Vol 19, No 2 (2020)

The article presents mathematical formulation of the problem of synthesizing the image of complex harnesses as an integral part of the on-board complex of aircraft equipment. This problem arises in the design of the on-board cable network of each individual aircraft. The article describes the language that we use to form the basis of applied methods for synthesizing the structures of a set of objects, irrespective of their specific nature, but taking into account their relative position and their properties that are characterized by various features. The article poses the problem of synthesizing a complex bundle in a closed form and proposes an algorithm for solving it. In the work, a matrix of relations between the set of objects and the set of their attributes is compiled. As applied to simple on-board cable bundles, features are introduced and their qualitative values are described that characterize the variety and complexity of the objects under study. Using the example of ten simple cabin harnesses of an arbitrary aircraft, an example is given of compiling a matrix of relations between objects and features, ranked in a certain order. Based on algorithms for comparing the values of attributes, a conclusion is drawn on the aggregation of objects into classes, among which the combination of simple bundles into a complex one is most appropriate.

The buildup of thermodynamic cycle parameters is the main way to increase gas turbine engine efficiency. However, the growth of engine pressure and temperature ratio leads to the increase in the turbine heat load, which reduces the engine lifetime dramatically. In terms of gas turbine engines, to avoid the engine life loss is a crucial problem especially for small engines, because the limited size of a small gas turbine engine does not allow implementing various measures for nozzle vane cooling. In light of this, the contribution of the turbine heat control is essentially increasing. It places great demands on the accuracy of control over the main engine variables (such as the rotor speed and turbine outlet temperature). The state-of-the-industry gas turbine engines use an on-board engine mathematical model to improve the quality of the control. These models deal with engine processes of short duration and considerable overshooting. For that reason, the model accuracy is the main aspect in the control process. However, the issues of accurate and at the same time resource-saving calculation of rapidly varying processes of changing the rotor speed and the turbine gas temperature remain under-investigated. In the work, neural network methods were used to model the unsteady modes of a small gas turbine engine. Using the data obtained as a result of firing tests of the JetCat P-60 engine, the engine regression neural network model was created. The main issue that arose during the creation of the model was to describe the dynamics of rapidly varying processes with pronounced overshoot. For this purpose, modification of the architecture of the classical LSTM network was carried out, the essence of which was to add a functional dependence of the exit node on the memory tensor. This allowed us to make the memory size independent of the number of model outputs, thereby increasing the modeling accuracy. The developed architecture was proposed a new name - VMLSTM network. As a result of comparison with the traditional Elman network and the classic LSTM network, the developed VMLSTM network showed the least value of the average error with a comparable number of modifiable model parameters. In addition, unlike the existing neural networks, the developed network demonstrated the ability to simulate turbine outlet gas over-temperature at the moments when the engine operating mode changes. The developed neural network architecture increases the reliability of modeling the dynamics of a small gas turbine engine as an object of control, which in the conditions of economical use of computing resources opens up possibilities of its application in on-board microcomputers.

In this article we deal with the problem of cyclic compression of a multilayer multi-span corrugated package by using the finite element method (FEM) and a three-dimensional model (3-D model) of deformation in Ansys. We take into account plastic deformation of the package, as well as the complex law of its propagation and mutual elastic slippage with dry friction over tops of corrugation and in local regions at the tops of corrugation along the package tapes, valid for any geometrical shape of corrugation. This solution can be considered as the second part of the general complex nonlinear problem of cyclic compression of a multilayer multi-span corrugated package with dry friction on contact surfaces. The solution obtained makes it possible to construct any loading processes in the field of elastic-hysteresis package loops. The comparison of elastic-frictional characteristics of the package (EFCs) obtained by calculation and the experimental ones showed their good agreement. The influence of the corrugated package parameters on its EFCs was studied. A number of properties of the package were determined allowing us to draw conclusions and formulate recommendations that make it possible to define the number of package tapes, the required accuracy in the manufacture of corrugations of its tapes, and the choice of the geometric shape of corrugations in almost all cases of practical use of corrugated packages. The solution obtained can be used to determine the effectiveness of a bumper and other protective devices during crash tests of a car for frontal and side impacts and to determine the optimal parameters of these devices by calculating. Certain results and recommendations of this paper can be useful for the calculation of parameters of damping elements of a blisk, hollow wide-chord blades of aircraft GTE fans, ring dampers of rocket engine rotors, as their damping elements are made in the form of multilayer, multi-span corrugated packages.

It is necessary to ensure appropriate information content of the measuring instruments used for intelligent diagnosing systems of energy and technological complexes based on the measurement of dynamic parameters. Sensors and measuring equipment should possess sufficient accuracy, reliability, speed and consistency of performance. Types of sensors for measuring dynamic parameters are selected depending on the system’s structure. They can be, for example, sensors for the electrohydromechanical systems of these complexes, pressure sensors, as well as sensors of flow and temperature of the working media, displacement of moving elements and vibration of the base members. The type of sensor intended for use in the diagnostic system is largely determined by the dynamics of the processes taking place in it. It is necessary that the sensors satisfy their performance requirements. If the sensors have lower speed than is necessary for the process dynamics in the electrohydromechanical system, it can lead to dynamic measurement error and an error in the diagnostics of technical condition. In technical literature, the requirement for the sensor speed is indicated by the fact that it should be an order of magnitude higher than the dynamics of the processes occurring in the system. This approach is not acceptable for choosing the type of sensors for diagnostic systems, taking into account the process dynamics. Firstly, sensors for measuring with this required parameter may not be available. Secondly, even if there is a sensor with a parameter close in speed to the dynamics of the system processes, it is necessary to know in advance what dynamic error it can lead to and how it will affect the accuracy of the diagnostic system. An analytically generalized dependence of the dynamic measurement error of electrohydromechanical system parameters on the relative sensor speed is obtained in this paper. This dependence allows you to choose a sensor with a dynamic error that does not exceed a given value. The calculation of the dynamic measurement error is shown using the MI-8 helicopter hydraulic system as an example.

Currently, the priority for improvement of the combustion chambers of aircraft gas turbine engines and ground-based gas turbine plants is associated with a decrease in the concentration of harmful substances in the exhaust gases while ensuring fuel economy and operational efficiency. Pride of place in the design of a gas turbine power plant goes to solving the problem of organizing the combustion process, i.e. the development of a low-emission combustion system that provides high efficiency and environmental safety. Thus, ecology today determines not only the appearance of a combustion chamber, but also that of a gas turbine power plant as a whole. Below, an attempt is made to summarize the results of developing a low-emission combustion system for various types of combustion chambers of convertible gas turbine power plants and to present a unified approach to the problem  of designing a conceptual structure of a low-emission combustion chamber.