Organic-inorganic hybrid perovskite solar cells have generated wide interest due to the rapid development of their photovoltaic conversion effciencies.However,the majority of the reported devices have been fabricated ...Organic-inorganic hybrid perovskite solar cells have generated wide interest due to the rapid development of their photovoltaic conversion effciencies.However,the majority of the reported devices have been fabricated via spin coating with a device areaof<1 cm2.In this study,we fabricated a wide-bandgap formamidi-nium lead bromide(FAPbBr3)film using a cost-effective,high-yielding doctor-blade-coating process.The effects of different surfactants,such as I-α-phosphatidylcholine,polyoxyethylene sorbitan monooleate,sodium lauryl sulfonate,and hexadecyl trimethyl ammonium bromide,were studied during the printing process.Accompanying the optimization of the blading temperature,crystal sizes of over 10μm and large-area perovskite films of5cm×5 cm were obtained using this method.The printed FAPbBr3 solar cells exhibited a short-circuit current density of 8.22 mA/cm2,an open-circuit voltage of 1.175 V,and an efficiency of 7.29%.Subsequently,we replaced the gold with silver nanowires as the top electrode to prepare a semitransparent perovskite solar cell with an average transmittance(400-800 nm)of 25.42%,achieving a high-power efficiency of 5.11%.This study demonstrates efficient doctor-blading printing for preparing large-area FAPbBr3 films that possess high potential for applications in building integrated photovoltaics.展开更多
Ocean energy has progressively gained considerable interest due to its sufficient potential to meet the world’s energy demand,and the blade is the core component in electricity generation from the ocean current.Howev...Ocean energy has progressively gained considerable interest due to its sufficient potential to meet the world’s energy demand,and the blade is the core component in electricity generation from the ocean current.However,the widened hydraulic excitation frequency may satisfy the blade resonance due to the time variation in the velocity and angle of attack of the ocean current,even resulting in blade fatigue and destructively interfering with grid stability.A key parameter that determines the resonance amplitude of the blade is the hydrodynamic damping ratio(HDR).However,HDR is difficult to obtain due to the complex fluid-structure interaction(FSI).Therefore,a literature review was conducted on the hydrodynamic damping characteristics of blade-like structures.The experimental and simulation methods used to identify and obtain the HDR quantitatively were described,placing emphasis on the experimental processes and simulation setups.Moreover,the accuracy and efficiency of different simulation methods were compared,and the modal work approach was recommended.The effects of key typical parameters,including flow velocity,angle of attack,gap,rotational speed,and cavitation,on the HDR were then summarized,and the suggestions on operating conditions were presented from the perspective of increasing the HDR.Subsequently,considering multiple flow parameters,several theoretical derivations and semi-empirical prediction formulas for HDR were introduced,and the accuracy and application were discussed.Based on the shortcomings of the existing research,the direction of future research was finally determined.The current work offers a clear understanding of the HDR of blade-like structures,which could improve the evaluation accuracy of flow-induced vibration in the design stage.展开更多
Gas quenching and vacuum quenching process are widely applied to accelerate solvent volatilization to induce nucleation of perovskites in blade-coating method.In this work,we found these two pre-crystallization proces...Gas quenching and vacuum quenching process are widely applied to accelerate solvent volatilization to induce nucleation of perovskites in blade-coating method.In this work,we found these two pre-crystallization processes lead to different order of crystallization dynamics within the perovskite thin film,resulting in the differences of additive distribution.We then tailor-designed an additive molecule named 1,3-bis(4-methoxyphenyl)thiourea to obtain films with fewer defects and holes at the buried interface,and prepared perovskite solar cells with a certified efficiency of 23.75%.Furthermore,this work also demonstrates an efficiency of 20.18%for the large-area perovskite solar module(PSM)with an aperture area of 60.84 cm^(2).The PSM possesses remarkable continuous operation stability for maximum power point tracking of T_(90)>1000 h in ambient air.展开更多
To facilitate the low-noise design of tandem lift bodies as applied in aeroengines and aircraft,the acoustic features of tandem blades are investigated by wind-tunnel experiments.This is further specialized for the ro...To facilitate the low-noise design of tandem lift bodies as applied in aeroengines and aircraft,the acoustic features of tandem blades are investigated by wind-tunnel experiments.This is further specialized for the rotating blades applied in contra-rotating open rotors under the concept of frozen-rotor.A 70-channel phased microphone array and nine high-precision free-field microphones are employed.The beamforming method,enhanced by a source filtering technique,is employed to locate noise sources,providing insights into the source patterns of blade-blade interaction noise concerning flow speed,blade spacing,and aft blade clipping.The results show the following:(A)Sources of tandem-blade noise exist in the form of concentrated source clusters,resulting in two major clusters:the mid-span interaction noise and the tip-induced noise.(B)These source clusters tend to separate as flow speed or blade spacing increases.(C)By increasing blade spacing,the band-pass filtered overall sound pressure level is reduced by 2.9 dB.(D)A two-phase noise suppression pattern is observed with blade clipping,resulting in a total reduction of 3.0 dB for the interaction noise through the removal of tip-induced noise sources and the replacement of mid-span noise sources.Based on these findings,suggestions concerning blade spacing and clipping are discussed.展开更多
Anti-aliasing spectrum analysis is essential for rotor blade condition monitoring based on Blade Tip Timing(BTT).The Multiple Signal Classification(MUSIC)algorithm,which exploits the orthogonality between signal and n...Anti-aliasing spectrum analysis is essential for rotor blade condition monitoring based on Blade Tip Timing(BTT).The Multiple Signal Classification(MUSIC)algorithm,which exploits the orthogonality between signal and noise subspaces,has been successfully applied for this purpose.However,conventional subspace selection methods relying on fixed thresholds are sensitive to variations in large eigenvalues.Furthermore,the complex disturbances during rotor operation and measurement complicate the identification of blade vibration characteristics.To overcome these challenges,this paper proposes Adaptive Subspace Separation(ASS)and Local Spectral Centroid(LSC)methods to improve the adaptability of subspace selection and the stability of frequency identification,respectively.The impacts of overestimating and underestimating the subspace dimensions on MUSIC's performance are derived mathematically.Simulation and experiments demonstrate the effectiveness of proposed approaches:ASS offers more accurate and stable subspace dimension selection and tracking,while LSC reduces the standard deviation of estimated frequencies by 30 percent.展开更多
Blade Tip Timing(BTT)enables non-contact measurements of rotating blades by placing probes strategically.Due to the uneven probe layout,BTT signals exhibit periodic irregularities.While recovering parameters like freq...Blade Tip Timing(BTT)enables non-contact measurements of rotating blades by placing probes strategically.Due to the uneven probe layout,BTT signals exhibit periodic irregularities.While recovering parameters like frequency from such signals is possible,achieving high-precision vibration parameters remains challenging.This paper proposed a novel two-stage off-grid estimation method.It leverages a unique array layout(coprime array)to obtain a regular augmented covariance matrix.Subsequently,parameters in the matrix are recovered using the sparse iterative covariance-based estimation method based on covariance fitting criteria.Finally,high-precision estimates of imprecise parameters are obtained using unconditional maximum likelihood estimation,effectively eliminating the effects of basis mismatch.Through substantial numerical and experimental validation,the proposed method demonstrates significantly higher accuracy compared to classical BTT parameter estimation methods,approaching the lower bound of unbiased estimation variance.Furthermore,due to its immunity to frequency gridding,it can track minor frequency deviations,making it more suitable for indicating blade condition.展开更多
This paper proposes a new approach to eliminate aerodynamic lift oscillation,called the Dominant Sector Individual Blade Control(DS-IBC)method for rigid rotor helicopters.An Advancing Blade Concept(ABC)rotor model for...This paper proposes a new approach to eliminate aerodynamic lift oscillation,called the Dominant Sector Individual Blade Control(DS-IBC)method for rigid rotor helicopters.An Advancing Blade Concept(ABC)rotor model for aerodynamic analysis based on the free-wake method is applied.DS-IBC avoids applying active control on the rotor's retreating side by employing and restricting active control inputs to a sector area of the rotor disc.Outside this sector,only primary collective and cyclic pitch control are used.Each blade takes turns entering the sector,creating a“relay”active control form to ensure continuous control inputs.The method also includes outer-trim and inner-trim iteration modules.Results show that DS-IBC can eliminate aerodynamic lift oscillation using much smaller control inputs than the sine-trim method.By focusing active control on the rotor's advancing side,DS-IBC improves the effective lift-to-drag ratio and reduces the implementation difficulty of active rotor control for aerodynamic oscillation elimination,especially at a large lift-offset.展开更多
A two-dimensional transition metal carbide/nitride/carbonitride(MXene)and waterborne polyurethane(WPU)were uniformly mixed to form an MXene/WPU coating,which was loaded on polyethylene terephthalate(PET)fabric through...A two-dimensional transition metal carbide/nitride/carbonitride(MXene)and waterborne polyurethane(WPU)were uniformly mixed to form an MXene/WPU coating,which was loaded on polyethylene terephthalate(PET)fabric through blade coating to prepare an MXene/WPU@PET composite fabric with electromagnetic shielding properties.The micro-morphology and composition,surface wettability,tensile properties,electrical conductivity,and electromagnetic shielding properties of the composite fabric were studied.The results showed that the MXene/WPU@PET composite fabric exhibited the cha-racteristics of flexibility and firmness,and a unit area load capacity of MXene/WPU was 1.9 mg/cm^(2),the conductivity 760 S/m,and the electromagnetic shielding effectiveness up to 42 dB(8.2-12.4 GHz);and this convenient and effective method can be used to prepare lightweight and flexible electromagnetic shielding materials,promising broad application prospects in the field of wearable products.展开更多
Considering the fracture problem of the silica-based ceramic core in the integrated casting of hollow turbine blades during directional solidification,the influence of various whiskers,including silicon carbide whiske...Considering the fracture problem of the silica-based ceramic core in the integrated casting of hollow turbine blades during directional solidification,the influence of various whiskers,including silicon carbide whiskers,silicon nitride whiskers,and mullite whiskers,on the high-temperature strength of the silica-based ceramic core was investigated.Additionally,the formation of microstructure morphology and phase structure was analyzed.Research results show that silicon carbide whiskers can reduce the microcracks caused by the shrinkage of cristobalite.During the sintering process,some of the silicon carbide whiskers oxidize and react with aluminum powder to form mullite,which can improve the high-temperature strength of the ceramic cores.When the content of silicon carbide whiskers is 3wt.%,the high-temperature bending strength of the cores reaches the maximum value of 21 MPa.Silicon nitride whiskers decompose in a high-temperature environment and react with aluminum powder in the matrix material to form mullite whiskers.When the content of silicon nitride whiskers is 5wt.%,the high-temperature bending strength of the cores reaches 20 MPa.By adding mullite whiskers,a structure of cristobalite wrapped mullite whiskers can be formed to achieve toughening.When the content of mullite whiskers is 4wt.%,the high-temperature bending strength can reach 17.2 MPa.By comparing the performance of silicon carbide whiskers,silicon nitride whiskers,and mullite whiskers,along with conducting slurry viscosity tests and casting experiments,it is determined that a ceramic slurry containing 4wt.%mullite whiskers is the most suitable for making the cores used in the integrated casting of hollow turbine blades.展开更多
This study investigates the forced vibration response of a two-row model of an Inlet Guide Vane(IGV)and rotor at resonance speed through numerical simulations.A resonant response prediction method based on equivalent ...This study investigates the forced vibration response of a two-row model of an Inlet Guide Vane(IGV)and rotor at resonance speed through numerical simulations.A resonant response prediction method based on equivalent damping balance has been validated,which ensures computational accuracy while reducing response calculation time to only 1%of the traditional transient response method.At resonance speed,unsteady pressure disturbances on the rotor blade surface mainly arise from two sources:IGV wakes and blade vibrations.The unsteady pressure caused by the IGV wakes provides excitation for the system,while the unsteady pressure caused by rotor blade vibrations provides damping.By studying the characteristics of unsteady pressure caused by IGV wakes and vibrations at resonance speed,a method for separating unsteady pressure caused by stator wakes and vibrations has been presented,accurately obtaining aerodynamic damping under multi-row resonance conditions.Compared to the aerodynamic damping obtained from multi-row scenarios without separating unsteady pressures caused by stator wakes and vibrations,and the traditional isolated blade row scheme,the aerodynamic damping considering the effects of multi-row and IGV wakes at resonance speed is smaller.Based on the separated unsteady pressures caused by IGV wakes and vibrations,and combined with the equivalent damping balance method for predicting forced response,a forced response analysis method considering both flow field disturbance excitation and damping effects has been established.展开更多
As a key component of the plant antioxidant enzymatic system,superoxide dismutase(SOD)can efficiently protect cells from oxidative stress and maintain redox homeostasis.Currently,there are few studies related to SOD g...As a key component of the plant antioxidant enzymatic system,superoxide dismutase(SOD)can efficiently protect cells from oxidative stress and maintain redox homeostasis.Currently,there are few studies related to SOD genes in various taxa of algae,and the specific functions and evolutionary patterns of these family members remain unclear.In this study,comprehensively evolutionary analysis of SOD gene family in the bladed Bangiales was carried out.A total of 9,10,and 12 SOD genes were identified from three species of Pophyra umbilicalis,Pyropia haitanensis,and Pyropia yezoensis,respectively.Based on phylogenetic analysis,SOD gene members within the same subfamily exhibited similar motif patterns as well as conserved domains,which could be attribute to Cu/Zn-SOD and Fe/Mn-SOD.The promoter regions of SOD genes were rich in hormone-responsive,stress-responsive,and growth cis-acting elements,with variations and similarities observed among different species of other red algae and subfamilies.According to subcellular location prediction,it is suggested that Cu/Zn-SOD was predominantly located in chloroplasts,while Fe/Mn-SOD was primarily located in mitochondria.Also,the two subfamilies differed significantly in the two-/three-dimensional protein structures.In terms of gene evolution,the strongest collinearity relationship was shown between Pyropia haitanensis and Pyropia yezoensis,with all the 1꞉1 orthologous gene pair being subjected to a purifying selection(Ka/Ks<1,Ka:non-synonymy rate;Ks:synonymy rate).Moreover,12 SOD genes underwent positive selection during the evolutionary process.Furthermore,gene expression analysis based on transcriptomic data from Pyropia haitanensis showed that the expression patterns of SOD genes varied under different stress conditions.Together,this study revealed the evolutionary pattern of SOD genes in three bladed Bangiales species,which will lay the foundation for subsequent studies on the function of SOD genes.展开更多
The machining precision of blades is critical to the service performance of aero engines.The Leading Edge(LE) of high-pressure compressor blades poses a challenge for precision machining due to its thin size, high deg...The machining precision of blades is critical to the service performance of aero engines.The Leading Edge(LE) of high-pressure compressor blades poses a challenge for precision machining due to its thin size, high degree of bending, and significant change of curvature. Aimed at optimizing the machining error, this paper presents a framework that integrates toolpath planning and process parameter regulation. Firstly, an Iterative Subdivision Algorithm(ISA) for clamped Bspline curve is proposed, based on which toolpath planning method towards the LE is developed.Secondly, the removal effect of Cutter Contact(CC) point on the sampling points is investigated in the calculation of grinding dwell time by traversing in u-v space. A global material removal model is constructed for the solution. Thirdly, the previous two steps are interconnected based on the Improved Whale Optimization Algorithm(IWOA), and the optimal parameter combination is searched using the Root Mean Square Error(RMSE) of the machining error as the objective function. Based on this, the off-line programming and robotic grinding experiments are carried out. The experimental results show that the proposed method with error optimization can achieve 0.0143 mm mean value and 0.0160 mm standard deviations of LE surface error, which is an improvement of32.5% and 33.9%, respectively, compared with previous method.展开更多
The turbine blades operate under high temperature and high pressure conditions,and when using radiation thermometry,the influence of radiation from surrounding blades leads to measurement errors.To address this issue,...The turbine blades operate under high temperature and high pressure conditions,and when using radiation thermometry,the influence of radiation from surrounding blades leads to measurement errors.To address this issue,this paper develops a three-dimensional discretized dynamic radiation transfer model based on the blade shape of the turbine.The relationship between the radiation angle coefficient of the surrounding blades and the rotation angle of the blade under test is analyzed.The radiation angle coefficient is calculated using the triangular element method,and temperature inversion is performed based on the effective emissivity to compute the measurement error.The results show that under dynamic high temperature conditions,the temperature measurement error caused by reflection at the selected 60%leaf height point varies with the rotation angle,and the maximum reaches 25.58K.The angular coefficient exhibits periodic fluctuations with changes in rotation angle,and the maximum effective emissivity increases as the rotation angle increases.As the blade height increases,the impact of reflected radiation on radiometric temperature measurement errors shows a decreasing trend.This study provides a reference for radiation thermometry in dynamic high-temperature environments.展开更多
Blades are important parts of rotating machinery such as marine gas turbines and wind turbines,which are exposed to harsh environments during mechanical operations,including centrifugal loads,aerodynamic forces,or hig...Blades are important parts of rotating machinery such as marine gas turbines and wind turbines,which are exposed to harsh environments during mechanical operations,including centrifugal loads,aerodynamic forces,or high temperatures.These demanding working conditions considerably influence the dynamic performance of blades.Therefore,because of the challenges posed by blades in complex working environments,in-depth research and optimization are necessary to ensure that blades can operate safely and efficiently,thus guaranteeing the reliability and performance of mechanical systems.Focusing on the vibration analysis of blades in rotating machinery,this paper conducts a comprehensive literature review on the research advancements in vibration modeling and structural optimization of blades under complex operational conditions.First,the paper outlines the development of several modeling theories for rotating blades,including one-dimensional beam theory,two-dimensional plate-shell theory,and three-dimensional solid theory.Second,the research progress in the vibrational analysis of blades under aerodynamic loads,thermal environments,and crack factors is separately discussed.Finally,the developments in rotating blade structural optimization are presented from material optimization and shape optimization perspectives.The methodology and theory of analyzing and optimizing blade vibration characteristics under multifactorial operating conditions are comprehensively outlined,aiming to assist future researchers in proposing more effective and practical approaches for the vibration analysis and optimization of blades.展开更多
The performance of an aero-engine is closely related to the cooling ability of the hollow turbine blades.Ceramic core is an important component in the production of hollow turbine blades with a complex structure.As th...The performance of an aero-engine is closely related to the cooling ability of the hollow turbine blades.Ceramic core is an important component in the production of hollow turbine blades with a complex structure.As the pace of updating and iteration in turbine blade design continues to accelerate,the internal cavity structures of turbine blades have become increasingly complex.Traditional hot injection process is difficult to meet the production requirements of ceramic cores with complex structures.3D printing technology can manufacture ceramic cores without the need for moulds,significantly shortening the production cycle and providing a new technology for the production of ceramic cores with complex structures.To meet the technical requirements of the investment casting process,ceramic cores must possess adequate mechanical strength and appropriate porosity.In this work,the ceramic slurry with polysilazane(PSZ)precursor was successfully prepared,and the Al_(2)O_(3)-based ceramic cores with high performance were fabricated using 3D printing technology.The regulation mechanism of polysilazane on the performance of ceramic cores was investigated.The results show that with the increase of PSZ content,the fiexural strength of ceramic cores firstly increases and then decreases.When the content of PSZ is 5%,the fiexural strength at 25℃and 1,500℃are 31.5 MPa and 13.1 MPa,respectively,and the porosity is 36.7%.This work is expected to advance the research and practical application of high-performance ceramic cores fabricated via 3D printing.展开更多
Centrifugal pumps are extensively employed in ocean engineering,such as ship power systems,water transportation,and mineral exploitation.Pressure fluctuation suppression is essential for the operation stability and se...Centrifugal pumps are extensively employed in ocean engineering,such as ship power systems,water transportation,and mineral exploitation.Pressure fluctuation suppression is essential for the operation stability and service life of the centrifugal pump.In this paper,a new method of bionic structure is proposed for the blade surface of a centrifugal pump,which is inspired by the fish scale and comprises a leading edge,a trailing edge,and two symmetrical side edges.This fish scale structure is applied to the blade pressure and suction surfaces,and an impeller with a fish scale structure is constructed.A test rig for a centrifugal pump is developed to determine the pressure fluctuation in the pump with a prototype impeller and fish scale structure impeller.Results reveal that the dominant frequency of pressure fluctuation in volute is the blade passing frequency(f_(bpf))of 193.33 Hz,which is triggered by the interaction between the tongue and the impeller.The bionic structure of the fish scale effectively suppresses the pressure fluctuation amplitude at f_(bpf).From flow rates of 0.6 Q_(d)to 1.2 Q_(d),the average suppressions in pressure fluctuation amplitudes at f_(bpf)are 20.98%,5.85%,19.20%,and 25.77%.展开更多
The sedimentary bed morphology modulated by the wake flow of a wall-mounted flexible aquatic vegetation blade across various structural aspect ratios(A_(R)=l/b,where l and b are the length and width of the blade,respe...The sedimentary bed morphology modulated by the wake flow of a wall-mounted flexible aquatic vegetation blade across various structural aspect ratios(A_(R)=l/b,where l and b are the length and width of the blade,respectively)and incoming flow velocities was experimentally investigated in a water channel.A surface scanner was implemented to quantify bed topography,and a tomographic particle image velocimetry system was used to characterize the three-dimensional wake flows.The results showed that due to the deflection of incoming flow,the velocity magnitude increased at the lateral sides of the blade,thereby producing distinctive symmetric scour holes in these regions.The normalized morphology profiles of the sedimentary bed,which were extracted along the streamwise direction at the location of the maximum erosion depth,exhibited a self-similar pattern that closely followed a sinusoidal wave profile.The level of velocity magnitude enhancement was highly correlated to the postures of the flexible blade.At a given flow velocity,the blade with lower aspect ratios exhibited less significant deformation,causing more significant near-bed velocity enhancement in the wake deflection zone and therefore leading to higher erosion volumes.Further investigation indicated that when the blade underwent slight deformation,the larger velocity enhancement close to the bed can be attributed to more significant flow deflection effects at the lateral sides of the blade and stronger flow mixing with high momentum flows away from the bed.Supported with measurements,a basic formula was established to quantify the shear stress acting on the sedimentary bed as a function of incoming flow velocity and blade aspect ratio.展开更多
With the gradual increase in the size and flexibility of composite blades in large wind turbines,problems related toaeroelastic instability and blade vibration are becoming increasingly more important.Given their impa...With the gradual increase in the size and flexibility of composite blades in large wind turbines,problems related toaeroelastic instability and blade vibration are becoming increasingly more important.Given their impact on thelifespan of wind turbines,these subjects have become important topics in turbine blade design.In this article,firstaspects related to the aeroelastic(structural and aerodynamic)modeling of large wind turbine blades are summarized.Then,two main methods for blade vibration control are outlined(passive control and active control),including the case of composite blades.Some improvement schemes are proposed accordingly,with a specialfocus on the industry’s outstanding suppression scheme for stall-induced nonlinear flutter and a new high-frequencymicro-vibration control scheme.Finally,future research directions are indicated based on existingresearch.展开更多
Accurate measurement of helicopter rotor motion parameters(flap,lead-lag,torsion,and azimuth angles)is essential for rotor blade design,helicopter dynamics modeling,and flight safety and health monitoring.However,the ...Accurate measurement of helicopter rotor motion parameters(flap,lead-lag,torsion,and azimuth angles)is essential for rotor blade design,helicopter dynamics modeling,and flight safety and health monitoring.However,the existing methods face challenges in testing equipment installation,calibration,and data transmission,resulting in limited reports on real-time in-flight measurements of blade motion parameters.This paper proposes a non-contact optoelectronic method based on two-dimensional position-sensitive detectors for in-flight measurement and a ground calibration system to obtain real-time rotor motion parameters during helicopter flight.The proposed method establishes the time evolution relationship of rotor motion parameters and verifies the performance of the in-flight measurement system regarding measurement resolution and accuracy through the construction of a blade motion posture experimental platform.The proposed method has been applied to the flight measurement of a medium-sized single-rotor helicopter,and the obtained results have been compared with theoretical analysis outcomes.Furthermore,this paper examines the characteristics of blade motion parameters during flight and discusses the challenges and potential solutions for measuring rotor motion parameters during helicopter flight using the proposed method.展开更多
基金supported by the National Key Research and Development Plan(No.2017YFE0131900)the National Natural Science Foundation of China(Grant Nos.51672202 and 21875178)J.Z.thanks the support from the"Chutian Scholar Program" of Hubei Province,China.
文摘Organic-inorganic hybrid perovskite solar cells have generated wide interest due to the rapid development of their photovoltaic conversion effciencies.However,the majority of the reported devices have been fabricated via spin coating with a device areaof<1 cm2.In this study,we fabricated a wide-bandgap formamidi-nium lead bromide(FAPbBr3)film using a cost-effective,high-yielding doctor-blade-coating process.The effects of different surfactants,such as I-α-phosphatidylcholine,polyoxyethylene sorbitan monooleate,sodium lauryl sulfonate,and hexadecyl trimethyl ammonium bromide,were studied during the printing process.Accompanying the optimization of the blading temperature,crystal sizes of over 10μm and large-area perovskite films of5cm×5 cm were obtained using this method.The printed FAPbBr3 solar cells exhibited a short-circuit current density of 8.22 mA/cm2,an open-circuit voltage of 1.175 V,and an efficiency of 7.29%.Subsequently,we replaced the gold with silver nanowires as the top electrode to prepare a semitransparent perovskite solar cell with an average transmittance(400-800 nm)of 25.42%,achieving a high-power efficiency of 5.11%.This study demonstrates efficient doctor-blading printing for preparing large-area FAPbBr3 films that possess high potential for applications in building integrated photovoltaics.
基金Supported by the National Natural Science Foundation of China(Nos.52222904 and 52309117)China Postdoctoral Science Foundation(Nos.2022TQ0168 and 2023M731895).
文摘Ocean energy has progressively gained considerable interest due to its sufficient potential to meet the world’s energy demand,and the blade is the core component in electricity generation from the ocean current.However,the widened hydraulic excitation frequency may satisfy the blade resonance due to the time variation in the velocity and angle of attack of the ocean current,even resulting in blade fatigue and destructively interfering with grid stability.A key parameter that determines the resonance amplitude of the blade is the hydrodynamic damping ratio(HDR).However,HDR is difficult to obtain due to the complex fluid-structure interaction(FSI).Therefore,a literature review was conducted on the hydrodynamic damping characteristics of blade-like structures.The experimental and simulation methods used to identify and obtain the HDR quantitatively were described,placing emphasis on the experimental processes and simulation setups.Moreover,the accuracy and efficiency of different simulation methods were compared,and the modal work approach was recommended.The effects of key typical parameters,including flow velocity,angle of attack,gap,rotational speed,and cavitation,on the HDR were then summarized,and the suggestions on operating conditions were presented from the perspective of increasing the HDR.Subsequently,considering multiple flow parameters,several theoretical derivations and semi-empirical prediction formulas for HDR were introduced,and the accuracy and application were discussed.Based on the shortcomings of the existing research,the direction of future research was finally determined.The current work offers a clear understanding of the HDR of blade-like structures,which could improve the evaluation accuracy of flow-induced vibration in the design stage.
基金supported by National Natural Science Foundation of China(62104082)Guangdong Basic and Applied Basic Research Foundation(2022A1515010746,2022A1515011228,and 2022B1515120006)the Science and Technology Program of Guangzhou(202201010458).
文摘Gas quenching and vacuum quenching process are widely applied to accelerate solvent volatilization to induce nucleation of perovskites in blade-coating method.In this work,we found these two pre-crystallization processes lead to different order of crystallization dynamics within the perovskite thin film,resulting in the differences of additive distribution.We then tailor-designed an additive molecule named 1,3-bis(4-methoxyphenyl)thiourea to obtain films with fewer defects and holes at the buried interface,and prepared perovskite solar cells with a certified efficiency of 23.75%.Furthermore,this work also demonstrates an efficiency of 20.18%for the large-area perovskite solar module(PSM)with an aperture area of 60.84 cm^(2).The PSM possesses remarkable continuous operation stability for maximum power point tracking of T_(90)>1000 h in ambient air.
基金supported by grants from the National Natural Science Foundation of China(Nos.12102451,12072186)the National Science and Technology Major Project,China(No.J2019-II-0006-0026)AVIC Aerodynamics Research Institute,China(No.XFX20220201).
文摘To facilitate the low-noise design of tandem lift bodies as applied in aeroengines and aircraft,the acoustic features of tandem blades are investigated by wind-tunnel experiments.This is further specialized for the rotating blades applied in contra-rotating open rotors under the concept of frozen-rotor.A 70-channel phased microphone array and nine high-precision free-field microphones are employed.The beamforming method,enhanced by a source filtering technique,is employed to locate noise sources,providing insights into the source patterns of blade-blade interaction noise concerning flow speed,blade spacing,and aft blade clipping.The results show the following:(A)Sources of tandem-blade noise exist in the form of concentrated source clusters,resulting in two major clusters:the mid-span interaction noise and the tip-induced noise.(B)These source clusters tend to separate as flow speed or blade spacing increases.(C)By increasing blade spacing,the band-pass filtered overall sound pressure level is reduced by 2.9 dB.(D)A two-phase noise suppression pattern is observed with blade clipping,resulting in a total reduction of 3.0 dB for the interaction noise through the removal of tip-induced noise sources and the replacement of mid-span noise sources.Based on these findings,suggestions concerning blade spacing and clipping are discussed.
基金supported by the National Natural Science Foundation of China(Nos.52405088 and 92360306)the Postdoctoral Fellowship Program of CPSF,China(No.GZC20241446)+2 种基金the Natural Science Basic Research Program of Shaanxi,China(No.2024JC-YBMS-402)the Fundamental Research Funds for the Central Universities,CHD(No.300102254102)the Foundation of Beilin District,China(No.GX2455)。
文摘Anti-aliasing spectrum analysis is essential for rotor blade condition monitoring based on Blade Tip Timing(BTT).The Multiple Signal Classification(MUSIC)algorithm,which exploits the orthogonality between signal and noise subspaces,has been successfully applied for this purpose.However,conventional subspace selection methods relying on fixed thresholds are sensitive to variations in large eigenvalues.Furthermore,the complex disturbances during rotor operation and measurement complicate the identification of blade vibration characteristics.To overcome these challenges,this paper proposes Adaptive Subspace Separation(ASS)and Local Spectral Centroid(LSC)methods to improve the adaptability of subspace selection and the stability of frequency identification,respectively.The impacts of overestimating and underestimating the subspace dimensions on MUSIC's performance are derived mathematically.Simulation and experiments demonstrate the effectiveness of proposed approaches:ASS offers more accurate and stable subspace dimension selection and tracking,while LSC reduces the standard deviation of estimated frequencies by 30 percent.
基金the National Natural Science Foundation of China(Nos.52105117,52222504&51875433)the Funds for Distinguished Young talent of Shaanxi Province,China(No.2019JC-04)。
文摘Blade Tip Timing(BTT)enables non-contact measurements of rotating blades by placing probes strategically.Due to the uneven probe layout,BTT signals exhibit periodic irregularities.While recovering parameters like frequency from such signals is possible,achieving high-precision vibration parameters remains challenging.This paper proposed a novel two-stage off-grid estimation method.It leverages a unique array layout(coprime array)to obtain a regular augmented covariance matrix.Subsequently,parameters in the matrix are recovered using the sparse iterative covariance-based estimation method based on covariance fitting criteria.Finally,high-precision estimates of imprecise parameters are obtained using unconditional maximum likelihood estimation,effectively eliminating the effects of basis mismatch.Through substantial numerical and experimental validation,the proposed method demonstrates significantly higher accuracy compared to classical BTT parameter estimation methods,approaching the lower bound of unbiased estimation variance.Furthermore,due to its immunity to frequency gridding,it can track minor frequency deviations,making it more suitable for indicating blade condition.
基金supported by the National Natural Science Foundation of China(No.12372229)the Aeronautical Science Foundation of China(No.2020Z006063001)+1 种基金the Science and Technology on Rotorcraft Aeromechanics Laboratory Foundation,China(No.61422202110)the Fundamental Research Funds for the Central Universities of China(No.DUT22LK12)。
文摘This paper proposes a new approach to eliminate aerodynamic lift oscillation,called the Dominant Sector Individual Blade Control(DS-IBC)method for rigid rotor helicopters.An Advancing Blade Concept(ABC)rotor model for aerodynamic analysis based on the free-wake method is applied.DS-IBC avoids applying active control on the rotor's retreating side by employing and restricting active control inputs to a sector area of the rotor disc.Outside this sector,only primary collective and cyclic pitch control are used.Each blade takes turns entering the sector,creating a“relay”active control form to ensure continuous control inputs.The method also includes outer-trim and inner-trim iteration modules.Results show that DS-IBC can eliminate aerodynamic lift oscillation using much smaller control inputs than the sine-trim method.By focusing active control on the rotor's advancing side,DS-IBC improves the effective lift-to-drag ratio and reduces the implementation difficulty of active rotor control for aerodynamic oscillation elimination,especially at a large lift-offset.
文摘A two-dimensional transition metal carbide/nitride/carbonitride(MXene)and waterborne polyurethane(WPU)were uniformly mixed to form an MXene/WPU coating,which was loaded on polyethylene terephthalate(PET)fabric through blade coating to prepare an MXene/WPU@PET composite fabric with electromagnetic shielding properties.The micro-morphology and composition,surface wettability,tensile properties,electrical conductivity,and electromagnetic shielding properties of the composite fabric were studied.The results showed that the MXene/WPU@PET composite fabric exhibited the cha-racteristics of flexibility and firmness,and a unit area load capacity of MXene/WPU was 1.9 mg/cm^(2),the conductivity 760 S/m,and the electromagnetic shielding effectiveness up to 42 dB(8.2-12.4 GHz);and this convenient and effective method can be used to prepare lightweight and flexible electromagnetic shielding materials,promising broad application prospects in the field of wearable products.
文摘Considering the fracture problem of the silica-based ceramic core in the integrated casting of hollow turbine blades during directional solidification,the influence of various whiskers,including silicon carbide whiskers,silicon nitride whiskers,and mullite whiskers,on the high-temperature strength of the silica-based ceramic core was investigated.Additionally,the formation of microstructure morphology and phase structure was analyzed.Research results show that silicon carbide whiskers can reduce the microcracks caused by the shrinkage of cristobalite.During the sintering process,some of the silicon carbide whiskers oxidize and react with aluminum powder to form mullite,which can improve the high-temperature strength of the ceramic cores.When the content of silicon carbide whiskers is 3wt.%,the high-temperature bending strength of the cores reaches the maximum value of 21 MPa.Silicon nitride whiskers decompose in a high-temperature environment and react with aluminum powder in the matrix material to form mullite whiskers.When the content of silicon nitride whiskers is 5wt.%,the high-temperature bending strength of the cores reaches 20 MPa.By adding mullite whiskers,a structure of cristobalite wrapped mullite whiskers can be formed to achieve toughening.When the content of mullite whiskers is 4wt.%,the high-temperature bending strength can reach 17.2 MPa.By comparing the performance of silicon carbide whiskers,silicon nitride whiskers,and mullite whiskers,along with conducting slurry viscosity tests and casting experiments,it is determined that a ceramic slurry containing 4wt.%mullite whiskers is the most suitable for making the cores used in the integrated casting of hollow turbine blades.
基金co-supported by the National Natural Science Foundation of China(No.52306034)the National Science and Technology Major Project,China(No.J2022-IV-00100024)+1 种基金the Fundamental Research Funds for the Central Universities,Chinathe National Science and Technology Major Project,China(No.J2017-IV-0002-0039)。
文摘This study investigates the forced vibration response of a two-row model of an Inlet Guide Vane(IGV)and rotor at resonance speed through numerical simulations.A resonant response prediction method based on equivalent damping balance has been validated,which ensures computational accuracy while reducing response calculation time to only 1%of the traditional transient response method.At resonance speed,unsteady pressure disturbances on the rotor blade surface mainly arise from two sources:IGV wakes and blade vibrations.The unsteady pressure caused by the IGV wakes provides excitation for the system,while the unsteady pressure caused by rotor blade vibrations provides damping.By studying the characteristics of unsteady pressure caused by IGV wakes and vibrations at resonance speed,a method for separating unsteady pressure caused by stator wakes and vibrations has been presented,accurately obtaining aerodynamic damping under multi-row resonance conditions.Compared to the aerodynamic damping obtained from multi-row scenarios without separating unsteady pressures caused by stator wakes and vibrations,and the traditional isolated blade row scheme,the aerodynamic damping considering the effects of multi-row and IGV wakes at resonance speed is smaller.Based on the separated unsteady pressures caused by IGV wakes and vibrations,and combined with the equivalent damping balance method for predicting forced response,a forced response analysis method considering both flow field disturbance excitation and damping effects has been established.
基金Supported by the National Key R&D Program of China(No.2023 YFD 2400102)the Guangxi Key Laboratory of Beibu Gulf Marine Biodiversity Conservation,Beibu Gulf University(No.2024 KA 04)。
文摘As a key component of the plant antioxidant enzymatic system,superoxide dismutase(SOD)can efficiently protect cells from oxidative stress and maintain redox homeostasis.Currently,there are few studies related to SOD genes in various taxa of algae,and the specific functions and evolutionary patterns of these family members remain unclear.In this study,comprehensively evolutionary analysis of SOD gene family in the bladed Bangiales was carried out.A total of 9,10,and 12 SOD genes were identified from three species of Pophyra umbilicalis,Pyropia haitanensis,and Pyropia yezoensis,respectively.Based on phylogenetic analysis,SOD gene members within the same subfamily exhibited similar motif patterns as well as conserved domains,which could be attribute to Cu/Zn-SOD and Fe/Mn-SOD.The promoter regions of SOD genes were rich in hormone-responsive,stress-responsive,and growth cis-acting elements,with variations and similarities observed among different species of other red algae and subfamilies.According to subcellular location prediction,it is suggested that Cu/Zn-SOD was predominantly located in chloroplasts,while Fe/Mn-SOD was primarily located in mitochondria.Also,the two subfamilies differed significantly in the two-/three-dimensional protein structures.In terms of gene evolution,the strongest collinearity relationship was shown between Pyropia haitanensis and Pyropia yezoensis,with all the 1꞉1 orthologous gene pair being subjected to a purifying selection(Ka/Ks<1,Ka:non-synonymy rate;Ks:synonymy rate).Moreover,12 SOD genes underwent positive selection during the evolutionary process.Furthermore,gene expression analysis based on transcriptomic data from Pyropia haitanensis showed that the expression patterns of SOD genes varied under different stress conditions.Together,this study revealed the evolutionary pattern of SOD genes in three bladed Bangiales species,which will lay the foundation for subsequent studies on the function of SOD genes.
基金supported by the National Natural Science Foundation of China (No. 52075059)Graduate Scientific Research and Innovation Foundation of Chongqing (No. CYB23021)the Innovation Fund of Aero Engine Corporation of China (No. ZZCX-2022-019)。
文摘The machining precision of blades is critical to the service performance of aero engines.The Leading Edge(LE) of high-pressure compressor blades poses a challenge for precision machining due to its thin size, high degree of bending, and significant change of curvature. Aimed at optimizing the machining error, this paper presents a framework that integrates toolpath planning and process parameter regulation. Firstly, an Iterative Subdivision Algorithm(ISA) for clamped Bspline curve is proposed, based on which toolpath planning method towards the LE is developed.Secondly, the removal effect of Cutter Contact(CC) point on the sampling points is investigated in the calculation of grinding dwell time by traversing in u-v space. A global material removal model is constructed for the solution. Thirdly, the previous two steps are interconnected based on the Improved Whale Optimization Algorithm(IWOA), and the optimal parameter combination is searched using the Root Mean Square Error(RMSE) of the machining error as the objective function. Based on this, the off-line programming and robotic grinding experiments are carried out. The experimental results show that the proposed method with error optimization can achieve 0.0143 mm mean value and 0.0160 mm standard deviations of LE surface error, which is an improvement of32.5% and 33.9%, respectively, compared with previous method.
文摘The turbine blades operate under high temperature and high pressure conditions,and when using radiation thermometry,the influence of radiation from surrounding blades leads to measurement errors.To address this issue,this paper develops a three-dimensional discretized dynamic radiation transfer model based on the blade shape of the turbine.The relationship between the radiation angle coefficient of the surrounding blades and the rotation angle of the blade under test is analyzed.The radiation angle coefficient is calculated using the triangular element method,and temperature inversion is performed based on the effective emissivity to compute the measurement error.The results show that under dynamic high temperature conditions,the temperature measurement error caused by reflection at the selected 60%leaf height point varies with the rotation angle,and the maximum reaches 25.58K.The angular coefficient exhibits periodic fluctuations with changes in rotation angle,and the maximum effective emissivity increases as the rotation angle increases.As the blade height increases,the impact of reflected radiation on radiometric temperature measurement errors shows a decreasing trend.This study provides a reference for radiation thermometry in dynamic high-temperature environments.
基金Supported by the National Natural Science Foundation of China under Grant No.52271309Natural Science Foundation of Heilongjiang Province of China under Grant No.YQ2022E104.
文摘Blades are important parts of rotating machinery such as marine gas turbines and wind turbines,which are exposed to harsh environments during mechanical operations,including centrifugal loads,aerodynamic forces,or high temperatures.These demanding working conditions considerably influence the dynamic performance of blades.Therefore,because of the challenges posed by blades in complex working environments,in-depth research and optimization are necessary to ensure that blades can operate safely and efficiently,thus guaranteeing the reliability and performance of mechanical systems.Focusing on the vibration analysis of blades in rotating machinery,this paper conducts a comprehensive literature review on the research advancements in vibration modeling and structural optimization of blades under complex operational conditions.First,the paper outlines the development of several modeling theories for rotating blades,including one-dimensional beam theory,two-dimensional plate-shell theory,and three-dimensional solid theory.Second,the research progress in the vibrational analysis of blades under aerodynamic loads,thermal environments,and crack factors is separately discussed.Finally,the developments in rotating blade structural optimization are presented from material optimization and shape optimization perspectives.The methodology and theory of analyzing and optimizing blade vibration characteristics under multifactorial operating conditions are comprehensively outlined,aiming to assist future researchers in proposing more effective and practical approaches for the vibration analysis and optimization of blades.
基金supported by the National Natural Science Foundation of China(Nos.52402094,U234120139,and U22A20129)National Defense Basic Scientific Research Program of China(No.JCKY2022130C005)+7 种基金China Postdoctoral Science Foundation(No.2023M743571)Postdoctoral Fellowship Program of CPSF(No.GZC20232743)Innovation Project of IMR(No.2024-PY11)Open Research Fund of National Key Laboratory of Advanced Casting Technologies(No.CAT2023-006)Graduate Education Quality Engineering Project of Anhui Province(No.2023cxcysj015)Science and Technology Plan Project of Liaoning Province(No.2024JH2/101900011)National Key Research and Development Program of China(Nos.2024YFB3714500 and 2018YFB1106600)the China United Gas Turbine Technology Co.,Ltd.(No.J790)。
文摘The performance of an aero-engine is closely related to the cooling ability of the hollow turbine blades.Ceramic core is an important component in the production of hollow turbine blades with a complex structure.As the pace of updating and iteration in turbine blade design continues to accelerate,the internal cavity structures of turbine blades have become increasingly complex.Traditional hot injection process is difficult to meet the production requirements of ceramic cores with complex structures.3D printing technology can manufacture ceramic cores without the need for moulds,significantly shortening the production cycle and providing a new technology for the production of ceramic cores with complex structures.To meet the technical requirements of the investment casting process,ceramic cores must possess adequate mechanical strength and appropriate porosity.In this work,the ceramic slurry with polysilazane(PSZ)precursor was successfully prepared,and the Al_(2)O_(3)-based ceramic cores with high performance were fabricated using 3D printing technology.The regulation mechanism of polysilazane on the performance of ceramic cores was investigated.The results show that with the increase of PSZ content,the fiexural strength of ceramic cores firstly increases and then decreases.When the content of PSZ is 5%,the fiexural strength at 25℃and 1,500℃are 31.5 MPa and 13.1 MPa,respectively,and the porosity is 36.7%.This work is expected to advance the research and practical application of high-performance ceramic cores fabricated via 3D printing.
基金supported by the Open Fund of Science and Technology on Thermal Energy and Power Laboratory[TPL2021A02]the State Key Laboratory of Hydroscience and Engineering[sklhse-2023-E-01].
文摘Centrifugal pumps are extensively employed in ocean engineering,such as ship power systems,water transportation,and mineral exploitation.Pressure fluctuation suppression is essential for the operation stability and service life of the centrifugal pump.In this paper,a new method of bionic structure is proposed for the blade surface of a centrifugal pump,which is inspired by the fish scale and comprises a leading edge,a trailing edge,and two symmetrical side edges.This fish scale structure is applied to the blade pressure and suction surfaces,and an impeller with a fish scale structure is constructed.A test rig for a centrifugal pump is developed to determine the pressure fluctuation in the pump with a prototype impeller and fish scale structure impeller.Results reveal that the dominant frequency of pressure fluctuation in volute is the blade passing frequency(f_(bpf))of 193.33 Hz,which is triggered by the interaction between the tongue and the impeller.The bionic structure of the fish scale effectively suppresses the pressure fluctuation amplitude at f_(bpf).From flow rates of 0.6 Q_(d)to 1.2 Q_(d),the average suppressions in pressure fluctuation amplitudes at f_(bpf)are 20.98%,5.85%,19.20%,and 25.77%.
基金supported by the National Science Foundation under Grant No.2327916.
文摘The sedimentary bed morphology modulated by the wake flow of a wall-mounted flexible aquatic vegetation blade across various structural aspect ratios(A_(R)=l/b,where l and b are the length and width of the blade,respectively)and incoming flow velocities was experimentally investigated in a water channel.A surface scanner was implemented to quantify bed topography,and a tomographic particle image velocimetry system was used to characterize the three-dimensional wake flows.The results showed that due to the deflection of incoming flow,the velocity magnitude increased at the lateral sides of the blade,thereby producing distinctive symmetric scour holes in these regions.The normalized morphology profiles of the sedimentary bed,which were extracted along the streamwise direction at the location of the maximum erosion depth,exhibited a self-similar pattern that closely followed a sinusoidal wave profile.The level of velocity magnitude enhancement was highly correlated to the postures of the flexible blade.At a given flow velocity,the blade with lower aspect ratios exhibited less significant deformation,causing more significant near-bed velocity enhancement in the wake deflection zone and therefore leading to higher erosion volumes.Further investigation indicated that when the blade underwent slight deformation,the larger velocity enhancement close to the bed can be attributed to more significant flow deflection effects at the lateral sides of the blade and stronger flow mixing with high momentum flows away from the bed.Supported with measurements,a basic formula was established to quantify the shear stress acting on the sedimentary bed as a function of incoming flow velocity and blade aspect ratio.
基金supported by the Natural Science Foundation of Shandong Provincial of China(Grant Number ZR2022ME093)the Natural Science Foundation of China(Grant Number 51675315).
文摘With the gradual increase in the size and flexibility of composite blades in large wind turbines,problems related toaeroelastic instability and blade vibration are becoming increasingly more important.Given their impact on thelifespan of wind turbines,these subjects have become important topics in turbine blade design.In this article,firstaspects related to the aeroelastic(structural and aerodynamic)modeling of large wind turbine blades are summarized.Then,two main methods for blade vibration control are outlined(passive control and active control),including the case of composite blades.Some improvement schemes are proposed accordingly,with a specialfocus on the industry’s outstanding suppression scheme for stall-induced nonlinear flutter and a new high-frequencymicro-vibration control scheme.Finally,future research directions are indicated based on existingresearch.
基金the funding provided by the National Helicopter Development Project of China。
文摘Accurate measurement of helicopter rotor motion parameters(flap,lead-lag,torsion,and azimuth angles)is essential for rotor blade design,helicopter dynamics modeling,and flight safety and health monitoring.However,the existing methods face challenges in testing equipment installation,calibration,and data transmission,resulting in limited reports on real-time in-flight measurements of blade motion parameters.This paper proposes a non-contact optoelectronic method based on two-dimensional position-sensitive detectors for in-flight measurement and a ground calibration system to obtain real-time rotor motion parameters during helicopter flight.The proposed method establishes the time evolution relationship of rotor motion parameters and verifies the performance of the in-flight measurement system regarding measurement resolution and accuracy through the construction of a blade motion posture experimental platform.The proposed method has been applied to the flight measurement of a medium-sized single-rotor helicopter,and the obtained results have been compared with theoretical analysis outcomes.Furthermore,this paper examines the characteristics of blade motion parameters during flight and discusses the challenges and potential solutions for measuring rotor motion parameters during helicopter flight using the proposed method.
