Vol 16, No 1 (2017)

The paper considers development of the Information Control System (ICS) of the Russian Segment of the International Space Station (ISS). The main ICS modules for carrying out scientific experiments comprise the Service Module, the Multipurpose Laboratory Module and the Science Power Module. At present specialists of “Energia” RSC are working to create high-tech conditions for scientific experiments on the new ISS modules, modernize the existing ones and combine them into a single onboard ISS information control complex. The information control system (ICS) is intended for automatic and manual control of space experiments. The effectiveness of modernization was confirmed by the results obtained during space experiments on the basis of the Information Control System. The ICS modernization started in 2012. At that time the ICS consisted of 4 onboard computers. The main task of ICS modernization was to introduce new computers and software-hardware systems. The software was supposed to have a flexible architecture and provide resources for all future onboard payloads. At the first stage one onboard computer was replaced. The main purpose of that stage was to test the new ISS hardware and software. The rest of the ICS computers will be replaced at the second stage, the Multipurpose Laboratory Module and the Science Power Module will also be equipped. The reliability of the system hardware is improved using functional backup. In 2014 2 cameras were installed on the ISS together with UrtheCast company (Canada).One of the cameras is a middle resolution camera; the other one is a high resolution camera. Today ground preparation of an experiment with “Icarus” scientific equipment is being carried out, jointly with the German Center of Aviation, DLR, and the SpaceTech company (Germany). The experience of the first stage of modernization suggests that the modernized ISS RS ICS will become an up-to-date system allowing the realization of most ambitious space experiments in automatic mode.

The geographic location of the Russian Federation determines regional apartness of the Arctic and Far East territories which are mostly isolated. The necessity of development of the Russian North Polar regions calls for the development of transport infrastructure and specifies requirements to flight characteristics of regional airplanes, which requires new research and development solutions. Positioning the Arctic territory as an exclusive economic zone on the world political arena necessitates the development of the regional transport network including all-cargo and passenger services for sustainable development of the region. An up-to-date approach to aircraft design should be based on Arctic exploiation requirements, infrastructure-climate limitations and design methods that include methods of moment-inertia analysis, structural-parametric analysis of Arctic-based aircraft taking into account the choice of rational moment-inertia configuration. Synthesizing the limitations and required operation characteristics we designed an Arctic-based airplane that can perform transport operations in the Russian Arctic zone safely and successfully.

In development and maintenance of liquid rockets it is essential to ensure its stability in relation to longitudinal oscillations of the body (longitudinal stability, pogo effect) for all possible disturbances. It is known that one of the most effective ways to ensure the longitudinal stability is to use gas dampers-accumulators installed in the feed line at the engine inlet. The damper in the feed line produces additional compliance, thus making it possible to eliminate the coincidence of the fundamental natural frequency of the pressure fluctuations in the feed line and the natural frequencies of the rocket body, which is necessary for providing the longitudinal stability. The damper parameters are selected on the basis of mathematical modeling and experimental data. In this paper, a nonlinear mathematical model of a coaxial gas damper is developed with the use of the ideal-gas law equation for an adiabatic process and the Bernoulli and Saint-Venant – Vantsel equations. The mathematical model is used to calculate the frequency characteristics of the damper in the form of input acoustic conductance. The results obtained make it possible to take into account the contribution of passage sections of the throttles to the performance of the damper at the design stage, as well as to select its parameters in simulating processes in the feed lines to solve the longitudinal stability problem.

The article considers the influence of different tolerance values on the stiffness of elastic rings in squeeze film dampers. This type of damper is widely used in gas turbine engine supports. The available analytical solutions have a number of limitations. A parametric finite-element model of an elastic ring, a set of two interconnected elastic rings and a simplified segment is presented. The results obtained show the discrepancy between values of compliance for different numerical models as compared to analytical approaches. The effect of assembly tolerances on the value of compliance is shown.

A real process was analyzed for presence of self-oscillations. Absence of self-oscillations was revealed as its attributes such as progressive wave and beating were not discovered. A model of oscillatory process was proposed on the basis of the kind of oscillograms and the linear superposition theory for several simultaneously excited oscillation modes. In accordance with the theory two vibrations with frequencies equal to 919 and 469 Hz were summed up. As a result of addition of these frequencies and comparison of the derived oscillograms with the real process it was found that the proposed model agrees with the original well enough. Moving further into the process, a third frequency component equal to 1002 Hz originates in addition to those of 465 and 918 Hz. Addition of three frequencies carried out similarly to the first example also yields a satisfactory result. Oscillograms of real and model processes have a similar appearance. The frequency components calculated on the basis of the oscillogram of the model process practically coincided with the real process frequencies. Classification of aeroelastic oscillations was analyzed in order to determine the oscillatory type of the process under investigation. Three main phenomena were distinguished: forced oscillations, flutter and non-synchronous oscillations. Almost all foreign engine companies faced the latter phenomenon, sometimes mistaken for flutter. The analyzed example was labeled as non-synchronous oscillations according to features of non-synchronous oscillations, namely, aliquant rotation frequency and resonant behavior of oscillations.

The paper focuses on the choice of mathematical models of squeeze film dampers and methods of their numerical implementations for gas turbine engine rotor dynamics problems. The present contribution is aimed at establishing criteria for the application of mathematical models of a squeeze film damper depending on the damper characteristics and operating conditions. The models are grouped by the dimension of the considered physical space, i.e. three-dimensional, two-dimensional and one-dimensional modeling patterns. The work presents principles of setting boundary conditions for mechanical seals to be adequately simulated. Criteria of assessing the necessity of taking into account such physical phenomena as turbulence, fluid inertia, and cavitation are presented. The proposed mathematical models are primarily developed for the computation of integral characteristics of squeeze film dampers, such as reaction forces and dynamic stiffness and damping coefficients required for solving rotor dynamics problems.

The use of corset reference specimens for carrying out fatigue tests and smooth reference specimens for determining residual stresses in a surface layer to assess the sufficiency of nitriding (thermochemical processing) is substantiated in the paper. The calculations are carried out by finite element simulation using the ANSYS and PATRAN/NASTRAN software complexes. The ANSYS complex is used to determine the stress concentration factor for the case of corset specimen bending. The employed models with harmonic axisymmetric finite elements make it possible to find the stress concentration factors in the case of tension- and- compression and bending of body-of-rotation parts. The obtained value of the influence of the coefficient of residual stresses on the endurance limit increase is in quite good agreement with its experimental values for nitriding and other types of thermochemical treatment of corset specimens. The PATRAN/NASTRAN complex is used to calculate the stress-strain state in corset specimens depending on residual stresses arising on a part surface under nitriding. Modeling is performed by the thermoelasticity method, with experimental diagrams of residual stresses in smooth specimens used as initial data. It is established that the distribution of axial residual stresses in the dangerous (smallest) section of a corset specimen practically does not differ from the distribution in smooth specimens. The results obtained provide the basis for determining average integral residual stresses by the distribution of residual stresses in smooth specimens and using them to calculate the endurance limit for hardened corset specimens. The results of the study allow making a conclusion that the most optimal nitriding practices are those wherein the average integral residual stresses are maximal. 

The article investigates a hydro-mechanical system of regular feed and principal movement of a production machine (as illustrated by a mobile drilling rig).We study the behavior of a dynamic hydro-mechanical system under varying external processes of well drilling. The task of maintaining the optimal drilling process is solved by using an original design (multivariate sensor, additional hydraulic lines linking the principal movement and the tool-feeding movement). Travel time characteristics and dynamic behavior of the regular feed are provided with one power plant. A dual-mass mathematical model of a dynamic multi-mass hydro-mechanical system (MHS) is proposed in Matlab Simulink software environment. The model contains an analytical description of mechanical, hydraulic and control subsystems and is implemented by subsequent complications of the basic model starting from a single-mass linear model to a nonlinear dual- mass one with active submodels of all subsystems. The application of the model makes it possible to study the duty cycle of a multi-branch MHS, while maintaining the consistency of the results of solutions that are getting increasingly complicated.