Aerospace Systems最新文献

During flight, dragonfly wings can be thought of as an extreme light-weight airfoil. Many of the flight properties of tiny dragonfly wings are also shared by micro aerial vehicles (MAVs), which are nowadays finding widespread use in military and other commercial applications. It is observed that dragonflies have distinct cross-sectional corrugation that function to produce different local-aerodynamic characteristics. Along the wing’s longitudinal axis, there are significant variations in corrugation profile which adapts to different flight condition accordingly. Dragonflies fly in the extremely low-Reynolds-number zone, showcasing their outstanding flying characteristics even in turbulent conditions. The current study focuses on understanding the effect of free-stream turbulence on three distinct 2D corrugation profile located at 0.3, 0.5, 0.7 relative to wing span length during dragonfly’s gliding phase. The corrugation pattern required for computational analysis was designed in CATIA and imported to the commercially available CFD software ANSYS. The computational study is conducted on 2D, static non-flapping three corrugated profile at 10,000 Reynolds number subject to turbulence intensity of 0.5%, 1–10% at various angle of attack. This study examines the aerodynamic performance of each corrugation profile. The current numerical analysis shows that at a positive angle of attack, the increase in the lift coefficient remains largely unaffected by the corrugated pattern on the wing’s suction area. Virtual airfoils are created by rotating vortices that are trapped in profile valleys of corrugation patterns.

This paper presents an image-feature-aware (IFA) planner for quadrotors, which integrates image feature tracking into its path-planning framework. The IFA-planner aims to improve the visual localization performance of quadrotors in multifarious environments where feature points may be sparse or diverse. Unlike traditional methods that decouple visual localization and path planning, the IFA-planner adaptively identifies and tracks feature-rich spatial units, called anchors, along a feasible path. The anchors provide additional feature points to the visual localization module, especially in scenarios with sparse or uneven features, thus enhancing localization robustness. Via clustering-based method, the anchor selection can handle different feature point distributions without manual tuning. Moreover, a detachment prediction mechanism is incorporated to convert the selected anchors into yaw constraints and update them according to the quadrotor’s predicted state. This mechanism ensures the environmental adaptability of the anchors and avoids sudden feature changes. The effectiveness of the IFA-planner is demonstrated in simulation experiments. The source code has been released at https://github.com/ximuzi2023/IFA-planner.

Essential qualities which a drone can effortlessly accomplish for every task include performance, safety, accessibility, and adaptability because of its efficiency. For different reasons, the efficiency of the drone is affected by an extensive number of parameters. Thus, a focus on improving drone’s efficiency has been proposed in this study. Usually, operational speed affects efficiency. Propellers have the potential to regulate operating speed. The propeller is an essential component of the drone's operation, and experts are always looking for new ways to improve its performance through novel studies. Multiple studies have been conducted and the findings indicate that employing leading-edge (LE) tubercles on propellers produces superior outcomes. For this computational study, the re-normalization group (RNG) equations with a k − ℇ turbulence model have been solved, using the Ansys Fluent solver. The range of RPM was 2000–8000, while the flow velocity ranged from 0.1 to 0.6 J (advance ratio). Calculations showed that the propeller with serrations had a significant improvement in thrust, power, thrust coefficient and power coefficient values. The outcomes were contrasted with the computational results from the available literature. Aerodynamic and overall performance trends showed a good degree of consistency, suggesting that tubercle propellers will be superior to baseline propellers in terms of efficiency.

Microburst is a common low-level wind shear weather, and it seriously threatens the safety of civil aviation flights. It is characterized by suddenness, short duration, small scale and large intensity, which leads to difficulties in accurately obtaining real data, in real-time assessing the degree of harm. In this paper, based on the characteristics of microburst, according to computational fluid dynamics, taking into account the changes of temperature and pressure with height, establish a three-dimensional wind field simulation model, and verify the validity of the model by experimental data. Using the F-factor, construct the quantitative model of each position in the wind shear region, and analyze the danger degree of the micro downwash storm flow. Investigate the influence of inlet velocity, inlet height and inlet diameter on the hazard radius, and the simulation results show that the hazard radius increases logistically with the decrease of altitude, and when the inlet velocity increases by 5 m/s or the inlet height increases by 80 m, the hazard radius increases by about 10% on average. The method of this paper can provide a new way to quantitatively analyze the wind field characteristics of micro downburst storms.

Acoustic impedance model of slits plays a crucial role in addressing noise reduction challenges in aircraft engines. To gain further insights into the sound absorption mechanisms of slits and to develop acoustic impedance model, this study investigates the bias flow effect on the acoustic impedance of compressor blade tip slit. The evolution of the blade tip leakage flow is calculated by the combination of two-dimensional discrete vortex model and one-dimensional acoustic propagation model. In this manner, the bias flow effects on the acoustic characteristics of the blade tip slits, such as slit impedance and sound absorption coefficient, are investigated. The model is validated through the experiment of bias flow effect on a circular orifice. It is further extended to calculate the flow field response of slits with different blade height and different aspect ratios. The results show that the acoustic impedance of equal area slits aligns closer with circular orifice experimental results than the acoustic impedance of equal width slits. Larger hub to shroud distances causes less influence on the blade slits of the same width. Increasing hub to shroud distance reduces the Ma of the maximum absorption coefficient. As aspect ratio increases, the acoustic reactance component corresponding to the acoustic mass of the slit decreases. Increasing the hub to shroud distance and increasing the aspect ratio of blade chord length to slit width can both improve the sound absorption under feasible conditions.

The bleed air system is an important part of the aircraft, and the normal operation of the bleed air system has an important impact on the safety and comfort of the aircraft. A deep learning-based method was proposed for the fault diagnosis of the precooler and pressure regulating valve (PRV) in the aircraft bleed air system. This method used long short-term memory network (LSTM) and Informer as prediction models. It also used the mean square error of the predicted and actual values as an anomaly detection indicator. The QAR data of the Airbus A320 series aircraft were used for experimental verification, and the model was evaluated and analyzed from the aspects of prediction performance, fault detection rate, false alarm rate, miss rate, etc. The results showed that the accuracy of our method reached more than 92%, and compared with LSTM, the accuracy of informer increased by 0.5%, the false alarm rate decreased by 0.4%, and the miss rate decreased by 6.7%, proving the effectiveness and superiority of the method of this paper.

The present article considers a modified optimal control model (MOCM) of the pilot. The main idea behind the proposed modification is moving the time delay element, initially located at the input of the model, to its output. Such relocation eliminates the need for introducing a “predictor” block to the model’s structure, which simplifies the algorithm for calculating the parameters of the optimal model. Besides a description of the modified algorithm, the paper assesses the agreement between the performance achieved using the algorithm and the results of experimental investigations. In addition, the results of modeling are compared to the results obtained using a structural model. The comparison is carried out for a model of a second-generation supersonic transport for this vehicle. The MOCM’s potential in evaluating alternative flight control system laws is discussed as well.

Accidental mechanical damage resulting from impact on the structure of the aircraft during its operation can lead to both easily detectable (visible impact damage—VID) and non-detectable damage during visual inspection production or operational damage (barely visible impact damage—BVID). At the same time, for each category of damage, strength from the required loads must be provided, so, for example, for damage of the first category (BVID), static strength from the design load must be provided throughout the entire service life. The provision of this requirement is carried out by experimental and computational methods. To carry out numerical calculations using the finite element method (FEM), it is necessary to use the PCM model, which will allow reproducing the damage resulting from the impact with high accuracy. Currently, monolayer strength criteria based on the implementation of a plane stress–strain state (PSSS), which takes into account only the components of the stress tensor in the plane of the layer, are widely used. But in case of impact, the direction from the layer also plays an important role. The scientific novelty of the proposed mathematical model of polymer composite material (PCM) is the addition of a monolayer strength criterion for volumetric FE, taking into account the direction from the plane of the layer. In this paper, a comparative assessment of the strength criteria for PCM in the simulation of impact was carried out Hu et al. (Polymers 14: 2946, 2022), Wang et al. (3D Progressive damage modeling for laminated composite based on crack band theory and continuum damage mechanics, 2015). Models with layer-by-layer modeling of a PCM sample with a cohesive interface between layers were developed to account for delaminations arising from impact Falcó et al. (Composite Structures 190: 137-159, 2018).

Polymer composite materials (PCM) are increasingly used in various fields of technology, primarily in the aviation industry, due to their high specific characteristics of structural properties and high manufacturability of molding methods for products of various functionality and undeniable advantages over traditional metal materials. The volume of PCM application in the airframe design of a number of modern and promising passenger aircraft is currently beginning to exceed 40% by weight and 80% by the area of the external contour of the aircraft. The development of automated technologies for laying out prepregs determines global trends in this direction, which consist in replacing traditional, manual methods of forming packages with automated methods of laying out. This gives significant advantages, such as a significant increase in the speed and accuracy of the process of laying out a semi-finished composite. The high demand for automation is due to increased requirements for the mechanical and precision characteristics of products. The key place in the article is given to determining the economic efficiency of methods of manufacturing composite parts for civil aviation equipment. The results of a comparative analysis of the technological cost of manufacturing parts from composite materials are presented, including assessment of the labor intensity of manufacturing work piece, material usage coefficients, share of manual labor, and degree of automation for polymer products through manual and automated technological calculations. It is shown that the use of automated technologies in the production of standard large-sized PCM panels makes it possible to reduce the consumption of basic materials by 15%, the labor intensity of manufacturing by 36% and the total manufacturing time by 28% compared to the existing level of pilot production. The key indicator of waste-free technological process (material utilization coefficient (MUC)) reaches values of 0.85–0.95.

Due to the excellent performance of carbon fiber-reinforced polymer (CFRP), they are widely used in the world's aircraft manufacturing industry, including aeroengine blades. During aircraft service, engine blades are often impacted by foreign objects such as breakstone, seriously affecting the airworthiness and safety of aircraft. Therefore, studying the impact resistance of carbon fiber composite materials is crucial for improving aircraft safety. In this paper, ABAQUS is used to establish a simulation model for impacting composite blades with breakstone. The VUMAT user subroutine is compiled to predict the damage of inner layer elements based on 3D-Hashin failure criterion and stiffness reduction scheme; cohesive elements based on the bilinear model are inserted between adjacent laminas to predict the delamination damage of the composite material. The damage initiation of cohesive elements is judged by QUADS criterion, and the damage evolution is performed using the B–K criterion of the energy method. Finally, based on the simulation results, the impact force, failure mode, and energy transformation during the impact process are analyzed.