VESTNIK of Samara University. Aerospace and Mechanical Engineering

A generalized kinematic scheme of the installation of quadcopter motors is presented and its main advantages are described. In accordance with the scheme, a mathematical model of the kinematics of the quadcopter was developed. The model was implemented in the MatLab software environment. The presented mathematical expressions are used to calculate kinematic characteristics, such as the values of the thrust of the motors and the reverse effect of the motors on the body of the quadcopter. The comparison of the obtained data with the experimental characteristics showed a 5% deviation of the magnitude of the dependence of the thrust on the average value of the voltage on the motors and a 30% deviation of the magnitude of the dependence of the motor action on the thrust magnitude.

The paper describes possibilities of increasing the energy efficiency and reducing the takeoff weight of unmanned medium-heavy vertical takeoff and landing aerial vehicles of the airplane type. The authors propose a new hybrid type of unmanned aerial vehicle with a hybrid propulsion system, its aerodynamic design, method of realization of vertical takeoff/landing and cruising mode of flight which make it possible to reduce the takeoff weight of the aircraft, the weight of the basic propulsion system and the mass growth factor in comparison with the existing unmanned aerial vehicle of similar class, made according to the previously known technical solutions. The authors propose a methodology for optimizing the parameters of the configuration of the unmanned aerial vehicle considering the peculiarities of the implementation of vertical takeoff. The paper presents calculations of characteristics of vertical takeoff and landing unmanned aerial vehicles of existing types and the new hybrid type. The authors give quantitative estimates of improving unmanned aerial vehicle characteristics due to the new proposed technical solutions.

The main purpose of the article is to identify the main approaches and define the concept when modeling the hydro-mechanical control systems of an aircraft. The advantages and importance of a computational experiment with the aid of a virtual test bed at the stage of constructive parametric debugging of the elements of complex hydraulic systems are emphasized. The characteristics obtained from the results of the computational experiment will allow us to determine the level of adequacy of the models and subsequently choose the most optimal design and operational parameters.

A method for developing a numerical rotor model and its further verification based on the results of virtual static structural and modal tests was proposed. Approbation of the method was performed on a model of a low pressure rotor of a high-bypass turbofan engine constructed in a software system for rotor dynamics simulation DYNAMICS R4. Refined on the basis of the results of virtual static structural tests, the model of the rotor main force action line showed good agreement in frequencies and mode shapes with the results of a finite element model, obtained during a virtual modal test.

One of the most important gas turbine engine components is the combustion chamber, the main source of harmful emissions. The study is devoted to the central issues of designing and testing of an automatic control system of harmful emissions and pressure pulsations in flame tubes of a gas turbine plant with a capacity of 16 MW GTP-16 based on a PI-controller with a built-in neural network mathematical model of a low-emission combustor (LEС). Algorithms for a neural network controller of emission of nitrogen oxides and carbon monoxide into the atmosphere, as well as pressure pulsations in the LEC’s flame tubes were developed. The algorithms are given in a graphical programming environment and integrated into the automatic control system of GTP-16, implemented on the PXI NI hardware and software platform. The performance of the emission controller was checked during bench tests on the GTP-16 simulator with LEС neural network model serving as a virtual emission sensor. The errors in estimating the emission of nitrogen and carbon oxides and pressure pulsations in the flame tubes were determined. The normality of the error distribution of the developed nitrogen oxide emission model was proven. A conclusion about the prospects of using neural networks for the development of an adaptive control system of emissions and flame tube pressure pulsations for LECs of the gas turbine plants was drawn.

The study addresses the effect of 1580 and 1590 alloys cold rolled strip annealing practices on the alloys’ grain structure and mechanical properties. The 1590 alloy differs from the 1580 alloy by hafnium and erbium additions. Samples of such alloys were produced by casting into a steel mold. After that they were homogenized during 4 h at 440°С. Then the samples were hot rolled at 440°С, with further cold rolling to 2 mm, with the cumulative percentage reduction equal to 66%. The cold rolled strip was annealed at the temperature ranging from 330 to 440°С with 1 h soaking. The sizes and morphology of Al₃Sc strengthening nanoparticles were examined in homogenized condition using transmission microscopy. The mechanical properties and grain structure were defined in cold rolled and annealed conditions. During homogenizing annealing in the 1590 alloy finer strengthening nanoparticles are formed compared to the 1580 alloy. Such features of the microstructure can be explained by the presence of erbium, promoting formation of additional Al₃Sc-type nanoparticles nuclei, and hafnium, preventing their further growth. Non-recrystallized structure was identified in both alloys after cold rolling and final annealing. The 1590 alloy has better mechanical properties, regardless of the annealing temperature, which is explained by a larger portion and smaller size of strengthening nanoparticles.

The effect of broadband disturbances on the operation of a noise-immune digital speckle pattern interferometer with a continuous wave laser emitter and a diffuse-scattering element arranged in front of an oscillating turbine wheel has been studied. Visibility dependences of the recorded interference patterns were obtained under the action of different types of artificially created disturbances. It is shown that the most dangerous mechanical disturbances for the operation of a speckle pattern interferometer are periodic noise and pink noise, whereas white noise and natural vibrations of the floor in the room where the experimental setup was accommodated do not significantly influence the quality of the information recorded by the interferometer. This article analyzes the influence of the mechanical properties of the diffuse-scattering element arranged in the speckle pattern interferometer on the quality of the obtained interference patterns. A relationship between the growth of forced tangential oscillations of the diffuse-scattering element and a decrease in the contrast of interference fringes was noted. In this case, an increase in the thickness of the organic glass plate of the diffuse-scattering element up to 8 mm leads to the neutralization of the pink noise action on the speckle pattern interferometer operation. At the same time, the effect of periodic noises decreases the contrast of interference patterns recorded for the cases of using 5 mm and 8 mm thick organic glass plates.

This paper discusses a composite material from chopped thin narrow polymer tapes reinforced with carbon fibers and a polymer binder. The problem is posed to analytically determine the elastic and strength characteristics of the composite with a known minimum set of basic characteristics of the components. A methodology for sequential solving of the problem at the micro- and meso-levels is proposed. The key point in the methodology is the introduction of the “effective fiber volume factor” in the short filament and the way to calculate it using the “load-carrying factor” criterion. The following are presented: the results of calculating  Young’s modulus and tensile strength of material samples from parts of tapes with fixed lengths (6, 12, 18 and 24 mm); comparison with the experimental data and evaluation of accuracy and limits of the applicability of this methodology.