Meshing temperature analyses of polymer gears reported in the literature mainly concern the effects of various material combinations and loading conditions,as their impacts could be seen in the first few meshing cycle...Meshing temperature analyses of polymer gears reported in the literature mainly concern the effects of various material combinations and loading conditions,as their impacts could be seen in the first few meshing cycles.However,the effects of tooth geometry parameters could manifest as the meshing cycles increase.This study investigated the effects of tooth geometry parameters on the multi-cycle meshing temperature of polyoxymethylene(POM)worm gears,aiming to control the meshing temperature elevation by tuning the tooth geometry.Firstly,a finite element(FE)model capable of separately calculating the heat generation and simulating the heat propagation was established.Moreover,an adaptive iteration algorithm was proposed within the FE framework to capture the influence of the heat generation variation from cycle to cycle.This algorithm proved to be feasible and highly efficient compared with experimental results from the literature and simulated results via the full-iteration algorithm.Multi-cycle meshing temperature analyses were conducted on a series of POM worm gears with different tooth geometry parameters.The results reveal that,within the range of 14.5°to 25°,a pressure angle of 25°is favorable for reducing the peak surface temperature and overall body temperature of POM worm gears,which influence flank wear and load-carrying capability,respectively.However,addendum modification should be weighed because it helps with load bearing but increases the risk of severe flank wear.This paper proposes an efficient iteration algorithm for multi-cycle meshing temperature analysis of polymer gears and proves the feasibility of controlling the meshing temperature elevation during multiple cycles by tuning tooth geometry.展开更多
Fluidic Thrust Vectoring(FTV)is used for the yaw attitude control of tailless flying wing,which can significantly improve stealth performance,maneuverability and lateral/heading maneuverability.The FTV control scheme ...Fluidic Thrust Vectoring(FTV)is used for the yaw attitude control of tailless flying wing,which can significantly improve stealth performance,maneuverability and lateral/heading maneuverability.The FTV control scheme of co-directional secondary flow was designed based on a 30 kgf thrust turbojet engine,an equivalent rudder deflection control variable of Mass Flow Combination(MFC)was proposed,and a control model was established to form a FTV control system scheme,which was integrated with the flight control system of a 100 kg tailless flying wing with medium aspect ratio to achieve closed-loop control of the yaw attitude based on FTV.The heading stability augmentation and maneuvering control characteristics and time response characteristics of tailless flying wing by FTV were quantitatively studied through virtual flight test in a wind tunnel at a wind speed of 35 m/s.The results show that the control strategy based on MFC achieves bidirectional continuous and stable control of thrust vector angle in a range of±11°,and the thrust vector angle varies monotonically with MFC;the co-directional FTV realizes bidirectional continuous and stable control of the yaw attitude of tailless flying wing,without longitudinal/lateral coupling moment.The increment of the maximum yawing moment coefficient is 0.0029,the maximum yaw rate is 7.55(°)/s,and the response time of the yaw rate of the vectoring nozzle actuated by the secondary flow is about 0.06 s,which satisfies the heading stability augmentation and maneuvering control response requirements of the aircraft with statically unstable heading,and provides new control means for the heading rudderless attitude control of tailless flying wing.展开更多
The Urumqi foreland thrust tectonic belt exhibits complex geological structures and strong seismicity.Imaging its shallow crustal structure is of great significance for understanding its tectonic mechanism and seismog...The Urumqi foreland thrust tectonic belt exhibits complex geological structures and strong seismicity.Imaging its shallow crustal structure is of great significance for understanding its tectonic mechanism and seismogenic environment.We obtained a high-resolution S-wave velocity model of the shallow crust at depths of 0–8 km using ambient noise tomography applied to data from a dense seismic array.Sediments are generally thinner in the southeast and thicker in the northwest,with a maximum thickness of more than 8 km.Variations in the velocity structure near the Xishan,Wanyaogou,and Yamalike faults indicate that their formation was related to differences in the physical properties on either side of the fault.In addition,the faults exhibit thrusting of the low-velocity sides towards the high-velocity sides.In the study area,earthquakes rarely occur at depths of less than 3 km and are mostly concentrated in the high-velocity zone in the southern part.Below 3 km depth,more earthquakes were observed,mainly distributed near faults or in relatively high-velocity areas in the southern part.This suggests that high-velocity structures are more prone to stress accumulation,resulting in earthquakes.At 6–8 km depth,the densely distributed earthquakes in the northwestern part of the Bogda mountains are well-aligned with the northwest-oriented low-velocity zone observed in this study,suggesting that this weak zone likely controls seismicity in this area.展开更多
Wing design is a critical factor in the aerodynamic performance of flapping-wing(FW)robots.Inspired by the natural wing structures of insects,bats,and birds,we explored how bio-mimetic wing vein morphologies,combined ...Wing design is a critical factor in the aerodynamic performance of flapping-wing(FW)robots.Inspired by the natural wing structures of insects,bats,and birds,we explored how bio-mimetic wing vein morphologies,combined with a bio-inspired double wing clap-and-fling mechanism,affect thrust generation.This study focused on increasing vertical force and payload capacity.Through systematic experimentation with various vein configurations and structural designs,we developed innovative wings optimized for thrust production.Comprehensive tests were conducted to measure aerodynamic forces,power consumption,and wing kinematics across a range of flapping frequencies.Additionally,wings with different aspect ratios,a key factor in wing design,were fabricated and extensively evaluated.The study also examined the role of bio-inspired vein layouts on wing flexibility,a critical component in improving flight efficiency.Our findings demonstrate that the newly developed wing design led to a 20%increase in thrust,achieving up to 30 g-force(gf).This research sheds light on the clap-and-fling effect and establishes a promising framework for bio-inspired wing design,offering significant improvements in both performance and payload capacity for FW robots.展开更多
Based on the differences in production mode and operation process between gas storage and gas reservoir,we established a phase balance test procedure and a theoretical simulation model of phase balance during multi-cy...Based on the differences in production mode and operation process between gas storage and gas reservoir,we established a phase balance test procedure and a theoretical simulation model of phase balance during multi-cycles of injection and production of underground gas storage(UGS)rebuilt from condensate gas reservoir to study the phase characteristics of produced and remaining fluids during multi-cycles of injection and production.Take condensate reservoir gas storage as example,the composition of produced fluid and remaining fluid,phase state of remaining fluid,retrograde condensate saturation and condensate recovery degree in the process of multi-cycles of injection-production were studied through multi-cycle injection-production experiment and phase equilibrium theory simulation.The injected gas could greatly improve the recovery of condensate oil in the gas reservoir,and the condensate oil recovery increased by 42% after 5 cycles of injection and production;the injected gas had significant evaporative and extraction effects on the condensate,especially during the first two cycles;the condensate oil saturation of the formation decreased with the increase of injection-production cycles,and the condensate oil saturation after multi-cycles of injection-production was almost 0;the storage capacity increased by about 7.5% after multi-cycles of injection and production,and the cumulative gas injection volume in the 5 th cycle increased by about 25%compared with that in the 1 st cycle.展开更多
Chemical looping dry reforming（CLDR） is an innovative technology for CO2 utilization using the chemical looping principle.The CLDR process consists of three stages,i.e.CH4 reduction,CO2 reforming,and air oxidation.S...Chemical looping dry reforming（CLDR） is an innovative technology for CO2 utilization using the chemical looping principle.The CLDR process consists of three stages,i.e.CH4 reduction,CO2 reforming,and air oxidation.Spinel nickel ferrite（NiFe2O4） was prepared and its multi-cycle performance as an oxygen carrier for CLDR was experimentally investigated.X-ray diffraction（XRD） and Laser Raman spectroscopy showed that a pure spinel crystalline phase（NiFe2O4） was obtained by a parallel flow co-precipitating method.NiFe2O4was reduced into Fe-Ni alloy and wustite（FexO） during the CH4 reduction process.Subsequent oxidation of the reduced oxygen carrier was performed with CO2 as an oxidant to form an intermediate state：a mixture of spinel Ni（1-x）Fe（2＋x）O4,Fe（2＋y）O4 and metallic Ni.And CO was generated in parallel during this stage.Approximate 185 mL of CO was generated for 1 g spinel NiFe2O4 in a single cycle.The intermediate oxygen carrier was fully oxidized in the air oxidation stage to form a mixture of Ni（1＋x）Fe（2-x）O4 and Fe2O3.Although the original state of oxygen carrier（NiFe2O4） was not fully regenerated and agglomeration was observed,a good recyclability was shown in 10 successive redox cycles.展开更多
Low oil prices under the influence of economic structure transformation and slow economic growth have hit the existing markets of traditional big oil suppliers and upgraded the conflict of oil production capacity and ...Low oil prices under the influence of economic structure transformation and slow economic growth have hit the existing markets of traditional big oil suppliers and upgraded the conflict of oil production capacity and interest between OPEC producers and other big oil supplier countries such as the USA and Russia. Forecasting global oil production is significant for all countries for energy strategy planning, although many past forecasts have later been proved to be very seriously incorrect. In this paper,the original generalized Weng model is expanded to a multi-cycle generalized Weng model to better reflect the multi-cycle phenomena caused by political, economic and technological factors. This is used to forecast global oil production based on parameter selection from a large sample, depletion rate of remaining resources, constraints on oil reserves and cycle number determination. This research suggests that the world will reach its peak oil production in 2022, at about 4340×10~6 tonnes. China needs to plan for oil import diversity, a domestic oil production structure based on the supply pattern of large oil suppliers worldwide and the oil demand for China＇s own development.展开更多
Permeability sensitivity to stress experiments were conducted on standard core samples taken from Wen 23 Gas Storage at multi-cycle injection and production conditions of the gas storage to study the change pattern of...Permeability sensitivity to stress experiments were conducted on standard core samples taken from Wen 23 Gas Storage at multi-cycle injection and production conditions of the gas storage to study the change pattern of stress sensitivity of permeability.A method for calculating permeability under overburden pressure in the multi-cycle injection and production process was proposed,and the effect of stress sensitivity of reservoir permeability on gas well injectivity and productivity in UGS was analyzed.Retention rate of permeability decreased sharply first and then slowly with the increase of the UGS cycles.The stress sensitivity index of permeability decreased with the increase of cycle number of net stress variations in the increase process of net stress.The stress sensitivity index of permeability hardly changed with the increase of cycle number of net stress variations in the decrease process of net stress.With the increase of cycle number of net stress variation,the stress sensitivity index of permeability in the increase process of net stress approached that in the decrease process of net stress.The lower the reservoir permeability,the greater the irreversible permeability loss rate,the stronger the cyclic stress sensitivity,and the higher the stress sensitivity index of the reservoir,the stronger the reservoir stress sensitivity.The gas zones with permeability lower than 0.3’10-3 mm2 are not suitable as gas storage regions.Stress sensitivity of reservoir permeability has strong impact on gas well injectivity and productivity and mainly in the first few cycles.展开更多
An efficient method for attosecond extreme ultraviolet source generation under the two-color multi-cycle weak pulse has been theoretically presented by using the concept of the plasmonic field enhancement in the vicin...An efficient method for attosecond extreme ultraviolet source generation under the two-color multi-cycle weak pulse has been theoretically presented by using the concept of the plasmonic field enhancement in the vicinity of metallic nanostructures. The results show that by properly choosing the inhomogeneity of the two-color multi-cycle(20 fs) weak pulse(1013W/cm2), not only the harmonic cutoff has been extended, resulting in a broadband XUV continuum, but also the single short quantum path has been selected to contribute to the harmonic. As a result, two isolated XUV pulses with durations of 68 as and 66 as can be obtained.展开更多
Thrust-vectoring capability has become a critical feature for propulsion systems as space missions move from static to dynamic.Thrust-vectoring is a well-developed area of rocket engine science.For electric propulsion...Thrust-vectoring capability has become a critical feature for propulsion systems as space missions move from static to dynamic.Thrust-vectoring is a well-developed area of rocket engine science.For electric propulsion,however,it is an evolving field that has taken a new leap forward in recent years.A review and analysis of thrust-vectoring schemes for electric propulsion systems have been conducted.The scope of this review includes thrust-vectoring schemes that can be implemented for electrostatic,electromagnetic,and beam-driven thrusters.A classification of electric propulsion schemes that provide thrust-vectoring capability is developed.More attention is given to schemes implemented in laboratory prototypes and flight models.The final part is devoted to a discussion on the suitability of different electric propulsion systems with thrust-vectoring capability for modern space mission operations.The thrust-vectoring capability of electric propulsion is necessary for inner and outer space satellites,which are at a disadvantage with conventional unidirectional propulsion systems due to their limited maneuverability.展开更多
This paper proposes a novel impulsive thrust strategy guided by optimal continuous thrust strategy to address two-player orbital pursuit-evasion game under impulsive thrust control.The strategy seeks to enhance the in...This paper proposes a novel impulsive thrust strategy guided by optimal continuous thrust strategy to address two-player orbital pursuit-evasion game under impulsive thrust control.The strategy seeks to enhance the interpretability of impulsive thrust strategy by integrating it within the framework of differential game in traditional continuous systems.First,this paper introduces an impulse-like constraint,with periodical changes in thrust amplitude,to characterize the impulsive thrust control.Then,the game with the impulse-like constraint is converted into the two-point boundary value problem,which is solved by the combined shooting and deep learning method proposed in this paper.Deep learning and numerical optimization are employed to obtain the guesses for unknown terminal adjoint variables and the game terminal time.Subsequently,the accurate values are solved by the shooting method to yield the optimal continuous thrust strategy with the impulse-like constraint.Finally,the shooting method is iteratively employed at each impulse decision moment to derive the impulsive thrust strategy guided by the optimal continuous thrust strategy.Numerical examples demonstrate the convergence of the combined shooting and deep learning method,even if the strongly nonlinear impulse-like constraint is introduced.The effect of the impulsive thrust strategy guided by the optimal continuous thrust strategy is also discussed.展开更多
The frontal edge of the Makran accretionary wedge is characterized by the development of multiple imbricate thrust faults trending E-W and relatively parallel.However,the mechanisms underlying their formation and the ...The frontal edge of the Makran accretionary wedge is characterized by the development of multiple imbricate thrust faults trending E-W and relatively parallel.However,the mechanisms underlying their formation and the factors controlling their development remain subjects of debate.This paper,based on seismic profile analysis,employs physical simulation experiments to establish a'wedge'type subduction model.The study explores the influence of the initial wedge angle,horizontal sand layer thickness,and the presence or absence of a decollement layer on the structural styles of the thrust wedge.Experimental results indicate that as the initial wedge angle decreases from 11°to 8°,the lateral growth of the thrust wedge increases,whereas vertical growth diminishes.When the horizontal sand layer thickness is reduced from 4.5 cm to 3.0 cm,the spacing between the frontal thrusts decreases and the number of thrust faults increases.Both lateral and vertical growth are relatively reduced,resulting in a smaller thrust wedge.When a decollement layer is present,the structural style exhibits layered deformation.The decollement layer constrains the development of back thrusts and promotes the localized formation of frontal thrusts.In conclusion,the imbricate thrust faults at the frontal edge of the Makran accretionary wedge are primarily controlled by the characteristics of the wedge itself and the presence of the decollement layer.展开更多
The development of the adaptive cycle engine is a crucial direction of advanced fighter power sources in the near future.However,this new technology brings more uncertainty to the design of the control system.To addre...The development of the adaptive cycle engine is a crucial direction of advanced fighter power sources in the near future.However,this new technology brings more uncertainty to the design of the control system.To address the versatile thrust demand under complex dynamic characteristics of the adaptive cycle engine,this paper proposes a direct thrust estimation and control method based on the Model-Free Adaptive Control(MFAC)algorithm.First,an improved Sliding Mode Control-MFAC(SMC-MFAC)algorithm has been developed by introducing a sliding mode variable structure into the standard Full Format Dynamic Linearization-MFAC(FFDL-MFAC)and designing self-adaptive weight coefficients.Then a trivariate double-loop direct thrust control structure with a controller-based thrust estimator and an outer command compensation loop has been established.Through thrust feedback and command correction,accurate control under multi-mode and operation conditions is achieved.The main contribution of this paper is the improved algorithm that combines the tracking capability of the MFAC and the robustness of the SMC,thus enhancing the dynamic performance.Considering the requirements of the online thrust feedback,the designed MFAC-based thrust estimator significantly speeds up the calculation.Additionally,the proposed command correction module can achieve the adaptive thrust control without affecting the operation of the inner loop.Simulations and Hardware-in-Loop(HIL)experiments have been performed on an adaptive cycle engine component-level model to investigate the estimation and control effect under different modes and health conditions.The results demonstrate that both the thrust estimation precision and operation speed are significantly improved compared with Extended Kalman Filter(EKF).Furthermore,the system can accelerate the response of the controlled plant,reduce the overshoot,and realize the thrust recovery within the safety range when the engine encounters the degradation.展开更多
Accurate thrust assessment is crucial for characterizing the performance of micro-thrusters.This paper presents a comprehensive evaluation of the thrust generated by a needle-type indium field emission electric propul...Accurate thrust assessment is crucial for characterizing the performance of micro-thrusters.This paper presents a comprehensive evaluation of the thrust generated by a needle-type indium field emission electric propulsion(In-FEEP)micro-thruster using three methods based on a pendulum:direct thrust measurement,indirect plume momentum transfer and beam current diagnostics.The experimental setup utilized capacitive displacement sensors for force detection and a voice coil motor as a feedback actuator,achieving a resolution better than 0.1μN.Key performance factors such as ionization and plume divergence of ejected charged particles were also examined.The study reveals that the high applied voltage induces significant electrostatic interference,becoming the dominant source of error in direct thrust measurements.Beam current diagnostics and indirect plume momentum measurements were conducted simultaneously,showing strong agreement within a deviation of less than 0.2N across the operational thrust range.The results from all three methods are consistent within the error margins,verifying the reliability of the indirect measurement approach and the theoretical thrust model based on the electrical parameters of In-FEEP.展开更多
Exploring solid propellants for electric thrusters can simplify the propellant storage and supply units in propulsion systems.In this study,polytetrafluoroethylene(PTFE),commonly used as a propellant in pulsed plasma ...Exploring solid propellants for electric thrusters can simplify the propellant storage and supply units in propulsion systems.In this study,polytetrafluoroethylene(PTFE),commonly used as a propellant in pulsed plasma thrusters,was embedded in the discharge chamber of a radio frequency ion thruster(RIT-4)to investigate the performance of an ablation-type RIT.Experimental results indicate that PTFE can decompose and ionize stably under plasma ablation within the discharge chamber,producing-C-F-and F-ion clusters that form a stable plasma.By adjusting the length of the PTFE propellant,it was observed that its decomposition rate influences the ion beam current of the thruster.Compared with xenon,PTFE generates an ion plume with a larger divergence angle,ranging from 16.05°to 22.74°at an ion beam current of 25 mA,with a floating potential distribution of 8‒56 V.Assuming that the proportion of neutral gas in the vacuum chamber matches the ion species ratio in the ion plume,thrust,specific impulse and efficiency parameters were calculated for the RIT-4 with embedded PTFE.Under 50 W RF power,the thrust was approximately 1.02 mN,the specific impulse was around 1236 s and the power-to-thrust ratio was approximately 93.14 W/mN.All results indicate that PTFE is a viable propellant for RIT,but the key is to control the rate of decomposition.展开更多
Strong tectonic activities and diagenetic evolution encourage the development of natural fractures as typical features in deep tight sandstone reservoirs of foreland thrust belts.This study focused on the Jurassic in ...Strong tectonic activities and diagenetic evolution encourage the development of natural fractures as typical features in deep tight sandstone reservoirs of foreland thrust belts.This study focused on the Jurassic in the southern Junggar Basin to comprehensively analyze the fracture characteristics and differential distribution and,ultimately,addressed the controlling mechanisms of tectonism and diagenesis on fracture effectiveness.Results revealed that the intensity of tectonic activities determines the complexity of tectonic fracture systems to create various fracture orientations when they have been stronger.The intense tectonic deformation would impact the stratum occurrence,which results in a wide range of fracture dip angles.Moreover,as the intensity of tectonic activities and deformations weakens,the scale and degree of tectonic fractures would decrease continuously.The control of tectonism on fracture effectiveness is reflected in the notable variations in the filling of multiple group fractures developed during different tectonic activity periods.Fractures formed in the early stages are more likely to be filled with minerals,causing their effectiveness to deteriorate significantly.Additionally,the strong cementation in the diagenetic evolution can cause more fractures to be filled with minerals and become barriers to fluid flow,which is detrimental to fracture effectiveness.However,dissolution is beneficial in improving their effectiveness by increasing fracture aperture and their connectivity to the pores.These insights can refine the development pattern of natural fractures and contribute to revealing the evolutionary mechanisms of fracture effectiveness in deep tight sandstone reservoirs of foreland thrust belts.展开更多
Direct Thrust Control(DTC) is effective in dealing with the mismatch between thrust and rotor speed in traditional engine control. Among the DTC architecture, model-based thrust estimation method has less arithmetic c...Direct Thrust Control(DTC) is effective in dealing with the mismatch between thrust and rotor speed in traditional engine control. Among the DTC architecture, model-based thrust estimation method has less arithmetic consumption and better real-time performance. In this paper,a direct thrust controller design approach for gas turbine engine based on parameter dependent model is proposed. In order to ensure the stability of DTC control system based on parameter dependent model, there are usually conservatism detects. For the purpose of reducing the conservatism in the solution process of filter and controller, an Equilibrium Manifold Expansion(EME) model with bounded parameter variation of engine is established. The design conditions of Kalman filter for discrete-time EME system are introduced, and the proposed conditions have a certain suppression effect on the input noise of the system with bounded parameter variation.The engine thrust estimator stability and H∞filtering problems are solved by the polytopic quadratic Lyapunov function based on the Linear Matrix Inequalities(LMIs). To meet the performance requirements of thrust control, the Grey Wolf Optimization(GWO) algorithm is applied to optimize the PID control parameters. The proposed method is verified on a Hardware-in-Loop(HIL) platform. The simulation results demonstrate that the DTC framework can ensure the stability of engine closed-loop system in large range deviation tests. The filter and controller solution method considering the parameter variation boundary can obtain a solution that makes the system have better performance parameters. Moreover, the proposed filter has better thrust estimation performance than the traditional Kalman filter under the condition of sensor noise. Compared with Augmented Linear Quadratic Regulator(ALQR) controller, the PID controller optimized by GWO has a faster response in simulation.展开更多
Rotating machinery in the aviation industry is increasingly embracing high speeds and miniaturization,and foil dynamic pressure gas bearing has great application value due to its self-lubrication and self-adaptive def...Rotating machinery in the aviation industry is increasingly embracing high speeds and miniaturization,and foil dynamic pressure gas bearing has great application value due to its self-lubrication and self-adaptive deformation characteristics.This study explores the interaction mechanism between micro-scale variable-sectional shearing flow with hyper-rotation speeds and a three-layer elastic foil assembly through bidirectional aero-elastic coupling in a Multi-layer Thrust Gas Foil Bearing(MTGFB).The bearing capacity of the MTGFB varies non-linearly with the decrease of gas film clearance,while the collaborative deformation of the three-layer elastic foil assembly can deal with different load conditions.As the load capacity increases,the enhanced dynamic pressure effect causes the top foil to evolve from a single arch to multiple arches.The hydrodynamic effects in the gas film evolve to form multiple segmented wedges with different pitch ratios,while the peak pressure of the gas film always occurs near the vaults of the top foil.As the rotational speed frequency approaches the natural frequency,the resonance of the gas film and elastic foil assembly system occurs,and a phase delay occurs between the pressure pulsation and the vibration of foils.The load capacity of the MTGFB also depends on the elastic moduli of the elastic foil assembly.Increasing the elastic modulus decreases the deformation amplitude of the top foil,whereas it increases those of the backboard and middle foil,increasing the load capacity.展开更多
Linear flux-switching permanent magnet motors(LFSPMs) have been proposed for long stator applications such as rail transit. However, the conventional linear permanent magnet synchronous motor(LPMSM) suffers from thrus...Linear flux-switching permanent magnet motors(LFSPMs) have been proposed for long stator applications such as rail transit. However, the conventional linear permanent magnet synchronous motor(LPMSM) suffers from thrust ripple, which degrades the motor performance. The thrust ripple in LFSPMs is mainly caused by detent force and asymmetric electromagnetic parameters, excluding external disturbances. Moreover, the 12/13 slot-pole LFSPM exhibits unique inductance characteristics, which lead to different effects on thrust ripple. First, the detent force in the LFSPM is analyzed through finite element method(FEM). In addition, new finite element(FE) models are proposed for further analysis of the cogging force in LFSPMs. Second, the unique inductance characteristics of the 12/13 slot-pole LFSPM are investigated, and then the thrust ripple caused by asymmetric electromagnetic parameters is calculated by the virtual displacement method. Third, the mathematical model considering the thrust ripple is established for the LFSPM, which provides a foundation for subsequent research on thrust ripple suppression control strategies. Finally, the thrust ripple analysis is validated by comparing FEM results, modeling simulations, and experimental data.展开更多
The Taiji program is focused on achieving space-based gravitational wave detection in the frequency range of 0.1 mHz-1 Hz.To achieve drag-free control,Taiji satellites must be equipped with micro-thrusters that satisf...The Taiji program is focused on achieving space-based gravitational wave detection in the frequency range of 0.1 mHz-1 Hz.To achieve drag-free control,Taiji satellites must be equipped with micro-thrusters that satisfy stringent requirements,including a continuously adjustable thrust,thrust resolution of 0.1μN,thrust noise of 0.1μN·Hz^(-0.5)and response time of less than 100 ms.This paper presents the progress of a variable cold gas micro-thruster being developed for the Taiji program.A series of technologies such as a bidirectional piezoelectric drive,spherical valve core,conical nozzle seal,miniature gas chamber,high thruster integration,combined digital and analogue communication and high-frequency closed-loop thrust control were employed to achieve engineering prototypes of a low-noise and fast-response micro-thruster.Ground performance tests indicate that the micro-thruster achieved a minimum thrust of close to 1.1 nN,a thrust resolution of 0.05μN and a maximum specific impulse of 69.1 s using nitrogen gas as the working fluid.The thrust noise was less than 0.1μN·Hz^(-0.5)in the frequency band of 10 mHz-1 Hz,and the thrust response time was 140 ms.The control parameters were further optimised to achieve a flow response time of 50 ms.The results indicate that the developed micro-thruster essentially met the performance requirements for drag-free control to facilitate space-based gravitational wave detection.展开更多
基金Supported by National Key R&D Program of China(Grant No.2019YFE0121300)。
文摘Meshing temperature analyses of polymer gears reported in the literature mainly concern the effects of various material combinations and loading conditions,as their impacts could be seen in the first few meshing cycles.However,the effects of tooth geometry parameters could manifest as the meshing cycles increase.This study investigated the effects of tooth geometry parameters on the multi-cycle meshing temperature of polyoxymethylene(POM)worm gears,aiming to control the meshing temperature elevation by tuning the tooth geometry.Firstly,a finite element(FE)model capable of separately calculating the heat generation and simulating the heat propagation was established.Moreover,an adaptive iteration algorithm was proposed within the FE framework to capture the influence of the heat generation variation from cycle to cycle.This algorithm proved to be feasible and highly efficient compared with experimental results from the literature and simulated results via the full-iteration algorithm.Multi-cycle meshing temperature analyses were conducted on a series of POM worm gears with different tooth geometry parameters.The results reveal that,within the range of 14.5°to 25°,a pressure angle of 25°is favorable for reducing the peak surface temperature and overall body temperature of POM worm gears,which influence flank wear and load-carrying capability,respectively.However,addendum modification should be weighed because it helps with load bearing but increases the risk of severe flank wear.This paper proposes an efficient iteration algorithm for multi-cycle meshing temperature analysis of polymer gears and proves the feasibility of controlling the meshing temperature elevation during multiple cycles by tuning tooth geometry.
文摘Fluidic Thrust Vectoring(FTV)is used for the yaw attitude control of tailless flying wing,which can significantly improve stealth performance,maneuverability and lateral/heading maneuverability.The FTV control scheme of co-directional secondary flow was designed based on a 30 kgf thrust turbojet engine,an equivalent rudder deflection control variable of Mass Flow Combination(MFC)was proposed,and a control model was established to form a FTV control system scheme,which was integrated with the flight control system of a 100 kg tailless flying wing with medium aspect ratio to achieve closed-loop control of the yaw attitude based on FTV.The heading stability augmentation and maneuvering control characteristics and time response characteristics of tailless flying wing by FTV were quantitatively studied through virtual flight test in a wind tunnel at a wind speed of 35 m/s.The results show that the control strategy based on MFC achieves bidirectional continuous and stable control of thrust vector angle in a range of±11°,and the thrust vector angle varies monotonically with MFC;the co-directional FTV realizes bidirectional continuous and stable control of the yaw attitude of tailless flying wing,without longitudinal/lateral coupling moment.The increment of the maximum yawing moment coefficient is 0.0029,the maximum yaw rate is 7.55(°)/s,and the response time of the yaw rate of the vectoring nozzle actuated by the secondary flow is about 0.06 s,which satisfies the heading stability augmentation and maneuvering control response requirements of the aircraft with statically unstable heading,and provides new control means for the heading rudderless attitude control of tailless flying wing.
基金supported by the Key Research and Development Program of the Xinjiang Uygur Autonomous Region(No.2020B03006-1)the National Natural Science Foundation of China(Nos.42304069,and 42102275).
文摘The Urumqi foreland thrust tectonic belt exhibits complex geological structures and strong seismicity.Imaging its shallow crustal structure is of great significance for understanding its tectonic mechanism and seismogenic environment.We obtained a high-resolution S-wave velocity model of the shallow crust at depths of 0–8 km using ambient noise tomography applied to data from a dense seismic array.Sediments are generally thinner in the southeast and thicker in the northwest,with a maximum thickness of more than 8 km.Variations in the velocity structure near the Xishan,Wanyaogou,and Yamalike faults indicate that their formation was related to differences in the physical properties on either side of the fault.In addition,the faults exhibit thrusting of the low-velocity sides towards the high-velocity sides.In the study area,earthquakes rarely occur at depths of less than 3 km and are mostly concentrated in the high-velocity zone in the southern part.Below 3 km depth,more earthquakes were observed,mainly distributed near faults or in relatively high-velocity areas in the southern part.This suggests that high-velocity structures are more prone to stress accumulation,resulting in earthquakes.At 6–8 km depth,the densely distributed earthquakes in the northwestern part of the Bogda mountains are well-aligned with the northwest-oriented low-velocity zone observed in this study,suggesting that this weak zone likely controls seismicity in this area.
基金Nguyen Tat Thanh University,Ho Chi Minh City,Vietnam for supporting this study。
文摘Wing design is a critical factor in the aerodynamic performance of flapping-wing(FW)robots.Inspired by the natural wing structures of insects,bats,and birds,we explored how bio-mimetic wing vein morphologies,combined with a bio-inspired double wing clap-and-fling mechanism,affect thrust generation.This study focused on increasing vertical force and payload capacity.Through systematic experimentation with various vein configurations and structural designs,we developed innovative wings optimized for thrust production.Comprehensive tests were conducted to measure aerodynamic forces,power consumption,and wing kinematics across a range of flapping frequencies.Additionally,wings with different aspect ratios,a key factor in wing design,were fabricated and extensively evaluated.The study also examined the role of bio-inspired vein layouts on wing flexibility,a critical component in improving flight efficiency.Our findings demonstrate that the newly developed wing design led to a 20%increase in thrust,achieving up to 30 g-force(gf).This research sheds light on the clap-and-fling effect and establishes a promising framework for bio-inspired wing design,offering significant improvements in both performance and payload capacity for FW robots.
基金Supported by the National Natural Science Foundation of China(51974268)the PetroChina Science and Technology Major Project(2015E-4002)China Postdoctoral Science Foundation(2019M663563)。
文摘Based on the differences in production mode and operation process between gas storage and gas reservoir,we established a phase balance test procedure and a theoretical simulation model of phase balance during multi-cycles of injection and production of underground gas storage(UGS)rebuilt from condensate gas reservoir to study the phase characteristics of produced and remaining fluids during multi-cycles of injection and production.Take condensate reservoir gas storage as example,the composition of produced fluid and remaining fluid,phase state of remaining fluid,retrograde condensate saturation and condensate recovery degree in the process of multi-cycles of injection-production were studied through multi-cycle injection-production experiment and phase equilibrium theory simulation.The injected gas could greatly improve the recovery of condensate oil in the gas reservoir,and the condensate oil recovery increased by 42% after 5 cycles of injection and production;the injected gas had significant evaporative and extraction effects on the condensate,especially during the first two cycles;the condensate oil saturation of the formation decreased with the increase of injection-production cycles,and the condensate oil saturation after multi-cycles of injection-production was almost 0;the storage capacity increased by about 7.5% after multi-cycles of injection and production,and the cumulative gas injection volume in the 5 th cycle increased by about 25%compared with that in the 1 st cycle.
基金the financial support by the National Natural Science Foundation of China(51406214 and51406208)supported by the Natural science Foundation of Guangdong Province(2015A030313719)the Science&Technology Research Project of Guangdong Province(2013B050800008)
文摘Chemical looping dry reforming（CLDR） is an innovative technology for CO2 utilization using the chemical looping principle.The CLDR process consists of three stages,i.e.CH4 reduction,CO2 reforming,and air oxidation.Spinel nickel ferrite（NiFe2O4） was prepared and its multi-cycle performance as an oxygen carrier for CLDR was experimentally investigated.X-ray diffraction（XRD） and Laser Raman spectroscopy showed that a pure spinel crystalline phase（NiFe2O4） was obtained by a parallel flow co-precipitating method.NiFe2O4was reduced into Fe-Ni alloy and wustite（FexO） during the CH4 reduction process.Subsequent oxidation of the reduced oxygen carrier was performed with CO2 as an oxidant to form an intermediate state：a mixture of spinel Ni（1-x）Fe（2＋x）O4,Fe（2＋y）O4 and metallic Ni.And CO was generated in parallel during this stage.Approximate 185 mL of CO was generated for 1 g spinel NiFe2O4 in a single cycle.The intermediate oxygen carrier was fully oxidized in the air oxidation stage to form a mixture of Ni（1＋x）Fe（2-x）O4 and Fe2O3.Although the original state of oxygen carrier（NiFe2O4） was not fully regenerated and agglomeration was observed,a good recyclability was shown in 10 successive redox cycles.
基金financial support from the National Natural Science Foundation of China (Grant Nos. 71303258, 71373285, and 71503264)National Social Science Funds of China (13&ZD159)+1 种基金MOE (Ministry of Education in China) Project of Humanities and Social Sciences (13YJC630148, 15YJC630121)Science Foundation of China University of Petroleum, Beijing (ZX20150130)
文摘Low oil prices under the influence of economic structure transformation and slow economic growth have hit the existing markets of traditional big oil suppliers and upgraded the conflict of oil production capacity and interest between OPEC producers and other big oil supplier countries such as the USA and Russia. Forecasting global oil production is significant for all countries for energy strategy planning, although many past forecasts have later been proved to be very seriously incorrect. In this paper,the original generalized Weng model is expanded to a multi-cycle generalized Weng model to better reflect the multi-cycle phenomena caused by political, economic and technological factors. This is used to forecast global oil production based on parameter selection from a large sample, depletion rate of remaining resources, constraints on oil reserves and cycle number determination. This research suggests that the world will reach its peak oil production in 2022, at about 4340×10~6 tonnes. China needs to plan for oil import diversity, a domestic oil production structure based on the supply pattern of large oil suppliers worldwide and the oil demand for China＇s own development.
基金Supported by the Chongqing Technical Innovation and Application&Development Special Project(cstc2020jscx-msxmX0189)。
文摘Permeability sensitivity to stress experiments were conducted on standard core samples taken from Wen 23 Gas Storage at multi-cycle injection and production conditions of the gas storage to study the change pattern of stress sensitivity of permeability.A method for calculating permeability under overburden pressure in the multi-cycle injection and production process was proposed,and the effect of stress sensitivity of reservoir permeability on gas well injectivity and productivity in UGS was analyzed.Retention rate of permeability decreased sharply first and then slowly with the increase of the UGS cycles.The stress sensitivity index of permeability decreased with the increase of cycle number of net stress variations in the increase process of net stress.The stress sensitivity index of permeability hardly changed with the increase of cycle number of net stress variations in the decrease process of net stress.With the increase of cycle number of net stress variation,the stress sensitivity index of permeability in the increase process of net stress approached that in the decrease process of net stress.The lower the reservoir permeability,the greater the irreversible permeability loss rate,the stronger the cyclic stress sensitivity,and the higher the stress sensitivity index of the reservoir,the stronger the reservoir stress sensitivity.The gas zones with permeability lower than 0.3’10-3 mm2 are not suitable as gas storage regions.Stress sensitivity of reservoir permeability has strong impact on gas well injectivity and productivity and mainly in the first few cycles.
基金Supported by the Scientific Research Fund of Liaoning University of Technology of China under Grant No.X201319the Scientific Research Fund of Liaoning Provincial Education Department under Grant No.L2014242
文摘An efficient method for attosecond extreme ultraviolet source generation under the two-color multi-cycle weak pulse has been theoretically presented by using the concept of the plasmonic field enhancement in the vicinity of metallic nanostructures. The results show that by properly choosing the inhomogeneity of the two-color multi-cycle(20 fs) weak pulse(1013W/cm2), not only the harmonic cutoff has been extended, resulting in a broadband XUV continuum, but also the single short quantum path has been selected to contribute to the harmonic. As a result, two isolated XUV pulses with durations of 68 as and 66 as can be obtained.
基金performed at large-scale research facility"Beam-M"of Bauman Moscow State Technical University following the government task by the Ministry of Science and Higher Education of the Russian Federation(No.FSFN-2024-0007).
文摘Thrust-vectoring capability has become a critical feature for propulsion systems as space missions move from static to dynamic.Thrust-vectoring is a well-developed area of rocket engine science.For electric propulsion,however,it is an evolving field that has taken a new leap forward in recent years.A review and analysis of thrust-vectoring schemes for electric propulsion systems have been conducted.The scope of this review includes thrust-vectoring schemes that can be implemented for electrostatic,electromagnetic,and beam-driven thrusters.A classification of electric propulsion schemes that provide thrust-vectoring capability is developed.More attention is given to schemes implemented in laboratory prototypes and flight models.The final part is devoted to a discussion on the suitability of different electric propulsion systems with thrust-vectoring capability for modern space mission operations.The thrust-vectoring capability of electric propulsion is necessary for inner and outer space satellites,which are at a disadvantage with conventional unidirectional propulsion systems due to their limited maneuverability.
基金funded by the National Natural Science Foundation of China(No.U21B6001)。
文摘This paper proposes a novel impulsive thrust strategy guided by optimal continuous thrust strategy to address two-player orbital pursuit-evasion game under impulsive thrust control.The strategy seeks to enhance the interpretability of impulsive thrust strategy by integrating it within the framework of differential game in traditional continuous systems.First,this paper introduces an impulse-like constraint,with periodical changes in thrust amplitude,to characterize the impulsive thrust control.Then,the game with the impulse-like constraint is converted into the two-point boundary value problem,which is solved by the combined shooting and deep learning method proposed in this paper.Deep learning and numerical optimization are employed to obtain the guesses for unknown terminal adjoint variables and the game terminal time.Subsequently,the accurate values are solved by the shooting method to yield the optimal continuous thrust strategy with the impulse-like constraint.Finally,the shooting method is iteratively employed at each impulse decision moment to derive the impulsive thrust strategy guided by the optimal continuous thrust strategy.Numerical examples demonstrate the convergence of the combined shooting and deep learning method,even if the strongly nonlinear impulse-like constraint is introduced.The effect of the impulsive thrust strategy guided by the optimal continuous thrust strategy is also discussed.
基金the National Natural Science Foundation of China(No.42076069)。
文摘The frontal edge of the Makran accretionary wedge is characterized by the development of multiple imbricate thrust faults trending E-W and relatively parallel.However,the mechanisms underlying their formation and the factors controlling their development remain subjects of debate.This paper,based on seismic profile analysis,employs physical simulation experiments to establish a'wedge'type subduction model.The study explores the influence of the initial wedge angle,horizontal sand layer thickness,and the presence or absence of a decollement layer on the structural styles of the thrust wedge.Experimental results indicate that as the initial wedge angle decreases from 11°to 8°,the lateral growth of the thrust wedge increases,whereas vertical growth diminishes.When the horizontal sand layer thickness is reduced from 4.5 cm to 3.0 cm,the spacing between the frontal thrusts decreases and the number of thrust faults increases.Both lateral and vertical growth are relatively reduced,resulting in a smaller thrust wedge.When a decollement layer is present,the structural style exhibits layered deformation.The decollement layer constrains the development of back thrusts and promotes the localized formation of frontal thrusts.In conclusion,the imbricate thrust faults at the frontal edge of the Makran accretionary wedge are primarily controlled by the characteristics of the wedge itself and the presence of the decollement layer.
基金supported by National Natural Science Foundation of China(No.52302472)。
文摘The development of the adaptive cycle engine is a crucial direction of advanced fighter power sources in the near future.However,this new technology brings more uncertainty to the design of the control system.To address the versatile thrust demand under complex dynamic characteristics of the adaptive cycle engine,this paper proposes a direct thrust estimation and control method based on the Model-Free Adaptive Control(MFAC)algorithm.First,an improved Sliding Mode Control-MFAC(SMC-MFAC)algorithm has been developed by introducing a sliding mode variable structure into the standard Full Format Dynamic Linearization-MFAC(FFDL-MFAC)and designing self-adaptive weight coefficients.Then a trivariate double-loop direct thrust control structure with a controller-based thrust estimator and an outer command compensation loop has been established.Through thrust feedback and command correction,accurate control under multi-mode and operation conditions is achieved.The main contribution of this paper is the improved algorithm that combines the tracking capability of the MFAC and the robustness of the SMC,thus enhancing the dynamic performance.Considering the requirements of the online thrust feedback,the designed MFAC-based thrust estimator significantly speeds up the calculation.Additionally,the proposed command correction module can achieve the adaptive thrust control without affecting the operation of the inner loop.Simulations and Hardware-in-Loop(HIL)experiments have been performed on an adaptive cycle engine component-level model to investigate the estimation and control effect under different modes and health conditions.The results demonstrate that both the thrust estimation precision and operation speed are significantly improved compared with Extended Kalman Filter(EKF).Furthermore,the system can accelerate the response of the controlled plant,reduce the overshoot,and realize the thrust recovery within the safety range when the engine encounters the degradation.
基金Project supported by the National Key Research and Development Program of China(Grant No.2020YFC2201001)the Guangdong Major Project of Basic and Applied Basic Research(Grant No.2019B030302001)+1 种基金the National Natural Science Foundation of China(Grant Nos.12105373,12105374,and 11927812)the Science and Technology Research Project of Jiangxi Provincial Department of Education(Grant No.GJJ2402105).
文摘Accurate thrust assessment is crucial for characterizing the performance of micro-thrusters.This paper presents a comprehensive evaluation of the thrust generated by a needle-type indium field emission electric propulsion(In-FEEP)micro-thruster using three methods based on a pendulum:direct thrust measurement,indirect plume momentum transfer and beam current diagnostics.The experimental setup utilized capacitive displacement sensors for force detection and a voice coil motor as a feedback actuator,achieving a resolution better than 0.1μN.Key performance factors such as ionization and plume divergence of ejected charged particles were also examined.The study reveals that the high applied voltage induces significant electrostatic interference,becoming the dominant source of error in direct thrust measurements.Beam current diagnostics and indirect plume momentum measurements were conducted simultaneously,showing strong agreement within a deviation of less than 0.2N across the operational thrust range.The results from all three methods are consistent within the error margins,verifying the reliability of the indirect measurement approach and the theoretical thrust model based on the electrical parameters of In-FEEP.
基金supported by the National Key R&D Program of China(No.2021YFC2202800)the Youth Innovation Promotion Association CAS(No.2023022)Institute of Mechanics Outstanding Young Talent Training Program(No.E1Z1030201).
文摘Exploring solid propellants for electric thrusters can simplify the propellant storage and supply units in propulsion systems.In this study,polytetrafluoroethylene(PTFE),commonly used as a propellant in pulsed plasma thrusters,was embedded in the discharge chamber of a radio frequency ion thruster(RIT-4)to investigate the performance of an ablation-type RIT.Experimental results indicate that PTFE can decompose and ionize stably under plasma ablation within the discharge chamber,producing-C-F-and F-ion clusters that form a stable plasma.By adjusting the length of the PTFE propellant,it was observed that its decomposition rate influences the ion beam current of the thruster.Compared with xenon,PTFE generates an ion plume with a larger divergence angle,ranging from 16.05°to 22.74°at an ion beam current of 25 mA,with a floating potential distribution of 8‒56 V.Assuming that the proportion of neutral gas in the vacuum chamber matches the ion species ratio in the ion plume,thrust,specific impulse and efficiency parameters were calculated for the RIT-4 with embedded PTFE.Under 50 W RF power,the thrust was approximately 1.02 mN,the specific impulse was around 1236 s and the power-to-thrust ratio was approximately 93.14 W/mN.All results indicate that PTFE is a viable propellant for RIT,but the key is to control the rate of decomposition.
基金supported by the CNPC Innovation Found(No.2023DQ02-0103)National Major Science and Technology Projects of China(No.2016ZX05003-001).
文摘Strong tectonic activities and diagenetic evolution encourage the development of natural fractures as typical features in deep tight sandstone reservoirs of foreland thrust belts.This study focused on the Jurassic in the southern Junggar Basin to comprehensively analyze the fracture characteristics and differential distribution and,ultimately,addressed the controlling mechanisms of tectonism and diagenesis on fracture effectiveness.Results revealed that the intensity of tectonic activities determines the complexity of tectonic fracture systems to create various fracture orientations when they have been stronger.The intense tectonic deformation would impact the stratum occurrence,which results in a wide range of fracture dip angles.Moreover,as the intensity of tectonic activities and deformations weakens,the scale and degree of tectonic fractures would decrease continuously.The control of tectonism on fracture effectiveness is reflected in the notable variations in the filling of multiple group fractures developed during different tectonic activity periods.Fractures formed in the early stages are more likely to be filled with minerals,causing their effectiveness to deteriorate significantly.Additionally,the strong cementation in the diagenetic evolution can cause more fractures to be filled with minerals and become barriers to fluid flow,which is detrimental to fracture effectiveness.However,dissolution is beneficial in improving their effectiveness by increasing fracture aperture and their connectivity to the pores.These insights can refine the development pattern of natural fractures and contribute to revealing the evolutionary mechanisms of fracture effectiveness in deep tight sandstone reservoirs of foreland thrust belts.
基金supported by the National Natural Science Foundation of China(No.52372371)the Science Center for Gas Turbine Project,China(Nos.P2022-B-V-002-001,P2022-B-V-001-001).
文摘Direct Thrust Control(DTC) is effective in dealing with the mismatch between thrust and rotor speed in traditional engine control. Among the DTC architecture, model-based thrust estimation method has less arithmetic consumption and better real-time performance. In this paper,a direct thrust controller design approach for gas turbine engine based on parameter dependent model is proposed. In order to ensure the stability of DTC control system based on parameter dependent model, there are usually conservatism detects. For the purpose of reducing the conservatism in the solution process of filter and controller, an Equilibrium Manifold Expansion(EME) model with bounded parameter variation of engine is established. The design conditions of Kalman filter for discrete-time EME system are introduced, and the proposed conditions have a certain suppression effect on the input noise of the system with bounded parameter variation.The engine thrust estimator stability and H∞filtering problems are solved by the polytopic quadratic Lyapunov function based on the Linear Matrix Inequalities(LMIs). To meet the performance requirements of thrust control, the Grey Wolf Optimization(GWO) algorithm is applied to optimize the PID control parameters. The proposed method is verified on a Hardware-in-Loop(HIL) platform. The simulation results demonstrate that the DTC framework can ensure the stability of engine closed-loop system in large range deviation tests. The filter and controller solution method considering the parameter variation boundary can obtain a solution that makes the system have better performance parameters. Moreover, the proposed filter has better thrust estimation performance than the traditional Kalman filter under the condition of sensor noise. Compared with Augmented Linear Quadratic Regulator(ALQR) controller, the PID controller optimized by GWO has a faster response in simulation.
基金the financial support from the National Natural Science Foundation of China(No.52206091)the Aeronautical Science Foundation of China(No.201928052008)the Natural Science Foundation of Jiangsu Province,China(No.BK20210303)。
文摘Rotating machinery in the aviation industry is increasingly embracing high speeds and miniaturization,and foil dynamic pressure gas bearing has great application value due to its self-lubrication and self-adaptive deformation characteristics.This study explores the interaction mechanism between micro-scale variable-sectional shearing flow with hyper-rotation speeds and a three-layer elastic foil assembly through bidirectional aero-elastic coupling in a Multi-layer Thrust Gas Foil Bearing(MTGFB).The bearing capacity of the MTGFB varies non-linearly with the decrease of gas film clearance,while the collaborative deformation of the three-layer elastic foil assembly can deal with different load conditions.As the load capacity increases,the enhanced dynamic pressure effect causes the top foil to evolve from a single arch to multiple arches.The hydrodynamic effects in the gas film evolve to form multiple segmented wedges with different pitch ratios,while the peak pressure of the gas film always occurs near the vaults of the top foil.As the rotational speed frequency approaches the natural frequency,the resonance of the gas film and elastic foil assembly system occurs,and a phase delay occurs between the pressure pulsation and the vibration of foils.The load capacity of the MTGFB also depends on the elastic moduli of the elastic foil assembly.Increasing the elastic modulus decreases the deformation amplitude of the top foil,whereas it increases those of the backboard and middle foil,increasing the load capacity.
基金partly supported by the CAS Project for Young Scientists in Basic Research under Grant YSBR-045the National Natural Science Foundation of China under Grant 52307071。
文摘Linear flux-switching permanent magnet motors(LFSPMs) have been proposed for long stator applications such as rail transit. However, the conventional linear permanent magnet synchronous motor(LPMSM) suffers from thrust ripple, which degrades the motor performance. The thrust ripple in LFSPMs is mainly caused by detent force and asymmetric electromagnetic parameters, excluding external disturbances. Moreover, the 12/13 slot-pole LFSPM exhibits unique inductance characteristics, which lead to different effects on thrust ripple. First, the detent force in the LFSPM is analyzed through finite element method(FEM). In addition, new finite element(FE) models are proposed for further analysis of the cogging force in LFSPMs. Second, the unique inductance characteristics of the 12/13 slot-pole LFSPM are investigated, and then the thrust ripple caused by asymmetric electromagnetic parameters is calculated by the virtual displacement method. Third, the mathematical model considering the thrust ripple is established for the LFSPM, which provides a foundation for subsequent research on thrust ripple suppression control strategies. Finally, the thrust ripple analysis is validated by comparing FEM results, modeling simulations, and experimental data.
基金the National Key Research and Development Program of China(Nos.2021YFC2202800 and 2021YFC2202604)the Opening Project of the Key Laboratory of Microgravity of the Chinese Academy of Sciences(No.NML202401)+1 种基金the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2023022)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA1502110105)。
文摘The Taiji program is focused on achieving space-based gravitational wave detection in the frequency range of 0.1 mHz-1 Hz.To achieve drag-free control,Taiji satellites must be equipped with micro-thrusters that satisfy stringent requirements,including a continuously adjustable thrust,thrust resolution of 0.1μN,thrust noise of 0.1μN·Hz^(-0.5)and response time of less than 100 ms.This paper presents the progress of a variable cold gas micro-thruster being developed for the Taiji program.A series of technologies such as a bidirectional piezoelectric drive,spherical valve core,conical nozzle seal,miniature gas chamber,high thruster integration,combined digital and analogue communication and high-frequency closed-loop thrust control were employed to achieve engineering prototypes of a low-noise and fast-response micro-thruster.Ground performance tests indicate that the micro-thruster achieved a minimum thrust of close to 1.1 nN,a thrust resolution of 0.05μN and a maximum specific impulse of 69.1 s using nitrogen gas as the working fluid.The thrust noise was less than 0.1μN·Hz^(-0.5)in the frequency band of 10 mHz-1 Hz,and the thrust response time was 140 ms.The control parameters were further optimised to achieve a flow response time of 50 ms.The results indicate that the developed micro-thruster essentially met the performance requirements for drag-free control to facilitate space-based gravitational wave detection.
