Mechanism of internal thermal runaway propagation in blade batteries

Blade batteries are extensively used in electric vehicles,but unavoidable thermal runaway is an inherent threat to their safe use.This study experimentally investigated the mechanism underlying thermal runaway propagation within a blade battery by using a nail to trigger thermal runaway and thermocouples to track its propagation inside a cell.The results showed that the internal thermal runaway could propagate for up to 272 s,which is comparable to that of a traditional battery module.The velocity of the thermal runaway propagation fluctuated between 1 and 8 mm s^(-1),depending on both the electrolyte content and high-temperature gas diffusion.In the early stages of thermal runaway,the electrolyte participated in the reaction,which intensified the thermal runaway and accelerated its propagation.As the battery temperature increased,the electrolyte evaporated,which attenuated the acceleration effect.Gas diffusion affected thermal runaway propagation through both heat transfer and mass transfer.The experimental results indicated that gas diffusion accelerated the velocity of thermal runaway propagation by 36.84%.We used a 1D mathematical model and confirmed that convective heat transfer induced by gas diffusion increased the velocity of thermal runaway propagation by 5.46%-17.06%.Finally,the temperature rate curve was analyzed,and a three-stage mechanism for internal thermal runaway propagation was proposed.In Stage I,convective heat transfer from electrolyte evaporation locally increased the temperature to 100℃.In Stage II,solid heat transfer locally increases the temperature to trigger thermal runaway.In StageⅢ,thermal runaway sharply increases the local temperature.The proposed mechanism sheds light on the internal thermal runaway propagation of blade batteries and offers valuable insights into safety considerations for future design.

Surfactant-assisted doctor-blading-printed FAPbBr3 films for efficient semitransparent perovskite solar cells

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.

风电机组电气与机械联合仿真研究

本文基于GH Bladed软件建立风电机组电气与机械联合仿真平台,通过主控及发电系统自定义模型,与Bladed内置模型进行正确交互,针对电网电压故障的故障程度、故障类型、穿越策略等因素,分析风电机组电气与机械相互作用机理与特性。以上因素均能通过直接影响发电机电磁暂态过渡过程对结构载荷产生影响,并且不同故障因素对机组部件载荷的影响具有其规律性。

Chemical vapor deposition for perovskite solar cells and modules

Metal halide perovskites are promising materials for solar cells because of high power conversion efficiency(PCE),tun-able bandgap,high defect tolerance,long carrier diffusion length,and low-cost fabrication[1-7].The PCE for perovskite solar cells(PSCs)reaches 26.14%for single-junction cells,29.1%for perovskite/perovskite tandem cells and 33.9%for perovskite/silicon tandem cells,being comparable to that for silicon and other thin-film solar cells[8-10].Perovskite solar cells have been made by solution methods including spin-coat-ing,blade coating and printing[11,12].

Blade Wrap Angle Impact on Centrifugal Pump Performance:Entropy Generation and Fluid-Structure Interaction Analysis

The centrifugal pump is a prevalent power equipment widely used in different engineering patterns,and the impeller blade wrap angle significantly impacts its performance.A numerical investigation was conducted to analyze the influence of the blade wrap angle on flow characteristics and energy distribution of a centrifugal pump evaluated as a low specific speed with a value of 69.This study investigates six impellermodels that possess varying blade wrap angles(95°,105°,115°,125°,135°,and 145°)that were created while maintaining the same volute and other geometrical characteristics.The investigation of energy loss was conducted to evaluate the values of total and entropy generation rates(TEG,EGR).The fluid-structure interaction was considered numerically using the software tools ANSYS Fluent and ANSYSWorkbench.The elastic structural dynamic equation was used to estimate the structural response,while the shear stress transport k–ωturbulence model was utilized for the fluid domain modeling.The findings suggest that the blade wrap angle has a significant influence on the efficiency of the pump.The impeller featuring a blade wrap angle of 145°exhibits higher efficiency,with a notable increase of 3.76%relative to the original model.Variations in the blade wrap angle impact the energy loss,shaft power,and pump head.The model with a 145°angle exhibited a maximum equivalent stress of 14.8MPa and a total deformation of 0.084 mm.The results provide valuable insights into the intricate flow mechanism of the centrifugal pump,particularly when considering various blade wrap angles.

Climate change and human health: Last call to arms for us

Climate change,now the foremost global health hazard,poses multifaceted challenges to human health.This editorial elucidates the extensive impact of climate change on health,emphasising the increasing burden of diseases and the exacerbation of health disparities.It highlights the critical role of the healthcare sector,particularly anaesthesia,in both contributing to and mitigating climate change.It is a call to action for the medical community to recognise and respond to the health challenges posed by climate change.

Nonlinear Flap-Wise Vibration Characteristics ofWind Turbine Blades Based onMulti-Scale AnalysisMethod

This work presents a novel approach to achieve nonlinear vibration response based on the Hamilton principle.We chose the 5-MW reference wind turbine which was established by the National Renewable Energy Laboratory(NREL),to research the effects of the nonlinear flap-wise vibration characteristics.The turbine wheel is simplified by treating the blade of a wind turbine as an Euler-Bernoulli beam,and the nonlinear flap-wise vibration characteristics of the wind turbine blades are discussed based on the simplification first.Then,the blade’s large-deflection flap-wise vibration governing equation is established by considering the nonlinear term involving the centrifugal force.Lastly,it is truncated by the Galerkin method and analyzed semi-analytically using the multi-scale analysis method,and numerical simulations are carried out to compare the simulation results of finite elements with the numerical simulation results using Campbell diagram analysis of blade vibration.The results indicated that the rotational speed of the impeller has a significant impact on blade vibration.When the wheel speed of 12.1 rpm and excitation amplitude of 1.23 the maximum displacement amplitude of the blade has increased from 0.72 to 3.16.From the amplitude-frequency curve,it can be seen that the multi-peak characteristic of blade amplitude frequency is under centrifugal nonlinearity.Closed phase trajectories in blade nonlinear vibration,exhibiting periodic motion characteristics,are found through phase diagrams and Poincare section diagrams.

Surface Defect Detection and Evaluation Method of Large Wind Turbine Blades Based on an Improved Deeplabv3+Deep Learning Model

The accumulation of defects on wind turbine blade surfaces can lead to irreversible damage,impacting the aero-dynamic performance of the blades.To address the challenge of detecting and quantifying surface defects on wind turbine blades,a blade surface defect detection and quantification method based on an improved Deeplabv3+deep learning model is proposed.Firstly,an improved method for wind turbine blade surface defect detection,utilizing Mobilenetv2 as the backbone feature extraction network,is proposed based on an original Deeplabv3+deep learning model to address the issue of limited robustness.Secondly,through integrating the concept of pre-trained weights from transfer learning and implementing a freeze training strategy,significant improvements have been made to enhance both the training speed and model training accuracy of this deep learning model.Finally,based on segmented blade surface defect images,a method for quantifying blade defects is proposed.This method combines image stitching algorithms to achieve overall quantification and risk assessment of the entire blade.Test results show that the improved Deeplabv3+deep learning model reduces training time by approximately 43.03%compared to the original model,while achieving mAP and MIoU values of 96.87%and 96.93%,respectively.Moreover,it demonstrates robustness in detecting different surface defects on blades across different back-grounds.The application of a blade surface defect quantification method enables the precise quantification of dif-ferent defects and facilitates the assessment of risk levels associated with defect measurements across the entire blade.This method enables non-contact,long-distance,high-precision detection and quantification of surface defects on the blades,providing a reference for assessing surface defects on wind turbine blades.

Research on Fatigue Damage Behavior of Main Beam Sub-Structure of Composite Wind Turbine Blade

Given the difficulty in accurately evaluating the fatigue performance of large composite wind turbine blades(referred to as blades),this paper takes the main beam structure of the blade with a rectangular cross-sectionas the simulation object and establishes a composite laminate rectangular beam structure that simultaneouslyincludes the flange,web,and adhesive layer,referred to as the blade main beam sub-structure specimen,throughthe definition of blade sub-structures.This paper examines the progressive damage evolution law of the compositelaminate rectangular beam utilizing an improved 3D Hashin failure criterion,cohesive zone model,B-K failurecriterion,and computer simulation technology.Under static loading,the layup angle of the anti-shear web hasa close relationship with the static load-carrying capacity of the composite laminate rectangular beam;under fatigueloading,the fatigue damage will first occur in the lower flange adhesive area of the whole composite laminaterectangular beam and ultimately result in the fracture failure of the entire structure.These results provide a theoreticalreference and foundation for evaluating and predicting the fatigue performance of the blade main beamstructure and even the full-size blade.

旋转带肋通道流阻特性研究

With the development of aero-engines, the turbine inlet temperature continues to rise. In order to ensure the safety and reliability of the turbine blades, cooling structures must be set inside turbine blades to cool them. Heat transfer coefficient and flow resistance are the key parameters to measure the cooling characteristics of internal cooling structures. In this paper, the characteristics of flow resistance in a rotating ribbed channel is presented numerical simulation under different rib spacings, rib angles, and thermal boundary conditions. The results show that, separation and reattachment of fluid between ribs is the key effect of rib spacing on flow resistance. The flow resistance is small when the rib spacing is small, because it's difficult for the fluid to form reattachment between the ribs. With the increase of rib spacing, the reattachment phenomenon is more obvious and the flow resistance increases accordingly. In general,p: e=10 channel has the maximum flow resistance. Secondary flow caused by the ribs is the key factor affecting the flow resistance characteristics with different rib angles. The secondary flow interacts with the main flow and causes flow loss through mixing, thus affecting the flow resistance of the channel. Under static condition, the flow resistance of 60°ribbed channel is the largest. The flow resistance of channel was affected by the temperature rise ratio also. And with the increase of the Ro, the temperature rise ratio has a more obvious effect on the flow resistance of the ribbed channel.When Ro=0.45, the flow resistance of the channel with a temperature rise ratio of 0.4 is 2.4 times that of the channel without temperature rise, while when Ro=0.3, it is 1.6 times, and when Ro=0.15, it is 1.2 times.

PFNA2 versus 95 Degree Condylar Blade Plate in the Management of Unstable Trochanteric Fractures

Purpose: The proximal femoral nail anti-rotation (PFNA) is known to have advantages in enhancing the anchorage ability of internal fixation in elderly unstable osteoporotic intertrochanteric fracture patients. However whether it is superior to condylar blade fixation is not clear. This study aimed to determine which treatment has better clinical outcomes in older patients. Materials and Methods: A total of 86 patients over the age of 60 with unstable trochanteric fractures within the past 3 weeks, were included in this prospective study conducted from June 1, 2018, to May 31, 2021. All the intertrochanteric fractures were classified according to AO/OTA classification. Among them, 44 cases were treated with the Proximal Femoral Nail (PFNA2) with or without an augmentation screw, and 42 cases were treated with the Condylar Blade Plate. In addition, the operative time, intraoperative blood loss, intraoperative and postoperative blood transfusion, postoperative weight-bearing time, hospitalization time, Harris score of hip function, Kyle’s criteria and postoperative complications were compared between the two groups. Results: The mean duration of surgery for the PFN group was 66.8 minutes (on average), whereas for the condylar blade plate group, it was 99.30 minutes (on average). The PFNA2 group experienced less blood loss (average of 80 mL) compared to the condylar blade plate group (average of 120 mL). Union and partial weight-bearing occurred earlier in the PFNA2 group (14.1 weeks and 10.6 weeks, respectively) compared to the Condylar blade plate group (18.7 weeks and 15.8 weeks). In two patients from the PFNA2 group, screw backing out and varus collapse complications were encountered;however, these patients remained asymptomatic and did not require revision surgery. In two other patients, screw cut out and breakage of the nail at the helical screw hole leading to non-union of the proximal femur were observed during the nine-month follow-up, necessitating revision surgery with prosthetic replacement. Among the condylar blade plate group, three patients experienced complications, including blade breakage at the blade and plate junction. In two cases, the fracture united in varus, and in one case, the blade cut through, resulting in non-union of the femoral head, which required revision surgery. According to the Harris hip score and Kyle’s criteria, a good-excellent outcome was observed in 92.85% of cases in the PFNA2 group and 90.90% of cases in the condylar blade plate group. Conclusion: Both the Proximal Femoral Nail A2 and Condylar blade plate are effective implants for the treatment of unstable trochanteric fractures. The intramedullary implant promotes biological healing and allows for early ambulation with minimal complications. Similarly satisfactory restoration of anatomy and favorable radiological and functional results can be achieved with the biological fixation provided by the 95-degree condylar blade plate. However, the use of PFNA2 internal fixation technique has the advantage of less trauma in elderly patients than the 95-degree condylar blade plate.

Flashover Probability of Wind Turbine Blade and Impact of Strong Electromagnetic Pulse from Lightning Strikes on Wind Turbine Safety

This paper systematically studies the flashover probability of wind turbine blade lightning arrester and the impact of strong electromagnetic pulses on the local and surrounding wind turbines during lightning strikes.The research results indicate that the flashover probability of direct lightning strikes by the wind turbine blade lightning arrester is almost negligible,and the strong electromagnetic pulse of wind turbine blade during lightning strikes has a serious impact on the electronic equipment of the machine,while the impact on the surrounding wind turbine is relatively small.At the same time,the calculation formula for the reflection of lightning current on the carbon brush between the wind turbine hub and the engine compartment during the flashing of the wind turbine blades is provided,and the calculation method for calculating the spatial gradient distribution of electromagnetic field intensity using Biot-Savart Law theorem is applied.The limitations of using wind turbine blades for lightning protection are pointed out,and a technical route for achieving wind turbine lightning safety is proposed,which can be used as a reference for wind turbine lightning protection technicians.

基于流程的风电主场控自动化测试设计与实现

随着我国风力发电的迅速发展,单机容量和风电场规模都在不断扩大,怎样对风电机组及风场控制系统进行全面有效的测试,提高风电机组控制系统的质量,也逐渐成为亟待解决的问题。由于主场控制系统组成复杂,仿真软件和采用变流器、发电机和变桨系统实物进行测试从技术上和经济上都不可行,所以我们基于济南中车风电CW3000-131级风电主场控系统开发设计了一套风电主场控自动化测试平台。该测试平台包括整个风电机组的全部测点,能够测试完整的主场控场景,包括主控的变流器系统、偏航系统、变桨系统、发电机系统和所有的外部工IO等,场控系统的调频控制、AGC指令控制、AVC指令控制。

时域谐波平衡求解器中非物理解出现根源探析

The time domain harmonic balance method is an attractive reduced order method of analyzing unsteady flow for turbomachines. However, the method can admit non-physical solutions. Non-physical solutions were encountered from a three-blade-row compressor configuration in a time domain harmonic balance analysis. This paper aims to investigate the root cause of the non-physical solutions. The investigation involves several strategies, which include increasing the number of harmonics, increasing the number of time instants, including scattered modes,including the rotor-rotor interaction, and the use of a new method-the approximate time domain nonlinear harmonic method. Numerical analyses pertinent to each strategy are presented to reveal the root cause of the non-physical solution. It is found that the nonlinear interaction of unsteady flow components with different fundamental frequencies is the cause of the non-physical solution. The non-physical solution can be eliminated by incorporating extra scattered modes or using the approximate time domain nonlinear harmonic method.

组合载荷下海上风机塔架受力特性数值分析

研究组合载荷下海上风机塔架的受力特性。基于江苏启东海域6 MW海上风机资料,采用GH Bladed软件开展组合载荷下海上风机塔架的受力特性数值模拟,得到以下主要结论:与风载荷作用相比,在风载荷+波浪载荷组合作用下,风机塔架基础底面所受峰值剪力提升72.0%,峰值弯矩提升8.3%;波浪载荷对基础所受剪力和弯矩的影响显著,在相对波高为4时,基础底面所受相对剪力和相对弯矩分别为3.04和1.44;与风载荷作用相比,在风载荷+地震载荷组合作用下,风机塔架基础底面所受峰值剪力提升76%,峰值弯矩提升21%。研究成果可为启东海域海上风机设计及施工提供理论支撑。

Extraction of Strain Characteristic Signals from Wind Turbine Blades Based on EEMD-WT

Analyzing the strain signal of wind turbine blade is the key to studying the load of wind turbine blade,so as to ensure the safe and stable operation of wind turbine in natural environment.The strain signal of the wind turbine blade under continuous crosswind state has typical non-stationary and unsteady characteristics.The strain signal contains a lot of noise,which makes the analysis error.Therefore,it is very important to denoise and extract features of measured signals before signal analysis.In this paper,the joint algorithm of ensemble empirical mode decomposition(EEMD)and wavelet transform(WT)is used for the first time to achieve sufficient noise reduction and effectively extract the feature signals of non-stationary strain signals.The application process of EEMD-WT is optimized.This optimization can avoid the repeated selection of wavelet basis function and the number of decomposition layers due to different crosswind conditions.EEMD adaptively decomposes the strain signal into intrinsic mode functions,to judge the frequency of IMFs,remove the high-frequency noise components,retain the useful components.The useful components are denoised twice by the wavelet transform,the components and residual terms after the secondary denoising are reconstructed to obtain the characteristic signal.The EEMD-WT was applied to process the simulating signals andmeasured the strain signals.The results were compared with the results of the EEMD.The results showed that the EEMD-WTmethod has better noise reduction performance,and can effectively extract the characteristics of strain signals,which lays a solid foundation for accurate analysis of wind turbine blade strain signals under crosswind conditions.

Numerical Study on the Duct Noise Control of Single-Stage Axial Flow Fan with Wave Leading Edge Stator Blade Configurations

This study focuses on a single-stage axial flow fan, investigating the effect of three kinds of wave leading edge stator blades on its noise reduction. The DDES method and the duct acoustic analogy theory based on the penetrable data surface were used for noise prediction. The results showed that the three kinds of wave leading edge blades were effective in reducing the rotor-stator interaction tonal noise and also have a certain inhibitory effect on broadband noise. The A10W15 stator blade can effectively reduce broadband noise in the frequency range of 2200 - 4200 Hz. When the amplitude is increased to 20, the noise reduction effect is further enhanced. However, when the amplitude is increased to 30, the broadband noise reduction effect is no longer significant. Further research shows that the wave leading edge stator blades can significantly change the pressure fluctuation distribution on the leading edge and suction surface, which control the modal energy distribution. Finally, this paper analyzed multiple factors affecting the broadband noise reduction, such as the noise source cut-off and cut-on effect and correlation. The purpose of this paper is to explore the laws of the influence of wave leading edge blades on the duct noise of real fan, and to reveal its noise control mechanism. .

Detecting Icing on the Blades of a Wind Turbine Using a Deep Neural Network

The blades of wind turbines located at high latitudes are often covered with ice in late autumn and winter,where this affects their capacity for power generation as well as their safety.Accurately identifying the icing of the blades of wind turbines in remote areas is thus important,and a general model is needed to this end.This paper proposes a universal model based on a Deep Neural Network(DNN)that uses data from the Supervisory Control and Data Acquisition(SCADA)system.Two datasets from SCADA are first preprocessed through undersampling,that is,they are labeled,normalized,and balanced.The features of icing of the blades of a turbine identified in previous studies are then used to extract training data from the training dataset.A middle feature is proposed to show how a given feature is correlated with icing on the blade.Performance indicators for the model,including a reward function,are also designed to assess its predictive accuracy.Finally,the most suitable model is used to predict the testing data,and values of the reward function and the predictive accuracy of the model are calculated.The proposed method can be used to relate continuously transferred features with a binary status of icing of the blades of the turbine by using variables of the middle feature.The results here show that an integrated indicator systemis superior to a single indicator of accuracy when evaluating the prediction model.

Diagnostic accuracy of the tongue blade test combined with clinical signs to detect maxillary and mandibular fractures in the emergency department

BACKGROUND: To evaluate the diagnostic accuracy of clinical signs combined with the tongue blade test(TBT) to detect maxillary and mandibular fractures.METHODS: A cross-sectional study enrolled patients with maxillary and mandibular injuries in the emergency department. Physical examination and the TBT were performed, followed by radiological imaging(facial X-ray or computed tomography [CT]). The diagnostic accuracy was calculated for individuals and a combination of clinical findings at predicting maxillary and mandibular fractures.RESULTS: A total of 98 patients were identified, of whom 31.6% had maxillary fractures and9.2% had mandibular fractures. The combination of malocclusion, tenderness on palpation and swelling with positive TBT had 100% specificity to detect maxillary and mandibular fractures. In the absence of malocclusion, the combination of tenderness on palpation and swelling with positive TBT produced a specificity of 97.8% for maxillary fracture and a specificity of 96.2% for mandibular fracture. A clinical decision tool consisting of malocclusion, tenderness on palpation, swelling and TBT revealed a specificity of 100% and a positive predictive value of 100%.CONCLUSION: The clinical decision tool is potentially useful to rule out mandibular fractures,thus preventing unnecessary radiation exposure.

大偏航角下基于IPC的风力机变速率停机控制研究

通过分析机组在触发偏航超限停机过程中,叶片在不同方位角下的受力情况,指出大偏航角下叶片受载不均衡是导致轮毂中心出现极限载荷的根源,并研究桨距角与偏航角方向对不均衡受载的影响,在原始控制策略的基础上,引入基于叶轮方位角的独立变桨控制(IPC)变速率停机策略,减小机组在负向大偏航下的气动不平衡,大大降低了轮毂与偏航轴承中心极限载荷,依据IEC标准,并以某7.0 MW海上风力机为研究对象,通过偏航超限工况载荷计算,对比分析发现,基于叶轮方位角IPC变速率停机策略,可减小不平衡推力引入的倾覆弯矩,达到减小机组载荷的目的,为此特定风况下的降载提供了可靠依据。