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The reliability of diesel locomotive operation largely depends on its temperature conditions. The stability of temperature conditions should be provided by the cooling system, which regulates the heat removal from the coolant depending on its temperature and the operating mode of the diesel engine. During operation, with the existing algorithms for the operation of standard cooling systems, significant temperature drops of the coolant are observed over fairly short time intervals. This negatively affects the reliability of the diesel engine. On different series of diesel locomotives, the system for regulating the operation of refrigerator fans may differ significantly. To regulate the air flow through the refrigerator sections, an algorithm is used to turn on or off a certain number of motor fans or to change the oil flow through an axial piston type hydraulic machine, or to regulate the oil level in a torque converter. To develop an algorithm for controlling the operation of the cooling system in order to stabilize temperature conditions, it is necessary to study the processes implemented in operation. The article presents the results of the study of temperature fluctuations of the coolant during the operation of locomotives. According to the results of the study, the realizable rates of increase and decrease in the temperature of the coolant, taking into account the inertia of the process, are established. It has been established that standard cooling systems do not allow exceeding the established limits, but do not exclude significant changes in the temperature of the coolant when changing the operating mode of the diesel engine. The obtained results can be used to improve the management of heat exchange processes in order to stabilize the temperature conditions of the diesel engine, which will increase the reliability of its operation.

Currently, according to regulatory documents, the resistivity of power line wires is assumed to be the same for any permissible load current and the heating temperature of the wires is equal to 20 degrees. This account of resistivity causes significant errors that significantly affect the operating modes of power transmission lines. This article analyzes the influence of outdoor air temperature, load current, solar radiation intensity, wind speed and direction on the heating temperature of overhead power lines, and as a result, on the value of the resistivity of the wires and power and electricity losses in them. The example of the BAM highway shows that even in the conditions of one region, the outdoor air temperature varies, depending on the time of year, within a very wide range. This in turn requires careful consideration of the dependence of the resistivity value of the line wires on the external air temperature. At the same time, it is shown that it is permissible to ignore the intensity of solar radiation, wind speed and direction on the heating temperature of overhead power lines due to the lack of comprehensive information about these factors and their opposite direction. However, this assumption will only be valid for operating currents in the range from zero to double the current value corresponding to the economic density. When calculating power losses, especially in heavily loaded lines, it is necessary to take into account all external temperature influences. Due to the appearance of sensor temperature sensors, it is proposed to use them directly to measure the heating temperature of line wires and then calculate their resistivity.

The article is devoted to numerical methods for solving nonlinear heat conduction problems with considering for the relaxation of heat flow. A mathematical model is developed on the basis of a non-linear heat equation of the hyperbolic type for calculating the temperature field in an infinitely extended (unlimited) plate. The implementation of the grid method using a three-layer implicit difference scheme for solving the nonlinear hyperbolic heat conduction problem is presented for the case when the absorption of radiation energy is modeled by a volumetric heat source. A numerical solution of the nonlinear heat conduction problem in an unbounded plate is obtained taking into account the relaxation of the heat flow on the basis of the finite difference technique using the sweep method and iterative refinement of the coefficients. A calculation algorithm with a graphical representation of the results of calculating the temperature field in an unbounded plate under the influence of concentrated energy flows is described. A comparison of the results of calculations of temperature fields in mathematical modeling on the basis of the nonlinear hyperbolic heat equation and the corresponding linear model using the mean integral values of thermophysical and optical characteristics is presented. The significant differences obtained between the temperature fields corresponding to the nonlinear and linear problems justify the need to take into account the temperature dependence of the thermophysical characteristics and the absorptivity in the study of high-intensity processes of heating the bodies. The developed nonlinear mathematical model of body heating with allowance for the finite speed of heat distribution and the temperature dependence of the material properties, can be used to select the modes for processing mode bodies with high-intensity energy flows.

The use of new self-supporting insulated wires and high-temperature wires in the operation of power lines allows increasing the capacity of lines and, as a rule, reducing operational costs. An optimal utilization of the power line load capacity depends on the precise determination of the permissible current loads. The values of permissible currents and steady-state temperature are the main parameters of the line operating mode, affecting the strength and sag of the conductor. The temperature of the wire depends on weather conditions and current load. There are methods for determining the temperature and permissible currents for widely used traditional wires such as AC. They are partially outlined in the EIS (Electrical Installation Standard) and the standard of PJSC FGC UES (Federal Grid Company of Unified Energy System) of 2013. However, there is lack of studies in new types of wires. The paper considers the effect of weather conditions and load on the temperature and real-power losses in insulated and high-temperature wire, and solar radiation is under special consideration. For comparison, we present the results of calculations on traditional AC wires. The research shows that solar radiation, being taken into account, provides an increase of real-power losses of about 2 % with the given values of load and weather conditions. Calculations of permissible current values according to the developed technique for classical AC wires reveal a high coincidence with the values from PJSC FGC UES standard. The relative error is within two percent, and the proposed method is more generalized. It allows simultaneous analysis of both uninsulated and insulated wires. Due to the widespread use of self-supporting insulated wires, power industry experts can use the developed software in the design and operation of modern power lines to optimize capacity.