DOI 10.51955/2312-1327_2022_1_73

Sergey V. Skorobogatov

Dmitry V. Vostretsov

Abstract. Aircraft flight is the main operation of any airline. To ensure competitiveness and good economical indices the flight time should be considerably longer than the total time an airplane spends on the ground. Aircraft flight is provided by a power plant, which is based on heat engines – heat machines that convert heat energy into effective mechanical work. The heat additive to the operating fluid in such engines nearly always occurs by means of hydrocarbon fuel (kerosene or aviation gasoline) combustion. While burning, the combustion products are released, some of which cause significant harm to the environment. Increasing environmental friendliness is an actual task today, and non-compliance of engines with ICAO standards on hazardous emissions limits the domestic aircraft sales and exploitation abroad. In this regard, the search for ways to improve the environmental performance of aircraft engines is a priority for the aviation industry.

Key words: combustion chamber, aviation gas-turbine engine, emissions of harmful substances, environmental friendliness.

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Danilenko N. V.

The article deals with the issues of circulation of the Earth’s environments in the area of its rotation relative to pole axis NS. The research of circulation of the Earth’s environments is based on the Biot-Savart law in its simplest form on the basis of an infinitely long vortex which has found wide application in airfoil aerodynamics, gas dynamics and in hydrodynamics. When applying the Biot-Savart law to the Earth’s material environments in its daily rotation we found a dependence of circulation of speed Г of the elementary particle under study with its relative height (depth) ±Н relative to the Earth’s averaged surface and geographical latitude.  The essence of this dependence is presented in a mathematical expression of physical parameters of our planet. The obtained intensity of circulation of speed Г of the Earth’s environments is converted in non-dimensional criterial parameters.  On their basis the vortex characteristics for the Earth’s environments are proposed. Their classification is given.  The authors developed a package of consequences of the vortex characteristics and proposed a working process of little known vortex phenomena of geophysics in terms of vortex dynamics of freely balanced environments of a planet of “Earth” type. The consequences of the vortex characteristics of the Earth’s environments and peculiarities of the working process of geophysical phenomena on the Sun are proposed.

Keywords: daily rotation, circulation of the Earth’s environments, vortex characteristics, consequences of the vortex characteristics of the Earth’s environments.

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Skorobogatov S. V.

Design and production of aircraft gas-turbine engines and their components is a high-scale and complex process. As separate branches of science develop, technological innovations are implemented and feed-back of their use is received, the design-and-production chain gets more complicated as well. On the one hand, this gives an opportunity to improve the product due to implementation of new ideas and approaches in its design, on the other hand, this brings about growth in the knowledge-intensity and increases the cost of the final product. In its turn, need for improvement of the product is required by the system of continued airworthiness with its standards improving over time as well.

Key words: combustor, aircraft gas-turbine engine, operational requirements, method of justification for requirements, airworthiness.

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Skorobogatov S. V.

The requirements for an aircraft engine as a whole are significantly influenced by processes inside its combustor. As justification for the nomenclature of operational requirements is based on some laws of effects of different parameters, it is necessary to carry out a factor analysis of the processes inside the combustor for revealing these laws both without any heat effect on the flow kinetics and with it during fuel combustion. For this purpose, an integrated system of forming external appearance of the research object has to be built and this, in its turn, implies its fragmentation into separate locations and detailed elaboration of the combustor block-diagram piece by piece. Then the results from separate parts have to be matched and integrated into a unified system for coherent configuration of the research object and during calculations this is the system which is under the factor analysis. The factor analysis of both the intermediate and final results of optimization according to the chosen criteria allows justifying the list of operational requirements necessary for the desired level of simulations. The article presents the factor analysis of processes in the inlet of the trapped vortex combustor.

Key words: combustor, aircraft gas-turbine engine, operational requirements, justification of requirements, factor analysis.

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UDK 629.735.33.015 BBK 39.15

Kirenchev A. G.

Danilenko N. V.

The article deals with the issue of possible vortex activation of the working process of the wing thrust over the underlying surface. The useful effect of this working process can manifest itself in reducing the aircraft take-off and landing roll in the field of wing vortex interference with the airfield ground. The area of practical use could cover the lifting surfaces of hydrofoil crafts, ram-wing crafts and similar vehicles at low flight altitudes. The vortex activation of the wing thrust is based on the professor N.Ye.Zhukovskiy’s theorem about the wing lift and the mirror effect of the underlying surface proposed by Prandtl. The authors defined the physical and kinematic essence of interference of a linear vortex with a flat underlying surface.  The effect of that kind of vortex interference is represented due to comparison of auto-travel of vortex smoke rings having a different diameter and generated by an identical force pulse. The authors stated the fact of force interaction between a vortex ring and a hard flat wall which forms the basis of the method of vortex activation of the wing thrust capable of reducing the drag. As an object of theoretical research the linear infinitely long vortex of intensity Г = 2p  allowing the mathematical expression of Biot-Savart law to be reduced to the function of vortex velocity с_в = f (1/(2h)). The kinematic vortex characteristic is represented as a dependence of travel speed on the height of its position above the screen. The article identifies the main consequences of vortex and screen interference and areas of their application.

Key words: thrust, circulation of velocity Г, vortex interference, flat screen, vortex travel, vortex characteristic.

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UDK 621.45.022 BBK 39.55

Skorobogatov S. V.

Isaev A. I.

With each passing year, the operational requirements for the aircraft power plants are getting stricter and stricter. The combustion chamber as one of the main parts of an aircraft engine determines the indicators of its efficiency, reliability and environmental compatibility. The indicators can be improved due to taking into account the operational requirements at the stage of designing a combustion chamber.

As the concept of a combustion chamber with a lateral system of reverse current area formation implies presence of a number of thin-walled elements as well as double-curved surfaces, designing a chamber of such construction is a complex engineering problem.

The article describes a technology of manufacturing a combustion chamber of the desired design on an example of experimental model for a chamber stand.

Key words: combustion chamber, aircraft gas-turbine engine, operational features, technology of manufacturing, combustion process.

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UDK 629.7.036.3 BBK 39.15

Kirenchev A. G.

Danilenko N. V.

The article considers the basic problems of vortex formation phenomenon and its natural and technogenic vortices. A new definition of vortex formation based on the physical essence of the working process is given. The mathematical foundation of the working process of vortex formation is presented with the use of Professor N. E. Zhukovsky’s theorem about the lifting force of the wing, as well as the equation for conservation of the gas movement energy and the Stokes theorem about the equality of the vortex tension and velocity circulation. Due to the analysis of the energy conservation equation the main factors of generation and accumulation of natural and technogenic vortices are revealed. The issue of the determining role of the underlying surface for forming effluent vortices of air intakes of aircraft gas-turbine propulsion systems is investigated. Influence of other external factors on the formation of technogenic vortices is noted. Classification of technogenic vortex formation and its vortices by the essence of the working process is given.

Keywords: vortex formation, technogenic vortices, vortex interference, the role of the underlying surface, gas turbine power plants, mathematical justification of Coriolis force vortices, air intake.

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UDK 621.438, 004.855 BBK З363.3, 32.813, 22.18

Novikova S. V.

Kremleva J. Sh.

The article presents a technique of increasing the robustness of a neural-net model of gas-turbine engine monitoring during stand tests due to decreasing the number of insignificant links in the neural network (neural network reduction). The technique is based on converting the problem of neural network learning into that of multi-criteria optimization which includes the error minimization criterion and the criterion of minimizing the absolute values of the weight links of a neural network. The latter requirement leads to reveal of insignificant links which can be deleted without any loss of accuracy. As a result, the ability of the model to summarize increases greatly, robustness increases as well, the calculation error of monitored parameters decreases.

Key words: model robustness, neural networks, stand tests, monitoring of a gas-turbine engine, reduction of a neural network.

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UDK 629.5.03-843.8 BBK 74.5

Karavaev Y.A.

Hodackij S.A.

The article presents general approaches to forming an estimation procedure of the residual operation life of the bypass turbojets operated on civil aircraft for long periods of time by taking actual operating conditions into account. With the example of D-436-148 aircraft engine having the standard control program the authors analyze how the size of turbine-blade tip clearances influences the rate of exhaustion of a bypass turbojet module – the gas turbine. A fraction of moving blade damage on takeoff is proposed to be used as a parameter defining the rate of exhaustion of the gas turbine.

Key words: gas-turbine engine lifetime, turbine-blade tip clearances, durability of moving blades, creep.

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UDC 004. 588 BBK 74.5

Yu. A. Karavaev

S. A. Khodatskiy

A significant number of aircraft engines taking out early from operation are associated with inter-shaft bearing failures. Possible causes of such failures are violations of their lubrication and cooling conditions. The article presents the results of experimental studies to assess the effect of reducing the performance of the oil tube with bending vibrations of the rotor on the thermal state of the inter-shaft bearing.

During the turbofan engine operation, its shaft co-performs bending vibrations due to the imbalance of the rotor. In this case, the oil tube, placed inside the engine shaft, will also make bending vibrations, which can be one of the reasons for reducing oil consumption through the oil tube with a significant level of vibrations. In this case, the working temperature of the inter-shaft bearing may increase significantly.

Keywords: aircraft engine, inter-shaft bearing, vibration velocity, bearing temperature, GTE oil system parameters.

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