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- ДокументAdiabated flowing streams in nozzles: influence of regular characteristics on relaxation steam formation(2019) O. Chekh, S. Sharapov, V. ArsenyevTwo-phase nozzles, in which the phase transition process takes place, can work in jet superchargers for various purposes, including jet thermal pumps (steam-water injectors) and thermal compressors. In such schemes of thermal transformers, the ejector performs the function of a preliminary compression stage in order to reduce the load on the compression of the working substance in the main compressor. The use of fluxes of boiling liquid as energy-efficient working fluids is inhibited due to the lack of a reliable description of the mechanism of their flow. Finding the dependence of the steam content on the pressure and temperature at the nozzle exit will make it possible to determine the variant of the initial parameters at which the overproduction of steam will be greatest. It is also worth determining the change in the velocity factor, as well as the change in the thrust of the nozzle in the studied range of parameters, in order to find out whether the pressure at the nozzle outlet is a determining factor when choosing the design parameters of the nozzles. The article proposes to investigate the boiling streams in such nozzles by the method of mathematical modeling using a model that takes into account the relaxation nature of vaporization. The study used a compressible two-phase medium model, a kinetic model of evaporation / condensation. The model also takes into account the dynamic and mechanical equilibrium of the process of evaporation-condensation. The calculations were performed using an Ansys CFX commercial CFD product. The value of the mean square relative error of pressure measurement does not exceed 0,119%. The average discrepancy between the obtained data between the mathematical model and the field experiment does not exceed 3%.
- ДокументThe relationship between the surface tension and the saturated vapor pressure of model nanofluids(2019) O. Ya. Khliyeva, D. A. Ivchenko, K. Yu. Khanchych, I. V. Motovoy, V. P. ZheleznyInformation on surface tension is necessary for modeling boiling processes in nanofluids. It was shown that the problem of predicting the surface tension of complex thermodynamic systems, such as nanofluids, remains outstanding. It should be noted that the surface tension of liquids and the saturated vapor pressure are due to a specific intermolecular interaction in the region of spatial heterogeneity of the substance (surface layer). Moreover, the compositions of the surface layer of nanofluid and its liquid phase are not equal. The presence of nanoparticles in the base fluid affects the composition of the surface layer of liquids. However, there are no methods for determining the composition of the surface layer of nanofluids and this fact complicates establishing the dependence of the surface tension on the state parameters of nanofluids. It should be mentioned that the number of possible methodological errors in measurements of the saturated vapor pressure of nanofluids is significantly lower than for the surface tension measurements. Therefore, in the development of models for predicting the surface tension, scientific and practical interest has establishing the relationship between the surface tension and the saturated vapor pressure of nanofluids. In the presented work, we consider the nanofluids of isopropanol/Al2O3 nanoparticles and o-xylene/fullerenes C60. Saturated vapor pressure and surface tension of nanofluids of isopropanol/Al2O3 nanoparticles have been studied in the temperature range 293 – 363 K and concentrations of Al2O3 nanoparticles 0-8.71 g/kg. Measurement of saturated vapor pressure and surface tension of nanofluids of o-xylene/fullerenes C60 have been performed in the temperature range 283 – 348 K and the concentration of C60 0-7.5 g/kg. It is shown that additives of Al2O3 nanoparticles and fullerenes C60 lead to a decrease in the surface tension and increase in the saturated vapor pressure. It is shown that there is a universal dependence between the reduced surface tension and saturated vapor pressure for the researched nanofluids.
- ДокументA new approach to increasing the efficiency of the ship main engine air waste heat recovery cooling system(2019) R. Radchenko, M. Pyrysunko, M. Bogdanov, Yu. ShcherbakThe efficiency of integrated cooling air at the intake of Turbocharger and Scavenge air at the inlet of working cylinders of the main diesel engine of dry-cargo ship by transforming the waste heat into a cold by an Refrigerant Ejector Chiller (ECh) as the most simple in design and reliable in operation and by complex in design but more efficient Absorption Lithium-Bromide Chiller (ACh) was analyzed. A ship power plant of cogeneration type using the relatively low-grade heat of water of a heat supply system with a temperature of about 90 °C, that significantly complicates the problem of its conversion into cold were considered. Because of the insufficiently high efficiency of transformation of the heat of hot water (low coefficient of performance) as compared with steam, the resulting cooling capacity may not be enough for cooling intake air of the turbocharger and scavenge air, that raises the problem of the rational distribution of heat loads between the Turbocharger Intake Air cooling circuit (subsystem) and Scavenge air cooling circuit and the need to use chillers of various types. This takes into account the rational parameters of cooling processes of the scavenge air in the cogeneration high-temperature stage of scavenge air cooler, in the intermediate stage of traditional cooling air with seawater, and in the low-temperature stage for deep cooling of the scavenge air by using a chiller. A new approach is proposed to improve the efficiency of integrated cooling Intake Air of the turbocharger and Scavenge Air at the inlet of the working cylinders of the ship main engine of a transport ship, which consists in comparing the required cooling capacity and the corresponding heat needs during the trade route with the available heat of exhaust gases and scavenge air of the cogeneration power plant, determining the deficit and excess cooling capacity of heat utilizing cooling machines of various types, that allows to identify and realize the reserves of improving the efficiency of cooling intake air of the turbocharger and the scavenge air of the main diesel engine through the joint use of chillers of various types.
- ДокументUsing the heat of recirculation gases of the ship main engine by an ejector refrigeration machine for intake air cooling(2019) R. Radchenko, D. Konovalov, M. Pyrysunko, M. RadchenkoOne of the promising ways in environmentalizing marine internal combustion engines is the neutralization of harmful substances in exhaust gases through particular gas recirculation (EGR-technology). However, the use of such techniques conflicts with the engine's energy efficiency. In the work presented, the scheme-design solution of the exhaust gas recirculation system with using the heat of recirculation gases by an ejector refrigeration machine for cooling the air at the intake of ship's main engine is proposed. The effect of using the heat of recirculation gases for cooling the air at the intake of the engine is analyzed taking into account the changing climatic conditions for a particular vessel's route line. It is shown that the use of an ejector refrigeration machine reduces the air temperature at the entrance of the main engine by 5-15 ° С, which reduces the specific fuel consumption by 0.5-1.5 g/(kW∙h). This reduces emissions of harmful substances when the engine is running with recirculation of gases, in particular, NOx by 30-35%; SOx by 10-12%.
- ДокументСтенд для дослідження розширювальних турбомашин малої потужності та агрегатів на їх основі(2019) С. М. Ванєєв, Д. В. Мірошниченко, В. О. Журба, Я. В. ЗнаменщиковВ даний час для вирішення проблем енергозбереження проводяться роботи з дослідження та використання малопотужних розширювальних машин для утилізаційних турбогенераторів. Перспективним є створення турбоагрегатів на базі відносно тихохідних вихрових розширювальних машин, але робіт по їх експериментальним дослідженням відомо мало. У зв'язку з цим необхідно створення матеріально-технічної бази, що включає нові і модернізовані стенди, експериментальні модельні та натурні установки, об'єкти дослідження, виробниче та технологічне обладнання, обчислювальні і програмні комплекси. У статті представлені результати розробки і тестування елементів стенду досліджень турбогенераторів малої потужності для утилізації енергії стиснутих газів. Створено експериментальний стенд, на якому можна проводити дослідження і випробування розширювальних турбомашин і турбогенераторів на їх основі різного конструктивного виконання потужності до 15 кВт, а також демонструвати роботу турбогенератора потенційним замовникам продукції. Прилади та обладнання стенду дозволяють плавно змінювати електричне навантаження і отримувати необхідні параметри і характеристики розширювальних машин і турбогенераторів. У складі стенду створена інформаційно-вимірювальна система, яка забезпечує контроль стану обладнання; здійснює реєстрацію інформації і обробку даних вимірювань з представленням результатів в табличному і графічному вигляді; забезпечує надійне зберігання отриманої інформації тощо. Створено дослідний зразок енергозберігаючого турбогенератора на основі вихрової розширювальної машини. Конструкція турбогенератора дозволяє досліджувати вплив основних геометричних параметрів проточної частини на ефективність вихрової розширювальної турбомашини і генератора в цілому. Результати роботи будуть використані для дослідження розширювальних турбомашин і утилізаційних турбогенераторів на їх основі, що використовують енергію стиснутого газу.