Chinese Journal of Aeronautics最新文献

{"title":"Design optimization of a hexapod vibration isolation system for electro-optical payload","authors":"Jing LI,&nbsp;Weipeng LI,&nbsp;Xiaoyan ZHANG,&nbsp;Hai HUANG","doi":"10.1016/j.cja.2023.12.003","DOIUrl":"10.1016/j.cja.2023.12.003","url":null,"abstract":"<div><p>The electro-optical payloads on mobile platforms generally suffer undesirable vibrations generated by maneuvers and turbulence. These vibrations are in six degrees of freedom and cause line-of-sight jitters, resulting in image blurring and loss of tracking accuracy. In this paper, a Hexapod Vibration Isolation System (HVIS) is proposed and optimized to solve this problem. The optimization aims to centralize and minimize the natural frequencies of HVIS, for expanding the vibration isolation bandwidth and improving the vibration isolation in the higher frequency band. Considering that the design space for HVIS is limited and interfered with the frames of the mobile platform, a non-collision algorithm is proposed and applied in the optimization to obtain the feasible optimal design. The optimization result shows that the natural frequency bandwidth has been reduced by 42.9 %, and the maximum natural frequency is reduced by 30.2 %. The prototypes of initial and optimal designs are manufactured and tested. Both simulated and experimental results demonstrate the validity of the optimization, and the optimal design provides a maximum of 15 dB more isolation in rotation direction than the initial design.</p></div>","PeriodicalId":55631,"journal":{"name":"Chinese Journal of Aeronautics","volume":"37 2","pages":"Pages 330-342"},"PeriodicalIF":5.7,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1000936123004181/pdfft?md5=2dc8d7d4fb033c58e4d9eb1794748338&pid=1-s2.0-S1000936123004181-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138609960","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An application of space-filling curves to improve results of turbulent aerodynamics modeling with convolutional neural networks","authors":"Mikhail PETROV,&nbsp;Sofia ZIMINA","doi":"10.1016/j.cja.2023.09.003","DOIUrl":"10.1016/j.cja.2023.09.003","url":null,"abstract":"<div><p>When carrying out calculations for turbulent flow simulation, one inevitably has to face the choice between accuracy and speed of calculations. In order to simultaneously obtain both a computationally efficient and more accurate model, a surrogate model can be built on the basis of some fast special model and knowledge of previous calculations obtained by more accurate base models from various test bases or some results of serial calculations. The objective of this work is to construct a surrogate model which allows to improve the accuracy of turbulent calculations obtained by a special model on unstructured meshes. For this purpose, we use 1D Convolutional Neural Network (CNN) of the encoder-decoder architecture and reduce the problem to a single dimension by applying space-filling curves. Such an approach would have the benefit of being applicable to solutions obtained on unstructured meshes. In this work, a non-local approach is applied where entire flow fields obtained by the special and base models are used as input and ground truth output respectively. Spalart-Allmaras (SA) model and Near-wall Domain Decomposition (NDD) method for SA are taken as the base and special models respectively. The efficiency and accuracy of the obtained surrogate model are demonstrated in a case of supersonic flow over a compression corner with different values for angle <span><math><mrow><mi>α</mi></mrow></math></span> and Reynolds number <em>Re</em>. We conducted an investigation into interpolation and extrapolation by <em>Re</em> and also into interpolation by <span><math><mrow><mi>α</mi></mrow></math></span>.</p></div>","PeriodicalId":55631,"journal":{"name":"Chinese Journal of Aeronautics","volume":"37 2","pages":"Pages 81-92"},"PeriodicalIF":5.7,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1000936123003072/pdfft?md5=d44f0f495e372bbe0e0f818d5605f9f5&pid=1-s2.0-S1000936123003072-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135254881","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Development of EPDM composites reinforced by CNTs@SiO2 for thermal protection systems of aerospace propulsion: Significant improvement in oxidation and ablation resistance properties","authors":"Li WANG,&nbsp;Jiang LI,&nbsp;Kang LI,&nbsp;Yiwei WANG,&nbsp;Chenyang MA","doi":"10.1016/j.cja.2023.11.005","DOIUrl":"10.1016/j.cja.2023.11.005","url":null,"abstract":"<div><p>Carbon Nanotubes (CNTs) reinforced Polymer-Matrix Composites (PMCs) is widely used as insulation materials in thermal protection system of aerospace propulsion. However, CNTs are prone to oxidation and have high thermal conductivities, which makes it difficult to improve the ablation resistance of insulation materials that contain CNTs. SiO₂ was encapsulated onto the surface of CNTs (CNTs@SiO₂), which were then added to Ethylene Propylene Diene Monomer (EPDM) rubber to prepare the insulation materials. Thermogravimetric analysis and ablation test were used to evaluate the resistance of the insulation materials to thermal oxidation and ablation. Additionally, scanning electron microscopy was performed to analyze their microstructures. Results revealed that the addition of CNTs@SiO₂ could visibly reduce the effects of hot corrosion and ablation on insulation materials. The C-CNTs@SiO₂-1 formulation had the best ablative resistance. Further, compared with the unencapsulated formulation (C-CNTs-10), the C-CNTs@SiO₂-1 formulation reduced the line ablation rate by 51% to 0.0130 mm/s after oxygen-acetylene experiments. Lastly, the ablation mechanism was investigated based on the effects of the CNTs@SiO₂ additive on their properties. Thus, the improvement in ablation performance may be attributed to CNTs@SiO₂-induced decreases in thermal conductivity, improvement in the hot corrosion resistance in the char layer, and changes in the microstructure.</p></div>","PeriodicalId":55631,"journal":{"name":"Chinese Journal of Aeronautics","volume":"37 2","pages":"Pages 471-481"},"PeriodicalIF":5.7,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1000936123003898/pdfft?md5=a7d96423e13f034a0d5cc206edafa820&pid=1-s2.0-S1000936123003898-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135564951","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Terminal attitude selection method of missile attack aircraft","authors":"Peng HOU ,&nbsp;Yang PEI ,&nbsp;Yuxue GE ,&nbsp;Mengjie ZHU","doi":"10.1016/j.cja.2023.09.019","DOIUrl":"10.1016/j.cja.2023.09.019","url":null,"abstract":"<div><p>The appropriate terminal attitude of missile is important to improve the damage effectiveness of fragmentation warhead against aircraft targets. In this paper, three missile terminal attitude selection methods are proposed to solve the problem of terminal attitude selection in different situations according to their respective evaluation indexes. The MVE-based method uses the damage probability of each detonation point around the aircraft at a given attitude of missile to calculate the Mean Volume of Effectiveness (MVE) at the corresponding attitude, and then uses the MVE for different attitudes to select the terminal strike attitude. The detonation position-based method addresses the case where the missile detonation position can be assessed in advance. Given the effects of missile guidance errors and fuze activation position errors, Monte Carlo simulations are used to calculate the damage probability of aircraft with different strike attitudes, from which the terminal strike attitude is selected. The BP-ANN model-based method uses the constructed Back Propagation Artificial Neural Network (BP-ANN) model instead of simulation to calculate the evaluation indexes in the corresponding cases of MVE-based method and Detonation position-based method, which can improve the efficiency of attitude selection. Simulations are conducted for different scenarios to verify the feasibility and effectiveness of the proposed method.</p></div>","PeriodicalId":55631,"journal":{"name":"Chinese Journal of Aeronautics","volume":"37 2","pages":"Pages 385-400"},"PeriodicalIF":5.7,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1000936123003308/pdfft?md5=0d98f14e4fe490d3763ac897b92d2016&pid=1-s2.0-S1000936123003308-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134918289","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reynolds-number scaling analysis on lift generation of a flapping and passive rotating wing with an inhomogeneous mass distribution","authors":"Suyang QIN,&nbsp;Haotian HANG,&nbsp;Yang XIANG,&nbsp;Hong LIU","doi":"10.1016/j.cja.2023.09.030","DOIUrl":"10.1016/j.cja.2023.09.030","url":null,"abstract":"<div><p>Insects usually fly by passively rotating wings, which has been applied to the design of flapping-wing Micro-Air Vehicles (MAVs) to reduce mechanical complexity. In this paper, a robotic passive rotating-wing model is designed to investigate wing kinematics and lift generation, which are measured by a high-speed camera and a force transducer, respectively. In addition, flow fields are measured using the Particle Image Velocimetry (PIV). Experimental results demonstrate that passive rotating motion has a coordinative relationship with actively stroking motion. As the stroke amplitude or frequency increases, the rotating amplitude is enlarged. To characterize the active stroking motion, a driving Reynolds number <em>Re</em>_driving is defined, which varies from 68 to 366 in this study. Moving the gravity center of the wing towards trailing edge induces the increase of additional torque <em>M</em>, which decreases the wing rotating amplitude and promotes the advance of wing rotation. We find that the timing of wing rotation is gradually delayed and the mean lift coefficient <span><math><mrow><mover><mrow><msub><mi>C</mi><mi>L</mi></msub></mrow><mrow><mo>¯</mo></mrow></mover></mrow></math></span> monotonously decreases as <em>Re</em>_driving increases. By increasing the additional torque <em>M</em>, <span><math><mrow><mover><mrow><msub><mi>C</mi><mi>L</mi></msub></mrow><mrow><mo>¯</mo></mrow></mover></mrow></math></span> is slightly improved and approaches to the lift coefficient of a real fruit fly at driving Re approximately equal to 230. The instantaneous lifts combined with the vortical structures further demonstrate that the lift generation associated with wing rotation is mainly attributed to the growth of the Leading-Edge Vortex (LEV) and the passive wake capture mechanism. Passive wake capture is influenced by LEV, reversal stroke motion and wing additional torque together, which can only maintain the lift at a high level for a considerable period. The high-lift generation mechanisms of flapping and passive rotating flight could shed light on the simplified design of MAVs and the improvement of their aerodynamic performance.</p></div>","PeriodicalId":55631,"journal":{"name":"Chinese Journal of Aeronautics","volume":"37 2","pages":"Pages 259-269"},"PeriodicalIF":5.7,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1000936123003424/pdfft?md5=4595a4c916de444fd940173e895ab63f&pid=1-s2.0-S1000936123003424-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134934709","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A module based modeling framework for estimating lunar dust deposition due to human activities","authors":"Chunjian PAN","doi":"10.1016/j.cja.2023.11.003","DOIUrl":"10.1016/j.cja.2023.11.003","url":null,"abstract":"<div><p>Lunar dust is considered to be one of the top challenges for enabling humans to have extended stays on the moon. Human activities such as module landings and launches, walking, rover operation and construction activities will inevitably produce a significant amount of dust. Therefore, it is important to estimate the potential range and intensity of dust deposition caused by these activities to minimize dust accumulation over time and for maintenance planning and execution. A modular model that correlates the dust deposition distribution with initial mean dust particle velocity, its mean ejected angle and the total amount of ejected mass is developed for an elementary mechanical movement. This modular model is further employed to form a modeling framework to estimate dust deposition of a trajectory based activity of similar repeated movements such as the landing process of a lander, walking and rover operation. The model forms a unified modeling framework for different trajectory-based activities and is shown to predict consistent and physically meaningful ranges and intensities of dust deposition provided reliable data to calibrate the model parameters.</p></div>","PeriodicalId":55631,"journal":{"name":"Chinese Journal of Aeronautics","volume":"37 2","pages":"Pages 501-510"},"PeriodicalIF":5.7,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1000936123003874/pdfft?md5=426cafd3af0f4854f78c2d97c5298631&pid=1-s2.0-S1000936123003874-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135566902","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Wind disturbance compensated path-following control for fixed-wing UAVs in arbitrarily strong winds","authors":"Hao LU ,&nbsp;Lan GAO ,&nbsp;Yunda YAN ,&nbsp;Mingzhe HOU ,&nbsp;Chenliang WANG","doi":"10.1016/j.cja.2023.09.020","DOIUrl":"10.1016/j.cja.2023.09.020","url":null,"abstract":"<div><p>Wind is the primary challenge for low-speed fixed-wing unmanned aerial vehicles to follow a predefined flight path. To cope with various wind conditions, this paper proposes a wind disturbance compensated path following control strategy where the wind disturbance estimate is incorporated with the nominal guiding vector field to provide the desired airspeed direction for the inner-loop. Since the control input vector for the outer-loop kinematic subsystem needs to satisfy a magnitude constraint, a scaling mechanism is introduced to tune the proportions of the compensation and nominal components. Moreover, an optimization problem is formulated to pursue a maximum wind compensation in strong winds, which can be solved analytically to yield two scaling factors. A cascaded inner-loop tracking controller is also designed to fulfill the outer-loop wind disturbance compensated guiding vector field. High-fidelity simulation results under sensor noises and realistic winds demonstrate that the proposed path following algorithm is less sensitive to sensor noises, achieves promising accuracy in normal winds, and mitigates the deviation from a desired path in wild winds.</p></div>","PeriodicalId":55631,"journal":{"name":"Chinese Journal of Aeronautics","volume":"37 2","pages":"Pages 431-445"},"PeriodicalIF":5.7,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S100093612300331X/pdfft?md5=3b981d82386e896a543b290f4d02ba53&pid=1-s2.0-S100093612300331X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134918631","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Flow instability of supercritical hydrocarbon fuel in a multi-channel cooling system","authors":"Yichao JIN ,&nbsp;Kun WU ,&nbsp;Xuejun FAN","doi":"10.1016/j.cja.2023.09.027","DOIUrl":"10.1016/j.cja.2023.09.027","url":null,"abstract":"<div><p>Thermally-induced flow instabilities are a critical issue in multi-channel regenerative cooling systems. In particular, the interactions between Density-Wave Oscillations (DWO) and Flow Maldistribution (FMD) can result in complex and disastrous instability phenomena. This study investigates the instability behaviors of hydrocarbon fluid in a four-channel system with a constant heat flux ratio using both frequency- and time-domain methods. As the heat flux increases, the in-tube flow sequentially destabilizes in each channel and converges to new equilibrium states, leading to the emergence of FMD phenomena. This also causes the system eigenvalue to change repeatedly from negative to positive rather than increasing monotonically. Additionally, the system eigenvalues are between those of the two most unstable channels, indicating that the stability behavior of the entire system is dictated by the most unstable channel. After FMD occurs, flow oscillations are activated in channels with weak stability, and the in-tube flow is observed to evolve into various flow patterns, including stable flow, self-sustained oscillation, oscillation divergence, quasi-periodic oscillation, and oscillation excursion. The novel instability mode of oscillation excursion involves a spontaneous transition of operating states. It oscillates from an equilibrium state and then stabilizes at a new operational state after oscillation-induced redistribution. However, the newfound stable state may also be only temporary, with the in-tube flow regressing to the initial state, resulting in quasi-periodic oscillation.</p></div>","PeriodicalId":55631,"journal":{"name":"Chinese Journal of Aeronautics","volume":"37 2","pages":"Pages 283-295"},"PeriodicalIF":5.7,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1000936123003382/pdfft?md5=33c842fba2ce6a74b9ebce993b6cd831&pid=1-s2.0-S1000936123003382-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134936094","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stage separation of recoverable liquid launch vehicle by using moving pulsating ball analogue for propellant sloshing","authors":"Yu LU ,&nbsp;Baozeng YUE ,&nbsp;Bailong HAO ,&nbsp;Bole MA ,&nbsp;Feng LIU ,&nbsp;Yuanyuan CHANG","doi":"10.1016/j.cja.2023.09.005","DOIUrl":"10.1016/j.cja.2023.09.005","url":null,"abstract":"<div><p>In the process of stage separation of recoverable liquid launch vehicles, because of the large amount of residual fuel in the storage tanks, the influence of liquid sloshing on separation safety must be considered. Considering calculation simplicity and operation practicability, the Moving Pulsating Ball Model (MPBM) of large amplitude liquid sloshing is introduced into the calculation of launch vehicle stage separation. Combining the dynamic equation of the model with the energy relationship during “breathing movement”, the formula calculating the force of liquid on the rigid body is derived. Compared with the calculations of commercial CFD calculation software, the accuracy of MPBM model is verified. Then, all the external forces and moments are applied to the rigid body of the stages, so that the translational and rotational dynamic equations of the stages are obtained respectively. According to the relative position of the two stages, the geometric shape of the interstage section and the engine of the second stage, the minimum clearance in the separation process can be decided to guarantee that the separation process is safe.</p></div>","PeriodicalId":55631,"journal":{"name":"Chinese Journal of Aeronautics","volume":"37 2","pages":"Pages 360-370"},"PeriodicalIF":5.7,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1000936123003096/pdfft?md5=f0a2015082005c65a9f0bbd35173c231&pid=1-s2.0-S1000936123003096-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135298346","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gear walk instability caused by brake-disc friction characteristics","authors":"Xiaoqiong DU ,&nbsp;Bin LI ,&nbsp;Wen CAI ,&nbsp;Linyin LUO","doi":"10.1016/j.cja.2023.12.011","DOIUrl":"10.1016/j.cja.2023.12.011","url":null,"abstract":"<div><p>A multi-body dynamic rigid-flexible coupling model of landing gear is established to study the gear walk instability caused by the friction characteristics of the brake disc. After validating the model with the experimental results, the influence of the landing gear structure and braking system parameters on gear walk is further investigated. Among the above factors, the slope of the graph for the friction coefficient of the brake disc and the relative velocity of brake stators and rotors is the most influential factor on gear walk instability. Phase trajectory analysis verifies that gear walk occurs when the coupling of multiple factors causes the system to exhibit an equivalent negative damping trend. To consider a more realistic braking case, a back propagation neural network method is employed to describe the nonlinear behavior of the friction coefficient of the brake disc. With the realistic nonlinear model of the friction coefficient, the maximum error in predicting the braking torque is less than 10% and the effect of the brake disc temperature on gear walk is performed. The results reveal that a more negative friction slope may contribute to a more severe unstable gear walk, and reducing the braking pressure is an effective approach to avoid gear walk, which provides help for future braking system design.</p></div>","PeriodicalId":55631,"journal":{"name":"Chinese Journal of Aeronautics","volume":"37 2","pages":"Pages 343-359"},"PeriodicalIF":5.7,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1000936123004260/pdfft?md5=b937238184c82b78a9745850cfb6dd9f&pid=1-s2.0-S1000936123004260-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138992911","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}