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Tomography system for measurement of gas properties in combustion flow field

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Chinese Journal of Aeronautics 2017年第5期30卷 1697-1707页

作者： Junling SONG Yanji HONG Mingyuan XIN Guangyu WANG Zhaoran LIU State Key laboratory of Laser propulsion & Application Space Engineering University Beijing 101416 China Science and Technology on Scramjet laboratory Hypervelocity Aerodynamics Institute CARDC Mianyang 621000 China

This paper describes a self-designed fiber-coupled tomography system and its application in combustion diagnostics. The tomographic technique, which combines tunable diode laser spectroscopy and algebraic reconstruction technique, enables the simultaneous reconstruction of temperature and gas concentration with both spatial and temporal resolutions. The system measures a maximum diameter of 35 cm in a circular area with a minimum spatial resolution of 1 mm×1 mm and temporal response of up to 1 kHz. Simulations validate the effects of the beam arrangement and discrete grid on reconstruction accuracy, and give the optimal beam arrangements. Experiments are made to demonstrate the tomography method, and systems are constructed in laboratory and on engineering test benches.

关键词： Absorption Combustion diagnostics Spectroscopy Temperature Tomographic image

SmallSat swarm gravimetry:Revealing the interior structure of asteroids and comets

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Astrodynamics 2021年第3期5卷 217-236页

作者： William Gordon Ledbetter Rohan Sood James Keane Jeffrey Stuart Astrodynamics and space Research laboratory The University of AlabamaTuscaloosaAL 35487USA Jet propulsion laboratory California Institute of TechnologyPasadenaCA 91109USA

A growing interest in small body exploration has motivated research into the rapid char-acterization of near-Earth objects to meet economic or scientific ***,knowledge of the internal density structure can aid with target selection and enables an understanding of prehistoric planetary formation to be *** this end,multi-layer extensions to the polyhedral gravity model are suggested,and an inversion technique is implemented to present their ***-orbit gravity gradiometry is simulated and employed in stochastic and deterministic algorithms,with results that imply robustness in both cases.

关键词： gravimetry asteroid exploration astrodynamics stochastic optimization

Wide-range characteristics of beam perveance and saddle point potential of LIPS-200 ion thruster

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Plasma Science and Technology 2022年第11期24卷 85-92页

作者： Xueer ZHANG Tianping ZHANG Detian LI Juanjuan CHEN Yanhui JIA Science and Technology on Vacuum Technology and Physics laboratory Key Laboratory of Space Electric Propulsion Technology of Gansu ProvinceLanzhou Institute of PhysicsLanzhou 730000People’s Republic of China

Both the long-life and multi-mode versions of LIPS-200 ion thruster are under investigation in LIP(Lanzhou Institute of Physics).To confirm the feasible ranges of the beam current and accel(abbreviation for accelaration)grid potential to apply to the thruster,the wide-range beam perveance(the state of beam focus)and saddle point potential(the lowest potential along beamlet centerline)characteristics of LIPS-200 are studied with a test-verified PIC-MCC(Particle in Cell-Monte Carlo Collisions)*** characteristics are investigated with both the initial and the eroded states of the accel grid aperture *** results show that the feasible ranges of these parameters with respect to perveance/crossover(overfocused)limit extend as the operating time accumulates,while the feasible range of accel grid potential narrows due to a reduced EBSF(electron backstreaming failure)*** feasible ranges determined by the initial condition are:(i)the beam current up to 0.981 A,and(ii)the accel grid potential up to−85 V.A 23%enlargement of the aperture diameter would bring up to 48 V of EBSF margin loss.

关键词： ion thruster perveance limit crossover limit saddle point potential parameter range

Thermal Stress Analysis of Welded Joint in 1420 Al-Li Alloy Induced by Thermal Cycling

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Journal of Materials Science & Technology 2003年第z1期19卷 205-208页

作者： Hongbin GENG Song HE Dezhuang YANG space Materials and Environment Engineering lab. Harbin Institute of Technology Harbin 150001 China Space Materials and Environment Engineering Lab. Harbin Institute of Technology Harbin 150001 China Space Materials and Environment Engineering Lab. Harbin Institute of Technology Harbin 150001 China

A model of double grains under plane stress state has been established. According to the double grain model, thermal stress induced by thermal cycling in welding fusion zone is numerically simulated by finite element method, and the microstructures before and after thermal cycling are observed. The effect of thermal stress on weld microstructure is discussed. Experimental and analysis results show that the difference between the coefficients of thermal expansion and elastic modulus for grains along different crystal directio n can produce alternate thermal misfit stress and strain near boundaries under thermal cycling. At the temperature of upper and lower limit, thermal stress nearby grain boundary reaches maxima. Thermal stress induced changes in microstructure, which expressed by the sending dislocations from boundaries to matrix, piling up against the boundaries and the increasing of dislocation density.

关键词： Thermal cycling, Al-Li alloy, Weld, Microstructure, Finite element method

Online condition diagnosis for a two-stage gearbox machinery of an aerospace utilization system using an ensemble multi-fault features indexing approach

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Chinese Journal of Aeronautics 2019年第5期32卷 1100-1110页

作者： Min ZHOU Ke WANG Yang WANG Kaiji LUO Hongyong FU Liang SI CAS Key lab of space Utilization Technology and Engineering Center for Space Utilization Chinese Academy of Sciences (CAS) University of Chinese Academy of Sciences

China manned space station is designed to operate for over ten years. Long-term and sustainable research on space science and technology will be conducted during its operation. The application payloads must meet the ‘‘long life and high reliability" mission requirement. Gearbox machinery is one of the essential devices in an aerospace utilization system, failure of which may lead to downtime loss even during some disastrous catastrophes. A fault diagnosis of gearbox has attracted attentions for its significance in preventing catastrophic accidents and guaranteeing sufficient maintenance. A novel fault diagnosis method based on the Ensemble Multi-Fault Features Indexing(EMFFI) approach is proposed for the condition monitoring of gearboxes. Different from traditional methods of signal analysis in the one-dimensional space, this study employs a supervised learning method to determine the faults of a gearbox in a two-dimensional space using the classification model established by training the features extracted automatically from diagnostic vibration signals captured. The proposed method mainly includes the following steps. First, the vibration signals are transformed into a bi-spectrum contour map utilizing bi-spectrum technology,which provides a basis for the following image-based feature extraction. Then, Speeded-Up Robustness Feature(SURF) is applied to automatically extract the image feature points of the bi-spectrum contour map using a multi-fault features indexing theory, and the feature dimension is reduced by Linear Discriminant Analysis(LDA). Finally, Random Forest(RF) is introduced to identify the fault types of the gearbox. The test results verify that the proposed method based on the multi-fault features indexing approach achieves the target of high diagnostic accuracy and can serve as a highly effective technique to discover faults in a gearbox machinery such as a two-stage one.

关键词： Aerospace utilization system Condition diagnosis Fault feature index Gearbox machinery Health monitoring Vibration

Numerical study of magnetic reconnection process near interplanetary current sheet

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Chinese Science Bulletin 2001年第2期46卷 111-117页

作者： Fengsi Wei Qiang Hu Xueshang Feng Ctr space Sci & Appl Res Lab Space Weather Beijing 100080 Peoples R China

The third order accurate upwind compact difference scheme has been applied to the numerical study of the magnetic reconnection process possibly occurring near the interplanetary current sheet, under the framework of the two-dimensional compressible magnetohydrodynamics (MHD). Our results here show that the driven reconnection near the current sheet can occur within 10-30 min for the interplanetary high magnetic Reynolds number, RM =2 000-10 000, the stable magnetic reconnection structure can be formed in hour-order of magnitude, and there are some basic properties such as the multiple X-line reconnections, vortical velocity structures, filament current systems, splitting and collapse of the high-density plasma bulk. These results are helpful in understanding and identifying the magnetic reconnection phenomena near the interplanetary current sheets.

关键词： interplanetary space current sheet magnetic recon-nection numerical simulation.

Long-term Integration Ability of the Submillimeter Wave Astronomy Satellite(SWAS)Spectral Line Receivers

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Research in Astronomy and Astrophysics 2024年第6期24卷 315-322页

作者： Bing-Ru Wang Di Li Paul F.Goldsmith Jingwen Wu Chao-Wei Tsai Rudolf Schieder Gary J.Melnick National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China Research Center for Astronomical Computing Zhejiang LaboratoryHangzhou 311100China Jet propulsion laboratory California Institute of TechnologyPasadenaCA 91109USA Institute for Frontiers in Astronomy and Astrophysics Beijing Normal UniversityBeijing 102206China KOSMA I.Physik.InstitutUniversität zu KölnZülpicher Str.7750937 KölnGermany Center for Astrophysics|Harvard&Smithsonian 60 Garden StreetMS 66CambridgeMA 02138USA

The Submillimeter Wave Astronomy Satellite(SWAS)was the first space telescope capable of high spectral resolution observations of terahertz spectral *** have investigated the integration ability of its two receivers and spectrometer during five and a half years of on-orbit *** CI,O_(2),H_(2)O,and^(13)CO spectra taken toward all observed Galactic sources were *** present results are based on spectra with a total integration time of up to 2.72×10~4hr(■10~8s).The noise in the spectra is generally consistent with that expected from the radiometer equation,without any sign of approaching a noise *** noise performance reflects the extremely stable performance of the passively cooled front end as well as other relevant components in the SWAS instrument throughout its mission lifetime.

关键词： telescopes space vehicles:instruments instrumentation:miscellaneous ISM:lines and bands

Phase shift effects of radio-frequency bias on ion energy distribution in continuous wave and pulse modulated inductively coupled plasmas

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Chinese Physics B 2018年第4期27卷 346-351页

作者： Chan Xue Fei Gao Yong-Xin Liu Jia Liu You-Nian Wang Key laboratory of Materials Modification by Laser Ion and Electron Beams (Ministry of Education) School of Physics Dalian University of Technology Dalian 116024 China Shanghai Institute of space propulsion Shanghai 201112 China

A retarding field energy analyzer（RFEA） is used to measure the time-averaged ion energy distributions（IEDs） on the substrate in both continuous wave（CW） and synchronous pulse modulated radio-frequency（RF） inductively coupled Ar plasmas（ICPs）.The effects of the phase shift θ between the RF bias voltage and the RF source on the IED is investigated under various discharge *** is found that as θ increases from 0 to π,the IED moves towards the low-energy side,and its energy width becomes *** order to figure out the physical mechanism,the voltage waveforms on the substrate are also *** results show that as θ increases from 0 to π,the amplitude of the voltage waveform decreases and,meanwhile,the average sheath potential decreases as ***,the potential drop in the sheath on the substrate exhibits a maximum value at the same phase（i.e.,θ = 0） and a minimum value at the opposite phase（i.e.,θ = π）.Therefore,when ions traverse across the sheath region above the substrate,they obtain less energies at lower sheath potential drop,leading to lower ion ***,as θ increases from π to 2π,the IEDs and their energy widths change reversely.

关键词： ion energy distribution phase shift synchronous pulse modulated inductively coupled plasmas

Data-driven surrogate model for aerodynamic design using separable shape tensor method

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CHINESE JOURNAL OF AERONAUTICS 2024年第9期37卷 41-58页

作者： Pang, Bo Zhang, Yang Li, Junlin Wang, Xudong Chang, Min Bai, Junqiang Xi An Jiao Tong Univ State Key Lab Strength & Vibrat Mech Struct Xian 710049 Peoples R China Northwestern Polytech Univ Unmanned Syst Res Inst Xian 710072 Peoples R China

In the context of increasing dimensionality of design variables and the complexity of constraints, the efficacy of Surrogate-Based Optimization (SBO) is limited. The traditional linear and nonlinear dimensionality reduction algorithms are mainly to decompose the mathematical matrix composed of design variables or objective functions in various forms, the smoothness of the design space cannot be guaranteed in the process, and additional constraint functions need to be added in the optimization, which increases the calculation cost. This study presents a new parameterization method to improve both problems of SBO. The new parameterization is addressed by decoupling affine transformations (dilation, rotation, shearing, and translation) within the Grassmannian submanifold, which enables a separate representation of the physical information of the airfoil in a highdimensional space. Building upon this, Principal Geodesic Analysis (PGA) is employed to achieve geometric control, compress the design space, reduce the number of design variables, reduce the dimensions of design variables and enhance predictive performance during the surrogate optimization process. For comparison, a dimensionality reduction space is defined using 95% of the energy, and RAE 2822 for transonic conditions are used as demonstrations. This method significantly enhances the optimization efficiency of the surrogate model while effectively enabling geometric constraints. In three-dimensional problems, it enables simultaneous design of planar shapes for various components of the aircraft and high-order perturbation deformations. Optimization was applied to the ONERA M6 wing, achieving a lift-drag ratio of 18.09, representing a 27.25% improvement compared to the baseline configuration. In comparison to conventional surrogate model optimization methods, which only achieved a 17.97% improvement, this approach demonstrates its superiority. (c) 2024 Production and hosting by Elsevier Ltd. on behalf of Chine

关键词： Aerodynamic design Grassmannian manifold Shape parameterization Surrogate-based optimization Data dimensionality reduction WING DESIGN OPTIMIZATION