An efficient multi-harmonic method is proposed for studying the effects of mistuning on resonant features of bladed disks with blade-to-blade dry friction damping. This method is able to predict accurately the forced ...An efficient multi-harmonic method is proposed for studying the effects of mistuning on resonant features of bladed disks with blade-to-blade dry friction damping. This method is able to predict accurately the forced response of bladed disks in frequency domain, which is validated by numerical integration method in time domain. The resonant features of both tuned and mistuned systems are investigated by using this method under various system coupling strengths, viscous dampings, and dry friction darnpings, etc. The results demonstrate that the proposed multi-harmonic method is very efficient for studying the mistuning effects on the resonant response of bladed disks with blade-to-blade dry friction damping, especially considering the combined effects of various system parameters.展开更多
Dry friction damping structures are widely-used in aero-engines to mitigate vibration.The nonlinear nature of friction and the two-dimensional in-plane motion on the contact interface bring challenges to accurately an...Dry friction damping structures are widely-used in aero-engines to mitigate vibration.The nonlinear nature of friction and the two-dimensional in-plane motion on the contact interface bring challenges to accurately and efficiently predict the forced response of frictionally damped structures.The state-of-the-art Multi-Harmonic Balance Method(MHBM)on quasi-3D contact model in engineering cannot precisely capture the kinematics on the friction interface although the efficiency is high.The full-3D contact model can describe the constitutive relationship of the interface in a more accurate manner;however,the efficiency and convergence are not guaranteed for large-scale models.In this paper,a semi-analytical MHBM on full-3D contact model is proposed.The original Trajectory Tracking Method(TTM)for evaluating the contact force is reformulated to make the calculation more concise and the derivation of the Analytical Jacobian Matrix(AJM)feasible.Based on the chain rule of derivation,the AJM which is the core to upgrade the performance is deduced.Through a shrouded blade finite element model,the accuracy and efficiency of the proposed method are compared with both the MHBM on full-3D contact model with numerical Jacobian matrix and the MHBM on quasi-3D contact model with AJM.The results show that the AJM improves significantly the efficiency of the MHBM on full-3D contact model.The time cost of the proposed method is in the same order of magnitude as that of the MHBM on quasi-3D contact model.We also confirm that the full-3D contact model is necessary for the dynamic analyses of shrouded blades.If one uses the quasi-3D model,the estimation relative error of damping can even reach 31.8%in some cases.In addition,the AJM also brings benefits for stability analysis.It is highly recommended that engineers use the MHBM on full-3D contact model for the dynamic analysis and design of shrouded blades.展开更多
How nonlinear joints affect the response of large space structures is an important problem to investigate.In this paper,a multi-harmonic equivalent modeling method is presented to establish a frequency-domain model of...How nonlinear joints affect the response of large space structures is an important problem to investigate.In this paper,a multi-harmonic equivalent modeling method is presented to establish a frequency-domain model of planar repetitive structures with nonlinear joints.First,at the local level,the nonlinear joint is modeled by the multi-harmonic describing function matrix.The element of the hybrid beam is obtained by the dynamic condensation of the beam-joint element.Second,at the global level,the displacement-equivalence method is used to model the multi-harmonic Euler continuum beam equivalent to the planar repetitive structure.Then,the pseudo-arc-length continuation method is applied to track the multi-harmonic trajectory of response.Afterwards,an experiment is conducted to validate the correctness of the modeling method,considering the effect of hanging rope and air damping.In the numerical studies,several simulation results indicate the similarity of response between a single-degree-of-freedom system with a single nonlinear joint and the system of the planar repetitive structure with a large number of nonlinear joints.Finally,the component of higher-order harmonics is shown to be important for predicting the resonance frequencies and amplitudes.展开更多
Rotor imbalance is identified as one of the predominant vibration sources in high-speed magnetically suspended motors.Due to factors such as rotor machining accuracy errors and uneven material distribution,synchronous...Rotor imbalance is identified as one of the predominant vibration sources in high-speed magnetically suspended motors.Due to factors such as rotor machining accuracy errors and uneven material distribution,synchronous vibration interference is caused.Moreover,sensor runout generates harmonic currents,which are attributed to material irregularities and inhomogeneity in the roundness of the sensor detection surface.Harmonic currents can generate harmonic vibrational forces that are transmitted to the motor housing,jeopardizing control accuracy and the device's operational lifespan.In order to achieve real-time reduction of harmonic currents at specified frequencies and improve the accuracy of harmonic suppression,this paper proposes an algorithm for variable phase anglefiltering of an adaptive cascaded mode notchfilter.This paper performed dynamic modeling and analysis of the magnetically suspended rotor system with rotor imbalance and verified the correctness of the dynamic model.Subsequently,the structure of an adaptive notchfilter with variable phase angle is introduced,highlighting the capability to maintain stability by adjusting the compensatory phase of the system.By comparing the harmonic current suppression performance of cascaded and parallel mode notchfilters,the cascaded method can better enhance the overall frequency selectivity,emphasizing its ability to adjust the compensation phase based on the phase angle of the input signal at different frequencies to maintain system stability.Simulation and experimental results show that harmonic currents can be successfully suppressed in the cascade mode,and the amplitude of the synchronous frequency current is reduced by 94.4%.展开更多
Purpose The continuous-wave(CW)linear accelerator,SSC-Linac,has been put into operation successfully as the new injector of Separate Sector Cyclotron(SSC)for Heavy Ion Research Facility in Lanzhou(HIRFL).The SSC-Linac...Purpose The continuous-wave(CW)linear accelerator,SSC-Linac,has been put into operation successfully as the new injector of Separate Sector Cyclotron(SSC)for Heavy Ion Research Facility in Lanzhou(HIRFL).The SSC-Linac is operated at the frequency of 53.667 MHz,which is the four times of the SSC operating frequency.In order to improve the longitudinal capture efficiency and increase the beam current extracted from the SSC,an independent multi-harmonics buncher(MHB)operating at a fundamental frequency of 13.417 MHz had been designed and manufactured.Method This buncher adopts the dual-gap structure and sawtooth waveform is generated by multi-harmonics synthetized technology.Beam dynamics simulation with MHB was carried out and discussed in this paper.Furthermore,the beam commissioning using 84Kr14+had been performed on SSC-Linac.Results and conclusion The measured maximum capture efficiency 86.5%was obtained,which was well agreed with the simulation results.Due to the successful commissioning of MHB and the outstanding-performance of SSC-Linac,the extracted beam current from SSC has been improved one order of magnitude higher than before.展开更多
Background Sawtooth wave buncher is widely used in low-energy ion injection at cyclotron accelerators.Its performance significantly impacts on the intensity of ion beam delivered to experimental terminals.In order to ...Background Sawtooth wave buncher is widely used in low-energy ion injection at cyclotron accelerators.Its performance significantly impacts on the intensity of ion beam delivered to experimental terminals.In order to meet the high-intensity requirement of physical experiments,we upgrade the existing B02 buncher in the axial injection line of the SFC with the dual-model sawtooth wave buncher for low-energy ion injection.Methods We use a three harmonics synthesis method in the dual-sawtooth wave buncher.First,we use three harmonics to generate a low-level sawtooth wave.Second,the low-level wave is amplified by a broadband amplifier to generate high voltage at a single-gap electrode.Third,the electrode is matched to the amplifier by a 1:9 transmission line transformer.Results The new buncher has been installed online since September 2022.Our tested results show that the buncher is capable of being operated at the full-frequency mode and half-frequency mode with the corresponding frequency ranging from 2.75 to 8.0 MHz and 5.5 to 16.0 MHz,respectively.The effective voltage can be up to 2.54 kV and 1.6 kV,respectively.Also,the sawtooth wave buncher works reliably,and a 4.5-8.6 times gain in the beam intensity is achieved.Conclusion By using the three-harmonic synthesis method,a new dual-mode high-voltage sawtooth wave buncher has been built.This sawtooth wave buncher has succeeded in being applied with the high buncher voltage over a wide frequency range with good reliability and stability.This newly-built sawtooth wave buncher significantly increases the ion beam current for low-energy ion injection at the HIRFL-SFC cyclotron.展开更多
基金National Nature Science Foundation of China (NO.50275121)
文摘An efficient multi-harmonic method is proposed for studying the effects of mistuning on resonant features of bladed disks with blade-to-blade dry friction damping. This method is able to predict accurately the forced response of bladed disks in frequency domain, which is validated by numerical integration method in time domain. The resonant features of both tuned and mistuned systems are investigated by using this method under various system coupling strengths, viscous dampings, and dry friction darnpings, etc. The results demonstrate that the proposed multi-harmonic method is very efficient for studying the mistuning effects on the resonant response of bladed disks with blade-to-blade dry friction damping, especially considering the combined effects of various system parameters.
基金financially supported by the National Natural Science Foundation of China(Nos.52175071,91860205)the Major Projects of Aero-engines and Gas turbines(No.J2019-IV-023-0091)。
文摘Dry friction damping structures are widely-used in aero-engines to mitigate vibration.The nonlinear nature of friction and the two-dimensional in-plane motion on the contact interface bring challenges to accurately and efficiently predict the forced response of frictionally damped structures.The state-of-the-art Multi-Harmonic Balance Method(MHBM)on quasi-3D contact model in engineering cannot precisely capture the kinematics on the friction interface although the efficiency is high.The full-3D contact model can describe the constitutive relationship of the interface in a more accurate manner;however,the efficiency and convergence are not guaranteed for large-scale models.In this paper,a semi-analytical MHBM on full-3D contact model is proposed.The original Trajectory Tracking Method(TTM)for evaluating the contact force is reformulated to make the calculation more concise and the derivation of the Analytical Jacobian Matrix(AJM)feasible.Based on the chain rule of derivation,the AJM which is the core to upgrade the performance is deduced.Through a shrouded blade finite element model,the accuracy and efficiency of the proposed method are compared with both the MHBM on full-3D contact model with numerical Jacobian matrix and the MHBM on quasi-3D contact model with AJM.The results show that the AJM improves significantly the efficiency of the MHBM on full-3D contact model.The time cost of the proposed method is in the same order of magnitude as that of the MHBM on quasi-3D contact model.We also confirm that the full-3D contact model is necessary for the dynamic analyses of shrouded blades.If one uses the quasi-3D model,the estimation relative error of damping can even reach 31.8%in some cases.In addition,the AJM also brings benefits for stability analysis.It is highly recommended that engineers use the MHBM on full-3D contact model for the dynamic analysis and design of shrouded blades.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.11827801,12172181 and 11732006).
文摘How nonlinear joints affect the response of large space structures is an important problem to investigate.In this paper,a multi-harmonic equivalent modeling method is presented to establish a frequency-domain model of planar repetitive structures with nonlinear joints.First,at the local level,the nonlinear joint is modeled by the multi-harmonic describing function matrix.The element of the hybrid beam is obtained by the dynamic condensation of the beam-joint element.Second,at the global level,the displacement-equivalence method is used to model the multi-harmonic Euler continuum beam equivalent to the planar repetitive structure.Then,the pseudo-arc-length continuation method is applied to track the multi-harmonic trajectory of response.Afterwards,an experiment is conducted to validate the correctness of the modeling method,considering the effect of hanging rope and air damping.In the numerical studies,several simulation results indicate the similarity of response between a single-degree-of-freedom system with a single nonlinear joint and the system of the planar repetitive structure with a large number of nonlinear joints.Finally,the component of higher-order harmonics is shown to be important for predicting the resonance frequencies and amplitudes.
基金supported by the National Natural Science Foundation of China under Grant 32371868.
文摘Rotor imbalance is identified as one of the predominant vibration sources in high-speed magnetically suspended motors.Due to factors such as rotor machining accuracy errors and uneven material distribution,synchronous vibration interference is caused.Moreover,sensor runout generates harmonic currents,which are attributed to material irregularities and inhomogeneity in the roundness of the sensor detection surface.Harmonic currents can generate harmonic vibrational forces that are transmitted to the motor housing,jeopardizing control accuracy and the device's operational lifespan.In order to achieve real-time reduction of harmonic currents at specified frequencies and improve the accuracy of harmonic suppression,this paper proposes an algorithm for variable phase anglefiltering of an adaptive cascaded mode notchfilter.This paper performed dynamic modeling and analysis of the magnetically suspended rotor system with rotor imbalance and verified the correctness of the dynamic model.Subsequently,the structure of an adaptive notchfilter with variable phase angle is introduced,highlighting the capability to maintain stability by adjusting the compensatory phase of the system.By comparing the harmonic current suppression performance of cascaded and parallel mode notchfilters,the cascaded method can better enhance the overall frequency selectivity,emphasizing its ability to adjust the compensation phase based on the phase angle of the input signal at different frequencies to maintain system stability.Simulation and experimental results show that harmonic currents can be successfully suppressed in the cascade mode,and the amplitude of the synchronous frequency current is reduced by 94.4%.
基金supported by the National Natural Science Foundation of China(No.11375243)Guangdong Innovative and Entrepreneurial Research Team Program(No.2016ZT06G373).
文摘Purpose The continuous-wave(CW)linear accelerator,SSC-Linac,has been put into operation successfully as the new injector of Separate Sector Cyclotron(SSC)for Heavy Ion Research Facility in Lanzhou(HIRFL).The SSC-Linac is operated at the frequency of 53.667 MHz,which is the four times of the SSC operating frequency.In order to improve the longitudinal capture efficiency and increase the beam current extracted from the SSC,an independent multi-harmonics buncher(MHB)operating at a fundamental frequency of 13.417 MHz had been designed and manufactured.Method This buncher adopts the dual-gap structure and sawtooth waveform is generated by multi-harmonics synthetized technology.Beam dynamics simulation with MHB was carried out and discussed in this paper.Furthermore,the beam commissioning using 84Kr14+had been performed on SSC-Linac.Results and conclusion The measured maximum capture efficiency 86.5%was obtained,which was well agreed with the simulation results.Due to the successful commissioning of MHB and the outstanding-performance of SSC-Linac,the extracted beam current from SSC has been improved one order of magnitude higher than before.
基金provided by Chinese Academy of Sciences,(Y9HIRLL100)National Natural Science Foundation of China,(11975289),Yan Cong.
文摘Background Sawtooth wave buncher is widely used in low-energy ion injection at cyclotron accelerators.Its performance significantly impacts on the intensity of ion beam delivered to experimental terminals.In order to meet the high-intensity requirement of physical experiments,we upgrade the existing B02 buncher in the axial injection line of the SFC with the dual-model sawtooth wave buncher for low-energy ion injection.Methods We use a three harmonics synthesis method in the dual-sawtooth wave buncher.First,we use three harmonics to generate a low-level sawtooth wave.Second,the low-level wave is amplified by a broadband amplifier to generate high voltage at a single-gap electrode.Third,the electrode is matched to the amplifier by a 1:9 transmission line transformer.Results The new buncher has been installed online since September 2022.Our tested results show that the buncher is capable of being operated at the full-frequency mode and half-frequency mode with the corresponding frequency ranging from 2.75 to 8.0 MHz and 5.5 to 16.0 MHz,respectively.The effective voltage can be up to 2.54 kV and 1.6 kV,respectively.Also,the sawtooth wave buncher works reliably,and a 4.5-8.6 times gain in the beam intensity is achieved.Conclusion By using the three-harmonic synthesis method,a new dual-mode high-voltage sawtooth wave buncher has been built.This sawtooth wave buncher has succeeded in being applied with the high buncher voltage over a wide frequency range with good reliability and stability.This newly-built sawtooth wave buncher significantly increases the ion beam current for low-energy ion injection at the HIRFL-SFC cyclotron.
