A vibration-based energy harvester is essentially a resonator working in a limited frequency range.To increase the working frequency range is a challenging problem.This paper reveals a novel possibility for enhancing ...A vibration-based energy harvester is essentially a resonator working in a limited frequency range.To increase the working frequency range is a challenging problem.This paper reveals a novel possibility for enhancing energy harvesting via internal resonance.An internal resonance energy harvester is proposed.The excitation is successively assumed as the Gaussian white noise,the colored noise defined by a second-order filter,the narrow-band noise,and exponentially correlated noise.The corresponding averaged root-meansquare output voltages are computed.Numerical results demonstrate that the internal resonance increases the operating bandwidth and the output voltage.展开更多
Crankshaft assembly failure is one of the main factors that affects the reliability and service life of engines.The linear lumped mass method,which has been universally applied to the dynamic modeling of engine cranks...Crankshaft assembly failure is one of the main factors that affects the reliability and service life of engines.The linear lumped mass method,which has been universally applied to the dynamic modeling of engine crankshaft assembly,reveals obvious simulation errors.The nonlinear dynamic characteristics of a crankshaft assembly are instructionally significant to the improvement of modeling correctness.In this paper,a general expression for the non-constant inertia of a crankshaft assembly is derived based on the instantaneous kinetic energy equivalence method.The nonlinear dynamic equations of a multi-cylinder crankshaft assembly are established using the Lagrange rule considering nonlinear factors such as the non-constant inertia of reciprocating components and the structural damping of shaft segments.The natural frequency and mode shapes of a crankshaft assembly are investigated employing the eigenvector method.The forced vibration response of a diesel engine crankshaft assembly taking into account the non-constant inertia is studied using the numerical integral method.The simulation results are compared with a lumped mass model and a detailed model using the system matrix method.Results of non-linear torsional vibration analysis indicate that the additional excitation torque created by non-constant inertia activates the 2nd order rolling vibration,and the additional damping torque resulting from the non-constant inertia is the main nonlinear factor.The increased torsional angular displacement evoked by the high order excitation torque relates to the non-constant inertia.This research project is aimed at improving nonlinear dynamics theory,and the confirmed nonlinear parameters can be used for the structure design of a crankshaft assembly.展开更多
This study experimentally examines the coupling response of an S-shaped flexible riser exposed to internal gas-liquid two-phase flow and external shear current using the optical non-intrusive measurement.The vibration...This study experimentally examines the coupling response of an S-shaped flexible riser exposed to internal gas-liquid two-phase flow and external shear current using the optical non-intrusive measurement.The vibration tests were conducted with the internal fluid transported at a constant velocity of vi=0.9 m/s with three representative gas-liquid ratios(Q_(g)/Q_(l))and the depth-averaged reduced velocity of external current(Urm)ranging from 9.32 to 23.19.The riser top was hanged underneath an oscillating cylindrical platform.The out-of-plane response is enhanced in the presence of external current,while the in-plane response is suppressed due to the more even distribution of liquid slugs.The response competition among the riser,buoyancy module and platform is quantified in terms of dominant frequencies and interaction lengths,which are sensitive to Q_(g)/Q_(l),Urm.The shift of zero value among the coupling length,affecting length and affected length indicates the switching of dominant role.In general,the response competition in the in-plane direction is more intense than that in the out-of-plane direction.展开更多
基金supported by the State Key Program of National Natural Science of China(Grant No.11232009)Shanghai Leading Academic Discipline Project(Grant No.S30106)
文摘A vibration-based energy harvester is essentially a resonator working in a limited frequency range.To increase the working frequency range is a challenging problem.This paper reveals a novel possibility for enhancing energy harvesting via internal resonance.An internal resonance energy harvester is proposed.The excitation is successively assumed as the Gaussian white noise,the colored noise defined by a second-order filter,the narrow-band noise,and exponentially correlated noise.The corresponding averaged root-meansquare output voltages are computed.Numerical results demonstrate that the internal resonance increases the operating bandwidth and the output voltage.
基金supported by National Natural Science Foundation of China (Grant No. 50975026)Ministerial Eleventh Five-Year Plan Basic Product Pre-research Project of China (Grant No. D2220062905)
文摘Crankshaft assembly failure is one of the main factors that affects the reliability and service life of engines.The linear lumped mass method,which has been universally applied to the dynamic modeling of engine crankshaft assembly,reveals obvious simulation errors.The nonlinear dynamic characteristics of a crankshaft assembly are instructionally significant to the improvement of modeling correctness.In this paper,a general expression for the non-constant inertia of a crankshaft assembly is derived based on the instantaneous kinetic energy equivalence method.The nonlinear dynamic equations of a multi-cylinder crankshaft assembly are established using the Lagrange rule considering nonlinear factors such as the non-constant inertia of reciprocating components and the structural damping of shaft segments.The natural frequency and mode shapes of a crankshaft assembly are investigated employing the eigenvector method.The forced vibration response of a diesel engine crankshaft assembly taking into account the non-constant inertia is studied using the numerical integral method.The simulation results are compared with a lumped mass model and a detailed model using the system matrix method.Results of non-linear torsional vibration analysis indicate that the additional excitation torque created by non-constant inertia activates the 2nd order rolling vibration,and the additional damping torque resulting from the non-constant inertia is the main nonlinear factor.The increased torsional angular displacement evoked by the high order excitation torque relates to the non-constant inertia.This research project is aimed at improving nonlinear dynamics theory,and the confirmed nonlinear parameters can be used for the structure design of a crankshaft assembly.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51979238,52301338)supported by the Sichuan Science and Technology Program(Grant Nos.2023NSFSC1953,2024NSFSC0968).
文摘This study experimentally examines the coupling response of an S-shaped flexible riser exposed to internal gas-liquid two-phase flow and external shear current using the optical non-intrusive measurement.The vibration tests were conducted with the internal fluid transported at a constant velocity of vi=0.9 m/s with three representative gas-liquid ratios(Q_(g)/Q_(l))and the depth-averaged reduced velocity of external current(Urm)ranging from 9.32 to 23.19.The riser top was hanged underneath an oscillating cylindrical platform.The out-of-plane response is enhanced in the presence of external current,while the in-plane response is suppressed due to the more even distribution of liquid slugs.The response competition among the riser,buoyancy module and platform is quantified in terms of dominant frequencies and interaction lengths,which are sensitive to Q_(g)/Q_(l),Urm.The shift of zero value among the coupling length,affecting length and affected length indicates the switching of dominant role.In general,the response competition in the in-plane direction is more intense than that in the out-of-plane direction.
