Nanjing University Of Aeronautics And Astronautics Research Articles

Hydrovoltaics brings a new solution in alternative energy: an interview with Prof. Wanlin Guo.

The Water Hub Project at the Three Gorges, also known as the 'Sanxia Project', now provides more than 1 billion kilowatt-hours of electricity daily to 10 provinces in eastern China. Facing rising energy demands and climate change, despite being the largest hydroelectric power station in the world, this project may still not live up to the vision of the inventor of hydroelectric power, Nikola Tesla, when he said: 'Electric power is everywhere present in unlimited quantities and can drive the world's machinery without the need of common fuels.' Hydrovoltaic technology, invented by Prof. Wanlin Guo of Nanjing University of Aeronautics and Astronautics (NUAA), aims to generate electricity through processes such as evaporation and the motion of water droplets on synthetic nanomaterials. National Science Review recently invited Prof. Guo for an in-depth interview to discuss this exciting new technology and how it may represent the next great opportunity to transition from fossil fuels to renewable energy sources.

Preface

The 2021 International Conference on Information Technology and Intelligent Control (CITIC 2021) was held on 23-25 July 2021 as a virtual conference due to the growing concerns over the coronavirus outbreak (COVID-19), and in order to protect the well-being of our attendees, partners, and staff as our number one priority. With the rapid progress of informatization globally, the world's demand for information multiplies, and information technology has become the cornerstone of economic activities and social life. With the development of information technology, intelligent control methods and technologies have gradually updated and grown. Intelligent control has rapidly moved to various professional fields and applied to different complex controlled objects' control problems.CITIC 2021 is an international forum for scientists, engineers, and practitioners to present their latest research and development results in all areas of Information Technology and Intelligent Control. Conference topics mainly include but are not limited to the Application of Information Technology; Artificial Intelligence; Programming Languages; Digital Devices and Computer Components; Health and Medical Science and Technology; GIS; Data Mining and Data Warehousing; Intelligent system. CITIC 2021 welcomes all high-quality research papers and presentations from related research fields.This scientific event brings together more than 200 national and international researchers in Information Technology and Intelligent Control. On top of the local participants coming from different national universities, international participants are also registered from different countries, namely Singapore, Australia, and USA. During the conference, the conference model was divided into three sessions, including oral presentations, keynote speeches, and online Q&A discussion. In the first part, some scholars, whose submissions were selected as the excellent papers, were given about 5-10 minutes to perform their oral presentations one by one. Then in the second part, keynote speakers were each allocated 30-45 minutes to hold their speeches.In the second part, we invited five professors as our keynote speakers. Prof. Hui Bi, Nanjing University of Aeronautics and Astronautics (NUAA), China performed a speech: Sparse SAR Imaging: From Theory to Practical Application. And then we had Prof. Weinan Gao, from Florida Institute of Technology, USA. He presented an insightful speech: Learning-Based Adaptive Optimal Control and Applications to Connected and Autonomous Vehicles. Prof. Bingkun Bao, from Nanjing University of Posts and Telecommunications. She delivered a wonderful speech: Analysis and Perception of Multimedia Data. Prof. Farhad Shahnia, from Murdoch University, Australia, performed a speech: Recent and Future Research on Microgrid Clusters. Prof. Zhihong Man, as our finale keynote speaker, from Swinburne University of Technology, Australia. He delivered a wonderful speech: A new theoretical framework of parameter estimation of linear systems. Their insightful speeches had triggered heated discussion in the third session of the conference. Every participant praised this conference for disseminating useful and insightful knowledge.The proceedings are a compilation of the accepted papers and represent an interesting outcome of the conference. Topics include but are not limited to the following areas: Aerospace Technology, Automation technology and equipment, Data Mining and Data Warehousing, Information Systems, Robotics and more related topics. All the papers have been through rigorous review and process to meet the requirements of International publication standard.We would like to acknowledge all of those who supported CITIC 2021. The help and contribution of each individual and institution was instrumental in the success of the conference. In particular, we would like to thank the organizing committee for its valuable inputs in shaping the conference program and reviewing the submitted papers.List of titles Committee member, TPC Chair, Publication Chair, Organizing Committee, International Technical Program Committee are available in this Pdf.

Hydrovoltaic Energy on the Way

Jun Yin obtained his PhD from Nanjing University of Aeronautics and Astronautics (NUAA) in 2016, after which he worked in the University of Manchester as a research associate for 3 years. Then, he joined NUAA in 2019 as a professor. His research focuses on surface/interface interaction of nanomaterials and their applications. Jianxin Zhou is an associate professor of mechanics at NUAA. He obtained his PhD (2007) in condensed matter physics from Nanjing University. His research focuses on the utilization of energy conversion and energy transfer properties of low-dimensional materials. His research interests also include fabrication, assembly, and microscopic characterization of nanosized structures for sensing and energy applications. Sunmiao Fang received his BS in College of Science from NUAA in 2013. He is currently a PhD candidate in Nanomechanics at Institute of Nanoscience, NUAA. His main research interests focus on functional materials associated with charge transport and energy conversion. Wanlin Guo obtained his PhD from Northwestern Polytechnical University in 1991, and in 2017 he was elected as an academician of the Chinese Academy of Science. He is a Chair Professor at NUAA and the founding director of the Key Laboratory of Intelligent Nano Materials and Devices of Ministry of Education. His research focuses on intelligent nano materials and devices, novel conception and technology for efficient energy conversion, molecular physical mechanics for neuronal signaling and molecular biomimics, as well as strength and safety of aircraft and engine.

Wind load and wind-induced effect of the large wind turbine tower-blade system considering blade yaw and interference

The yaw and interference effects of blades affect aerodynamic performance of large wind turbine system significantly, thus influencing wind-induced response and stability performance of the tower-blade system. In this study, the 5MW wind turbine which was developed by Nanjing University of Aeronautics and Astronautics (NUAA) was chosen as the research object. Large eddy simulation on flow field and aerodynamics of its wind turbine system with different yaw angles (0, 5, 10,20, 30 and 45) under the most unfavorable blade position was carried out. Results were compared with codes and measurement results at home and abroad, which verified validity of large eddy simulation. On this basis, effects of yaw angle on average wind pressure, fluctuating wind pressure, lift coefficient, resistance coefficient, streaming and wake characteristics on different interference zone of tower of wind turbine were analyzed. Next, the blade-cabin-tower-foundation integrated coupling model of the large wind turbine was constructed based on finite element method. Dynamic characteristics, wind-induced response and stability performance of the wind turbine structural system under different yaw angle were analyzed systematically. Research results demonstrate that with the increase of yaw angle, the maximum negative pressure and extreme negative pressure of the significant interference zone of the tower present a V-shaped variation trend, whereas the layer resistance coefficient increases gradually. By contrast, the maximum negative pressure, extreme negative pressure and layer resistance coefficient of the non-interference zone remain basically same. Effects of streaming and wake weaken gradually. When the yaw angle increases to 45, aerodynamic force of the tower is close with that when there\' s no blade yaw and interference. As the height of significant interference zone increases, layer resistance coefficient decreases firstly and then increases under different yaw angles. Maximum means and mean square error (MSE) of radial displacement under different yaw angles all occur at circumferential 0 and 180 of the tower. The maximum bending moment at tower bottom is at circumferential 20. When the yaw angle is 0, the maximum downwind displacement responses of different blades are higher than 2.7 m. With the increase of yaw angle, MSEs of radial displacement at tower top, downwind displacement of blades, internal force at blade roots all decrease gradually, while the critical wind speed decreases firstly and then increases and finally decreases. The comprehensive analysis shows that the worst aerodynamic performance and wind-induced response of the wind turbine system are achieved when the yaw angle is 0, whereas the worst stability performance and ultimate bearing capacity are achieved when the yaw angle is 45.

Aerodynamic performance and wind-induced effect of large-scale wind turbine system under yaw and wind-rain combination action

Blade yaw will change aerodynamic performance of large-scale wind turbine structure, especially under rainstorm conditions. Structural responses and stability of large-scale wind turbine system during rainstorm are more complicated due to the impact force of rainstorm on the structural surface and its influences on the incoming turbulence. In this study, the 5 MW wind turbine tower-blade system which was developed by Nanjing University of Aeronautics and Astronautics (NUAA) was used as the research object. Firstly, the surrounding wind field of the 5 MW wind turbine tower-blade system under different yaw angles (0°, 5°, 10°, 20°, 30° and 45°) was simulated by the computational fluid dynamics (CFD) technology based on the wind-rain two-way coupling algorithm. Secondly, the wind-rain coupling synchronous iteration was carried out by adding the discrete phase model (DPM). Based on numerical simulation results, the influencing law of yaw angle on wind-driven rainfall, additional acting force of raindrops and rain-induced pressure coefficient was discussed. The velocity flow line, turbulence energy strength, raindrop running speed and trajectory action mechanism on the structural surface in wind-rain coupling field was disclosed. Moreover, the distribution laws and fitting formula of wind-rain equivalent pressure coefficient under different yaw angles were constructed. Finally, large-scale wind turbine tower-blade coupling model under different yaw angles was constructed by combining the finite element method. Structural responses, buckling stability and ultimate bearing capacity of the large-scale wind turbine system with considerations to different yaw angles under wind condition and wind-rain condition were discussed. Results demonstrated that yaw angle can affect aerodynamic force and comprehensive stress performance of the wind turbine system significantly. The wind-rain load enhances structural responses of the system, and decreases the overall buckling stability and ultimate bearing capacity of the wind turbine. Main conclusions not only can provide references for accurate load evaluation under extreme complex conditions, but also are conducive to deepen understandings on the action mechanism of wind-rain load.

Tuning the energy gap of bilayer α-graphyne by applying strain and electric field**Project supported by the National Key Basic Research Program of China (Grant Nos. 2013CB932604 and 2012CB933403), the National Natural Science Foundation of China (Grant Nos. 51472117 and 51535005), the Research Fund of State Key Laboratory of Mechanics and Control of Mechanical Structures, China (Grant No. 0414K01), the Nanjing

Our density functional theory calculations show that the energy gap of bilayer α-graphyne can be modulated by a vertically applied electric field and interlayer strain. Like bilayer graphene, the bilayer α-graphyne has electronic properties that are hardly changed under purely mechanical strain, while an external electric field can open the gap up to 120 meV. It is of special interest that compressive strain can further enlarge the field induced gap up to 160 meV, while tensile strain reduces the gap. We attribute the gap variation to the novel interlayer charge redistribution between bilayer α-graphynes. These findings shed light on the modulation of Dirac cone structures and potential applications of graphyne in mechanical-electric devices.

Design Work of a Compressor Stage Through High-To-Low Speed Compressor Transformation

Low-speed model testing has advantages such as great accuracy and low cost and risk, so it is widely used in the design procedure of the high pressure compressor (HPC) exit stage. The low-speed model testing project is conducted in Nanjing University of Aeronautics and Astronautics (NUAA) to represent aerodynamic load and flow field structure of the seventh stage of a high-performance ten-stage high-pressure compressor. This paper outlines the design work of the low speed four-stage axial compressor, the third stage of which is the testing stage. The first two stages and the last stage provide the compressor with entrance and exit conditions, respectively. The high-to-low speed transformation process involves both geometric and aerodynamic considerations. Accurate similarities demand the same Mach number and Reynolds number, which will not be maintained due to motor power/size and its low-speed feature. Compromises of constraints are obvious. Modeling principles are presented in high-to-low speed transformation. Design work was carried out based on these principles. Four main procedures were conducted successively in the general design, including establishment of low-speed modeling target, global parameter design of modeling stage, throughflow aerodynamic design, and blading design. In global parameter design procedure, rotational speed, shroud diameter, hub-tip ratio, midspan chord, and axial spacing between stages were determined by geometrical modeling principles. During the throughflow design process, radial distributions of aerodynamic parameters such as D-factor, pressure-rise coefficient, loss coefficients, stage reaction, and other parameters were obtained by determined aerodynamic modeling principles. Finally, rotor and stator blade profiles of the low speed research compressor (LSRC) at seven span locations were adjusted to make sure that blade surface pressure coefficients agree well with that of the HPC. Three-dimensional flow calculations were performed on the low-speed four-stage axial compressor, and the resultant flow field structures agree well with that of the HPC. It is worth noting that a large separation zone appears in both suction surfaces of LSRC and HPC. How to diminish it through 3D blading design in the LSRC test rig is our further work.

Comparison of Nondestructive Testing Methods on Detection of Delaminations in Composites

Delamination is one of the most common defects in carbon fibre reinforced plastic (CFRP) components, such as those used in aircraft and wind turbine blades. To detect delaminations, different NDT methods such as ultrasonic (UT), eddy current (EC) scanning, flash thermography, and recent developed pulsed-eddy-current-(PEC-) simulated thermography are conducted for comparison and evaluation of the new developed PEC thermography system at Nanjing University of Aeronautics and Astronautics (NUAA), China through UK-China collaboration. A PEC-stimulated thermography system is built at NUAA, extended from previous joint work between Newcastle and Bath Universities. Using these NDT systems, man-made, dedicated delaminations with varied diameters and depths are investigated and studied. Through this comparison, PEC-stumilated and flash thermography show relatively good indications of the shape of delaminations. The joint studies also show that PEC-stimulated thermography has unique advantage for fibre orientation evaluation.

Design of Flight Control System for a Small Unmanned Tilt Rotor Aircraft

A tilt rotor is an aircraft of a special kind, which possesses the characteristics of a helicopter and a fixed-wing airplane. However, there are a great number of important technical problems waiting for settlements. Of them, the flight control system might be a critical one. This article presents the progresses of the research work on the design of flight control system at Nanjing University of Aeronautics and Astronautics (NUAA). The flight control law of the tilt rotor aircraft is designed with the help of an inner/outer loop control structure and an eigenstructure assignment algorithm on the basis of a proper mathematical model already verified by the wind tunnel tests. The proposed control law has been born out through the construction of the flight control system and the flight tests. Now, the flight tests are still underway on a prototype of small unmanned tilt rotor aircraft. The results have evidenced the credibility of the aircraft design and the effectiveness of the flight control system for the tilt rotor working in the helicopter mode. A full envelope flight test is planned to carry out further researches on the flight control law.

Recent Progress on Distributed Structural Health Monitoring Research at NUAA

This study introduces recent research advances on the structural health monitoring (SHM) at Nanjing University of Aeronautics and Astronautics (NUAA). Distributed SHM technology for large-scale engineering structures is discussed. First, a hybrid wing box health monitoring evaluation system is presented. This evaluation system is developed to verify the piezoelectric sensor array-based active Lamb wave diagnostic method and the fiber Bragg grating sensor-based structural strain monitoring method. Second, distributed health monitoring technology based on the multi-agent system (MAS) technology is discussed. This research includes the individual agent design, the MAS-based SHM system architecture design, and three important aspects in designing the MAS-based SHM system. An evaluation case is presented in detail to show the advantages of the MAS-based SHM system. Finally, the study illustrates the motivation of the agents realized by a wireless sensor network. The developed wireless sensor nodes are also described.

Unsteady Rolling Moment Characteristics for a Fighter Oscillating with Yawing-Rolling Coupled Motion

T HE maneuvering flight of an aircraft is very complicated. It usually consists of coupled motions about three body axes; therefore, it is very important to simulate maneuvering flight and measure the unsteady aerodynamics in the wind tunnel. Simple flight maneuvers such as the cobra maneuver [1] and the wing rock can be simulated easily, and tests have been conducted in many wind tunnels [2,3]. However, for the complicated flight maneuvers, such as theHerbstmaneuver [4], there is a yawing–rolling coupledmotion about the body axes when the aircraft encounters high angles of attack. Up to now, the wind-tunnel test data for such complicated coupled motions are very few. The method of the linear superposition is usually used to calculate the unsteady forces and moments of coupled motion to analyze the maneuvering characteristics of the aircraft. The linear superposition model is suitable at low angles of attack, but whether it is suitable at high angles of attack is still not clear. In [5], Zhongjun and Edward adopted the quasi-steady aerodynamic model and the unsteady aerodynamic model to simulate the coupled motion of the aircraft. The results of the two methods are very different. In this investigation, an aircraft configuration with a strake wing was tested in a 3-m low-speedwind tunnel at NanjingUniversity ofAeronautics and Astronautics (NUAA) with large amplitude oscillation. The unsteadiness of the rolling moment as the model oscillates in a yawing–rolling coupled motion is compared with that of in pure yawing motion and rolling motion. The lateral dynamic derivatives were obtained using a mathematical model with the fuzzy logic algorithm and the dynamic derivative simulation. The unsteady rolling moment for the yawing–rolling coupledmotion was obtained by using the quasi-steady aerodynamic model or the unsteady aerodynamic model, respectively, and the results are compared with the experimental data. It is shown that the wind-tunnel tests can provide better results for the unsteady aerodynamics of coupled motion at large angles of attack.