The purpose of this article is to evaluate four different gas turbine cogeneration cycles which are basic, absorption cooling, air heating and air fuel heating cogeneration cycles by using the most important six evaluation criteria for different excess air coefficient, different compression rates, and different compressor inlet air temperatures. These six evaluation criteria are electrical heat ratio, exergy efficiency, incremental heat rate, artificial thermal efficiency, fuel energy saving ratio, and specific fuel consumption. It is seen that the air-fuel heating cogeneration cycle is the most efficient among the cycles examined for a certain compressor compression ratio, followed by the air heating, basic, and absorption cooling cycles.
The electrical energy consumption is increasing in our country and in the world. The electrical energy and heat energy are primary energies and has a vital role on industry and our lives. The production of these two energies in different cycles leads to energy loss and low efficiency. With the production of both in the same cycle, the efficiency increases a lot, and the energy losses and emission values decrease a lot. By installing cogeneration system to produce electrical and heat energy, the energy consumption costs can be reduced importantly. The cycle in which the fuel and the air entering into combustion chamber is heated by the heat taken from the exhaust gases at the outlet of the gas turbine is analyzed by using exergy analysis method and, first and second laws of thermodynamics. The heat energy remained in the exhaust gases are used to produce in steam production, after some heat energy is consumed to heat the air and the fuel, in this cycle. The performance analysis of the devices that make up the cycle such as turbine, recuperator compressor, combustion chamber, and heat exchanger and for the whole cycle and were obtained and discussed. Exergy efficiency, exergy losses and other performance parameters of the devices were obtained and discussed.
Internal combustion engines use generally fossil fuel products. World resources of it is limited. Renewable alternative energy sources are getting important solution for energy demand. Hazelnut oil ethyl ester is obtained from raw hazelnut and mixed with diesel oil in certain proportions to use in a four-stroke direct injected single cylinder diesel engine. In this study the effects of the mixture of diesel oil with hazelnut oil ethyl ester on the engine performance and exhaust gas emissions are investigated for the first time in literature. The fuel injection system is regulated to use the mixture in the engine for the investigation. The results show that, the mixture with 25% ethyl ester extracted from hazelnut oil can be used as an alternative fuel without any change or regulation of the diesel engine.
Cryogenics has an important influence on industry and science. In this study, optimum working conditions are obtained by applying exergy analysis and local optimization methods to two- and three-stage vapor compression cascade cryogenic cycle. The first and second laws of thermodynamics, exergy analysis, and local optimization methods are applied to the two- and three-stage cascade cryogenic cycle. By considering the needs and demands, it is possible to create new cycles by adding new devices and/or new stages to these cycles. The results of the optimum operating conditions are obtained for the two- and three-stage vapor compression cascade cryogenic cycle. It is seen that to achieve high COP values and high efficiency; it is necessary to reduce the compression ratio of the compressor as much as the fluid allows. For the two-stage cycle, the minimum total work required for cryogenic cooling is around P 7 = 2,400 kPa. The COP value is 0.30 between P 7 = 2,400 and 2,800 kPa, and the maximum exergy efficiency is obtained around 0.235. It is seen operating the first-stage compressor at high pressures increases the total losses of the entire cycle from 7,500 to 18,550 kW. The increase in total exergy losses is around 247%, and operating the first-stage compressor at high pressures increases the exergy efficiency of the entire cycle. The increase in total exergy efficiency is around 160%. When the second-stage compressor is operated at low pressure, the COP value increases by 2%, the exergy efficiency increases by 20%, and the exergy losses decrease by around 40%.
Aircraft engines such as gas turbines and detonation engines have very important attention by the researchers in the last decades. However, using detonation engines for producing electrical and heat power was not researched efficiently. In this study, gas turbine and pulse detonation engines cogeneration systems were analyzed and compared by using first and second laws of thermodynamics and exergy analysis method. Three different cycles, namely, basic gas turbine, Zeldovich–von Neumann–Döring (ZND) detonation engine and steam injected regenerative ZND detonation engine cogeneration systems were investigated. The performance analyses and the advantage of these three cycles were obtained and discussed. The performance analyses were done for different compression ratios (r), and the combustion outlet temperatures and pressures, exergy efficiencies, specific fuel consumption, electrical efficiency, exergy fuel consumption, electrical heat rates and other performance parameters of the three cycles were obtained and discussed. It is found that gas turbine cogeneration systems have some advantages and disadvantages in some conditions than ZND cycle. The steam injected regenerative ZND detonation engine cogeneration systems can compete with the Brayton cycle cogeneration systems.
There are a limited number of studies in the literature that include detailed exergy analysis of vehicle air conditioning systems. In this study, in order to increase the performance of the air conditioning system in vehicles, a detailed exergy analysis has been made with the assumption that different refrigerants are used. R-134A, R-E245cb2, R-404A, R-1234ze(Z), R-161, R-1234zd(E), R-513A, R-1234ze(E) and R-1234yf has been chosen as the refrigerant. In the analysis, a comparison has been made by considering the environment, performance and safety values. While the COP values of the cycles increase with increasing evaporator temperatures, the COP values decrease at increasing condenser temperatures. On the other hand, exergy efficiency decreases with increasing evaporator and condenser temperatures. Also it is aimed to evaluate all the elements of a vehicle air conditioning system with exergy analysis.
In this article, oil obtained from vegetable was used to lubricate a single-cylinder 2-stroke gasoline engine as lubricating oil, and tribological function of the obtained oil was investigated. To investigate the tribological functions of the lubricating oils, a 2-stroke single-cylinder gasoline engine was used. For mineral oil and hazelnut oil, the test engine was run for 100 hours for each one and were used to lubricate in the test engine as lubricating oils. Samples were prepared for the aim of the determining the wear on the cylinder surface, and also EDS (Energy Dispersive Spectrograph) analysis were obtained. The results of the analyses showed that, the wear on the cylinder surface were increased in the studies using hazelnut oil and the C content of the cylinder sample increased compared to the study with mineral oil. Al element was detected in the cylinder sample in the hazelnut study, that the reason for this, is the transport of the Al element during the friction event in the piston material to the cylinder surface.
The use of the electrical energy is increasing in our life and in the world. The electrical energy is lost in the connection lines about 11%, as it is known. By producing the electrical and the heat energy in a cogeneration system to meet the needs, it can be obtained more efficiency in the use of fuel, and that can reduce energy costs. In a cogeneration cycle, by the absorption cooling system, the air entering into the compressor is cooled, and the cooling is obtained from energy of the heat of the exhaust gases. The system in this study is analyzed by using exergy analysis method and 1. and 2. laws of thermodynamics. Some of the heat energy is consumed to cool the air, in this cycle and the remaining heat is used to produce steam. The performance analysis of the whole cycle and also the devices that make up the cycle such as compressor, combustion chamber, turbine and heat exchanger were obtained and discussed. Also exergy losses, exergy efficiency and other performance parameters of the devices were obtained and discussed. The results showed that using absorption cooling (abc) system in a basic cycle made better than the basic one in electrical efficiency. However, because of the absorption cooling (abc) system the exergy efficiency is slightly less than the basic one. The absorption cooling (abc) cogeneration system can be used when the steam demand decreases or electrical demand increases for production more electricity.
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