The design of counter-rotating turbine is one of new techniques to improve the thrust-weight ratio of jet propulsion engines.Numerical analysis of a low pressure（LP）counter-rotating turbine rotor blade is presented ...The design of counter-rotating turbine is one of new techniques to improve the thrust-weight ratio of jet propulsion engines.Numerical analysis of a low pressure（LP）counter-rotating turbine rotor blade is presented by using ANSYS/CFX software.Interaction of aerodynamics and solid mechanics coupling in the computation is applied.In some rating of turbine,stress distribution and vibration characteristics of low pressure turbine（LPT）blade are computed.The wake aerodynamic forces and LPT blade vibration are transformed in frequency domain using fast Fourier transform（FFT）method.The results show that under wake aerodynamic force excitation,the first order modal vibration is more easily aroused and the higher order response cannot be ignored.Moreover,with different temperature fields,the vibration responses of blade are also different.展开更多
Though high accuracy of the thermal contour was obtained while adopting finite element method,it could not meet the real-time requirement.One-dimensional finite difference method could realize real-time control in the...Though high accuracy of the thermal contour was obtained while adopting finite element method,it could not meet the real-time requirement.One-dimensional finite difference method could realize real-time control in the case of neglecting both the circumferential and radical heat exchange,but the over-simplified modes resulted in poor accuracy.And two-dimensional full explicit difference was also limited in practical application since its time step was restricted to keep the model stable.Consequently,a new method of alternating direction finite difference was introduced and discussed in the model's stability,calculating speed and precision.Specific work roll after one real rolling unit was researched,The result shows that error of temperature on work roll surface between measured and calculated values is within 5 ℃.The influence of rolling rhythm and strip width on thermal crown was also studied.The conclusion is verified theoretically and practically that it can maintain absolutely stable and meet the online requirement.展开更多
The application of fine blanking to the manufacturing of helical gears directly from a strip has been restricted due to the traditional linear cutting stroke of the punch and die.In this work,rotational fine blanking ...The application of fine blanking to the manufacturing of helical gears directly from a strip has been restricted due to the traditional linear cutting stroke of the punch and die.In this work,rotational fine blanking which combined the linear and rotational motion of punch and counterpunch was applied for the forming of helical gears.A three-dimensional(3D) rigid-plastic finite element model was developed on the DEFORM-3D platform.By finite element simulation and analysis,the influences of key parameters on the punch load and cut surface were investigated.It is shown that: 1) with increasing the counterforce or helical angle,the punch load and the depth of die roll increase; 2) with increasing blank holder force,the punch load increases while the depth of die roll decreases; 3) V-ring indenter facilitates an improvement in the quality.The results of this research reveal the deformation mechanism of rotational fine blanking of helical gears,and provide valuable guidelines for further experimental studies.展开更多
In order to study the transmission efficiency of engine and optimize the structure of driving wheel,the rotational speed storage test device of driving wheel in tracked vehicle based on magnetoelectric sensor was desi...In order to study the transmission efficiency of engine and optimize the structure of driving wheel,the rotational speed storage test device of driving wheel in tracked vehicle based on magnetoelectric sensor was designed.The device consisted of a mounting bracket,a sensor and a tester.The mounting bracket was installed in vehicle body after fixing the tester and sensor to mounting bracket beside the driving wheel.Using the storage test instrument,the wireless trigger technology was applied to synchronously record and stored the rotational speed data of the driving wheel in tracked vehicle.After the experiment was finished,the data was read out through the upper computer.Both valid data and satisfactory results were obtained through both simulated and actual vehicle tests.展开更多
A dynamic model of a helical gear rotor system is proposed.Firstly,a generally distributed dynamic model of a helical gear pair with tooth profile errors is developed.The gear mesh is represented by a pair of cylinder...A dynamic model of a helical gear rotor system is proposed.Firstly,a generally distributed dynamic model of a helical gear pair with tooth profile errors is developed.The gear mesh is represented by a pair of cylinders connected by a series of springs and the stiffness of each spring is equal to the effective mesh stiffness.Combining the gear dynamic model with the rotor-bearing system model,the gear-rotor-bearing dynamic model is developed.Then three cases are presented to analyze the dynamic responses of gear systems.The results reveal that the gear dynamic model is effective and advanced for general gear systems,narrow-faced gear,wide-faced gear and gear with tooth profile errors.Finally,the responses of an example helical gear system are also studied to demonstrate the influence of the lead crown reliefs and misalignments.The results show that both of the lead crown relief and misalignment soften the gear mesh stiffness and the responses of the gear system increase with the increasing lead crown reliefs and misalignments.展开更多
The initiation and evolution of short-pitch corrugation in Beijing metro line 4 was studied from the viewpoint of wheelset vibration.A three-dimensional elastic model was set up.Numerical simulations were undertaken w...The initiation and evolution of short-pitch corrugation in Beijing metro line 4 was studied from the viewpoint of wheelset vibration.A three-dimensional elastic model was set up.Numerical simulations were undertaken with this model to analyze the corrugation by the wheelset vertical vibration and torsional vibration.Based on numerical results,the relation between rail corrugation and wheelset vibration,and the relation between the position of electromotor and wheelset vibration were indicated.It is found that avoiding the wheelset-rail resonance is one method of controlling the rail short-pitch corrugation and solving the vibration and noise problem in metro lines.展开更多
A novel twin-rotor piston engine （TRPE） mechanism with high volumetric output and power density was introduced. This new engine comprises an energy conversion system and a differential velocity drive mechanism （DVD...A novel twin-rotor piston engine （TRPE） mechanism with high volumetric output and power density was introduced. This new engine comprises an energy conversion system and a differential velocity drive mechanism （DVDM）. Two special geared four-bar mechanisms, DVDM-1 and DVDM-2, were utilized and compared. Based on the closed loop vector method, a mathematical model for position, velocity, and acceleration of the two mechanisms was established. Numerical examples illustrate that the kinematic characteristics were presented. Expression of the displacement and compression ratio of the two engine mechanisms were derived and compared. It is concluded that both DVDM-1 and DVDM-2 adopted in the proposed TRPE with six vane pistons create thirty-six power strokes per revolution of the output shaft, and the summation of two angles covered by each rocker is always 2x/N as the output shaft rotates an angle of x/N. In DVDM-1, the span angle of a vane piston should be designed to be 10.2°, and the compression ratio should be equal to 10; in DVDM-2, the span angle of a vane piston should be designed to be 10.6°, and the compression ratio should be equal to 4.3.展开更多
The wear rate between the rotors of a hypotrochoidal gear pump is characterized.Using the knowledge of shape design on the rotors,the contact stresses without hydrodynamic effect between the rotor teeth were evaluated...The wear rate between the rotors of a hypotrochoidal gear pump is characterized.Using the knowledge of shape design on the rotors,the contact stresses without hydrodynamic effect between the rotor teeth were evaluated through the calculation of the Hertzian contact stress.Based on the above results and the sliding velocity between the rotors,a genetic algorithm (GA) was used as an optimization technique forminimizing the wear rate proportional factor (WRPF).The result shows that the wear rate or the WRPF can be reduced considerably,e.g.approximately 12.8%,throughout the optimization using GA.展开更多
A roller rack pinion(RRP)system,which consists of a rack-bar and a cam pinion,transforms a rotation motion into linear motion.The rack-bar has a series of roller train and meshes with the cam pinion.First,the exact to...A roller rack pinion(RRP)system,which consists of a rack-bar and a cam pinion,transforms a rotation motion into linear motion.The rack-bar has a series of roller train and meshes with the cam pinion.First,the exact tooth profile of the cam pinion and the non-undercut condition to satisfy the required performance have been proposed with the introduction of the profile shift coefficient.Then,the load stress factors are investigated under the variation of the shape design parameters to predict the gear surface fatigue limit which is strongly related to the gear noise and vibration at the contact patch.The results show that the pitting life can be extended significantly with the increase of the profile shift coefficient.展开更多
A new castor wheel mechanism for omni-directional mobile platform is presented. A motion of translation is transformed into a rotation to steer the wheel with the help of a helical path fits into a translation joint a...A new castor wheel mechanism for omni-directional mobile platform is presented. A motion of translation is transformed into a rotation to steer the wheel with the help of a helical path fits into a translation joint and three rollers whose axes are connected to the driving shaft of the wheel. When the path moves in translation it acts on the rollers for steering. The path-roller friction transmission, the wheel kinematics and the maneuverability have been analyzed.展开更多
文摘The design of counter-rotating turbine is one of new techniques to improve the thrust-weight ratio of jet propulsion engines.Numerical analysis of a low pressure（LP）counter-rotating turbine rotor blade is presented by using ANSYS/CFX software.Interaction of aerodynamics and solid mechanics coupling in the computation is applied.In some rating of turbine,stress distribution and vibration characteristics of low pressure turbine（LPT）blade are computed.The wake aerodynamic forces and LPT blade vibration are transformed in frequency domain using fast Fourier transform（FFT）method.The results show that under wake aerodynamic force excitation,the first order modal vibration is more easily aroused and the higher order response cannot be ignored.Moreover,with different temperature fields,the vibration responses of blade are also different.
基金Project(2006BAE03A13) supported by the National Science and Technology Support Program during the 11th Five-Year Plan Period
文摘Though high accuracy of the thermal contour was obtained while adopting finite element method,it could not meet the real-time requirement.One-dimensional finite difference method could realize real-time control in the case of neglecting both the circumferential and radical heat exchange,but the over-simplified modes resulted in poor accuracy.And two-dimensional full explicit difference was also limited in practical application since its time step was restricted to keep the model stable.Consequently,a new method of alternating direction finite difference was introduced and discussed in the model's stability,calculating speed and precision.Specific work roll after one real rolling unit was researched,The result shows that error of temperature on work roll surface between measured and calculated values is within 5 ℃.The influence of rolling rhythm and strip width on thermal crown was also studied.The conclusion is verified theoretically and practically that it can maintain absolutely stable and meet the online requirement.
基金Project(51105287)supported by the National Natural Science Foundation of ChinaProject(2011-P05)supported by the State Key Laboratory of Materials Processing and Die&Mould Technology,Huazhong University of Science and Technology,ChinaProject(2011-IV-009)supported by the Fundamental Research Funds for the Central Universities,China
文摘The application of fine blanking to the manufacturing of helical gears directly from a strip has been restricted due to the traditional linear cutting stroke of the punch and die.In this work,rotational fine blanking which combined the linear and rotational motion of punch and counterpunch was applied for the forming of helical gears.A three-dimensional(3D) rigid-plastic finite element model was developed on the DEFORM-3D platform.By finite element simulation and analysis,the influences of key parameters on the punch load and cut surface were investigated.It is shown that: 1) with increasing the counterforce or helical angle,the punch load and the depth of die roll increase; 2) with increasing blank holder force,the punch load increases while the depth of die roll decreases; 3) V-ring indenter facilitates an improvement in the quality.The results of this research reveal the deformation mechanism of rotational fine blanking of helical gears,and provide valuable guidelines for further experimental studies.
基金Cultivation Programs for Young Scientific Research Personnel of Higher Education Institutions in Shanxi Province(No.2019QPJH18)Fund for“1331 Project”Key Innovative Research Team of Shanxi Province(No.1331KIPT)。
文摘In order to study the transmission efficiency of engine and optimize the structure of driving wheel,the rotational speed storage test device of driving wheel in tracked vehicle based on magnetoelectric sensor was designed.The device consisted of a mounting bracket,a sensor and a tester.The mounting bracket was installed in vehicle body after fixing the tester and sensor to mounting bracket beside the driving wheel.Using the storage test instrument,the wireless trigger technology was applied to synchronously record and stored the rotational speed data of the driving wheel in tracked vehicle.After the experiment was finished,the data was read out through the upper computer.Both valid data and satisfactory results were obtained through both simulated and actual vehicle tests.
基金Projects(51605361,51505357) supported by the National Natural Science Foundation of ChinaProjects(XJS16041,JB160411) supported by the Fundamental Research Funds for the Central Universities,China
文摘A dynamic model of a helical gear rotor system is proposed.Firstly,a generally distributed dynamic model of a helical gear pair with tooth profile errors is developed.The gear mesh is represented by a pair of cylinders connected by a series of springs and the stiffness of each spring is equal to the effective mesh stiffness.Combining the gear dynamic model with the rotor-bearing system model,the gear-rotor-bearing dynamic model is developed.Then three cases are presented to analyze the dynamic responses of gear systems.The results reveal that the gear dynamic model is effective and advanced for general gear systems,narrow-faced gear,wide-faced gear and gear with tooth profile errors.Finally,the responses of an example helical gear system are also studied to demonstrate the influence of the lead crown reliefs and misalignments.The results show that both of the lead crown relief and misalignment soften the gear mesh stiffness and the responses of the gear system increase with the increasing lead crown reliefs and misalignments.
基金Project(C11H00021) supported by Beijing Municipal Science & Technology Commission of ChinaProject(KCJB11063536) supported by Beijing Jiaotong University,China
文摘The initiation and evolution of short-pitch corrugation in Beijing metro line 4 was studied from the viewpoint of wheelset vibration.A three-dimensional elastic model was set up.Numerical simulations were undertaken with this model to analyze the corrugation by the wheelset vertical vibration and torsional vibration.Based on numerical results,the relation between rail corrugation and wheelset vibration,and the relation between the position of electromotor and wheelset vibration were indicated.It is found that avoiding the wheelset-rail resonance is one method of controlling the rail short-pitch corrugation and solving the vibration and noise problem in metro lines.
基金Project(7131109) supported the by National Defense Pre-research Foundation of ChinaProject(50975278) supported by National the Natural Science Foundation of China
文摘A novel twin-rotor piston engine （TRPE） mechanism with high volumetric output and power density was introduced. This new engine comprises an energy conversion system and a differential velocity drive mechanism （DVDM）. Two special geared four-bar mechanisms, DVDM-1 and DVDM-2, were utilized and compared. Based on the closed loop vector method, a mathematical model for position, velocity, and acceleration of the two mechanisms was established. Numerical examples illustrate that the kinematic characteristics were presented. Expression of the displacement and compression ratio of the two engine mechanisms were derived and compared. It is concluded that both DVDM-1 and DVDM-2 adopted in the proposed TRPE with six vane pistons create thirty-six power strokes per revolution of the output shaft, and the summation of two angles covered by each rocker is always 2x/N as the output shaft rotates an angle of x/N. In DVDM-1, the span angle of a vane piston should be designed to be 10.2°, and the compression ratio should be equal to 10; in DVDM-2, the span angle of a vane piston should be designed to be 10.6°, and the compression ratio should be equal to 4.3.
基金supported by Changwon National University in 2010,Korea
文摘The wear rate between the rotors of a hypotrochoidal gear pump is characterized.Using the knowledge of shape design on the rotors,the contact stresses without hydrodynamic effect between the rotor teeth were evaluated through the calculation of the Hertzian contact stress.Based on the above results and the sliding velocity between the rotors,a genetic algorithm (GA) was used as an optimization technique forminimizing the wear rate proportional factor (WRPF).The result shows that the wear rate or the WRPF can be reduced considerably,e.g.approximately 12.8%,throughout the optimization using GA.
基金Research financially supported by Changwon National University in 2011-2012,Korea
文摘A roller rack pinion(RRP)system,which consists of a rack-bar and a cam pinion,transforms a rotation motion into linear motion.The rack-bar has a series of roller train and meshes with the cam pinion.First,the exact tooth profile of the cam pinion and the non-undercut condition to satisfy the required performance have been proposed with the introduction of the profile shift coefficient.Then,the load stress factors are investigated under the variation of the shape design parameters to predict the gear surface fatigue limit which is strongly related to the gear noise and vibration at the contact patch.The results show that the pitting life can be extended significantly with the increase of the profile shift coefficient.
文摘A new castor wheel mechanism for omni-directional mobile platform is presented. A motion of translation is transformed into a rotation to steer the wheel with the help of a helical path fits into a translation joint and three rollers whose axes are connected to the driving shaft of the wheel. When the path moves in translation it acts on the rollers for steering. The path-roller friction transmission, the wheel kinematics and the maneuverability have been analyzed.
