Vol 26, No 4 (2018)

Study of power grid activity has been mainstreamed not only in terms of productive, but also in environmental aspect, reflecting the impact of power grid on environmental. Analysis of infrastructural model of Samara region industrial system showed, that enterprises of power grid have multiple connections with industrial enterprises of Samara city and Samara region. This fact highlights the need for exploration of power grid activity in conjunction with this manufacturing and economic systems. A control algorithm for the activity of a regional power grid system of Samara in conjunction with region and city manufacturing and economic systems was developed. The mathematical modelling of power grid activity was carried out with the help of Cobb-Douglas production functions. Double loops simulation control system which allows to explore ways of enhancing the economic and environment efficiency of regional power grid has been built. Proposed scenarios of power grid functioning and their environmental impact were analyzed. Recommendations on the management of activity of object could be applied on industry branch (region power grid) level as well as on industry region level (regional industrial complex).

The paper presents experts qualification assessment, its importance and productivity, selection of experts for the expert evaluation at the project planning stage. The analysis of literature, scientific publications, existing solutions and methods for assessing the competence of experts using the hierarchy method is carried out. Criteria, accurately reflecting the characteristics of this expert are proposed, how suitable it is for this expert evaluation, which allow the most effective assessment of its competence. The application of the method of analysis of hierarchies is considered to solve this problem its positive and negative sides regarding the application of the competency assessment. The qualification assessment method was developed using analytic hierarchy process elements. Decisionmaking behavior was described with application of developed method; competence affecting factors also were described, such as work experience, number of successfully completed expert ratings, compliance of education with the scope of work, and workgroup characterization. An example of calculation by the developed method is given, selection of the most suitable expert, according to the offered characteristics the comparison of calculations by the developed method with the classical calculation method of analysis of hierarchies. Exemplified the developed-method calculation, was made a comparison with classical hierarchy analysis method. The proposed method has the necessary accuracy and a small relative error and can be used to assess the competence of experts and other tasks to which the hierarchy analysis method is applicable.

The paper is dedicated to the principles of construction of the systems for measuring of radial clearances in compressors of gas-turbine engines. The methods realized in such systems are based on using of single-coil eddy-current sensors with sensitive elements made as a conductor strips and self-compensation of temperature influences on the sensor. The method also involves the using of only one sensor (it provides work and compensation functions) and as a result only one hole in the engine stator. The selfcompensation procedure is carried out in operation mode during rotation of the rotor. It involves measuring and fixing of extreme values of equivalent inductance of primary winding of matching transformer of single-coil eddy-current sensor at the moments when the controlled blade is in sensor sensitivity area and when the blade is out of it (when sensor’s sensitive element is in interblade zone) and further difference calculation between obtained results. This difference doesn’t depend on temperature influence on sensor constructive elements. Because of this self-compensation there is no need in additional sensor for temperature correction an as the result there is no need to make additional hole in engine stator. Hence the proposed method is better compared to existing. The article considers the general structural and functional scheme of the system that realized the method with temperature self-compensation. The main operation algorithms of the system such as the algorithm for seeking of extreme codes in interblade zone, the algorithm for difference calculation between codes with the removal of “non-compensated” temperature influences on the sensor and the algorithm for blades numbers detection during asynchronous sensors surveying are given too.

The paper analyzes the methods of reconstructing time-local information signals used in differential scanning calorimeters (DSC) and makes a choice on wavelet functions. Based on the selected maternal wavelet, a technique was proposed for approximating the signals obtained experimentally with a DSC device. Approbation of the technique for single-peak and two-peak signals was carried out. Having the possibility to change the parameters of the approximating function in the course of the mathematical description of the signal, the possibility of using the technique for working with substances possessing endo- and exothermic properties at the time of the phase transition was proved. Evaluations of the effect of digitizing the signals on the accuracy of the measured differential temperature were given. As a result, the relative error was estimated by the approximating function when using the proposed technique from the number of iterative calculations performed.

Dynamic of electromagnetic bearing incorporation in the capacity of a supercharger for the gas compressor unit (GCU) from PAO “Gazprom” demonstrates incremental increase beginning from 2005. Wherefore problem of electromagnetic bearing (EMB) performance build-up (reliability growth, power reduction, mass reduction, dimensional specifications reduction etc.) become progressively important. As a consequence, thermal effect problem along of specific electromagnetic load increase become on the front burner. Magnetic, thermal and fluid dynamic numerical simulation by finite-element method by custom-made software allows computational accuracy to advance as consequence reliability GCU. The results of geometry model EMB analysis for the gas compressor unit presented in this paper. It is educed singularity of heat carrier flow in cooling system of electromagnetic bearing. Near-wall modeling approach for turbulence flow and the most relevant turbulent model was analyzed. The turbulence mode and near-wall approach was selected according to operational features of electromagnetic bearing, an introduction was given for meshing and boundary conditions were determined.

The problem of determining the frequency and amplitude of temperature fluctuations of the heating furnace by resistance at positional regulation with the help of unipolar ideal relay and relay with loop characteristic is considered. The aim is to optimize the operation of the two furnaces in the power supply system so that the furnaces are not switched on simultaneously in the temperature stabilization mode. In the literature, as a rule, simplified examples of tracking systems with the use of an ideal relay are considered, various methods of accurate and approximate methods for determining the frequency and amplitude of symmetric oscillations are given, however, with asymmetric oscillations, taking into account the displacement, the most acceptable is the algebraic method using the harmonic linearization method, with the dependence of the frequency and amplitude of the oscillations on the relay characteristic loop parameter in order to assign this parameter at an acceptable temperature deviation. The coefficients of the harmonic linearization of a relay with a loop characteristic with allowance for bias are complex expressions involving the amount of displacement. To simplify the calculations, the limiting variant is adopted, when the magnitude of the amplitude of the oscillations is equal to the sum of the displacement and half the width of the relay loop.

In the paper the review of technical devices for connection of a three-phase winding of the stator of the asynchronous motor to a single-phase network is carried out, their main advantages and shortcomings are considered. A theorem on obtaining a threephase symmetric stress system using two single-phase sources of electromotive force is presented and proved. On the basis of the proved theorem the electric scheme for connection of a three-phase stator winding of the asynchronous motor to a single-phase network is offered. In the article authors calculate currents, active and reactive power, the power factor of the two single-phase sources of electromotive force and an asynchronous motor when changing the slip in the operating range. The phase resistances of the asynchronous motor were determined using an L-shaped equivalent circuit. In the program package Matlab Simulink was carried out simulation of the induction motor connected by means of the schema under consideration. For the practical implementation of the proposed scheme as one single – phase AC voltage source can be used single-phase network, as the other – a semiconductor converter connected to a single-phase network.