The switchless reluctance motor’s non-permanent magnet structure design ensures its high reliability in the marine environment;thus,it is a feasible solution for the generator of a sea wave power generation system.Ho...The switchless reluctance motor’s non-permanent magnet structure design ensures its high reliability in the marine environment;thus,it is a feasible solution for the generator of a sea wave power generation system.However,the corresponding thrust density and efficiency remain insufficient.This study focused on a new type of flat linear switched reluctance motor(LSRM),using the finite element software to establish a structural model,and optimized the design with the goal of improving the efficiency and energy density.The entropy method was adopted for sensitivity stratification to objectively select weights to avoid the influence of subjectively selected different proportional weights on the optimization results.Based on the entropy method,the sensitivity of different structural parameters was stratified,and the simulated annealing algorithm,response surface method,and single parameter scanning method were combined for optimization.Finally,the optimal structural size parameters of the motor were determined.Based on the two-dimensional finite element method,to simulate the electromagnetic performance of the reluctance motor under different operating conditions,such as thrust,loss,and efficiency,changes in motor performance before and after optimization were compared to verify the high power generation efficiency and energy density of the optimized linear motor.展开更多
This paper provides an overview of the global wave resource for energy exploration.The most popular metrics and estimators for wave energy resource characterization have been compiled and classified by levels of energ...This paper provides an overview of the global wave resource for energy exploration.The most popular metrics and estimators for wave energy resource characterization have been compiled and classified by levels of energy exploration.A review of existing prospective wave energy resource assessments worldwide is also given,and those studies have been collated and classified by continent.Finally,information about forty existing open sea wave energy test sites worldwide and their characteristics is depicted and displayed on a newly created global map.It has been found that wave power density is still the most consensual metric used for wave energy resource assessment purposes among researchers.Nonetheless,to accomplish a comprehensive wave resource assessment for exploitation,the computation of other metrics at the practicable,technical,and socio-economic levels has also been performed at both spatial and temporal domains.Overall,regions in latitudes between 40°and 60°of both hemispheres are those where the highest wave power density is concentrated.Some areas where the most significant wave power density occurs are in offshore regions of southern Australia,New Zealand,South Africa,Chile,the British Isles,Iceland,and Greenland.However,Europe has been the continent where most research efforts have been done targeting wave energy characterisation for exploitation.展开更多
For ion cyclotron resonance heating, the current on the antenna surface exists in a form of standing wave, and the phase of the poloidal current standing wave affects significantly on the performance of the coupling. ...For ion cyclotron resonance heating, the current on the antenna surface exists in a form of standing wave, and the phase of the poloidal current standing wave affects significantly on the performance of the coupling. In this paper, a coupling calculation is carried out based on a practical model for the loop antenna. The ion cyclotron wave coupling performance depends greatly on the antenna current propagation constant and the phase of standing wave. For a small antenna-current-propagation constant, the antenna coupling performance is more sensitive to a π/2 change in the phase of standing wave.展开更多
A theoretical model which couples the oscillation of cavitation bubbles with the equation of an acoustic wave is utilized to describe the sound fields in double-layer liquids, which can be used to realize the asymmetr...A theoretical model which couples the oscillation of cavitation bubbles with the equation of an acoustic wave is utilized to describe the sound fields in double-layer liquids, which can be used to realize the asymmetric transmission of acoustic waves. Numerical simulations show that the asymmetry is related to the properties of the host liquids and the input acoustic wave. Asymmetry can be enhanced if the maximum number density or the ambient radius of the cavitation bubbles in the low cavitation threshold liquid increases. Moreover, the direction of rectification will be reversed if the amplitude of the input acoustic wave becomes high enough.展开更多
The South China Sea is rich in wind and wave energy resources,and the wind-wave combined power generation device is currently in the concept research and development stage.In recent years,extreme sea conditions such a...The South China Sea is rich in wind and wave energy resources,and the wind-wave combined power generation device is currently in the concept research and development stage.In recent years,extreme sea conditions such as super typhoons have frequently occurred,which poses a serious challenge to the safety of offshore floating platforms.In view of the lack of safety analysis of wind-wave combined power generation devices in extreme sea conditions at present,this paper takes the OC4-WEC combined with semi-submersible wind turbine(Semi-OC4)and the oscillating buoy wave energy converter as the research object,and establishes a mesoscale WRF-SWANFVCOM(W-S-F)real-time coupling platform based on the model coupling Toolkit(MCT)to analyze the spatial and temporal evolution of wind-wave-current in offshore wind farms during the whole process of super typhoon“Rammasun”transit.Combined with the medium/small scale nested method,the flow field characteristics of OC4-WEC platform are analyzed.The results show that the simulation accuracy of the established W-S-F platform for typhoon track is 42.51%higher than that of the single WRF model.Under the action of typhoon-wave-current,the heave motion amplitude of OC4-WEC platform is reduced by 38.1%,the surge motion amplitude is reduced by 26.7%,and the pitch motion amplitude is reduced by 23.4%.展开更多
Wave energy is an important renewable energy source. Previous studies of wave energy conversion(WEC) have focused on the maximum power take-off(PTO) techniques of a single machine. However, there is a lack of research...Wave energy is an important renewable energy source. Previous studies of wave energy conversion(WEC) have focused on the maximum power take-off(PTO) techniques of a single machine. However, there is a lack of research on the energy and power quality of wave farm systems. Owing to the pulsating nature of ocean waves and popular PTO devices, the generated electrical power suffers from severe fluctuations. Existing solutions require extra energy storage and overrated power converters for wave power integration. In this study, we developed a master-slave wave farm system with rotor inertia energy storage; this system delivers self-smoothed power output to the grid and reduces the number of converters. Two control methods based on the moving average filter(MAF) and energy filter(EF) are proposed to smooth the output power of wave farms. RTDS simulations show that the proposed systems and control methods facilitate simple and smooth grid integration of wave energy.展开更多
This paper presents the concept of a Dielectric-lined Multiwave Cerenkov Generator producing high power millimeter waves, which has been investigated with a two and onehalf dimensional electromagnetic relativistic Par...This paper presents the concept of a Dielectric-lined Multiwave Cerenkov Generator producing high power millimeter waves, which has been investigated with a two and onehalf dimensional electromagnetic relativistic Particle-in-Cell (PIC) plasma simulation code. Themodified device can operate in a lower diode-voltage regime with much higher radiation efficiencyand slight downshift of operation frequency. There exist the optima for the permittivity of thedielectric liner and for the magnitude of the guiding magnetic field. The required intensity of theguiding field is reduced by the introduction of the liner. The enhanced propagation of the electronbeam is studied in the presence of the liner.展开更多
By investigating the interaction of an n-type silicon sample with the TM01 mode millimeter wave in a circular waveguide, a viable high-power TM01 millimeter wave sensor is proposed. Based on the hot electron effect, t...By investigating the interaction of an n-type silicon sample with the TM01 mode millimeter wave in a circular waveguide, a viable high-power TM01 millimeter wave sensor is proposed. Based on the hot electron effect, the silicon sample serving as a sensing element（SE） and appropriately mounted on the inner wall of the circular waveguide is devoted to the on-line measurement of a high-power millimeter wave pulse. A three-dimensional parallel finite-difference time-domain method is applied to simulate the wave propagation within the measuring structure. The transverse electric field distribution, the dependences of the frequency response of the voltage standing-wave ratio（VSWR） in the circular waveguide, and the average electric field amplitude within the SE on the electrophysical parameters of the SE are calculated and analyzed in the frequency range of 300–400 GHz. As a result, the optimal dimensions and specific resistance of the SE are obtained,which provide a VSWR of no more than 2.0, a relative sensitivity around 0.0046 kW-1 fluctuating within ±17.3%, and a maximum enduring power of about 4.3 MW.展开更多
The axial power flow (APF) magnitude and attenuation distributions of ultrasonic longitudinal guided waves in viscous liquid-filled elastic pipes are investigated. The optimal location, optimal mode and its frequency-...The axial power flow (APF) magnitude and attenuation distributions of ultrasonic longitudinal guided waves in viscous liquid-filled elastic pipes are investigated. The optimal location, optimal mode and its frequency-thickness product (fd) for the test of pipes filled with viscous liquid are chosen according to APF and attenuation distributions. The results show that the APF magnitude distribution is an important parameter in choosing the modes and parameters. A particular mode has weak dispersion in ranges of fd values with large group velocity, while other modes with smaller group velocity in the same fd ranges have stronger dispersion. It has been observed that, within these ranges, the chosen mode has a larger APF on the (pipe’s) wall. Therefore, in the region of fd values where a particular mode has a large group velocity, this mode will be effective to be used in testing elastic pipes filled with viscous liquid. The results obtained from both the APF analysis and attenuation distribution are consistent.展开更多
基金This work is supported by the National Natural Science Foundation of China(52077141)the Natural Science Foundation of Liaoning Province(2021-YQ-09)the Liaoning Bai Qian Wan Talents Program,China。
文摘The switchless reluctance motor’s non-permanent magnet structure design ensures its high reliability in the marine environment;thus,it is a feasible solution for the generator of a sea wave power generation system.However,the corresponding thrust density and efficiency remain insufficient.This study focused on a new type of flat linear switched reluctance motor(LSRM),using the finite element software to establish a structural model,and optimized the design with the goal of improving the efficiency and energy density.The entropy method was adopted for sensitivity stratification to objectively select weights to avoid the influence of subjectively selected different proportional weights on the optimization results.Based on the entropy method,the sensitivity of different structural parameters was stratified,and the simulated annealing algorithm,response surface method,and single parameter scanning method were combined for optimization.Finally,the optimal structural size parameters of the motor were determined.Based on the two-dimensional finite element method,to simulate the electromagnetic performance of the reluctance motor under different operating conditions,such as thrust,loss,and efficiency,changes in motor performance before and after optimization were compared to verify the high power generation efficiency and energy density of the optimized linear motor.
文摘This paper provides an overview of the global wave resource for energy exploration.The most popular metrics and estimators for wave energy resource characterization have been compiled and classified by levels of energy exploration.A review of existing prospective wave energy resource assessments worldwide is also given,and those studies have been collated and classified by continent.Finally,information about forty existing open sea wave energy test sites worldwide and their characteristics is depicted and displayed on a newly created global map.It has been found that wave power density is still the most consensual metric used for wave energy resource assessment purposes among researchers.Nonetheless,to accomplish a comprehensive wave resource assessment for exploitation,the computation of other metrics at the practicable,technical,and socio-economic levels has also been performed at both spatial and temporal domains.Overall,regions in latitudes between 40°and 60°of both hemispheres are those where the highest wave power density is concentrated.Some areas where the most significant wave power density occurs are in offshore regions of southern Australia,New Zealand,South Africa,Chile,the British Isles,Iceland,and Greenland.However,Europe has been the continent where most research efforts have been done targeting wave energy characterisation for exploitation.
文摘For ion cyclotron resonance heating, the current on the antenna surface exists in a form of standing wave, and the phase of the poloidal current standing wave affects significantly on the performance of the coupling. In this paper, a coupling calculation is carried out based on a practical model for the loop antenna. The ion cyclotron wave coupling performance depends greatly on the antenna current propagation constant and the phase of standing wave. For a small antenna-current-propagation constant, the antenna coupling performance is more sensitive to a π/2 change in the phase of standing wave.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11334005,11574150 and 11564006
文摘A theoretical model which couples the oscillation of cavitation bubbles with the equation of an acoustic wave is utilized to describe the sound fields in double-layer liquids, which can be used to realize the asymmetric transmission of acoustic waves. Numerical simulations show that the asymmetry is related to the properties of the host liquids and the input acoustic wave. Asymmetry can be enhanced if the maximum number density or the ambient radius of the cavitation bubbles in the low cavitation threshold liquid increases. Moreover, the direction of rectification will be reversed if the amplitude of the input acoustic wave becomes high enough.
基金jointly funded by the National Key Research and Development Projects(No.2017YFE0132000)the National Natural Science Foundation of China(Nos.5211101879,52078251,52108456)the Natural Science Foundation of Jiangsu Province(Nos.BK20211518,BK20210309)
文摘The South China Sea is rich in wind and wave energy resources,and the wind-wave combined power generation device is currently in the concept research and development stage.In recent years,extreme sea conditions such as super typhoons have frequently occurred,which poses a serious challenge to the safety of offshore floating platforms.In view of the lack of safety analysis of wind-wave combined power generation devices in extreme sea conditions at present,this paper takes the OC4-WEC combined with semi-submersible wind turbine(Semi-OC4)and the oscillating buoy wave energy converter as the research object,and establishes a mesoscale WRF-SWANFVCOM(W-S-F)real-time coupling platform based on the model coupling Toolkit(MCT)to analyze the spatial and temporal evolution of wind-wave-current in offshore wind farms during the whole process of super typhoon“Rammasun”transit.Combined with the medium/small scale nested method,the flow field characteristics of OC4-WEC platform are analyzed.The results show that the simulation accuracy of the established W-S-F platform for typhoon track is 42.51%higher than that of the single WRF model.Under the action of typhoon-wave-current,the heave motion amplitude of OC4-WEC platform is reduced by 38.1%,the surge motion amplitude is reduced by 26.7%,and the pitch motion amplitude is reduced by 23.4%.
基金supported by EPSRC under Grant EP/ L017725/1 and Grant EP/N032888/1
文摘Wave energy is an important renewable energy source. Previous studies of wave energy conversion(WEC) have focused on the maximum power take-off(PTO) techniques of a single machine. However, there is a lack of research on the energy and power quality of wave farm systems. Owing to the pulsating nature of ocean waves and popular PTO devices, the generated electrical power suffers from severe fluctuations. Existing solutions require extra energy storage and overrated power converters for wave power integration. In this study, we developed a master-slave wave farm system with rotor inertia energy storage; this system delivers self-smoothed power output to the grid and reduces the number of converters. Two control methods based on the moving average filter(MAF) and energy filter(EF) are proposed to smooth the output power of wave farms. RTDS simulations show that the proposed systems and control methods facilitate simple and smooth grid integration of wave energy.
文摘This paper presents the concept of a Dielectric-lined Multiwave Cerenkov Generator producing high power millimeter waves, which has been investigated with a two and onehalf dimensional electromagnetic relativistic Particle-in-Cell (PIC) plasma simulation code. Themodified device can operate in a lower diode-voltage regime with much higher radiation efficiencyand slight downshift of operation frequency. There exist the optima for the permittivity of thedielectric liner and for the magnitude of the guiding magnetic field. The required intensity of theguiding field is reduced by the introduction of the liner. The enhanced propagation of the electronbeam is studied in the presence of the liner.
基金Project supported by the National Natural Science Foundation of China(Grant No.61231003)
文摘By investigating the interaction of an n-type silicon sample with the TM01 mode millimeter wave in a circular waveguide, a viable high-power TM01 millimeter wave sensor is proposed. Based on the hot electron effect, the silicon sample serving as a sensing element（SE） and appropriately mounted on the inner wall of the circular waveguide is devoted to the on-line measurement of a high-power millimeter wave pulse. A three-dimensional parallel finite-difference time-domain method is applied to simulate the wave propagation within the measuring structure. The transverse electric field distribution, the dependences of the frequency response of the voltage standing-wave ratio（VSWR） in the circular waveguide, and the average electric field amplitude within the SE on the electrophysical parameters of the SE are calculated and analyzed in the frequency range of 300–400 GHz. As a result, the optimal dimensions and specific resistance of the SE are obtained,which provide a VSWR of no more than 2.0, a relative sensitivity around 0.0046 kW-1 fluctuating within ±17.3%, and a maximum enduring power of about 4.3 MW.
文摘The axial power flow (APF) magnitude and attenuation distributions of ultrasonic longitudinal guided waves in viscous liquid-filled elastic pipes are investigated. The optimal location, optimal mode and its frequency-thickness product (fd) for the test of pipes filled with viscous liquid are chosen according to APF and attenuation distributions. The results show that the APF magnitude distribution is an important parameter in choosing the modes and parameters. A particular mode has weak dispersion in ranges of fd values with large group velocity, while other modes with smaller group velocity in the same fd ranges have stronger dispersion. It has been observed that, within these ranges, the chosen mode has a larger APF on the (pipe’s) wall. Therefore, in the region of fd values where a particular mode has a large group velocity, this mode will be effective to be used in testing elastic pipes filled with viscous liquid. The results obtained from both the APF analysis and attenuation distribution are consistent.
