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Time-delay effect and design of closed-loop control system of circulation control airfoil

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Chinese Journal of Aeronautics 2024年第10期37卷 50-67页

作者： Lingxiao Li Heyong XU Zheng xiNG Abdul Samad KHAN School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China National Key Laboratory of Aircraft Configuration Design Xi’an 710072China

In this paper,unsteady numerical simulation of jet Circulation Control(CC)is carried out with the NACA0012-CC airfoil as the research *** dynamic process from the opening of jet slot and adjustment of jet intensity to the stable state of jet control effect is *** time-delay effect and flow mechanism of jet are *** mechanism of jet momentum coefficient and moment coefficient fluctuating with time is *** fluctuation of jet momentum coefficient is caused by the change of the pressure coefficient distribution on the Coanda surface or the structure of the wave system inside the jet,and the oscillation frequency of the wave system structure of the under-expansion supersonic jet reaches 1481 Hz at the opening *** on the aerodynamic model and Proportional-Integral-Derivative(PID)control theory,the closed-loop control system of CC airfoil is *** parameters of PID control system are adjusted by the Genetic Algorithm(GA),which significantly improves the response ability of the control system to step,ramp and sine signals,and improves the dynamic performance of the *** at the special time-delay effect of jet control,Long Short-Term Memory(LSTM)neural network module is added to the control system to predict the target input signal,which strengthens the prediction ability of GA-PID control system to the target signal at the next time *** using LSTM neural network correction,the control hysteresis caused by jet time-delay effect is alleviated,and the response ability of the control system is effectively ***,the designed LSTM-GA-PID control system is applied to the NACA0012-CC airfoil for the pitch control simulation *** test results show that the control system designed in this paper has good dynamic performance and can respond quickly and accurately to complex input signals,which confirms the effectiveness of the control system.

关键词： Circulation control Unsteady numerical simulation Time-delay effect Control system Long short-term memory

Construction of smart propellant with multi-morphologies

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Defence Technology（防务技术） 2024年第3期33卷 180-185页

作者： Weitao Yang Yuchen Gao Rui Hu Manman Li Fengqi Zhao He Jiang Xuan Zhang xi’an Modern Chemistry Research Institute Xi’an710065China Northwestern Polytechnical University Xi’an710072China

Smart materials,which exhibit shape memory behavior in response to external stimuli,have shown great potential for use in biomedical *** this study,an energetic composite was fabricated using a UV-assisted DIW 3D printing technique and a shape memory material(SMP)as the *** composite has the ability to reduce the impact of external factors and adjust gun propellant combustion *** composition and 3D printing process were delineated,while the internal structure and shape memory performance of the composite material were *** energetic SMP composite exhibits an angle of reversal of 18 s at 70°,with a maximum elongation typically reaching up to 280% of the original length and a recovery length of approximately 105%during ten ***,thermal decomposition and combustion behavior were also demonstrated for the energetic SMP composite.

关键词： Smart material Gun propellants Multi-morphologies Self-regulation

A novel subset assignment and matching method for DIC measurement of complex deformation in aircraft braking process

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Chinese Journal of Aeronautics 2024年第8期37卷 373-387页

作者： xin SHI xiang GUO Tao SUO Yingtao YUAN Hongli HE Zhiyong REN School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China International Research Laboratory of Impact Dynamics and its Engineering Application Xi’an 710072China Institute of Extreme Mechanics Northwestern Polytechnical UniversityXi’an 710072China Chinese Flight Test Establishment Xi’an 710089China

This paper proposes a measurement method related to the braking deformation of a complex *** the braking process,the deformation of the wheel includes large amounts of movement,vibration,warping,and distortion.A novel subset assignment and correlation method is proposed to measure the complex *** proposed method can greatly improve the accuracy and stability of the calculation of complex deformations by simplifying the complex deformation into translational deformations in logarithmic coordinate *** to the simulation and actual experiments,the proposed method can be utilized to measure the deformations of up to 100%tensile strain under complex *** to the accuracy verification experiment,the error of the proposed method is less than 50 *** results show that the proposed method can effectively carry out structural deformation measurement in the complex motion and deformation *** proposed method has great significance for structural performance analysis and optimization design considering complex motion and deformation.

关键词： Complex deformation Measurement Digital image correlation Aircraft braking Deformation field

Inverse aerodynamic design for distributed propulsion wing with expected circulation distribution

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Chinese Journal of Aeronautics 2024年第9期37卷 206-223页

作者： Pengbo SUN Zhou ZHOU Xu LI Kelei WANG School of Aeronautics Northwestern Polytechnical UniversityXi'an 710072China

Distributed Propulsion Wing(DPW)technology offers significant advantages in terms of flight energy savings,but the strong aerodynamic coupling between the propulsive internal flow and aerodynamic external flow brings significant design *** the primary DPW profile design is of great significance,this paper proposes a hybrid method to solve the inverse problem mainly based on the formula relationship between the required aerodynamic loads and the profile shape,which is more direct and instructive compared with traditional parametric iterative *** aerodynamic characteristics are described by the circulation distribution in the Fourier series form,then the mean camber line of the profile is solved through the re-derived airfoil theory considering disk's *** CFD correction methods are also *** validate the effectiveness and feasibility of the proposed hybrid inverse method,several DPW profile design tests are then ***,the relationship between 2D and realistic 3D unit shape is also *** results show that the proposed inverse design method has great accuracy and convergence speed in the design tests,and shows good robustness against changes of the design *** 2D profile shape and the actual 3D shape of DPW unit can establish an aerodynamic-propulsion equivalent relationship based on the same internal mass fluxes.

关键词： Propulsion Inverse problem Aerodynamic load Fourier series Flux

Effects of layer interactions on instantaneous stability of finite Stokes flows

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Applied Mathematics and Mechanics(English Edition) 2024年第1期45卷 69-84页

作者： Chen ZHAO Zhenli CHEN C.T.MUTASA Dong LI School of Aeronautics Northwestern Polytechnical UniversityXi'an 710072China

The stability analysis of a finite Stokes layer is of practical importance in flow control. In the present work, the instantaneous stability of a finite Stokes layer with layer interactions is studied via a linear stability analysis of the frozen phases of the base flow. The oscillations of two plates can have different velocity amplitudes, initial phases, and frequencies. The effects of the Stokes-layer interactions on the stability when two plates oscillate synchronously are analyzed. The growth rates of two most unstable modes when δ 0.68. However, the interactions always have a stabilizing effect on the other unstable mode. It is explained that one of the two unstable modes has much higher dissipation than the other one when the Stokes-layer interactions are strong. We also find that the stability of the Stokes layer is closely related to the inflectional points of the base-flow velocity profile. The effects of inconsistent velocity-amplitude, initial phase, and frequency of the oscillations on the stability are analyzed. The energy of the most unstable eigenvector is mainly distributed near the plate of higher velocity amplitude or higher oscillation frequency. The effects of the initial phase difference are complicated because the base-flow velocity is extremely sensitive to the initial phase.

关键词： finite Stokes layer instantaneous stability Stokes-layer interaction asynchronous oscillation

Optimal structural design for a certain near-space composite propeller of airship using adaptive region division blending model

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Chinese Journal of Aeronautics 2024年第5期37卷 301-316页

作者： Weigang AN Tianyu LIN Shigen WANG School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China

Near-space airship is a frontier and hotspot in current military research and development,and the near-space composite propeller is the key technology for its *** order to obtain higher aerodynamic efficiency at an altitude of 22 km,a certain near-space composite propeller is designed as a long and slender aerodynamic shape with a 10 m diameter,which brings many challenges to the composite structure *** initial design is obtained by the composite structure variable stiffness design method using based on fixed region division blending ***,it weighs 23.142 kg,exceeding the required 20 *** order to meet the structural design requirements of the propeller,a variable stiffness design method using the adaptive region division blending model is proposed in this *** with the methods using the fixed region division blending model,this method optimizes region division,stacking thickness and stacking sequence in a single level,considering the coupling effect among *** a more refined region division,this method can provide a more optimal design for composite tapered ***,to improve the efficiency of optimization subjected to manufacturing constraints,a hierarchical penalty function is proposed to quickly filter out the solutions that do not meet manufacturing *** above methods combined with a Genetic Algorithm(GA)using specific encoding are adopted to optimize the near-space composite *** optimal design of the structure weighs 18.831 kg,with all manufacturing constraints and all structural response constraints being *** with the initial design,the optimal design has a more refined region division,and achieves a weight reduction of 18.6%.This demonstrates that a refined region division can significantly improve the mechanical performance of the composite tapered structure.

关键词： Structural optimization Composite tapered structure Genetic algorithm Adaptive region division Manufacturing constraint Near-space composite propeller

Effect of hot isostatic pressure on the microstructure and tensile properties of γ'-strengthened superalloy fabricated through induction-assisted directed energy deposition

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International Journal of Minerals,Metallurgy and Materials 2024年第5期31卷 1089-1097页

作者： Jianjun Xu Hanlin Ding xin Lin Feng Liu Analytical&Testing Center Northwestern Polytechnical UniversityXi’an 710072China State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China

The microstructure characteristics and strengthening mechanism of Inconel738LC(IN-738LC) alloy prepared by using induction-assisted directed energy deposition(IDED) were elucidated through the investigation of samples subjected to IDED under 1050℃ preheating with and without hot isostatic pressing(HIP,1190℃,105 MPa,and 3 h).Results show that the as-deposited sample mainly consisted of epitaxial columnar crystals and inhomogeneously distributed γ’ phases in interdendritic and dendritic core *** HIP,grain morphology changed negligibly,whereas the size of the γ’ phase became increasingly *** further heat treatment(HT,1070℃,2 h + 845℃,24 h),the γ’ phase in the as-deposited and HIPed samples presented a bimodal size distribution,whereas that in the as-deposited sample showed a size that remained *** comparison of tensile properties revealed that the tensile strength and uniform elongation of the HIP + HTed sample increased by 5% and 46%,respectively,due to the synergistic deformation of bimodal γ’phases,especially large cubic γ’ ***,the relationship between phase transformations and plastic deformations in the IDEDed sample was discussed on the basis of generalized stability theory in terms of the trade-off between thermodynamics and kinetics.

关键词： directed energy deposition Ni-based superalloys high-temperature preheating hot isostatic pressing microstructure tensile properties

Thermo-kinetic characteristics on stabilizing hetero-phase interface of metal matrix composites by crystal plasticity finite element method

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Journal of Materials Science & Technology 2024年第2期169卷 53-67页

作者： Y.B.Zhang S.J.Song F.Liu State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China Analytical&Testing Center Northwestern Polytechnical UniversityXi’an 710072China

Using dislocation-based constitutive modeling in three-dimension crystal plasticity finite element(3D CPFE)simulations,co-deformation and instability of hetero-phase interface in different material systems were herein studied for polycrystalline metal matrix composites(MMCs).Local stress and strain fields in two types of 3layer MMCs such as fcc/fcc Cu-Ag and fcc/bcc Cu-Nb have been predicted under simple compressive ***,more severe strain-induced interface instability can be observed in the fcc/bcc systems than in the fcc/fcc systems upon refining to metallic nanolayered composites(MNCs).By detailed analysis of stress and strain localization,it has been demonstrated that the interface instability is always accompanied by high-stress concentration,i.e.,thermodynamic characteristics,or high strain prevention i.e.,kinetic characteristics,at the hetero-phase *** then follows that the thermodynamic driving forceG and the kinetic energy barrier Q during dislocation and shear banding can be adopted to classify the deformation modes,following the so-called thermo-kinetic *** by inserting a high density of high-energy interfaces into the Cu-Nb composites,such thermo-kinetic integration at the hetero-phase interface allows a successful establishment of MMCs with the high△G-high Q deformation mode,which ensures high hardening and uniform strain distri-bution,thus efficiently suppressing the shear band,stabilizing the hetero-phase interface,and obtaining an exceptional combination in strength and *** hetero-phase interface chosen by a couple of thermodynamics and kinetics can be defined as breaking the thermo-kinetic correlation and has been proposed for artificially designing MNCs.

关键词： Thermodynamics and kinetics Physics-based constitutive modeling Hetero-phase interface Crystal plasticity finite element

Novel data-driven sparse polynomial chaos and analysis of covariance for aerodynamics of compressor cascades with dependent geometric uncertainties

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Chinese Journal of Aeronautics 2024年第6期37卷 89-108页

作者： Zhengtao GUO Wuli CHU Haoguang ZHANG Tianyuan JI School of Power and Energy Northwestern Polytechnical UniversityXi’an 710072China

Polynomial Chaos Expansion(PCE)has gained significant popularity among engineers across various engineering disciplines for uncertainty ***,traditional PCE suffers from two major ***,the orthogonality of polynomial basis functions holds only for independent input variables,limiting the model’s ability to propagate uncertainty in dependent ***,PCE encounters the"curse of dimensionality"due to the high computational cost of training the model with numerous polynomial *** practical manufacturing,compressor blades are subject to machining precision limitations,leading to deviations from their ideal geometric *** deviations require a large number of geometric parameters to describe,and exhibit significant *** efficiently quantify the impact of high-dimensional dependent geometric deviations on the aerodynamic performance of compressor blades,this paper firstly introduces a novel approach called Data-driven Sparse PCE(DSPCE).The proposed method addresses the aforementioned challenges by employing a decorrelation algorithm to directly create multivariate basis functions,accommodating both independent and dependent random ***,the method utilizes an iterative Diffeomorphic Modulation under Observable Response Preserving Homotopy regression algorithm to solve the unknown coefficients,achieving model sparsity while maintaining fitting ***,the study investigates the simultaneous effects of seven dependent geometric deviations on the aerodynamics of a high subsonic compressor cascade by using the DSPCE method proposed and sensitivity analysis of *** joint distribution of the dependent geometric deviations is determined using Quantile-Quantile plots and normal copula functions based on finite measurement *** results demonstrate that the correlations between geometric deviations significantly impact the variance of aerodynamic performance and the flow ***,

关键词： Data-driven sparse polyno-mial chaos Analysis of covariance Dependent uncertainty Aerodynamic performance Compressor cascade