Aerospace Systems最新文献

This work investigates the dynamic characteristics of a system susceptible to flutter phenomena during aircraft flight operation while considering fluctuations in critical system parameters, including stiffness, damping, flap angle, angle of attack, and yaw angle. A parametric analysis was conducted to quantify the influence of each parameter on the system response, particularly focusing on bending and torsional mode. To substantiate the findings, comparing simulated, theoretical, and experimental results shows good agreement in overall trends. The results show that increasing stiffness from 100 N/m to 300 N/m reduced the peak bending displacement by approximately 80%, demonstrating a strong stabilizing effect. Similarly, increasing the damping coefficient from 0.1 to 1 resulted in a 40% reduction in torsional angle amplitude, highlighting the importance of damping in controlling the system’s oscillatory behavior. Additionally, aerodynamic variations such as yaw angle shifts from 0^o to 5^o increased bending displacement amplitude by 70%, revealing the system’s sensitivity to aerodynamic conditions. Similarly, increasing the angle of attack from 0^o to 10^o increases the bending displacement amplitude by 50%(:.) Emplacing the perturbative effect that elevated angles of attack exert on the system. The flap angle was also found to have a significant impact, with 60% increase in flutter speed observed when the flap angle was increased from 0^o to 30^o, reducing the system’s susceptibility to instability.

Hybrid-rocket propulsion, which combines the benefits of both liquid and solid propulsion, has gained attention for its safety, throttling capability, and cost-effectiveness. This study presents a combined experimental and theoretical investigation of a hybrid rocket engine using PVC/DBP as fuel and gaseous oxygen as the oxidizer. Four successive firings were conducted to analyze thrust, regression rate, chamber pressure, and specific impulse. NASA CEA was used to model the ideal combustion parameters. The PVC-DBP fuel formulation offers advantages such as ease of processing, availability, and controlled burning behavior. A series of experimental static tests were conducted using a hybrid-rocket engine equipped with a showerhead injector and a convergent-divergent nozzle. The findings demonstrate an inverse correlation between the mass flux of the oxidizer and the regression rate, with measurements dropping from 0.94 to 0.70 mm/s. over successive firings as port diameter increased from 15 to 28.15 mm. Thrust measurements followed a similar trend, declining from 220 to 50 N, reflecting reduced combustion intensity due to oxidizer dilution. Combustion efficiency improved from 52.16 to 59.55%, suggesting enhanced fuel regression dynamics across multiple firings. Additionally, comparative analysis reveals significant deviations from ideal behavior due to combustion inefficiencies and thermal losses, highlighting the need for nozzle and chamber optimization in practical hybrid engine systems.

To clarify the coupling mechanism between the aeroelastic responses and flow fields of helicopter blades experiencing subharmonic resonance, the experimental and numerical investigations are performed on a three-dimensional (3D) aeroelastic system that incorporates the tip vortex effect. The experimental results reveal subharmonic resonance phenomena occurring when the natural frequency is 1.45 times the driving frequency. For obtaining the 3D global flow fields, the high-fidelity numerical simulations are conducted under the conditions of subharmonic resonance. The dominant modes of flow fields and their spatio-temporal evolution are identified by proper orthogonal decomposition. It is shown that the subharmonic components in aeroelastic responses and aerodynamic loads result from the evolution of the flow fields. The decrease in reduced frequency leads to attenuation of the dynamic stall vortex, simultaneously enhancing flow stability and suppressing subharmonic components, which explains the saddle-node bifurcation of limit cycles during dynamical evolution. The formation of counter-rotating vortex pairs further enhances this stabilization mechanism.

Electromechanical actuators (EMAs) are extensively employed in small aircraft. However, inherent structural nonlinearities such as freeplay, arising from limitations in production and manufacturing processes, can adversely affect the dynamic behavior of fin-actuator systems. This paper studies the correlation between modal frequencies and freeplay through the developed simulation model of the fin-actuator, and the modal frequencies are obtained by the impact hammer test. Both freeplay and friction effects are incorporated into the model to evaluate the influence of freeplay gap length and external loads on the frequency response function (FRF). Comparative analyses reveal that, under consistent impact load, significant differences exist in the vibration frequency responses for a fin with/without an external weight load. These results suggest a positive correlation between the frequency discrepancy and the magnitude of the freeplay, offering a reference for the detection of freeplay in fin-actuator systems.

The present paper discusses issues related to dynamic deformation and failure of the jet engine case impacted by released blade of rotating rotor. It is shown that due to a local area of deformation of the jet engine case impacted by the released blade acceptable failure criterion for the case can be obtained on the base of model tests and corresponding numerical simulations. The equation of motion based on the variation principle of balance of virtual powers of work. The plasticity models of the materials are based on the von Mises yield surface with associated flow rule and isotropic hardening low depends on the strain rate. Numerical solutions of the problem are implemented by the finite element method and explicit scheme of numerical integration in time, realized in the code LOGOS. The uncoupled ductile fracture model is applied with the equivalent plastic strain as failure criterion. Validity of computer simulations is supported by proximity of numerical and experimental data for the depth of cutting of the targets at the impact sides and perforation and perforation time of the targets. Analysis of the principal strains and equivalent plastic strains as well as stress triaxiality parameters during the deformation process up to the failure of the targets is also presented. It is shown that destruction of the plane model of the jet engine case is initiated on the impact side when the equivalent plastic strain normalized by the elongation reaches the level ({overline{varepsilon }}_{pl1}^{f}=2.5) with triaxial compression and perforation of the plate takes place if ({overline{varepsilon }}_{pl2}^{f}=1.2) on the opposite side of the target plate with biaxial tension.

Controlling the landing path trajectories of a vertical takeoff and landing aircraft is a challenge that requires an accurate design algorithm. This study introduces an innovative approach to investigate the dynamic of such vehicles and implement an automatic controller such that the aircraft follows a desired landing path trajectory. By linearizing the governing equations of the aircraft around a specific reference path, the linear model of the aircraft system is established. The bank angle is used as the primary control input to adjust landing profile and ballistic paths, while landing speed is treated as an independent state variable. This design algorithm involves creating a linear quadratic regulator controller gain that minimizes the cost function of the aircraft system, establishing dynamic state equations. The Hamiltonian function is employed to generate and solve both state and co-state equations under specific boundary conditions, culminating in the solution of the Riccati matrix. Finally, the controller's performance is tested with different initial state values. Results reveal significant improvements in stability and performance considering the landing path. However, challenges such as conflicts between system states, control gain saturation, and abrupt state changes remain key design hinders. This study offers a sufficient method for controlling such an aircraft using linear control algorithms, which can be more efficient and cost-effective than complex nonlinear algorithms. By simplifying control systems, this approach ensures stable and effective flight operations, making it a valuable advancement in the field of vertical takeoff and landing aircraft technology.

In the aviation industry, drones are increasingly used for different purposes. They come in various types, shapes, and sizes based on their motive, ranging from small quadcopters to larger drones for cargo transport. Drones are generally prioritized due to their superior and safe performance, easy accessibility, and adaptable capabilities. Their efficiency depends on the speed at which the operation is carried out, which affects overall performance. The performance device that is most affected by increased speed is the drone’s propeller. On one hand, high speed can enhance lift and performance, whereas on the other hand, it imposes aerodynamic, mechanical, and power-related challenges. Thus, by focusing on the aerodynamic factor, speed balancing can be achieved by designing an efficient propeller to attain optimal performance while maintaining efficiency and stability in high-speed drones. Previous researchers have introduced the concept of variable pitch propellers (VPP), which adjust the blade angle to maintain optimal lift and efficiency at high speeds. However, VPPs still have not fully addressed challenges such as increased drag, potential stall, and tip-speed effects, ultimately affecting efficiency. To overcome these drawbacks, researchers have explored the idea of tubercles, which help improve propeller performance at high angles of attack and higher RPMs. However, tubercles also present certain performance drawbacks, such as a potential reduction in maximum efficiency, increased surface area, and added weight, which contribute to an increased drag coefficient and mixed performance across speeds. This study focuses on improving overall aerodynamic efficiency by addressing factors such as an increase in overall efficiency, thrust force, and power. By concentrating on these factors, the aim is to develop different propeller designs by modifying tubercle parameters such as amplitude, wavelength, and position. Many studies have been conducted on propellers to enhance drone operations, and experts continue to explore ways to improve efficiency. One effective approach is incorporating leading-edge (LE) tubercles on propellers, which enhance the overall efficiency of drones. To fulfil the purpose of this study, a numerical investigation is carried out by comparing the baseline model with a propeller featuring tubercles. Based on previous literature, the improved performance and increased overall efficiency of tubercle-equipped propellers demonstrate superior performance compared to baseline propellers.

Modern space exploration requires superior Propelling systems and dual bell nozzles present a promising solution for enhancing rocket propulsion system performance across varied flight regimes. This study offers a comprehensive optimization and analysis of dual bell nozzle design for advanced rockets. By employing Machine Learning with an Artificial Neural Network model, we developed a novel approach to rapidly optimize dual bell nozzle geometry for a specified exit Mach number, addressing the complex calculations typically associated with nozzle design. The algorithm generated a nozzle configuration capable of efficient operation in both low and high-altitude conditions. To validate results, we conducted detailed computational simulations using ANSYS Fluent. The analysis corroborated the model predictions, revealing key performance characteristics including a maximum exhaust velocity of approximately 2200 m/s and an exit Mach number of 5.8, aligning closely with the optimization. Our study contributes to the advancement of space propulsion technology by demonstrating the potential of AI-driven optimization in nozzle design.

The Very Long Chord Slat (VLCS) has emerged as a promising high-lift device configuration for commercial jetliners. This study focuses on the parametric shape design of two-dimensional high-lift devices incorporating VLCS, with particular emphasis on slat contour and position modifications. A surrogate-based optimization (SBO) framework, integrating Kriging metamodeling and the Non-dominated Sorting Genetic Algorithm, was employed to enhance the lift and drag performance at targeted angles of attack (AOA). The results reveal distinct Pareto fronts, demonstrating that a 25% slat chord extension yields a 7% improvement in lift-drag ratio at take-off AOA and a 4% increase in lift coefficient at landing AOA. The study also underscores the efficacy of the SBO method in preliminary aerodynamic design exploration for high-lift devices.

Software and hardware loosely coupled systems, characterized by their critical role in various high-reliability applications, require robust fault tolerance mechanisms due to their complexity and the intertwined nature of software and hardware components. However, the tight integration of diverse functions within the system-wide computing environment, coupled with the unclear mechanism of fault propagation, presents significant challenges in enhancing system reliability. Modern avionics systems, as a prominent example, are also inherently software-hardware loosely coupled systems, and they face similar challenges in ensuring fault tolerance. In response to these challenges, this paper proposes a fault propagation analysis method that comprehensively considers both temporal and spatial dimensions. Through in-depth analysis of dependency, fault probability, and fault propagation capability, the paper constructs a fault propagation model for software and hardware loosely coupled systems, providing a precise description of fault information. In the spatial dimension, the efficiency of fault propagation analysis is enhanced using the ant colony algorithm, while in the temporal dimension, task modeling is performed using the directed acyclic graph (DAG) model to improve the adaptability of fault propagation methods to real-time task requirements. The experimental results validate the effectiveness and efficiency of the proposed fault propagation method, demonstrating that the temporal dimension of fault propagation can effectively complement the shortcomings of spatial dimension fault propagation in meeting real-time task requirements.