The technology of electric propulsion aircraft(EPA)represents an important direction and an advanced stage in the development of aviation electrification.It is a key pathway for green development in aviation industry ...The technology of electric propulsion aircraft(EPA)represents an important direction and an advanced stage in the development of aviation electrification.It is a key pathway for green development in aviation industry and can significantly enhance the energy efficiency of aircraft propulsion system.Electric motor is the most critical electromechanical energy conversion component in an aircraft electric propulsion system(EPS).High-performance electric motors,power electronic converters and EPS control form the foundation of the EPA.This paper provides an overview of the characteristics of electric motors for EPA,analyzes the inverter topologies of EPSs,and reviews ongoing EPA projects.The article highlights the latest advancements in three types of motors:superconducting motors(SCMs),permanent magnet synchronous motors(PMSMs),and induction motors(IMs).It summarizes the control system architectures of current EPA initiatives and,building on this foundation,proposes future research directions for EPSs.These include cutting-edge areas such as high-performance motors and advanced manufacturing technologies,Ga N-or Si C-based inverter integration and innovation,electric propulsion control systems,and optimization of wiring systems.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
As the environmental problems become increasingly serious,distributed electrical propulsion systems with higher aerodynamic efficiency and lower pollution emission have received extensive attention in recent years.The...As the environmental problems become increasingly serious,distributed electrical propulsion systems with higher aerodynamic efficiency and lower pollution emission have received extensive attention in recent years.The distributed electrical propulsion usually employs the new aero-propulsion integrated configuration.A simulation strategy for internal and external flow coupling based on the combination of lifting line theory and body force method is proposed.The lifting line theory and body force method as source term are embedded into the Navier-Stokes formulation.The lift and drag characteristics of the aero-propulsion coupling configuration are simulated.The results indicate that the coupling configuration has the most obvious lift augmentation at 12°angle of attack,which can provide an 11.11%increase in lift for the airfoil.At 0°angle of attack,the pressure difference on the lip parts provides the thrust component,which results in a lower drag coefficient.Additionally,the failure impact of a ducted fan at the middle or edge on aerodynamics is investigated.For the two failure conditions,the lift of the coupling configuration is decreased significantly by 27.85%and 26.14%respectively,and the lip thrust is decreased by 70.74%and 56.48%respectively.展开更多
Currently,the International Maritime Organization(IMO)has approved and implemented the assessment requirement for Minimum Propulsion Power(MPP)of ships in adverse sea conditions.The assessment method and relevant infl...Currently,the International Maritime Organization(IMO)has approved and implemented the assessment requirement for Minimum Propulsion Power(MPP)of ships in adverse sea conditions.The assessment method and relevant influence factors will have a vital impact on ship's design and operation.On the other hand,MPP is essentially a criterion for manoeuvring safety at actual seas.However,the practical assessment methods adopted in IMO guidelines do not directly and accurately account for ship's coursekeeping ability in severe seas.A time-domain comprehensive method with supplementary course-keeping ability criteria has been proposed in the authors'preliminary research.Based on an updated mathematical model and criteria,this paper presents more detailed elaborations,results and discussions on the time-domain method,including the comparative analyses with a power line method and two steady-state equilibrium methods based on IMO guidelines and draft.Discussions on the influences of key factors,involving criterion conditions and calculation parameters,are also presented.The results indicate that different methods exhibit varying advantages and complexity in MPP assessment,thus constituting a multi-level assessment framework for MPP.In particular,the time-domain comprehensive assessment has a higher accuracy with more realistic description of manoeuvre behaviors,capable of offering a solution for the ships that cannot meet other assessments,or for the assessment requiring additional course-keeping ability.Furthermore,an expanded range of wave direction sets a stricter but potentially necessary requirement,while using the self-propulsion factors at low speeds can eliminate the unnecessary conservation of assessment result caused by those at design speed.展开更多
In designing modern vessels, calculating the propulsion performance of ships in ice is important, including propeller effective thrust, number of revolutions, consumed power, and ship speed. Such calculations allow fo...In designing modern vessels, calculating the propulsion performance of ships in ice is important, including propeller effective thrust, number of revolutions, consumed power, and ship speed. Such calculations allow for more accurate prediction of the ice performance of a designed ship and provide inputs for designers of ship power and automation systems. Preliminary calculations of ship propulsion and thrust characteristics in ice can enable predictions of full-scale ice resistance without measuring the propeller thrust during sea trials. Measuring propeller revolutions,ship speed, and the power delivered to propellers could be sufficient to determine the propeller thrust of the vessel. At present, significant difficulties arise in determining the thrust of icebreakers and ice-class ships in ice conditions. These challenges are related to the fact that the traditional system of propeller/hull interaction coefficients does not function correctly in ice conditions. The wake fraction becomes negative and tends to minus infinity starting from a certain value of the propeller advance coefficient. This issue prevents accurate determination of the performance characteristics, thrust, and rotational speed of the propulsors. In this study, an alternative system of propeller/hull interaction coefficients for ice is proposed. It enables the calculation of all propulsion parameters in ice based on standard hydrodynamic tests with selfpropulsion models. An experimental method is developed to determine alternative propeller/hull interaction coefficients. A prediction method is suggested to determine propulsion performance in ice based on the alternative interaction coefficient system. A case study applying the propulsion prediction method for ice conditions is provided. This study also discusses the following issues of ship operation in ice: the scale effect of icebreaker propellers and the prospects for introducing an ice interaction coefficient.展开更多
Polar marine equipment plays an important role in Arctic engineering,especially in the development of polar ships and ice-class propellers.When polar ships navigate in brash ice channels,the brash ice not only increas...Polar marine equipment plays an important role in Arctic engineering,especially in the development of polar ships and ice-class propellers.When polar ships navigate in brash ice channels,the brash ice not only increases resistance but also has adverse effects on their propulsion performance.On the basis of coupled computational fluid dynamics(CFD)and the discrete element method(DEM),this paper aims to numerically investigate the resistance and propulsion performance of a polar in a brash ice channel while considering the rotation status of the propeller by both experimental and numerical methods.Both ship resistance and ice motion under Froude numbers of 0.0557,0.0696,0.0836,0.975,and 0.1114 are studied when the propeller does not rotate.The influences of the rotating propeller on the ice brash resistance and flow are discussed.The thrust due to the propeller and ice resistance in the equilibrium state are also predicted.The errors between the thrust and total resistance are approximately 1.0%,and the maximum error between the simulated and predicted total resistance is 3.7%,which validates the CFD-DEM coupling method quite well.This work could provide a theoretical basis for the initial design of polar ships with low ice class notation and assist in planning navigation for merchant polar ships in brash ice fields.展开更多
The Distributed Propulsion Wing(DPW)presents prominent advantages in terms of energy conservation during flight,but the intense integration of propulsive internal flow with aerodynamic external flow brings significant...The Distributed Propulsion Wing(DPW)presents prominent advantages in terms of energy conservation during flight,but the intense integration of propulsive internal flow with aerodynamic external flow brings significant design challenges.To tackle this issue,this paper undertakes a comprehensive investigation of the aero-propulsive coupling performance of the DPW under both hovering and cruising conditions,and subsequently proposes a multi-level collaboration optimization design method based on the decomposition principle.Specifically,the complex 3D surfaces of DPW are systematically dissociated into simple 2D curves with inherent relationships for design.The decomposition is achieved based on the analysis results of the aero-propulsive coupling characteristics.And a DPW design case is conducted and subsequently analyzed in order to further validate the effectiveness and feasibility of the proposed design method.It is shown that a 115.75%drag reduction of DPW can be achieved at cruise under a specified thrust level.Furthermore,the DPW exhibits inherent characteristics of consistent lift-to-drag ratio with the thrust-drag balance constraint,regardless of variations in incoming flow velocity or total thrust.展开更多
The real-time capability of integrated flight/propulsion optimal control （IFPOC） is studied. An appli- cation is proposed for IFPOC by combining the onboard hybrid aero-engine model with sequential quadratic pro- gr...The real-time capability of integrated flight/propulsion optimal control （IFPOC） is studied. An appli- cation is proposed for IFPOC by combining the onboard hybrid aero-engine model with sequential quadratic pro- gramming （SQP）. Firstly, a steady-state hybrid aero-engine model is designed in the whole flight envelope with a dramatic enhancement of real-time capability. Secondly, the aero-engine performance seeking control including the maximum thrust mode and the minimum fuel-consumption mode is performed by SQP. Finally, digital simu- lations for cruise and accelerating flight are carried out. Results show that the proposed method improves real- time capability considerably with satisfactory effectiveness of optimization.展开更多
Technological miniaturization has enabled the development of small satellites weighing as little as 1 kg.Unfortunately,there is still a lack of suitable efficient micropropulsion systems at these scales.The pulsed pla...Technological miniaturization has enabled the development of small satellites weighing as little as 1 kg.Unfortunately,there is still a lack of suitable efficient micropropulsion systems at these scales.The pulsed plasma thruster is a structurally simple form of electric propulsion.This simplicity also makes it ideally suited for miniaturization.Its history can be traced back to applications in satellites that are much larger than micro/nano-satellites.The vast majority of modern pulsed plasma thrusters use solid polytetrafluoroethylene(PTFE)as a propellant.Unfortunately,at lower discharge energy levels such as those necessitated by the power limitations of micro/nano-satellites,PTFE has a tendency to exhibit carbon deposition,which can ultimately lead to thruster failure.In this new era of small satellites,it is important to consider alternative propellants in the miniaturization of pulsed plasma thrusters.This brief review discusses the needs and limitations of small satellites and alternative propellants that may be able to meet these needs.Such propellants may be able to offer advantages such as a longer thruster lifetime,a higher specific impulse,or a higher thrust-topower ratio.This would enable the development of different types of pulsed plasma thrusters that can be tailored towards specific mission requirements.展开更多
Emissions produced by the aviation industry are currently a severe environmental threat;therefore,aviation agencies and governments have set emission targets and formulated plans to restrict emissions within the next ...Emissions produced by the aviation industry are currently a severe environmental threat;therefore,aviation agencies and governments have set emission targets and formulated plans to restrict emissions within the next decade.Hybrid aircraft technology is being considered to meet these targets.The importance of these technologies lies in their advancements in terms of aircraft life cycles and environmental benignity.Owing to these advancements,hybrid electric systems with more than one power source have become promising for the aviation industry,considering that the growth of air traffic is projected to double in the next decade.Hybrid technologies have given future hybrid fans and motor-fan engines potential as alternative power generators.Herein,Turboelectric Distributed Propulsion(TeDP)is discussed in terms of power distribution and power sources.The fundamentals of turbofan and turboshaft engines are presented along with their electricitygeneration mechanism.TeDP is discussed from a design viewpoint,with a detailed discussion of different types of hybrid electric and turboelectric systems.Examples of proposed TeDP aircraft models and numerical modelling tools used to simulate the performance of TeDP models are reviewed.Finally,innovative turboelectric systems in which electric power savers and mechanical gear changers have been discarded for weight optimisation are presented along with other prospective models,engines,approaches,and architectures.The findings of this review indicate the knowledge gaps in the field of numerical modelling for NASA’s TeDP and its capability to increase the efficiency by up to 24%with a 50%reduction in emissions relative to those of conventional gas turbines.展开更多
Distributed Electric Propulsion(DEP)aircraft use multiple electric motors to drive the propulsors,which gives potential benefits to aerodynamic-propulsion interaction.To investigate and quantify the aerodynamic-propul...Distributed Electric Propulsion(DEP)aircraft use multiple electric motors to drive the propulsors,which gives potential benefits to aerodynamic-propulsion interaction.To investigate and quantify the aerodynamic-propulsion interaction effect of the wing section,we built a DEP demonstrator with 24"high-lift"Electric Ducted Fans(EDFs)distributed along the wing’s trailing edge.This paper explores and compares the aero-propulsion coupling characteristics under various upstream speed,throttle,and EDF mounting surface deflection angles using a series of wind tunnel tests.We compare various lift-augmentation power conditions to the clean configuration without propulsion unit under the experiment condition of 15-25 m/s freestream flow and angles of attack from-4°to 16°.The comparison of computational results to the experimental results verifies the effectiveness of the computational fluid dynamic analysis method and the modeling method for the DEP configuration.The results show that the EDFs can produce significant lift increment and drag reduction simultaneously,which is accordant with the potential benefit of Boundary Layer Ingestion(BLI)at low airspeed.展开更多
It is hypothesized that steady anguilliform swimming motion of aquatic animals is purely reactive such that no net vortex wake is left downstream. This is versus carangiform and tunniform swimming of fish, where vorte...It is hypothesized that steady anguilliform swimming motion of aquatic animals is purely reactive such that no net vortex wake is left downstream. This is versus carangiform and tunniform swimming of fish, where vortex streams are shed from tail, fins, and body. But there the animal movements are such to produce partial vortex cancellation downstream in maximizing propulsive efficiency. In anguilliform swimming characteristic of the eel family, it is argued that the swimming motions are configured by the animal such that vortex shedding does not occur at all. However, the propulsive thrust in this case is higher order in the motion amplitude, so that relatively large coils are needed to produce relatively small thrust; the speeds of anguilliform swimmers are less than the carangiform and tunniforrn, which develop first order thrusts via lifting processes. Results of experimentation on live lamprey are compared to theoretical prediction which assumes the no-wake hypothesis. Two-dimensional analysis is first performed to set the concept. This is followed by three-dimensional analysis using slender-body theory. Slender-body theory has been applied by others in studying anguilliform swimming, as it is ideally suited to the geometry of the lamprey and other eel-like animals. The agreement between this new approach based on the hypothesis of wakeless swimming and the experiments is remarkably good in spite of the physical complexities.展开更多
The rotating propagation of a continuous detonation engine (CDE) with different types of nozzles is investigated in three-dimensional numerical simulation using a one-step chemical reaction model. Flux terms are solve...The rotating propagation of a continuous detonation engine (CDE) with different types of nozzles is investigated in three-dimensional numerical simulation using a one-step chemical reaction model. Flux terms are solved by the so-called monotonicity-preserving weighted essentially non-oscillatory (MPWENO) scheme. The simulated flow field agrees well with the previous experimental results. Once the initial transient effects die down, the detonation wave maintains continuous oscillatory propagation in the annular chamber as long as fuel is continuously injected. Using a numerical flow field, the propulsion per- formance of a CDE is computed for four types of nozzles, namely the constant-area nozzle, Laval nozzle, diverging nozzle and converging nozzle. The gross specific impulse of the CDE ranges 1 540-1 750 s and the mass flux per square meter ranges 313-330 kg/(m2·s) for different nozzles. Among these four types of nozzles, Laval nozzle performs the best, and these parameters are 1 800 N, 1 750 s and 313 kg/(m2.s). A nozzle can greatly improve the propulsion performance.展开更多
Hypersonic airbreathing propulsion is one of the top techniques for future aerospace flight, but there are still no practical engines after seventy years’ development. Two critical issues are identified to be the bar...Hypersonic airbreathing propulsion is one of the top techniques for future aerospace flight, but there are still no practical engines after seventy years’ development. Two critical issues are identified to be the barriers for the ramjet-based engine that has been taken as the most potential concept of the hypersonic propulsion for decades. One issue is the upstream-traveling shock wave that develops from spontaneous waves resulting from continuous heat releases in combustors and can induce unsteady combustion that may lead to engine surging during scramjet engine operation.The other is the scramjet combustion mode that cannot satisfy thrust needs of hypersonic vehicles since its thermos-efficiency decreases as the flight Mach number increases. The two criteria are proposed for the ramjet-based hypersonic propulsion to identify combustion modes and avoid thermal choking. A standing oblique detonation ramjet(Sodramjet) engine concept is proposed based on the criteria by replacing diffusive combustion with an oblique detonation that is a unique pressure-gain phenomenon in nature. The Sodramjet engine model is developed with several flow control techniques, and tested successfully with the hypersonic flight-duplicated shock tunnel.The experimental data show that the Sodramjet engine model works steadily, and an oblique detonation can be made stationary in the engine combustor and is controllable. This research demonstrates the Sodramjet engine is a promising concept and can be operated stably with high thermal efficiency at hypersonic flow conditions.展开更多
A robotic fish driven by oscillating fins, 'Cownose Ray-I', is developed, which is in dorsoventrally flattened shape without a tail. The robotic fish is composed of a body and two lateral fins. A three-factor ...A robotic fish driven by oscillating fins, 'Cownose Ray-I', is developed, which is in dorsoventrally flattened shape without a tail. The robotic fish is composed of a body and two lateral fins. A three-factor kinematic model is established and used in the design of a mechanism. By controlling the three kinematic parameters, the robotic fish can accelerate and maneuver. Forward velocity is dependent on the largest amplitude and the number of waves in the fins, while the relative contribution of fin beat frequency to the forward velocity of the robotic fish is different from the usual result. On the other hand, experimental results on maneuvering show that phase difference has a stronger effect on swerving than the largest amplitude to some extent. In addition, as propulsion waves pass from the trailing edge to the leading edge, the robotic fish attains a backward velocity of 0. 15 m·s^(-1).展开更多
The introduction of nano-sized energetic ingredients first occurred in Russia about 60 years ago and arose great expectations in the rocket propulsion community, thanks to the higher energy densities and faster energy...The introduction of nano-sized energetic ingredients first occurred in Russia about 60 years ago and arose great expectations in the rocket propulsion community, thanks to the higher energy densities and faster energy release rates exhibited with respect to conventional ingredients. But, despite intense worldwide research programs, still today mostly laboratory level applications are reported and often for scientific purposes only. A number of practical reasons prevent the applications at industrial level: inert native coating of the energetic particles, nonuniform dispersion, aging, excessive viscosity of the slurry propellant, possible limitations in mechanical properties, more demanding safety issues, cost, and so on.This paper describes the main features in terms of performance of solid rocket propellants loaded with nanometals and intends to emphasize the unique properties or operating conditions made possible by the addition of the nano-sized energetic ingredients. Steady and unsteady combustion regimes are examined.展开更多
A dynamic marine propeller simulation system was developed, which is utilized for meeting the experimental requirement of theory research and engineering design of marine electric propulsion system. By applying an act...A dynamic marine propeller simulation system was developed, which is utilized for meeting the experimental requirement of theory research and engineering design of marine electric propulsion system. By applying an actual ship parameter and its accurate propeller J＇ -KT＇ and J＇ - Kp＇ curve data, functional experiments based on the simulation system were carried out. The experiment results showed that the system can correctly emulate the propeller characteristics, produce the dynamic and steady performances of the propeller under different navigation modes, and present actual load torque for electric propulsion motor.展开更多
Numerical study on the unsteady hydrodynamic characteristics of oscillating rigid and flexible tuna-tails in viscous flow-field is performed. Investigations are conducted using Reynolds-Averaged Navier-Stokes （RANS）...Numerical study on the unsteady hydrodynamic characteristics of oscillating rigid and flexible tuna-tails in viscous flow-field is performed. Investigations are conducted using Reynolds-Averaged Navier-Stokes （RANS） equations with a moving adaptive mesh. The effect of swimming speed, flapping amplitude, frequency and flexure amplitude on the propulsion performance of the rigid and flexible tuna-tails are investigated. Computational results reveal that a pair of leading edge vortices develop along the tail surface as it undergoes an oscillating motion. The propulsive efficiency has a strong correlation with various locomotive parameters. Peak propulsive efficiency can be obtained by adjusting these parameters. Particularly, when input power coeffcient is less than 2.8, the rigid tail generates larger thrust force and higher propulsive efficiency than flexible tail. However, when input power coefficient is larger than 2.8, flexible tail is superior to rigid tail.展开更多
基金supported by the National Nature Science Foundation of China(Grant No.52302507)。
文摘The technology of electric propulsion aircraft(EPA)represents an important direction and an advanced stage in the development of aviation electrification.It is a key pathway for green development in aviation industry and can significantly enhance the energy efficiency of aircraft propulsion system.Electric motor is the most critical electromechanical energy conversion component in an aircraft electric propulsion system(EPS).High-performance electric motors,power electronic converters and EPS control form the foundation of the EPA.This paper provides an overview of the characteristics of electric motors for EPA,analyzes the inverter topologies of EPSs,and reviews ongoing EPA projects.The article highlights the latest advancements in three types of motors:superconducting motors(SCMs),permanent magnet synchronous motors(PMSMs),and induction motors(IMs).It summarizes the control system architectures of current EPA initiatives and,building on this foundation,proposes future research directions for EPSs.These include cutting-edge areas such as high-performance motors and advanced manufacturing technologies,Ga N-or Si C-based inverter integration and innovation,electric propulsion control systems,and optimization of wiring systems.
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the funding support from the Taihang Laboratory,China(No.D2024-1-0201).
文摘As the environmental problems become increasingly serious,distributed electrical propulsion systems with higher aerodynamic efficiency and lower pollution emission have received extensive attention in recent years.The distributed electrical propulsion usually employs the new aero-propulsion integrated configuration.A simulation strategy for internal and external flow coupling based on the combination of lifting line theory and body force method is proposed.The lifting line theory and body force method as source term are embedded into the Navier-Stokes formulation.The lift and drag characteristics of the aero-propulsion coupling configuration are simulated.The results indicate that the coupling configuration has the most obvious lift augmentation at 12°angle of attack,which can provide an 11.11%increase in lift for the airfoil.At 0°angle of attack,the pressure difference on the lip parts provides the thrust component,which results in a lower drag coefficient.Additionally,the failure impact of a ducted fan at the middle or edge on aerodynamics is investigated.For the two failure conditions,the lift of the coupling configuration is decreased significantly by 27.85%and 26.14%respectively,and the lip thrust is decreased by 70.74%and 56.48%respectively.
文摘Currently,the International Maritime Organization(IMO)has approved and implemented the assessment requirement for Minimum Propulsion Power(MPP)of ships in adverse sea conditions.The assessment method and relevant influence factors will have a vital impact on ship's design and operation.On the other hand,MPP is essentially a criterion for manoeuvring safety at actual seas.However,the practical assessment methods adopted in IMO guidelines do not directly and accurately account for ship's coursekeeping ability in severe seas.A time-domain comprehensive method with supplementary course-keeping ability criteria has been proposed in the authors'preliminary research.Based on an updated mathematical model and criteria,this paper presents more detailed elaborations,results and discussions on the time-domain method,including the comparative analyses with a power line method and two steady-state equilibrium methods based on IMO guidelines and draft.Discussions on the influences of key factors,involving criterion conditions and calculation parameters,are also presented.The results indicate that different methods exhibit varying advantages and complexity in MPP assessment,thus constituting a multi-level assessment framework for MPP.In particular,the time-domain comprehensive assessment has a higher accuracy with more realistic description of manoeuvre behaviors,capable of offering a solution for the ships that cannot meet other assessments,or for the assessment requiring additional course-keeping ability.Furthermore,an expanded range of wave direction sets a stricter but potentially necessary requirement,while using the self-propulsion factors at low speeds can eliminate the unnecessary conservation of assessment result caused by those at design speed.
基金supported by a grant No. 23-19-00039 of Russian Research Fund “Theoretical basis and application tools for developing a system of intellectual fleet planning and support of decisions on Arctic navigation”。
文摘In designing modern vessels, calculating the propulsion performance of ships in ice is important, including propeller effective thrust, number of revolutions, consumed power, and ship speed. Such calculations allow for more accurate prediction of the ice performance of a designed ship and provide inputs for designers of ship power and automation systems. Preliminary calculations of ship propulsion and thrust characteristics in ice can enable predictions of full-scale ice resistance without measuring the propeller thrust during sea trials. Measuring propeller revolutions,ship speed, and the power delivered to propellers could be sufficient to determine the propeller thrust of the vessel. At present, significant difficulties arise in determining the thrust of icebreakers and ice-class ships in ice conditions. These challenges are related to the fact that the traditional system of propeller/hull interaction coefficients does not function correctly in ice conditions. The wake fraction becomes negative and tends to minus infinity starting from a certain value of the propeller advance coefficient. This issue prevents accurate determination of the performance characteristics, thrust, and rotational speed of the propulsors. In this study, an alternative system of propeller/hull interaction coefficients for ice is proposed. It enables the calculation of all propulsion parameters in ice based on standard hydrodynamic tests with selfpropulsion models. An experimental method is developed to determine alternative propeller/hull interaction coefficients. A prediction method is suggested to determine propulsion performance in ice based on the alternative interaction coefficient system. A case study applying the propulsion prediction method for ice conditions is provided. This study also discusses the following issues of ship operation in ice: the scale effect of icebreaker propellers and the prospects for introducing an ice interaction coefficient.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFE0107000)the Fundamental Research Funds for the Central Universities(Grant No.HYGJXM202319).
文摘Polar marine equipment plays an important role in Arctic engineering,especially in the development of polar ships and ice-class propellers.When polar ships navigate in brash ice channels,the brash ice not only increases resistance but also has adverse effects on their propulsion performance.On the basis of coupled computational fluid dynamics(CFD)and the discrete element method(DEM),this paper aims to numerically investigate the resistance and propulsion performance of a polar in a brash ice channel while considering the rotation status of the propeller by both experimental and numerical methods.Both ship resistance and ice motion under Froude numbers of 0.0557,0.0696,0.0836,0.975,and 0.1114 are studied when the propeller does not rotate.The influences of the rotating propeller on the ice brash resistance and flow are discussed.The thrust due to the propeller and ice resistance in the equilibrium state are also predicted.The errors between the thrust and total resistance are approximately 1.0%,and the maximum error between the simulated and predicted total resistance is 3.7%,which validates the CFD-DEM coupling method quite well.This work could provide a theoretical basis for the initial design of polar ships with low ice class notation and assist in planning navigation for merchant polar ships in brash ice fields.
基金co-supported by the Equipment Advance Research Project of China(No.50911040803)the National Defense Pre-research Foundation of China(No.2021-JCJQJJ-0805)the Aeronautical Science Foundation of China(No.2024Z006053001)。
文摘The Distributed Propulsion Wing(DPW)presents prominent advantages in terms of energy conservation during flight,but the intense integration of propulsive internal flow with aerodynamic external flow brings significant design challenges.To tackle this issue,this paper undertakes a comprehensive investigation of the aero-propulsive coupling performance of the DPW under both hovering and cruising conditions,and subsequently proposes a multi-level collaboration optimization design method based on the decomposition principle.Specifically,the complex 3D surfaces of DPW are systematically dissociated into simple 2D curves with inherent relationships for design.The decomposition is achieved based on the analysis results of the aero-propulsive coupling characteristics.And a DPW design case is conducted and subsequently analyzed in order to further validate the effectiveness and feasibility of the proposed design method.It is shown that a 115.75%drag reduction of DPW can be achieved at cruise under a specified thrust level.Furthermore,the DPW exhibits inherent characteristics of consistent lift-to-drag ratio with the thrust-drag balance constraint,regardless of variations in incoming flow velocity or total thrust.
基金Supported by the Aeronautical Science Foundation of China(2010ZB52011)the Funding of Jiangsu Innovation Program for Graduate Education(CXLX11-0213)the Nanjing University of Aeronautics and Astronautics Research Funding(NS2010055)~~
文摘The real-time capability of integrated flight/propulsion optimal control （IFPOC） is studied. An appli- cation is proposed for IFPOC by combining the onboard hybrid aero-engine model with sequential quadratic pro- gramming （SQP）. Firstly, a steady-state hybrid aero-engine model is designed in the whole flight envelope with a dramatic enhancement of real-time capability. Secondly, the aero-engine performance seeking control including the maximum thrust mode and the minimum fuel-consumption mode is performed by SQP. Finally, digital simu- lations for cruise and accelerating flight are carried out. Results show that the proposed method improves real- time capability considerably with satisfactory effectiveness of optimization.
基金supported by the National Natural Science Foundation of China(No.11802022)the Beijing Institute of Technology Research Fund Program for Young Scholars。
文摘Technological miniaturization has enabled the development of small satellites weighing as little as 1 kg.Unfortunately,there is still a lack of suitable efficient micropropulsion systems at these scales.The pulsed plasma thruster is a structurally simple form of electric propulsion.This simplicity also makes it ideally suited for miniaturization.Its history can be traced back to applications in satellites that are much larger than micro/nano-satellites.The vast majority of modern pulsed plasma thrusters use solid polytetrafluoroethylene(PTFE)as a propellant.Unfortunately,at lower discharge energy levels such as those necessitated by the power limitations of micro/nano-satellites,PTFE has a tendency to exhibit carbon deposition,which can ultimately lead to thruster failure.In this new era of small satellites,it is important to consider alternative propellants in the miniaturization of pulsed plasma thrusters.This brief review discusses the needs and limitations of small satellites and alternative propellants that may be able to meet these needs.Such propellants may be able to offer advantages such as a longer thruster lifetime,a higher specific impulse,or a higher thrust-topower ratio.This would enable the development of different types of pulsed plasma thrusters that can be tailored towards specific mission requirements.
文摘Emissions produced by the aviation industry are currently a severe environmental threat;therefore,aviation agencies and governments have set emission targets and formulated plans to restrict emissions within the next decade.Hybrid aircraft technology is being considered to meet these targets.The importance of these technologies lies in their advancements in terms of aircraft life cycles and environmental benignity.Owing to these advancements,hybrid electric systems with more than one power source have become promising for the aviation industry,considering that the growth of air traffic is projected to double in the next decade.Hybrid technologies have given future hybrid fans and motor-fan engines potential as alternative power generators.Herein,Turboelectric Distributed Propulsion(TeDP)is discussed in terms of power distribution and power sources.The fundamentals of turbofan and turboshaft engines are presented along with their electricitygeneration mechanism.TeDP is discussed from a design viewpoint,with a detailed discussion of different types of hybrid electric and turboelectric systems.Examples of proposed TeDP aircraft models and numerical modelling tools used to simulate the performance of TeDP models are reviewed.Finally,innovative turboelectric systems in which electric power savers and mechanical gear changers have been discarded for weight optimisation are presented along with other prospective models,engines,approaches,and architectures.The findings of this review indicate the knowledge gaps in the field of numerical modelling for NASA’s TeDP and its capability to increase the efficiency by up to 24%with a 50%reduction in emissions relative to those of conventional gas turbines.
基金supported by the National Natural Science Foundation of China(No.51877178)。
文摘Distributed Electric Propulsion(DEP)aircraft use multiple electric motors to drive the propulsors,which gives potential benefits to aerodynamic-propulsion interaction.To investigate and quantify the aerodynamic-propulsion interaction effect of the wing section,we built a DEP demonstrator with 24"high-lift"Electric Ducted Fans(EDFs)distributed along the wing’s trailing edge.This paper explores and compares the aero-propulsion coupling characteristics under various upstream speed,throttle,and EDF mounting surface deflection angles using a series of wind tunnel tests.We compare various lift-augmentation power conditions to the clean configuration without propulsion unit under the experiment condition of 15-25 m/s freestream flow and angles of attack from-4°to 16°.The comparison of computational results to the experimental results verifies the effectiveness of the computational fluid dynamic analysis method and the modeling method for the DEP configuration.The results show that the EDFs can produce significant lift increment and drag reduction simultaneously,which is accordant with the potential benefit of Boundary Layer Ingestion(BLI)at low airspeed.
文摘It is hypothesized that steady anguilliform swimming motion of aquatic animals is purely reactive such that no net vortex wake is left downstream. This is versus carangiform and tunniform swimming of fish, where vortex streams are shed from tail, fins, and body. But there the animal movements are such to produce partial vortex cancellation downstream in maximizing propulsive efficiency. In anguilliform swimming characteristic of the eel family, it is argued that the swimming motions are configured by the animal such that vortex shedding does not occur at all. However, the propulsive thrust in this case is higher order in the motion amplitude, so that relatively large coils are needed to produce relatively small thrust; the speeds of anguilliform swimmers are less than the carangiform and tunniforrn, which develop first order thrusts via lifting processes. Results of experimentation on live lamprey are compared to theoretical prediction which assumes the no-wake hypothesis. Two-dimensional analysis is first performed to set the concept. This is followed by three-dimensional analysis using slender-body theory. Slender-body theory has been applied by others in studying anguilliform swimming, as it is ideally suited to the geometry of the lamprey and other eel-like animals. The agreement between this new approach based on the hypothesis of wakeless swimming and the experiments is remarkably good in spite of the physical complexities.
基金Aeronautical Science Foundation of China (2008ZH71006)
文摘The rotating propagation of a continuous detonation engine (CDE) with different types of nozzles is investigated in three-dimensional numerical simulation using a one-step chemical reaction model. Flux terms are solved by the so-called monotonicity-preserving weighted essentially non-oscillatory (MPWENO) scheme. The simulated flow field agrees well with the previous experimental results. Once the initial transient effects die down, the detonation wave maintains continuous oscillatory propagation in the annular chamber as long as fuel is continuously injected. Using a numerical flow field, the propulsion per- formance of a CDE is computed for four types of nozzles, namely the constant-area nozzle, Laval nozzle, diverging nozzle and converging nozzle. The gross specific impulse of the CDE ranges 1 540-1 750 s and the mass flux per square meter ranges 313-330 kg/(m2·s) for different nozzles. Among these four types of nozzles, Laval nozzle performs the best, and these parameters are 1 800 N, 1 750 s and 313 kg/(m2.s). A nozzle can greatly improve the propulsion performance.
基金supported by the National Natural Science Foundation of China (No. 11532014)。
文摘Hypersonic airbreathing propulsion is one of the top techniques for future aerospace flight, but there are still no practical engines after seventy years’ development. Two critical issues are identified to be the barriers for the ramjet-based engine that has been taken as the most potential concept of the hypersonic propulsion for decades. One issue is the upstream-traveling shock wave that develops from spontaneous waves resulting from continuous heat releases in combustors and can induce unsteady combustion that may lead to engine surging during scramjet engine operation.The other is the scramjet combustion mode that cannot satisfy thrust needs of hypersonic vehicles since its thermos-efficiency decreases as the flight Mach number increases. The two criteria are proposed for the ramjet-based hypersonic propulsion to identify combustion modes and avoid thermal choking. A standing oblique detonation ramjet(Sodramjet) engine concept is proposed based on the criteria by replacing diffusive combustion with an oblique detonation that is a unique pressure-gain phenomenon in nature. The Sodramjet engine model is developed with several flow control techniques, and tested successfully with the hypersonic flight-duplicated shock tunnel.The experimental data show that the Sodramjet engine model works steadily, and an oblique detonation can be made stationary in the engine combustor and is controllable. This research demonstrates the Sodramjet engine is a promising concept and can be operated stably with high thermal efficiency at hypersonic flow conditions.
基金The supports of National Natural Science Foundation of China (No.50405006)the supports of the innovation foundation of graduate students of National University of Defense Technology (No.B060302) are also gratefully acknowledged
文摘A robotic fish driven by oscillating fins, 'Cownose Ray-I', is developed, which is in dorsoventrally flattened shape without a tail. The robotic fish is composed of a body and two lateral fins. A three-factor kinematic model is established and used in the design of a mechanism. By controlling the three kinematic parameters, the robotic fish can accelerate and maneuver. Forward velocity is dependent on the largest amplitude and the number of waves in the fins, while the relative contribution of fin beat frequency to the forward velocity of the robotic fish is different from the usual result. On the other hand, experimental results on maneuvering show that phase difference has a stronger effect on swerving than the largest amplitude to some extent. In addition, as propulsion waves pass from the trailing edge to the leading edge, the robotic fish attains a backward velocity of 0. 15 m·s^(-1).
文摘The introduction of nano-sized energetic ingredients first occurred in Russia about 60 years ago and arose great expectations in the rocket propulsion community, thanks to the higher energy densities and faster energy release rates exhibited with respect to conventional ingredients. But, despite intense worldwide research programs, still today mostly laboratory level applications are reported and often for scientific purposes only. A number of practical reasons prevent the applications at industrial level: inert native coating of the energetic particles, nonuniform dispersion, aging, excessive viscosity of the slurry propellant, possible limitations in mechanical properties, more demanding safety issues, cost, and so on.This paper describes the main features in terms of performance of solid rocket propellants loaded with nanometals and intends to emphasize the unique properties or operating conditions made possible by the addition of the nano-sized energetic ingredients. Steady and unsteady combustion regimes are examined.
基金supported by the Fund of Shanghai Committee of Science and Technology(Grant No.11170501700)the International Cooperation and Exchange Projects of the Ministry of Science and Technology(Grant No.2012DFG71850)
文摘A dynamic marine propeller simulation system was developed, which is utilized for meeting the experimental requirement of theory research and engineering design of marine electric propulsion system. By applying an actual ship parameter and its accurate propeller J＇ -KT＇ and J＇ - Kp＇ curve data, functional experiments based on the simulation system were carried out. The experiment results showed that the system can correctly emulate the propeller characteristics, produce the dynamic and steady performances of the propeller under different navigation modes, and present actual load torque for electric propulsion motor.
文摘Numerical study on the unsteady hydrodynamic characteristics of oscillating rigid and flexible tuna-tails in viscous flow-field is performed. Investigations are conducted using Reynolds-Averaged Navier-Stokes （RANS） equations with a moving adaptive mesh. The effect of swimming speed, flapping amplitude, frequency and flexure amplitude on the propulsion performance of the rigid and flexible tuna-tails are investigated. Computational results reveal that a pair of leading edge vortices develop along the tail surface as it undergoes an oscillating motion. The propulsive efficiency has a strong correlation with various locomotive parameters. Peak propulsive efficiency can be obtained by adjusting these parameters. Particularly, when input power coeffcient is less than 2.8, the rigid tail generates larger thrust force and higher propulsive efficiency than flexible tail. However, when input power coefficient is larger than 2.8, flexible tail is superior to rigid tail.
