Control of characteristics of closed gas turbine plants of submarines propulsion complexes

Подводная техника особенно нужна при работе и снабжении подводными судами объектов на Арктическом шельфе вдоль Северного морского пути, связанного с преодолением ледовых полей. Среди различных типов энергетических установок для подводной техники перспективны замкнутые газотурбинные установки (ЗГТУ), способные в одноконтурном варианте работать на углеводородных типах топлива. В качестве окислителя можно использовать воздух, который на судах можно хранить в сжатом виде. В этом случае не нужна специальная береговая инфраструктура, ограничивающая дальность плавания подводной техники. За основу базовой схемы ЗГТУ принят газотурбинный двигатель (ГТД) с регенерацией (Р) теплоты, как более экономичный по сравнению с ГТД простого цикла, и схемы которого характерны для микрогазотурбинных двигателей. Также рассмотрены ЗГТУ с турбокомпрессорным утилизатором (ТКУ) и регенерацией теплоты как более экономичные и обладающие удельной мощностью в 1,3…1,5 раза большей, чем в ЗГТУ с Р. Определены характеристики ЗГТУ на переменных режимах, так как подводная техника используется при исследовательских, технологических и транспортных работах при частичных нагрузках и различных видах нагружения. Для улучшения экономичности ЗГТУ на режимах частичного нагружения предложено применить регулируемый сопловой аппарат (РСА) в свободной силовой турбине. На частичных нагрузках посредством РСА можно перераспределить теплоперепад между турбинами, изменить расход газа через турбины, приблизить регулирование к количественному типу. При этом наблюдается увеличение эффективного КПД относительно других способов регулирования при уменьшении мощности двигателя и рост начальной температуры газа, который приближает параметры рабочего цикла двигателя к номинальным значениям. Underwater equipment is especially needed when operating and supplying objects by submarines on the Arctic shelf along the Northern Sea Route associated with ice fields overcoming. Among the various types of power plants for underwater equipment, closed gas turbine plants (CGTP) are promising, capable of operating in a single-circuit version on hydrocarbon types of fuel. Air can be used as an oxidizing agent, which can be stored compressed on ships. In this case, there is no need for a special coastal infrastructure that limits the range of navigation of underwater equipment. A gas turbine engine (GTE) with heat regeneration (R) is adopted as the basis for the basic scheme of CGTP, as it is more economical in comparison with a simple cycle GTE, and the schemes of which are typical for microgas turbine engines. Also considered are CGTP with a turbocompressor utilizer (TCU) and heat regeneration as more economical and having a specific power 1.3...1.5 times higher than in CGTP with R. The characteristics of CGTP in variable modes are determined, since underwater equipment is used in research, technological and transport works at partial modes and various types of loading. To improve the efficiency of CGTP in partial loading modes, it is proposed to use a variable area nozzle (VAN) in a free power turbine. At partial loads, by means of VAN, it is possible to redistribute the heat drop between the turbines, change the gas flow rate through the turbines, and bring the regulation closer to the quantitative type. At the same time, there is an increase in the effective efficiency relative to other control methods with a decrease in engine power and an increase in the initial gas temperature, which brings the parameters of the engine operating cycle closer to the nominal values.

Effect of Ketoprofenphonophoresis and Femoral Nerve Block in Knee Osteoarthritis

Objective: To evaluate the effect of ketoprofenphonophoresis and femoral nerve block in knee osteoarthritis. Methods: One hundred and fourteen patients with knee osteoarthritis were randomly divided into two groups. The control group consisted of 57 patients who were treated with only ketoprofenphonophoresis. The experimental group consisted of patients were treated with ketoprofenphonophoresis and femoral nerve block. The patients were followed for more than one month. The treatment effect assessed by observing their WOMAC index before and after therapy. Results: All the patients finished the follow-up. Their WOMAC indexes were reduced after therapy and one month after treatment, especially in the experimental group (P < 0.05). The effective efficiency of ketoprofenphonophoresis and femoral nerve block were higher than that in the control group after treatment and after one month of follow-up (P < 0.05). Conclusion: Compared with only ketoprofenphonophoresis, the combined treatment of ketoprofenphonophoresis and femoral nerve block was more appropriate in knee osteoarthritis.

One-Dimensional Modeling of Triple-Pass Concentric Tube Heat Exchanger in the Parabolic Trough Solar Air Collector

The parabolic trough solar collector has a very high absorber tube temperature due to the concentration of solar radiation. The high temperature leads to large heat loss to the environment which reduces efficiency of the parabolic trough collector. The heat loss reduction can be obtained by adopting a multi-pass fluid flow arrangement. In this chapter, airflow travels in three passes of the receiver to absorb heat from the glass covers and absorber tube to decrease surface temperatures. 1D mathematical model is developed to evaluate effective efficiency and the temperature distribution of surfaces and fluid. The mathematical modeling is based on air temperature gradients and solved by a numerical integration. Diameter ratios of outer glass to inner glass (r23) and inner glass to absorber tube (r12), Reynolds number (Re), and tube length (L) are varied to examine the efficiency and the temperature distribution. Results showed that the highest efficiency is archived at r23 = 1.55 and r12 in the range of 1.45 to 1.5. The efficiency increases with Re and decreases with L due to dominant heat transfer in terms of thermohydraulic behavior of a concentrating solar collector. With the optimum ratios, absorber tube temperature can reduce 15 K compared with another case.

RESEARCH OF CENTRIFUGAL GRINDER GRANTS

The processes of grinding dry and wet dispersed materials are common in alcohol, beer, sugar, meat, bakery, feed, chemical and a number of other industries, as well as in construction. Relevant for these processes, especially recently, in connection with the rise in the cost of energy resources, is the problem of reducing energy costs during their implementation, subject to high productivity, sufficient degree and uniformity of grinding and moderate cost of equipment for the process. The article proposes scientifically substantiated dependencies for calculating the minimum required electrical power of an experimental industrial grinder, which is considered as a replacement for hammer crushers, when used to grind wet grain of wheat, rye or corn and ensure the specified performance, taking into account the daily volume of raw materials processed at the enterprise. as well as the permissible degree of its refinement. In particular, equations were obtained to determine the power consumption for bringing the raw material in the grinder into rotary motion, for the friction between the grains of the raw material and the grinder discs, as well as the internal surfaces of its working chamber, for the friction between the grains themselves, the power required for grinding. The electric power of the grinder, the effective efficiency (41%) and the total efficiency (14%), by which it is superior to hammer crushers, have been calculated. In this work, based on the theory of contactless hydraulic seals, the analysis of possible trajectories of the particles of the processed raw materials in the working chamber of the grinder (grains of wheat, rye or corn moistened with water) is carried out, the forces acting on the particles of the raw material in the process of their movement from the axis of the grinder to the periphery of the working chamber are determined, as well as the analysis of the interaction of particles during their grinding, based on the theoretical provisions of the mechanics of quasi-solid and quasi-liquid bodies.

Performance Analysis Based on Experimental Data of Backpressure Steam Turbine for Cogeneration in Saturated Steam Applications

This paper aims to validate the performance capabilities of a Pressure Reducing Turbine (PRT) with respect to initial predictions based on analytic calculations. The designed equipment was installed in a beverage facility, located in Brazil. The validation procedure consists of analyzing the data collected in several periods of PRT’s operation, accessed remotely via an online server. The analysis of empirical data identifies the behavior of two key variables: generated power and effective efficiency. However, the observed boundary conditions differed significantly from expected values, forcing the turbine to operate in off-design conditions. The turbine model was hence refined and used to predict the PRT’s performance in such conditions. Results showed satisfactory accuracy for both power and efficiency predictions.

Thermo-Hydraulic Performance Characteristics and Optimization of Protrusion Rib Roughness in Solar Air Heater

To enhance the thermal performance of solar air heaters (SAHs), protrusion ribs on the absorber are considered to be an attractive solution due to their several advantages. These ribs do not cause a significant pressure drop in the SAH duct and help to enhance the heat transfer to flowing air. On the other hand, a degree of roughness of the protrusion rib on the absorber can be produced by pressing the indenting device without adding additional mass. In this paper, the thermo-hydraulic performances of different roughnesses of the conical protrusion rib on the absorber plate have been evaluated by the mutual consideration of thermal as well as hydraulic performance in term of net effective efficiency. Therefore, an analytical technique has been exploited to predict the characteristics of the net effective efficiency under various operating conditions, such as the flow Reynolds number, temperature increase parameter and insolation. The effects of the conical protrusion rib roughness—namely the relative rib pitch (p/e) and relative rib height e/D) in the ranges of 6–12 and 0.200–0.044, respectively—have been evaluated. The highest value of net effective efficiency of 70.92% was achieved at a p/e of 10 and e/D of 0.0289. The optimization of the rib parameters has been carried out in different ranges of temperature increase parameters for the highest values of net effective efficiency. A unique combination of rib parameters—a p/e of 10 and e/D of 0.044—are observed to lead to the best performance when operating a solar air heater with a temperature increase parameter of more than 0.00789 K·m2/W.

Effective Efficiency Evaluation for Solar Air Heater using Different Artificial Coarseness

Effective efficiency evaluation is one of the important parameters in designing and selection of SAH. In this research article author have evaluated the effective efficiency of SAH using different coarseness configuration attached to the underside of collector of SAH used by various research. Correlation developed by various researchers for various coarseness has been used for the evaluation of effective efficiency. Effective efficiency evaluated for each coarseness used in SAH has been compared and suggested that which coarseness is to be used on the basis of comparison.

First and Second Law Evaluation of Multipass Flat-Plate Solar Air Collector and Optimization Using Preference Selection Index Method

In this paper, different flow configurations of multipass flat-plate air collectors are explored. Multiple passes are formed from glass cover, absorber plate, and back plate. Five types of air collectors were analysed and optimized with respect to maximum efficiencies and minimum cost. The analytical prediction of the heat exchanger, pressure loss, and efficiencies was presented. The effects of mass flow rate from 0.01 to 0.02 kg/s, air channel depth from 15 to 30 mm, and collector length from 1.5 to 2.5 m on different configurations were examined and compared. The results of the parametric study show that the triple-pass type has the greatest efficiency, whereas the smallest efficiency is of the single-pass type. Among double-pass types, the type with two glass covers and natural convection heat transfer achieved the highest effective and exergy efficiencies due to a reduction in the top loss. Double-pass type with single glass cover is not recommended from both energy and exergy standpoints. As the collector length increases, the effective efficiency decreases, but the exergy efficiency increases. The exergy performance of the triple-pass type can reach up to 5% at the air flow rate of 0.005 kg/s. Finally, multiobjective optimization using the preference selection index method is conducted with three targets including effective efficiency, exergy efficiency, and number of plates. Optimal results show that the triple-pass type with the lowest air flow rate and the longest length is the best. The effective and exergy efficiencies for the best case were found to be about 52.1% and 4.7%, respectively. However, this type with the highest flow rate and the shortest length is the worst.

Efficiency of Stakeholders in Agricultural Innovation System

Efficiency is an ability to do things well, successfully and without waste of time and energy. It is a measurable concept that can be determined by using the ratio of useful output to total input. The resources might be men, money, machines and materials that are being used within time for accomplishment of desired activity. Being efficient means the system uses inputs in a right way. If the input-output ratio is adverse then system may work inefficiently. In present study, technical efficiency, cost-effective efficiency and allocative efficiency of stakeholders were identified. The present study was carried out in seven districts of South Gujarat during 2020. The six types of stakeholder were playing pivotal role in AIS hence the list of each type of stakeholder were obtained from the concerned authorities. A simple random sampling method was adopted to obtain respondents sample size. Thus, 30 researchers, 50 extensionists, 30 In-charge of NGOs, 30 managers of private agencies, 50 owner of agro-service providers and 50 progressive farmers were selected. All the 240 stakeholders were randomly selected. The statistical tools and method was used to analyze the data were frequency, percentage and arbitrary method. It can be concluded that more than two fifth (47.50%) of the stakeholders equally had good and excellent level of efficiency among stakeholders in Agricultural Innovation System.