Aircraft Engineering and Aerospace Technology最新文献

Purpose

This paper aims to synthesize and test Mn-Sb/TiO₂-CNT catalysts with different Sb/Mn molar ratios to be used in NH₃-SCR reaction.

Design/methodology/approach

A series of Sb-loaded carbon nanotubes (CNTs)-based Mn/TiO₂ catalysts were prepared by the incipient wetness co-impregnation method and tested for the selective catalytic reduction (SCR) of NOx with NH₃.

Findings

The Sb-loaded Mn/TiO₂-CNTs catalyst outperformed other catalysts and presented the highest activity in the temperature regime of 100–400°C. The catalyst loaded with Sb also showed good SO₂ and H₂O resistance and exhibited better thermal stability. A stepwise study of SO₂ addition evidenced that Mn-Sb/TiO₂-CNTs catalyst exhibited better SO₂ resistance than the base catalyst Mn/TiO₂, where the Sb doping greatly inhibited the sulphating of active phase of the catalyst.

Originality/value

In Sb-loaded catalysts, the formed SOx species fused with SbOx instead of MnOx. This favoured interaction of SO₂ with SbOx successfully prevents the MnOx from being sulphated by SO₂ which substantially improves the SO₂ tolerance of Sb-loaded catalysts.

Purpose

Regarding the broadening of the titanium alloy application field, the surface treatment coating of TC4 alloy has become an essential global research topic. This study aims to illustrate the titanium-based composite coating is created by laser cladding TC4+Ni60/hBN composite powder onto the surface of the TC4 alloy.

Design/methodology/approach

Different laser scanning speeds were initially selected to prepare TC4+Ni60/hBN titanium-based composite coating on the surface of TC4 alloy using RFL-C1000 Raycus fiber laser. Second, the cladding layers with different laser scanning speeds are composed of Ti₂Ni, TiN_0.3, TiC, TiB, α-Ti and other phases. Finally, precision balances, friction and wear testing machines were used to analyze and test the structure, phase, hardness, wear amount and friction coefficient of the composite coating and to study the effect of laser scanning speed on the microstructure and properties of the titanium-based composite coating.

Findings

It is evident that at the low laser scanning speed, the reinforcing phase agglomeration area is distributed in the substrate as a network. Increasing the laser scanning speed can reduce the cladding layer's friction coefficient and improve the cladding layer's hardness and wear resistance. But too high a laser scanning speed will cause defects such as pores and cracks in the cladding layer and also affect the cladding layer. The bonding performance of the layer and the substrate is optimal in this research at a laser scanning speed of 10 mm/s.

Originality/value

This research has practical value in improving the quality of surface treatment coating in modern aerospace and automotive companies.

Purpose

This study aims to simultaneously and stochastically maximize autonomous flight performance of a variable wing incidence angle having an unmanned aerial vehicle (UAV) and its flight control system (FCS) design.

Design/methodology/approach

A small UAV is produced in Iskenderun Technical University Drone Laboratory. Its wing incidence angle is able to change before UAV flight. FCS parameters and wing incidence angle are simultaneously and stochastically designed to maximize autonomous flight performance using an optimization method named simultaneous perturbation stochastic approximation. Obtained results are also benefitted during UAV flight simulations.

Findings

Applying simultaneous and stochastic design approach for a UAV having passively morphing wing incidence angle and its flight control system, autonomous flight performance is maximized.

Research limitations/implications

Permission of the Directorate General of Civil Aviation in Turkish Republic is necessary for real-time flights.

Practical implications

Simultaneous stochastic variable wing incidence angle having UAV and its flight control system design approach is so useful for maximizing UAV autonomous flight performance.

Social implications

Simultaneous stochastic variable wing incidence angle having UAV and its flight control system design methodology succeeds confidence, excellent autonomous performance index and practical service interests of UAV users.

Originality/value

Creating an innovative method to recover autonomous flight performance of a UAV and generating an innovative procedure carrying out simultaneous stochastic variable wing incidence angle having UAV and its flight control system design idea.

Purpose

This study aims to study the interaction effects between a rectangular supersonic jet with a flat wall computationally using wall length as a parameter. The purpose of this study is to investigate the effect of change in wall length on supersonic core length (SCL) reduction, jet deflection and jet decay behavior.

Design/methodology/approach

The design Mach number and aspect ratio at the rectangular exit were 1.8 and 2, respectively. To study the wall length effects on jet-wall interactions, wall length (L_w) was varied as 0.5D_h, 1D_h, 2D_h, 4D_h and 8D_h, where D_h was the hydraulic diameter of the nozzle exit. The flat wall with the matching width of the rectangular exit section of a supersonic nozzle was placed at the nozzle exit such that the supersonic jet grazed past the wall. The studies were carried out at over-expansion [nozzle pressure ratio (NPR) = 4], near optimum expansion (NPR = 6) and under-expansion (NPR = 8) levels.

Findings

Results indicated that significant reduction in wall-bounded SCL was noticed in the range of 0.5D_h ≤ L_w ≤ 1D_h for both over-expansion and under-expansion conditions. At L_w ≥ 4D_h, SCL got enhanced at NPR = 4 and 6 but had a negligible effect at NPR = 8.

Practical implications

Thrust vector control, noise reduction and easy take-off for high-speed aircraft.

Originality/value

The effect of change in flat wall length on interaction characteristics of a rectangular supersonic jet was not studied before in terms of SCL reduction and jet decay behavior.

Purpose

The advancements in battery technologies, while trailing behind technological progress, face challenges meeting the soaring energy demands of quadrotors, resulting in flight durations that are far from satisfactory. Hence, this study aims to empirically investigate the impact of wind on battery consumption.

Design/methodology/approach

Flight tests were conducted using the Pixhawk 4 along identical flight paths and durations. In these flight tests, the quadrotor was exposed to different wind speeds.

Findings

The amount of energy consumed in the flight tests was examined. It has been observed that wind poses a serious threat to battery consumption and thus flight safety.

Practical implications

It is predicted that the data obtained from these studies will be useful in the battery and route selection of quadrotors used in many areas in the future.

Originality/value

This experimental investigation involved conducting numerous flight trials at diverse wind speeds under genuine atmospheric conditions. The energy consumption data acquired holds significance as it directly mirrors real-world scenarios encountered in practical applications.

Purpose

Since the inception of aircraft, the phenomenon of spin has persistently accompanied aircraft, and research into spin has been ongoing. This paper aims to introduce an optimization technique to enhance the traditional geometric method for predicting steady spin, aiming to achieve more precise predictive outcomes.

Design/methodology/approach

To begin with, the force and moment equations used for motion analysis are initially presented, followed by the establishment of the motion model. Subsequently, the forward problem is set up, and the equilibrium solutions for the left and right spins of the aircraft are determined using the geometric method under the basic and wingtip configurations, thus solving the forward problem. In the final stage, nonlinear inversion is applied, and the inversion objective function is formulated based on the least squares approach. Through iterative processes, the measured data are interpolated, leading to the acquisition of the accurate equilibrium solution.

Findings

The findings indicate that the utilization of the nonlinear iterative inversion algorithm has effectively optimized the geometric method, yielding favorable outcomes. Postoptimization, the prediction accuracy has been enhanced, and the error has significantly diminished when compared to the preoptimization results.

Originality/value

The nonlinear inversion algorithm is used to refine the steady spin prediction for general aviation aircraft. This approach significantly mitigates the precision issues inherent in the forward problem. As demonstrated through the simulations provided, the application of the nonlinear iterative algorithm to resolve the inversion function yields promising optimization outcomes.

Purpose

This study aims to discuss the simultaneous longitudinal and lateral flight control of the octorotor, a rotary wing unmanned aerial vehicle (UAV), for the first time under the effect of morphing and to improve autonomous flight performance.

Design/methodology/approach

This study aims to design and control the octorotor flight control system with stochastic optimal tuning under morphnig effect. For this purpose, models of different arm lengths of the octorotor were drawn in the Solidworks program. The morphing was carried out by simultaneously lengthening or shortening the arm lengths of the octorotor. The morphing rate was estimated by using simultaneous perturbation stochastic approximation (SPSA). The stochastic gradient descent algorithm, which is frequently used in machine learning, was used to estimate the changing moments of inertia with the change of arm lengths. The proportional integral derivative (PID) controller has been preferred as an octorotor control algorithm because of its simplicity of structure. The PID gains required to control both longitudinal and lateral flight were also estimated with SPSA.

Findings

With SPSA, three longitudinal flight PID gains, three lateral flight PID gains and one morphing ratio were estimated. PID gains remained within the limits set for SPSA, giving satisfactory results. In addition, the cost index created was 93% successful. The gradient descent algorithm used for the moment of inertia estimation achieved the optimum result in 1,570 iterations. However, in the simulations made with the obtained data, longitudinal and lateral flight was successfully carried out.

Originality/value

Octorotor longitudinal and lateral flight control was performed quickly and effectively with the proposed method. In addition, the desired parameters were obtained with the optimization methods used, and the longitudinal and lateral flight of the octorotor was successfully carried out in the desired trajectory.