Vol 16, No 3 (2017)

Methods of coordinate measurement are reviewed and a possibility of their usage for fan blade geometry characterization and construction of a 3D CAD model is evaluated with account for actual blade airfoil deviations. Different components of blade geometry deviation from nominal geometry are considered. A technique of constructing a 3D model in a CAD-system on the basis of coordinate measurement, considering real manufacturing deviations of an airfoil is presented. To allow deformation of the nominal model according to the measurement data, the nominal model of the airfoil was recreated with account for the location of the measured sections. The issue of adding the measured profile of the blade root, edges and the peripheral area of the airfoil to the model is discussed. The influence of deviations of the out-of-the-flow path profile on the mechanical characteristics is assessed. A model with maximum and minimum deviations possible was constructed. Expected displacements and natural frequencies of the model were compared to the nominal ones. Further direction of investigation to determine airfoil geometry parameters most efficient for robust optimization is presented.

The paper presents the solution of the problem of simulation of the effect of radiant heat fluxes from infrared sources (IRS) on the surface of spacecraft and their modules during complex tests in a vacuum chamber (VC) 600/300. We suggest using empirical dependences as a solution to the problem of promptly obtaining the results of calculating the density of thermal radiation fluxes on the elements of the surface of a space vehicle when performing complex tests. A brief description of the design features of the IRS module is presented, which is necessary for constructing a mathematical model of thermal radiation distribution. The layout of IRS modules accommodation in VC 600/300 is shown and the main energy characteristics calculated in the modeling of radiant heat fluxes are determined. The article shows the empirical dependences obtained for calculating the energy characteristics of the IRS modules on the electric power supplied to the radiating elements. The results of  calculating the distribution of the IR flux density using empirical relationships are shown in comparison with the results of calculations using a software package and with the experimental measurements obtained.

We propose a method of selecting the orbit for spin-stabilized spacecraft in order to obtain maximum electric energy on board due to the spacecraft motion in the earth magnetic field. The article describes the peculiarities of using additional low-power energy sources for power supply systems of small space vehicles. A method is proposed for taking into account the complex dependence of the position of the resultant magnetic induction vector on the spatial attitude of the spacecraft for converting the energy of the earth magnetic field into electric power.

The article is devoted to the development of a set-theory model of the aircraft hydraulic system working fluid state using the mathematical apparatus of the set theory. The relevance of the work is connected with the necessity of developing a universal mathematical model of the hydraulic fluid state. The model is to form the basis of an intelligent system to control the working fluid state on board the aircraft. As a result, a general expression is obtained that allows describing the working fluid state at an arbitrary moment of time using its basic parameters, namely contamination, viscosity, density, chemical and temperature properties. A hierarchy of parameters of the working fluid state taking into account the diagnostic value of the information obtained during their measurement is constructed. The main classes of states are distinguished among all possible states of the working fluid. These are the ideal state, the normal state, pre-failure and failure. Each of them is described by a set of configurations of all possible values of the main parameters. А technique for optimizing the time of the inspection of technical condition based on the calculation of the change in the entropy of the working fluid is proposed. 

Various standard mathematical squeeze film damper (SFD) models that can be applied for solving rotor dynamics problems of gas turbine engines (GTE) are presently available. The accuracy of simulation is ultimately affected by the choice of a certain SFD formulation that depends on many factors – geometry parameters, oil supply method, oil inlet pressure, operating conditions etc. The present contribution suggests some recommendations for selecting a particular mathematical SFD model and compares the simulation results obtained with different SFD formulations. To this end a point rotor system is numerically analyzed with the aid of the DYNAMICS R4 (www.alfatran.com) software. 

The article deals with issues of constructing the flight pattern of an upper stage and its ballistic justification subject to minimization of the mission time taking into account the upper stage’s performance in the case of placing a group of spacecraft into the orbit plane with provision of a uniform angular distance between the satellites, and generating a motion control program to implement the chosen flight pattern. The solution of the problem is divided into two steps: the choice of a flight pattern with its project-ballistic analysis and generation of a centre-of-mass motion control program providing the required deployment of satellites. To solve the problem of the project-ballistic analysis of the flight pattern the author developed a mathematical apparatus allowing determination of a flight pattern that matches the specified criteria of time and fuel consumption by end formulae using the linear programming technique.

The problem of controlling rendezvous between a “debris collector” spacecraft and fragments of space debris in the geostationary orbit is studied. Relative motion in the orbital cylindrical coordinate system is considered. A linearized model of motion is used; relative motion is divided into periodic and secular components on the basis of the model. Motion control is carried out by thrust acceleration reversal. The problem of control is divided into two parts. The first iteration implies analytical determination of a control program using a linearized motion model. The program is based on the control of secular components of relative motion. The second iteration consists in refining the control program obtained earlier using the original math model and the analytical solution obtained in the first iteration. Numerical simulation of motion is carried out. We established that it is rational to start the rendezvous transfer at the moment when the “debris collector” spacecraft is positioned below and to the right or above and to the left relative to the space debris fragment.

The authors describe a calculation-experimental technique for the development and design of truck-based exhaust gas treatment systems on the basis of finite element modeling. The results of calculation and experimental research are presented, including distribution of sound pressure in the internal volume of the developed design of exhaust system. The design of a catalytic silencer with the best vibroacoustic characteristics was selected and tested on a truck.

The article describes experimental investigation of a method of reducing the drag of a circular cylinder. We consider installation of a flat plate parallel to the flow before the cylinder. The results for the cylinder drag coefficient depending on various locations of the flat plate relative to the cylinder are presented. The following geometric characteristics are studied: the reference chord of the plate and the angle of the plate’s position with respect to the cylinder. It was found that the drag coefficient depends on the location of the plate relative to the cylinder. The article presents experimental results that were obtained in the wind tunnel of Samara University. The locations of the plate relative to the cylinder that provide the lowest value of the drag coefficient are identified. 

The paper presents an approach to assessing structural states of space vehicles (complex organizational and technical objects) with support of taking decisions on their life cycle control. The analysis of the subject area showed the need to apply the new intellectual information technology presented in the article to the design of both the information system of a complex organizational and technical object, and the related systems for monitoring structural states and decision support as part of such an information system. We consider a version of a generalized computational model as a theoretical basis of this technology. The version discussed is a unified knowledge representation model that integrates a number of methods and approaches of the Artificial Intelligence theory and makes it possible to construct imitation-analytical polymodel complexes for monitoring states and controlling complex organizational and technical objects. The article shows that applying this technology allows comprehensive assessment of the technical state and reliability of the monitored object. The article also provides a brief overview of the software complex that solves the problems of estimating the structural states of space vehicles. The software complex is implemented on the basis of the examined intellectual information technology.

The article discusses and theoretically justifies a method and a device for non-destructive testing of conductive coatings of aircraft fuel tanks. The authors present a patented solution and display the essence of the measuring procedure that consists in scanning the surface by an electrode forming a capacitor with the test material. A mathematical model describes the process of detecting a closed defect with different sizes of the scanning electrode. The article contains metrological analysis of the developed device, considering the basic and additional errors that affect the results of the measurement procedure. By basic errors, in this paper, we mean the error in determining the coordinate of the defect and the systematic additive (methodological) error; by additional errors we understand thermal and dynamic ones. Among all types of errors that arise in the process of flaw detection, the most significant ones are identified. Also, methods for compensating various types of errors by constructive or algorithmic methods are proposed. Numerical analysis of the errors considered in the article is carried out. The analysis proves the possibility of defect localization with an error ≤ 6.5 mm. A summary table of the main types of errors is compiled.