Vol 26, No 1 (2018)

Proposedformulationandthemethodofsolutionoftheproblemoftime-optimalcontroloftemperaturefieldof an infinite slabwithtwo boundary control actions by the value of the external heat flux on its surfaces in conditions of a given accuracy of uniform approximation of the final temperature distribution of the thickness of the slab to a given one is proposed. The proposed method uses the procedure of preliminary parametrization of control actions based on analytical conditions of optimality, subsequent reduction to a special problem of mathematical programming and methods of its solution based on the alternance properties of the desired parametrical characteristics and knowledge of physical regularities of the subject area. The results and their analysis for different variants of the resulting temperature distribution curve are given.

The paper deals with the problem of functioning evaluation of complex structured objects. It is proposed to use a nonparametric Data Envelopment Analysismethod. Quantitative performance indicators for complex objects are formulated, these indicators not being expressed in monetary units. The solution of the fractional linear programming problem is solved, which determines the practical efficiency frontier on the basis of the selected limited set of object input and output variables. The proposed technique is used to assess the effectiveness of the implementation of customer relationship management (CRM) systems at a number of companies. The analysis of the location of the estimated objects in space of the input and output parameters on the practical efficiency frontier was carried out. As a result, it became possible to identify priority areas for optimizing company’s resources on a limited budget.

The analysis of random errors caused by discrete character of information from the single-coil eddy-current sensor in systems for measurements of radial clearances in compressors of turbo machines is provided. For the specified errors the distribution law of probabilities is received and the main statistical characteristics are defined. On the basis of this results the technique of assessment of computing resources of the measuring system is offered. For the given accuracy of restoration of an extremum of ADC codes on an output on condition of maintaining constant frequency of sampling in all range of changes of rotational speeds of a rotor of the turbomachine and invariable volume of a buffer memory, the algorithm of decimation of codes is offered and its parameters are determined.

An experimental stand to influence the rotor and to obtain its reactions in the form of vibration acceleration signals with the method of testing was developed. Using modern hardware, the information-measuring system for the stand was developed. The vibration acceleration signals were obtained when exposed to the rotor assembly unit at the anterior and posterior supports and along the middle part of the body unit, which became the result of the experimental search for the control capable diagnostic points. The experiment proved that the point on the front support of the body unit is control capable. The validity of using the criterion in the form of the relative peak frequency for determining the value of the preload of the assembly unit supports at exposition in the area of the front support is shown.

The main share in the annual electricity generation wind farms provide during the periods when the wind speed exceeds 8 m/s. Therefore, when designing a synchronous generator of wind power plants, it is necessary to provide maximum efficiency for rotor rotation frequencies corresponding to such values of wind speed. In the generators of wind turbines or micro hydroelectric power stations, it is not advisable to observe the known ratio of equality of constant and variable losses, which ensures the maximum efficiency in the nominal conditions. To increase the energy efficiency of the unit, the generator should be designed so that the maximum efficiency point is shifted to the zone of maximum loads and rotation frequencies - to the right of the nominal point

The paper deals with the design of a high-performance induction plant for heating viscous liquids when pumping through pipelines. Specific features of the technological process of transportation of viscous liquids through pipelines are noted. A new device built into the heater line is proposed, which makes it possible to reduce the overall length of the heatersignificantly. The device is made on the basis of a three-phase inductor with a rotating magnetic field. The device provides simultaneous mixing and heating of the liquid flow while passing through the heater. The results of numerical computation of electromagnetic and thermal fields in the "inductor-metal cylinder-hollow rotor-liquid" system are presented. It is shown that the use of the proposed device makes it possible to shorten the length of the heater by 40 ÷ 50%. The results of the studies are intended to solve the problems of calculating the optimal design and operation parameters of a multi-section heater.

It is the results of calculations of two types of underground laying of pipelines of heating networks laid in concrete (foam concrete) boxes. The first type is pipelines with applying thermal insulation on the surface of the pipe (concrete boxes). The second type is pipelines without this insulation (foam concrete boxes). Sincetheairlayerbetweenthepipeandtheshells of the boxes practically does not affect to the heat losses to the ground due to intensive convective heat transfer, we propose to reduce the dimensions of foam concrete rectangular boxes to the size of the pipe diameter. It will lead to significant (up to 50%) reduction in heat losses to the ground due to a much lower coefficient of thermal conductivity of the foam concrete compared to concrete as well as a smaller area of heat exchange with the soil. Inaddition, theweightofthestructure, itsdimensionsandcostare reducing.

In the temperature range 823-1073 K for Sn-Sb and Pb-Sb alloys the calculated steam pressure (Pa) for Sb (3.95-273.66), Pb (2.63.10-4-14.86.10-2) and Sn (3.32.10-9-8.12.10-5). High values of the ratio (p*Sb / p*Pb) .103 = 15.04-1.83 and p*Sb / p*Sn = 1.19.109-3.37.106 create a theoretical background for sequential selective separation of these metals by vacuum distillation, when the antimony, and then the lead is enriched in the gas phase, and tin - liquid. Phase diagrams for VLE (vapor liquid equilibrium), can be used the lever rule (rule lines) to help predict quantities of substances, residues and sublimates at a predetermined temperature. When calculating the parameters of the ternary alloy according to the equation of Wilson is enough to use the parameters obtained for binary systems. Equity is defined the free Gibbs energy, kJ/mol (-ΔGPb/Sb/Sn = 13.8-42.6/2.6-15.1/2.1-26.4), enthalpy, j/mol [±ΔНPb/Sb/Sn = (1.3-70.2)/(1.56-107.1)/(2.8-48.5)] and entropy,j/K.mol (ΔSPb/Sb/Sn = 15.8-25.0/3.0-17.4/2.4-15.8) for components in the Pb-Sb-Sn melts. Increasing the share of metals in the initial alloy of the magnitude of the Gibbs free energy decrease.Negative and positive values of enthalpy indicate the exothermic and endothermic nature of the processes in the melt by distillation of the components. Shown satisfactory correspondence between calculated and experimental values of thermodynamic parameters: average relative deviation of 1.9 % ; the standard deviation of 0.1 kJ/mol.

We studied the influence of a stochastic heterogeneous creep deformation on the relaxation residual stresses in the surface-hardened hollow cylinder of D16T alloy at a temperature of 125 C degrees. The surface is hardened by the air shot-peening under monoaxial tension. We have shown experimental data of local creep deformation distribution on spatial coordinate with the base of 6 mm at a length of working part of the specimen of 65 mm. We found a variation of the strains in the local sections of a specimen which strain may differ from each other by three or four times. The stochastic rheological straining determining equations with two random parameters are suggested. The parameters define individual straining properties of the local sections. The method for identification the parameters is developed. The relaxation of residual stresses in every local section taking into account define individual creep straining properties under four modes of tension stresses is studied. We observe, velocities of the relaxation residual stresses in the local sections may differ from each other by 2 or more time as a consequence of creep. Several recommendations for estimating the resource of hardened specimens under the creep conditions taking into account define individual straining properties on spatial coordinate.

The problem of carrying out technological calculations for oil separation systems in oil fields is considered. The use of the MiRPiA software for mathematical modeling of oil separation systems is proposed. Comparison of the calculation accuracy of the Mir PiA software with the software products Aspen Technologies HYSYS and Invensys Process Systems PRO/II is made. The correspondence of the obtained calculations to the experimental data of single degassing of oils with various gas factors is revealed.

The paper deals with the problems of automated testing system of database according to the thermophysical properties of chemicals. An offered set of simple criteria allows to decrease the errors in constant and temperature-dependent parameters of chemicals. This system was realized in the program platform for modeling and calculation of the processes and devices (“MiRPiA”). The testing of this system showed the feasibility of its use. Some errors can occur on the acentric factor for the light chemicals. The assessment of the standard liquid density for the heavy hydrocarbons is problematic.