This paper investigates the vibration characteristics of a double-overhung rub rotor considering gyroscopic couples and slanting contact between rotors and stators. This paper deduces a new contact model according to ...This paper investigates the vibration characteristics of a double-overhung rub rotor considering gyroscopic couples and slanting contact between rotors and stators. This paper deduces a new contact model according to slant contact between rotor and stator, which close to real rub condition, and compared with simple contact model.With rotating speed and support span changing, the dynamic behaviors of rotors are simulated by the fourth Runge-Kutta method. The results illustrate that gyroscopic couples and slant contact model can lead to rub occurrence at a lower speed compared with no gyroscopic couples or slant contact. Resonance has a huge effect on radial displacement and frequency spectrum of disk, and in resonance interval the frequency components are complex. At the same rotating speed, support span has a monotonous effect on amplitude of radial displacement. These results might provide some reference to estimate whether rubbing occurs and help to control rubbing force.展开更多
An innovative physical simulation apparatus, including high speed camera, red thermal imaging system, and mechanical quantity sensor, was used to investigate the friction heat generation and atom diffusion behavior du...An innovative physical simulation apparatus, including high speed camera, red thermal imaging system, and mechanical quantity sensor, was used to investigate the friction heat generation and atom diffusion behavior during Mg-Ti friction welding process. The results show that the friction coefficient mainly experiences two steady stages. The first steady stage corresponds to the Coulomb friction with material abrasion. The second steady stage corresponds to the stick friction with fully plastic flow. Moreover, the increasing rates of axial displacement, temperature and friction coefficient are obviously enhanced with the increase of rotation speed and axial pressure. It can also be found that the there exists rapid diffusion phenomenon in the Mg-Ti friction welding system. The large deformation activated diffusion coefficient is about 105 higher than that activated by thermal.展开更多
To reduce the excessive vibration of a high-speed rotor system at the critical speed, a friction damper with a flexible support structure is introduced. The mechanism of vibration reduction and support characteristics...To reduce the excessive vibration of a high-speed rotor system at the critical speed, a friction damper with a flexible support structure is introduced. The mechanism of vibration reduction and support characteristics are analyzed and a friction damper is designed. The effect on an unbalanced response is studied. Results show that the stiffness factor and the friction-damping factor of the damper are related to the cone angle and the friction factor of the inner-ring when adopting a proper structure. By changing these parameters and the Z-directional stiffness of the outer-ring, the stiffness and the damping characteristic of the damper can be varied. Introducing a friction damper into the support can reduce the stiffness and increase the damping of the support, thus decreasing the critical speed to avoid the operating speed, suppress the resonant response of a rotor system, and attenuate vibration forces to the outside.展开更多
Vibrations of a rotor-bearing system(RBS)can be affected by the frictional forces between the components of the inherent bearings.Thus,an in-depth investigation of the influences of the frictional moments of the beari...Vibrations of a rotor-bearing system(RBS)can be affected by the frictional forces between the components of the inherent bearings.Thus,an in-depth investigation of the influences of the frictional moments of the bearings on the vibrations of the RBS can be helpful for understanding the vibration mechanisms in the rotating machinery.In this study,an improved dynamic model of a RBS considering different frictional force models is presented.A comparative investigation on the influences of the empirical and analytical frictional force models on the vibration characteristics of the RBS is proposed.The empirical frictional force models include Palmgren’s and SKF’s models.The analytical frictional force model considers the rolling friction caused by the radial elastic material hysteresis,slipping friction between the ball and races,viscosity friction caused by the lubricating oil,and contact friction between the ball and cage.The influences of the external load and rotational speed on the vibrations of the RBS are analyzed.The comparative results show that the analytical frictional force model can give a more reasonable method for formulating the effects of the friction forces in the bearings on the vibrations of the RBS.The results also demonstrate that the friction forces in the bearings can significantly affect the vibrations of the RBSs.展开更多
In order to simulate the stress of turbine rotor in aeroengine, based on the ANSYS, the simplification model of the turbine rotor was built up. By applying the simplification model, the contact stress of turbine rotor...In order to simulate the stress of turbine rotor in aeroengine, based on the ANSYS, the simplification model of the turbine rotor was built up. By applying the simplification model, the contact stress of turbine rotor was computed. The maximum contact stress appears at the chamfer below the flank, which agrees with experiment result. At the same time, the contact stress changing with the flank angle and friction coefficient was calculated, The results show that the contact stress in the flank increases slowly with the increase of flank angle; with the friction coefficient increasing, the contact stress in flank length decreases; the contact stress will not change when the friction coefficient is over 0.25.展开更多
The mechanical properties and tribological behaviors of Cu-WS2 composites fabricated by spark plasma sintering（SPS） using two different WS2 particle sizes of 0.6 and 5.0 μm and Cu powders as raw materials were inve...The mechanical properties and tribological behaviors of Cu-WS2 composites fabricated by spark plasma sintering（SPS） using two different WS2 particle sizes of 0.6 and 5.0 μm and Cu powders as raw materials were investigated. The results indicate that the bending strength and tribological behavior of Cu-WS2 composites are greatly affected by the size of WS2 particles. The bending strength of Cu-WS2 composites with the WS2 particle size of 5.0 μm is 292.2 MPa. As the size of WS2 particle decreases to 0.6 μm, the bending strength also decreases to 181.5 MPa. Moreover, as the WS2 particle size decreases from 5.0 to 0.6 μm, the wear rate of Cu-WS2 composite sharply increases from 2.99×10^-14 to 6.13×10^-14 m^3/（N·m） and its friction coefficient increases from 0.158 to 0.172. The size of WS2 particle（5.0 μm） plays an important role in forming transfer film formed on the counter-face. The sample with 5.0 μm WS2 particle forms smoother and more continuous transfer film, which results in a low wear rate and friction coefficient of the Cu-WS2 composites.展开更多
The paper described experimental investigation of heat transfer and single-phase pressure drop through tubes with different rotor-assembled strands inserted in the Reynolds number range of 800-9000 with lubricant as w...The paper described experimental investigation of heat transfer and single-phase pressure drop through tubes with different rotor-assembled strands inserted in the Reynolds number range of 800-9000 with lubricant as working fluid. In the experiment, fixed mounts were employed to eliminate the entrance effect. The experimental results showed that the employment of fixed mounts led to a visible bias of friction factor in the laminar regime while it could not affect the Nusselt numbers significantly. Experiment for the tube inserted with rotors-assembled strand showed remarkable improvement for heat transfer with the Nusselt number increased by 200%-225% in the laminar regime and 125%-160% in the transitional regime. Meanwhile, the friction factor increased inevitably by 200%-300% within the same range of Reynolds number. The comparison of different rotor-assembled strands in-serted tubes and plain tube showed that the heat transfer benefited from the increase of the diameter of rotor-assembled strand with the same lead and the decrease of the lead of rotor-assembled strand, so does the friction factor. Based on experimental data and thorough multivariant linear normal regression method, the correlations of average Nusselt number and friction factor are established.展开更多
基金National Natural Science Foundation of China C Grant No.51335006
文摘This paper investigates the vibration characteristics of a double-overhung rub rotor considering gyroscopic couples and slanting contact between rotors and stators. This paper deduces a new contact model according to slant contact between rotor and stator, which close to real rub condition, and compared with simple contact model.With rotating speed and support span changing, the dynamic behaviors of rotors are simulated by the fourth Runge-Kutta method. The results illustrate that gyroscopic couples and slant contact model can lead to rub occurrence at a lower speed compared with no gyroscopic couples or slant contact. Resonance has a huge effect on radial displacement and frequency spectrum of disk, and in resonance interval the frequency components are complex. At the same rotating speed, support span has a monotonous effect on amplitude of radial displacement. These results might provide some reference to estimate whether rubbing occurs and help to control rubbing force.
基金Projects (51101126, 51071123) supported by the National Natural Science Foundation of ChinaProjects (20110491684, 2012T50817) supported by the China Postdoctoral Science FoundationProject (20110942K) supported by the Open Fund of State Key Laboratory of Powder Metallurgy of Central South University, China
文摘An innovative physical simulation apparatus, including high speed camera, red thermal imaging system, and mechanical quantity sensor, was used to investigate the friction heat generation and atom diffusion behavior during Mg-Ti friction welding process. The results show that the friction coefficient mainly experiences two steady stages. The first steady stage corresponds to the Coulomb friction with material abrasion. The second steady stage corresponds to the stick friction with fully plastic flow. Moreover, the increasing rates of axial displacement, temperature and friction coefficient are obviously enhanced with the increase of rotation speed and axial pressure. It can also be found that the there exists rapid diffusion phenomenon in the Mg-Ti friction welding system. The large deformation activated diffusion coefficient is about 105 higher than that activated by thermal.
文摘To reduce the excessive vibration of a high-speed rotor system at the critical speed, a friction damper with a flexible support structure is introduced. The mechanism of vibration reduction and support characteristics are analyzed and a friction damper is designed. The effect on an unbalanced response is studied. Results show that the stiffness factor and the friction-damping factor of the damper are related to the cone angle and the friction factor of the inner-ring when adopting a proper structure. By changing these parameters and the Z-directional stiffness of the outer-ring, the stiffness and the damping characteristic of the damper can be varied. Introducing a friction damper into the support can reduce the stiffness and increase the damping of the support, thus decreasing the critical speed to avoid the operating speed, suppress the resonant response of a rotor system, and attenuate vibration forces to the outside.
基金Projects(51605051,51975068)supported by the National Natural Science Foundation of ChinaProject(3102020HHZY030001)supported by the Fundamental Research Funds for the Central Universities,China。
文摘Vibrations of a rotor-bearing system(RBS)can be affected by the frictional forces between the components of the inherent bearings.Thus,an in-depth investigation of the influences of the frictional moments of the bearings on the vibrations of the RBS can be helpful for understanding the vibration mechanisms in the rotating machinery.In this study,an improved dynamic model of a RBS considering different frictional force models is presented.A comparative investigation on the influences of the empirical and analytical frictional force models on the vibration characteristics of the RBS is proposed.The empirical frictional force models include Palmgren’s and SKF’s models.The analytical frictional force model considers the rolling friction caused by the radial elastic material hysteresis,slipping friction between the ball and races,viscosity friction caused by the lubricating oil,and contact friction between the ball and cage.The influences of the external load and rotational speed on the vibrations of the RBS are analyzed.The comparative results show that the analytical frictional force model can give a more reasonable method for formulating the effects of the friction forces in the bearings on the vibrations of the RBS.The results also demonstrate that the friction forces in the bearings can significantly affect the vibrations of the RBSs.
基金Foundation item： Project（1774-107101027） supported by the National Defense Fund of China Project（1343-74236000006） supported by the Graduate Foundation of Flunan Province, China
文摘In order to simulate the stress of turbine rotor in aeroengine, based on the ANSYS, the simplification model of the turbine rotor was built up. By applying the simplification model, the contact stress of turbine rotor was computed. The maximum contact stress appears at the chamfer below the flank, which agrees with experiment result. At the same time, the contact stress changing with the flank angle and friction coefficient was calculated, The results show that the contact stress in the flank increases slowly with the increase of flank angle; with the friction coefficient increasing, the contact stress in flank length decreases; the contact stress will not change when the friction coefficient is over 0.25.
基金Projects(51674304,51604305)supported by the National Natural Science Foundation of ChinaProject(2016M592445)supported by the China Postdoctoral Science Foundation
文摘The mechanical properties and tribological behaviors of Cu-WS2 composites fabricated by spark plasma sintering（SPS） using two different WS2 particle sizes of 0.6 and 5.0 μm and Cu powders as raw materials were investigated. The results indicate that the bending strength and tribological behavior of Cu-WS2 composites are greatly affected by the size of WS2 particles. The bending strength of Cu-WS2 composites with the WS2 particle size of 5.0 μm is 292.2 MPa. As the size of WS2 particle decreases to 0.6 μm, the bending strength also decreases to 181.5 MPa. Moreover, as the WS2 particle size decreases from 5.0 to 0.6 μm, the wear rate of Cu-WS2 composite sharply increases from 2.99×10^-14 to 6.13×10^-14 m^3/（N·m） and its friction coefficient increases from 0.158 to 0.172. The size of WS2 particle（5.0 μm） plays an important role in forming transfer film formed on the counter-face. The sample with 5.0 μm WS2 particle forms smoother and more continuous transfer film, which results in a low wear rate and friction coefficient of the Cu-WS2 composites.
基金Supported by the National Natural Science Foundation of Beijing （3102023） and the National Science and Technology Support Plan Project （2011BAA04B02）.
文摘The paper described experimental investigation of heat transfer and single-phase pressure drop through tubes with different rotor-assembled strands inserted in the Reynolds number range of 800-9000 with lubricant as working fluid. In the experiment, fixed mounts were employed to eliminate the entrance effect. The experimental results showed that the employment of fixed mounts led to a visible bias of friction factor in the laminar regime while it could not affect the Nusselt numbers significantly. Experiment for the tube inserted with rotors-assembled strand showed remarkable improvement for heat transfer with the Nusselt number increased by 200%-225% in the laminar regime and 125%-160% in the transitional regime. Meanwhile, the friction factor increased inevitably by 200%-300% within the same range of Reynolds number. The comparison of different rotor-assembled strands in-serted tubes and plain tube showed that the heat transfer benefited from the increase of the diameter of rotor-assembled strand with the same lead and the decrease of the lead of rotor-assembled strand, so does the friction factor. Based on experimental data and thorough multivariant linear normal regression method, the correlations of average Nusselt number and friction factor are established.
