the amount of error that leads to destroying conjugate action and results in the changes of tbe instantaneous velocity ratio and so as to affect the smooth operation of cycloidal pin gearing. The idea of the relationship between amount of modification aud manufacture error and the smooth operation can be gotten from the curve diagrams of the instantaneous velocity ratio. Therefore, the directions for improving the reature of the cycloidal pin gear transmission are clear.展开更多
An active design method of tooth profiles for cycloid gears based on their meshing efficiency is proposed.This method takes the meshing efficiency as one of the design variables to determine the tooth profiles.The cal...An active design method of tooth profiles for cycloid gears based on their meshing efficiency is proposed.This method takes the meshing efficiency as one of the design variables to determine the tooth profiles.The calculation method for the meshing efficiency of planetary transmission is analyzed and the equation of the meshing efficiency is deduced.Relationships between the meshing efficiency,the radius of the pin wheel and the eccentric distance are revealed.The design constraint quations and the strength constraint quations are deduced.On the basis of this,a design procedure is laid out.Some examples using different input parameters are conducted to demonstrate the feasibility of the approach.A dynamic simulation of the rigid flexible coupling of cycloid gears is also presented.The results show that the proposed design method is more flexible to control the tooth profiles by changing the input values of the transmission efficiency.展开更多
A surrogate-model-based aerodynamic optimization design method for cycloidal propeller in hover was proposed,in order to improve its aerodynamic efficiency,and analyze the basic criteria for its aerodynamic optimizati...A surrogate-model-based aerodynamic optimization design method for cycloidal propeller in hover was proposed,in order to improve its aerodynamic efficiency,and analyze the basic criteria for its aerodynamic optimization design.The reliability and applicability of overset mesh method were verified.An optimization method based on Kriging surrogate model was proposed to optimize the geometric parameters for cycloidal propeller in hover with the use of genetic algorithm.The optimization results showed that the thrust coefficient was increased by 3.56%,the torque coefficient reduced by 12.05%,and the figure of merit(FM)increased by 19.93%.The optimization results verified the feasibility of this design idea.Although the optimization was only carried out at a single rotation speed,the aerodynamic efficiency was also significantly improved over a wide range of rotation speeds.The optimal configuration characteristics for micro and small-sized cycloidal propeller were:solidity of 0.2-0.22,maximum pitch angle of 25°-35°,pitch axis locating at 35%-45% of the blade chord length.展开更多
In order to improve the analysis accuracy of the influence of shape parameters on the aerodynamic performance of cycloidal propeller,a set of CFD methods suitable for the simulation of the cycloidal propeller flow fie...In order to improve the analysis accuracy of the influence of shape parameters on the aerodynamic performance of cycloidal propeller,a set of CFD methods suitable for the simulation of the cycloidal propeller flow field based on the dynamic overset mesh and Unsteady Reynolds time average method equation were established.The characteristics of the spanwise lift distribution and surface pressure distribution in case of different negative twist were provided.The influence of the negative twist on the aerodynamic performance of cycloidal propeller was emphasized.The results showed that,the change of negative twist caused the change of azimuth for cycloidal propeller lift.The larger the absolute value of negative twist,the lower the figure of merit of the cycloidal propeller;the smaller the negative twist,the more gentle the instantaneous aerodynamic fluctuation;the influence mechanism of negative twist on the aerodynamic performance of cycloidal propeller was generated from changing the non-uniform distribution of the cycloidal propeller’s effective angle of attack.展开更多
Hypocycloid and epicycloid motions of irregular grains （pine pollen） are observed for the first time in a dust plasma in a two-dimensional （2D） horizontal plane. These cycloid motions can be regarded as a combinat...Hypocycloid and epicycloid motions of irregular grains （pine pollen） are observed for the first time in a dust plasma in a two-dimensional （2D） horizontal plane. These cycloid motions can be regarded as a combination of a primary circle and a secondary circle. An inverse Magnus force originating from the spin of the irregular grain gives rise to the primary circle. Radial confinement resulting from the electrostatic force and the ion drag force, together with inverse Magnus force, plays an important role in the formation of the secondary circle. In addition, the cyclotron radius is seen to change periodically during the cycloid motion. Force analysis and comparison experiments have shown that the cycloid motions are distinctive features of an irregular grain immersed in a plasma.展开更多
The transmission performance of cycloid ball planetary transmission(CBPT) is affected by cycloid tooth undercutting directly, and the design of CBPT can be optimized by the non-undercutting condition. Firstly, the the...The transmission performance of cycloid ball planetary transmission(CBPT) is affected by cycloid tooth undercutting directly, and the design of CBPT can be optimized by the non-undercutting condition. Firstly, the theoretical equation of cycloid tooth is given, and the curvature radius of cycloid tooth profile is derived. Secondly, according to the relationship between the curvature radius and the distribution circle of balls, the non-undercutting condition of cycloid tooth profile is established, and the non-undercutting critical condition is deduced. Finally, the validity of the non-undercutting critical condition is verified by simulation. The result shows that the non-undercutting critical condition can be used to optimize the design of CBPT.展开更多
THz time-domain spectroscopy(THz-TDS)is used to study the THz-optical properties of a single crystal bismuth ferrite BiFeO3(BFO).It can be found that the anisotropy of BiFeO3 is strongly dependent on the temperature.A...THz time-domain spectroscopy(THz-TDS)is used to study the THz-optical properties of a single crystal bismuth ferrite BiFeO3(BFO).It can be found that the anisotropy of BiFeO3 is strongly dependent on the temperature.A giant birefringence up to around 3.6 is observed at 1 THz.The presence of a spatially modulated cycloidal antiferromagnetic structure leads to spin cycloid resonances(SCR)ψandΦ,corresponding to the out-of-plane and in-plane modes of the spin cycloid,respectively.We distinguish the SCR with respect to their response to orthogonal polarizations of the electric fields of the incident THz beam.In addition,we observe a resonance appearing below 140 K,which might be interpreted as an electromagnon mode and related to a spin reorientation transition.Our present observations present that the temperature and polarization,as the external control parameters,can be used to modulate the THz optical properties of BFO single crystal.展开更多
In order to improve the performances of a cycloid gerotor pump,the variations of the radial force induced by different rotating speeds and outlet pressures are analyzed numerically.Using the numerical simulations as a...In order to improve the performances of a cycloid gerotor pump,the variations of the radial force induced by different rotating speeds and outlet pressures are analyzed numerically.Using the numerical simulations as a basis,an improved oil inlet and outlet groove structure is proposed.The results show that the radial force decreases with the decrease of the outlet pressure and of the rotor speed.Compared with the original model,the large-end oil inlet line and pressure line of the new oil groove are claw-shaped.This configuration can effectively weaken the pressure changes inside the gerotor pump and reduce accordingly the radial force on the inner rotor.展开更多
In this work, the cycloidal rotor fan (CRF) performance was estimated by means of a numerical method based on Unsteady Reynolds Averaged Navier-Stokes equations (URANS). The fan with a cycloidal rotor belongs to the p...In this work, the cycloidal rotor fan (CRF) performance was estimated by means of a numerical method based on Unsteady Reynolds Averaged Navier-Stokes equations (URANS). The fan with a cycloidal rotor belongs to the positive displacement machines of the rotary type. The numerical algorithm for simulation of the flow in the cycloidal rotor as well as postprocessing of the CFD results was prepared using Ansys CFX CEL. The methodology for the assessment of the CRF performance was proposed and verified. It was found out that the CRF performance strongly depends on the shape of the profile of the applied rotor blade. The NACA 0012 and CLARK Y profiles were tested for the same CRF structure and flow conditions. Also, the crucial importance for the CRF performance has the range of the blade pitch angle change.展开更多
基金Sponsored by Natural Science Foundation of Hebei Province(Grant No.E2019209153)Tangshan Science and Technology Program(Grant No.22130219G).
文摘The contact characteristics between cycloidal gear teeth and pinwheel teeth significantly impact the operational performance of cycloidal pinwheel mechanisms.Current research methods tend to rely primarily on theoretical calculations,with limited use of experimental methods for detecting dynamic contact properties.We propose a novel method for testing the dynamic contact characteristics of cycloidal pinwheel mechanisms.By combining Hertzian contact theory and contact strength theory,we establish a force and meshing stiffness model for the cycloidal and pinwheel gears,and determine the maximum contact stress and variations in pinwheel gear force and meshing stiffness.Based on the principle of photoelasticity,we built a testing platform for the cycloidal pinwheel mechanism to assess its contact characteristics.This platform provides the stress distribution of the cycloidal pinwheel mechanism and allows us to deduce key parameters such as the number of meshing teeth and the meshing interval.This study provides an experimental method for investigating the contact characteristics of cycloidal pinwheel mechanisms.
基金National Natural Science Foundation of China(No.59075230).
文摘Based on the analysis of the pin-hole-output mechanism in the cycloid drive,a more accurate force analysis method is provided, in which the manufacture error is considered, bywhich the contact force between pin and pin-hole can be calculated more accurately in the wholedriving process.
文摘In recent years, a lot of research work has been carried out on the cycloidal rotors. However, it lacks thorough understanding about the effects of the blade platform shape on the hover efficiency of the cycloidal rotor, and the knowledge of how to design the platform shape of the blades. This paper presents a numerical simulation model based on Unsteady ReynoldsAveraged Navier–Stokes equations(URANSs), which is further validated by the experimental results. The effects of blade aspect ratio and taper ratio are analyzed, which shows that the cycloidal rotors with the same chord length have quite similar performance even though the blade aspect ratio varies from a very small value to a large one. By comparing the cycloidal rotors with different taper ratios, it is found that the rotors with large blade taper ratio outperform those with small taper ratio. This is due to the fact that the blade with larger taper ratio has longer chord and hence better efficiency. The analysis results show that the unsteady aerodynamic effects due to blade pitching motion play a more important role in the efficiency than the blade platform shape. Therefore we should pay more attention to the blade airfoil and pitching motion than the blade platform shape.The main contributions of this paper include: the analysis of the effects of aspect ratio and taper ratio on the hover efficiency of cycloidal rotor based on both the experimental and numerical simulation results; the finding of the main influencing factors on the hover efficiency; the qualitative guidance on how to design the blade platform shape for cycloidal rotors.
基金Project(51575062)supported by the National Natural Science Foundation of ChinaProject(51605049)supported by the National Natural Science Foundation for Young Scholar of ChinaProject(BA2015177)supported by the Science and Technology Achievements Transformation Program of Jiangsu Province of China
文摘Cycloid speed reducers are widely used in many industrial areas due to the advantages of compact size, high reduction ratio and high stiffness. However, currently, there are not many analytical models for the mesh stiffness calculation, which is a crucial parameter for the high-fidelity gear dynamic model. This is partially due to the difficulty of backlash determination and the complexity of multi-tooth contact deformation during the meshing process. In this paper, a new method to calculate the mesh stiffness is proposed including the effects of tooth profile modification and eccentricity error. The time-varying mesh parameters and load distribution of cycloid-pin gear pair are determined based on the unloaded tooth contact analysis （TCA） and the nonlinear Hertzian contact theory, allowing accurate calculations of the contact stiffness of single tooth pair and the torsional stiffness of multi-tooth pairs. A detailed parametric study is presented to demonstrate the influences of tooth profile modification, applied torque and eccentricity error on the torsional mesh stiffness, loaded transmission error, Hertzian contact stiffness and load sharing factor. This model can be applied to further study the lost motion and dynamic characteristics of cycloid speed reducer and assist the optimization of its precision, vibration and noise levels.
基金supported by the Changwon National University in 2011-2012,Korea
文摘The most conventional vehicle pretensioner system consists of an internal gear pair with involute teeth. However, it has been well known that the corresponding gear pairs are relatively weak under the situation of impact loadings. To improve this phenomenon, a new pretensioning gear system with cycloid teeth rather than the involute ones was proposed, and dual cycloidal gear mechanisms were designed for satisfying geometric constraints and dynamic loading conditions. The simulations of the prototypes were conducted by LS-DYNA program and the experiments for a prototype were performed for a dynamic model with impact loading devices. The results show that the better operation and the smoother motion are confirmed in the proposed cycloidal gear system rather than the conventional one without interferences between gear teeth under the impact of a crash.
基金This project is supported by National Natural Science Foundation of China (No.50175011).
文摘From the general formula for calculating the efficiency of planetary geartrains, the efficiency of the double crank ring-plate-type pin-cycloidal gear planetary drive isderived. To prove the theory, an experimental study has been conducted. The tested value of theefficiency of a sample set of the new-type drive in the experiment agrees with the calculated one.It shows that the new-type drive is of not merely high bearing capacity, but also quite highefficiency.
基金Project(E2019209153)supported by the Natural Science Foundation of Hebei Province,China。
文摘In order to analyze the lubricating characteristics at different meshing points in the cycloid pin wheel transmission process,the cycloid gear teeth were discretized,combined with the kinematic analysis of the cycloid pin gear transmission and the contact analysis of the gear teeth.The progressive mesh densification method(PMD)was used to numerically solve the film thickness.The influence of the design parameters and process parameters on the lubrication characteristics was analyzed.The elastohydrodynamic lubrication and mixed lubrication characteristics at different contact points were obtained.The optimal meshing area of the cycloid gear tooth was determined,and the film thickness ratio,contact load ratio,maximum contact pressure at different points,average film thickness and roughness after contact deformation were analyzed.The conclusion of this study provides effective guidance for the research on the modification of cycloid gear teeth.
文摘A cycloidal speed reducer employing gears with permanent magnets acting as teeth is described. The magnets, which have their axes radially oriented in both the orbiting gear and the fixed internal gear, are inserted in holes drilled in nonmagnetic rims without protruding from the cylindrical exposed surfaces. Because the orbiting gear is not restrained radially, it contacts the fixed gear and rolls on its inner surface. A normal force is developed at the contact point between the gears to balance the magnetic attraction and the centrifugal force of the orbiting gear. The friction available due to this normal force increases the transmission’s torque capacity, which is further increased by elimination of the gap between the gears. Also, the radial load on the supporting orbiting gear bearing is eliminated. A prototype with a reduction ratio of 26 is being tested.
文摘The paper considers the modification or the manufacture error of cycloidal gear, then analyzes the relationship of pin circle meshed with the modified cycloidal gear, discuases the amount of error that leads to destroying conjugate action and results in the changes of tbe instantaneous velocity ratio and so as to affect the smooth operation of cycloidal pin gearing. The idea of the relationship between amount of modification aud manufacture error and the smooth operation can be gotten from the curve diagrams of the instantaneous velocity ratio. Therefore, the directions for improving the reature of the cycloidal pin gear transmission are clear.
基金supported by the National Natural Science Foundation of China (Nos.51205335, 51375411)the Scientific Research for the High Level Talent of Nanjing Institute of Technology (No.YKJ201702)
文摘An active design method of tooth profiles for cycloid gears based on their meshing efficiency is proposed.This method takes the meshing efficiency as one of the design variables to determine the tooth profiles.The calculation method for the meshing efficiency of planetary transmission is analyzed and the equation of the meshing efficiency is deduced.Relationships between the meshing efficiency,the radius of the pin wheel and the eccentric distance are revealed.The design constraint quations and the strength constraint quations are deduced.On the basis of this,a design procedure is laid out.Some examples using different input parameters are conducted to demonstrate the feasibility of the approach.A dynamic simulation of the rigid flexible coupling of cycloid gears is also presented.The results show that the proposed design method is more flexible to control the tooth profiles by changing the input values of the transmission efficiency.
文摘A surrogate-model-based aerodynamic optimization design method for cycloidal propeller in hover was proposed,in order to improve its aerodynamic efficiency,and analyze the basic criteria for its aerodynamic optimization design.The reliability and applicability of overset mesh method were verified.An optimization method based on Kriging surrogate model was proposed to optimize the geometric parameters for cycloidal propeller in hover with the use of genetic algorithm.The optimization results showed that the thrust coefficient was increased by 3.56%,the torque coefficient reduced by 12.05%,and the figure of merit(FM)increased by 19.93%.The optimization results verified the feasibility of this design idea.Although the optimization was only carried out at a single rotation speed,the aerodynamic efficiency was also significantly improved over a wide range of rotation speeds.The optimal configuration characteristics for micro and small-sized cycloidal propeller were:solidity of 0.2-0.22,maximum pitch angle of 25°-35°,pitch axis locating at 35%-45% of the blade chord length.
基金Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘In order to improve the analysis accuracy of the influence of shape parameters on the aerodynamic performance of cycloidal propeller,a set of CFD methods suitable for the simulation of the cycloidal propeller flow field based on the dynamic overset mesh and Unsteady Reynolds time average method equation were established.The characteristics of the spanwise lift distribution and surface pressure distribution in case of different negative twist were provided.The influence of the negative twist on the aerodynamic performance of cycloidal propeller was emphasized.The results showed that,the change of negative twist caused the change of azimuth for cycloidal propeller lift.The larger the absolute value of negative twist,the lower the figure of merit of the cycloidal propeller;the smaller the negative twist,the more gentle the instantaneous aerodynamic fluctuation;the influence mechanism of negative twist on the aerodynamic performance of cycloidal propeller was generated from changing the non-uniform distribution of the cycloidal propeller’s effective angle of attack.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11205044 and 11405042)the Natural Science Foundation of Hebei Province,China(Grant Nos.A2011201006 and A2012201015)+2 种基金the Research Foundation of Education Bureau of Hebei Province,China(Grant No.Y2012009)the Program for Young Principal Investigators of Hebei Provincethe Midwest Universities Comprehensive Strength Promotion Project
文摘Hypocycloid and epicycloid motions of irregular grains （pine pollen） are observed for the first time in a dust plasma in a two-dimensional （2D） horizontal plane. These cycloid motions can be regarded as a combination of a primary circle and a secondary circle. An inverse Magnus force originating from the spin of the irregular grain gives rise to the primary circle. Radial confinement resulting from the electrostatic force and the ion drag force, together with inverse Magnus force, plays an important role in the formation of the secondary circle. In addition, the cyclotron radius is seen to change periodically during the cycloid motion. Force analysis and comparison experiments have shown that the cycloid motions are distinctive features of an irregular grain immersed in a plasma.
基金Funded by the National Natural Science Foundation of China(Grant No.51405003)
文摘The transmission performance of cycloid ball planetary transmission(CBPT) is affected by cycloid tooth undercutting directly, and the design of CBPT can be optimized by the non-undercutting condition. Firstly, the theoretical equation of cycloid tooth is given, and the curvature radius of cycloid tooth profile is derived. Secondly, according to the relationship between the curvature radius and the distribution circle of balls, the non-undercutting condition of cycloid tooth profile is established, and the non-undercutting critical condition is deduced. Finally, the validity of the non-undercutting critical condition is verified by simulation. The result shows that the non-undercutting critical condition can be used to optimize the design of CBPT.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61975110,11674213,61735010,and 11604202)the 111 Project,China(Grant No.D18014)+3 种基金the International Joint Lab Program supported by Science and Technology Commission Shanghai Municipality,China(Grant No.17590750300)the Key Project supported by Science and Technology Commission Shanghai Municipality,China(Grant No.YDZX20193100004960)Science and Technology Commission of Shanghai Municipality,China(Shanghai Rising-Star Program 18QA1401700)Shanghai Educational Development Foundation,China(Chen Guang Project 16CG45).
文摘THz time-domain spectroscopy(THz-TDS)is used to study the THz-optical properties of a single crystal bismuth ferrite BiFeO3(BFO).It can be found that the anisotropy of BiFeO3 is strongly dependent on the temperature.A giant birefringence up to around 3.6 is observed at 1 THz.The presence of a spatially modulated cycloidal antiferromagnetic structure leads to spin cycloid resonances(SCR)ψandΦ,corresponding to the out-of-plane and in-plane modes of the spin cycloid,respectively.We distinguish the SCR with respect to their response to orthogonal polarizations of the electric fields of the incident THz beam.In addition,we observe a resonance appearing below 140 K,which might be interpreted as an electromagnon mode and related to a spin reorientation transition.Our present observations present that the temperature and polarization,as the external control parameters,can be used to modulate the THz optical properties of BFO single crystal.
基金supported by the Zhejiang Provincial Natural Science Foundation of China(No.LY19E050003)the National Natural Science Foundation of China(No.51779226).
文摘In order to improve the performances of a cycloid gerotor pump,the variations of the radial force induced by different rotating speeds and outlet pressures are analyzed numerically.Using the numerical simulations as a basis,an improved oil inlet and outlet groove structure is proposed.The results show that the radial force decreases with the decrease of the outlet pressure and of the rotor speed.Compared with the original model,the large-end oil inlet line and pressure line of the new oil groove are claw-shaped.This configuration can effectively weaken the pressure changes inside the gerotor pump and reduce accordingly the radial force on the inner rotor.
文摘In this work, the cycloidal rotor fan (CRF) performance was estimated by means of a numerical method based on Unsteady Reynolds Averaged Navier-Stokes equations (URANS). The fan with a cycloidal rotor belongs to the positive displacement machines of the rotary type. The numerical algorithm for simulation of the flow in the cycloidal rotor as well as postprocessing of the CFD results was prepared using Ansys CFX CEL. The methodology for the assessment of the CRF performance was proposed and verified. It was found out that the CRF performance strongly depends on the shape of the profile of the applied rotor blade. The NACA 0012 and CLARK Y profiles were tested for the same CRF structure and flow conditions. Also, the crucial importance for the CRF performance has the range of the blade pitch angle change.
