IMPROVEMENT OF THE CONTROL SYSTEM OVER DRUM BOILERS FOR BURNING COMBUSTIBLE ARTIFICIAL GASES

According to expert estimates of the world economy growth, the demand for energy resources may grow by 36 % from 2011 to 2030 [1]. Key factors driving the increase in energy consumption will include the planet’s population growth (up to 8.3 billion by 2030) and the rise in global GDP (twice compared to 2011). Owing to rapid industrialization and urbanization of the low and middle-income countries, they will account for 70 % of the world GDP growth and for over 90 % of the increase in world demand for energy. A logical increase in the energy demand, that is in proportion to the GDP growth, will be limited by a continuous improvement of the efficiency of its use. Reduction in the energy intensity of production will be achieved by utilizing renewable energy resources, shale energy, and the new improved technologies for the production of industrial products and raw materials processing [2]. Under conditions when the price of conventional energy resources in global markets experiences sharp fluctuations and access to them can be restricted, it is required, first of all, to consider the geographical position and the availability of a certain type of energy resources. An implementation of low-cost activities with a fast payback period might become a promising direction in the development of energy sector. This will make it possible, without attracting significant funds, in the shortest possible time, to reduce fuel and electricity consumption. For example: employing new structural schemes and automated control systems at steam generators that are at operation today. Given this, there is a possibility to use as fuel combustible artificial gases without substantial modernization of equipment. The artificial gases, which are produced from solid fuel, include coke, shale, generator and blast-furnace gases. In most cases, these gases are a byproduct of chemical or metallurgical production and economically disadvantageous to be transported over long distances as they possess low calorific value (Table 1).

One of the promising directions in the development of power industry in Ukraine is the implementation of low-cost activities with a fast payback period, which would make it possible, without attracting significant funds, and in the shortest possible time, to bring down fuel and electricity consumption. Such activities could include the use of the new structural circuits of automated control at the existing steam generators running on organic fuel, which will allow, without a substantial equipment modernization, the use of combustible artificial gases as fuel.
A limiting factor for the combustion of artificial gases in energy drum boilers is their low calorific value and insufficient throughput of the regulating valve, which depends on density of the regulated medium.
We examined a possibility of burning artificial gases in energy boilers without considerable modernization of basic equipment (replacement of burners and controlling elements, installation of additional steam generating equipment) both for a single drum boiler and a group of boilers operating in the common steam line. In both cases, in order to increase the throughput, a gas compressor is employed. It was established that for the aligned work of the compressor with a heat load ACS of one boiler, it is necessary to define a transfer function of the communication device. To control a group of boilers, we synthesized multidimensional optimal ACS that would make it possible to improve the integrated quality indicators to regulate pressure and consumption of superheated steam.
The implementation of the obtained technical solutions will improve energy security and effectiveness of the industrial potential of Ukraine.
acterizing the process of cavitation. Approbation of the method for control over effectiveness of the cavitation process was carried out by measuring the vibrations at various temperatures of liquid at the outlet. The cavitation heat generator for decentralized heating of industrial buildings and facilities was examined and implemented for actual operation. On this basis, a thermal system for decentralized heating of buildings was designed and studied. The circuit of the thermal system differs by the following feature: two connected cavitation heat generators are connected in series for heating of the liquid. At the same time, the heated liquid passes through a heat generator operating at high frequency, then through a heat generator operating at lower frequency. In the generator with high frequency, smaller cavitation embryos are excited, which increase in size in the generator with low frequency. This leads to increased impulses of cavitation pressure and increases the effect of cavitation.
On this basis, a heat system for decentralized heating of buildings was designed, and studied, with its energy efficiency. To increase energy efficiency of the thermal system with cavitation heat generators, their sequential installation was proposed. The heated liquid must pass successively through a heat generator operating at high frequency, then through a heat generator operating at lower frequency.
The efficiency of the system developed exceeds 18 % compared to the system of centralized heating by natural gas, which is a convincing prospect of use.
A method for effective control over the cavitation process during operation of a heat generator was developed, based on the suppression of waves of oscillatory energy of the object. The method is based on direct measurements of vibrations -a parameter char- An application of tubes with punched spiral-tape finning is promising for heat exchange intensification in convective heating surfaces of boilers and boilers-utilizers. Results of experimental research into thermo-aerodynamic characteristics of specified heating surfaces are presented. As a result of research, heat exchange intensification by 17…32 % due to fin punching was established. Heat transfer increases at an increase in the Reynolds number and a decrease in the degree of finning. Dependence of heat transfer on the accepted parameter for characterizing the bank geometryrelative to longitudinal pitch of tubes -is extreme with peaks in domain of variability relative to longitudinal pitch of 2.7…3.5. Efficiency of punched finning was determined. Results of the study of aerodynamic resistance showed its increase by 18…40 % due to 17 We examined influence of the geometry of thermoelement branches and the distribution of thermoelements in cascades of the two-cascade thermoelectric cooling devices on the reliability indicators. An analysis was conducted for the operating range of temperature difference, nominal thermal load under the mode of maximum refrigeration capacity at preset current. A mathematical model was constructed, connecting reliability indicators of the cooler and the geometry of thermoelement branches, distribution of thermoelements in the cascades, temperature differential and operating current in the cascades, and thermal load.
We ran an analysis of the model, which showed that the failure rates and the probabilities of failure-free operation demonstrate clearly pronounced extrema that can be applied when designing the two-cascade thermoelectric cooling devices with enhanced reliability. The analysis of the obtained model revealed that the variation of the geometry of thermoelements and their distribution in the cascades could be employed to achieve a two-time reduction in the failure rate of a thermoelectric cooler and a corresponding increase in the probability of failure-free operation.
Keywords: two-cascade thermoelectric cooling device, geometry of thermoelement branches, reliability indicators. For analysis of thermal processes occurring in SA under conditions of presence of overvoltage of different nature in the electric network, it is necessary to conduct research using volt-ampere characteristics. Thus, energy, released in SA, has to be determined. This approach is essential for correct selection of parameters of SA not only in terms of protection of electrical networks, where it is installed, but also to provide proper operation of a protective device itself. This approach will allow choosing parameters of SA at a design stage, which greatly reduce emergency rate throughout the entire period of operation.
Presented We determined thermo-aerodynamic efficiency of in-line and staggered banks of tubes with punched spiral finning by results of experimental studies. In-line banks have higher efficiency. As a result of calculation research into thermo-aerodynamic efficiency of four types of heating surfaces of a powerful boiler-utilizer, inline tube banks with punched spiral finning turned out to be more efficient by this parameter. The Kirpichov criterion for these tube banks, located in one shell, is 319, for staggered tube banks with punched finning -228.8, for staggered tube banks with continuous finning -223.8, and for staggered bare-tube banks -143.0.
Keywords: heat exchange intensification, aerodynamic resistance, punched spiral finning. Based on mathematical and logical modeling, a technological support system for changing the battery capacity based on the prediction of voltage variation in measuring the temperature of electrolyte in the volume of the batteries was developed in the composition of a technological system for battery operation. The developed technology makes it possible: to control operational capacity of the accumulator battery in order to obtain a functional assessment of change in the total charge and discharge voltage; to obtain an integrated reference estimation of change in the charge and discharge volt-age; to develop an integrated system for assessing a change in the voltage of the battery, which enables maintaining capacity of the accumulator battery when measuring the temperature of electrolyte at the input to the battery. The limiting temperature change of electrolyte, -35 °C, was determined at charging with direct current supply and a limit-ing voltage change for a further charge and discharge was established with a change in the consumption of electric energy. The use of an integrated system for the estimation of voltage change obtained based on the alignment between electrochemical and diffusion processes of discharge and charge makes it possible to take timely decisions on recharg-ing to prevent recharge and unacceptable discharge. Coordination of the electrochemi-cal and diffusion processes that accompany charging and discharging of the battery makes it possible, for example under conditions of functioning of a wind power plant with a capacity of 10 kW, to reduce the cost of production of energy and the payback period of the wind power plant by up to 25 % due to a reduction of the charge period and prevention of gas formation.
Keywords: lead-acid accumulator, mathematical and logical modeling, decision making.
in the assigned network, because it may be different in values of amplitudes of lightning currents, rates of increase and the number of lightning strikes in one channel (as we know, there may be 10 of them). All presented parameters will influence thermal balance of SA, and, at some values, they can lead to its disturbance, which will cause the failure of SA and the damage to equipment of electric network. This conclusion emphasizes the need for detailed analysis of overvoltage that may occur within the network when selecting parameters and the place of SA installation. Taking into account the magnitudes and composition of overvoltage will make it possible to provide serviceability of SA throughout the entire period of operation.
It was established that dependences of change in the transition point from the spatial-vector to the one-time PWM on the temperature of traction motor for a tram and a diesel locomotive are not similar. Different level of the location of this point is predetermined by the different load in magnetic circle of the motor, by different level of saturation coefficient. The difference in saturation coefficient is 0.15-0.4 r.u.
Keywords: traction induction motor, identification of optimal operating modes, performance efficiency of traction drive. The study addresses determining optimal operating modes of the induction traction drive. We identified optimal operating modes of the autonomous voltage inverter at different temperatures of windings of the traction motors for a tram carriage and a diesel locomotive.

DOI
The identification is carried out of optimal parameters in the operating modes of autonomous voltage inverter of the traction drive of a tram and a diesel locomotive. We obtained dependences of performance efficiency and electromagnetic torque of the induction traction motor on the rotation frequency and temperature of the windings for the following modes: acceleration, recuperative braking, and maintaining preset speed.
We determined operating modes of induction traction drive of the tram Tatra T3 VPA and the diesel locomotive 2TE25A over the entire range of motors' rotation frequency at spatial-vector and one-time pulse-width modulation of the semiconductor inverter for different values of temperature of the motor's windings. A technique was devised for this purpose, which is based on solving a problem on the optimization of parameters of the traction drive using a combined method that employs genetic algorithms and the Nelder-Mead method.