جستجوی مقالات مرتبط با کلیدواژه "Gas Turbine" در نشریات گروه "مکانیک"

In this study, a combined cycle consisting of Brayton, Rankine and compression refrigeration cycles is thermodynamically evaluated for power generation and cooling. The combined cycle is simulated in EES software and its thermal efficiency is calculated using the first law of thermodynamics. Using three heat exchangers with a thermal efficiency of 90%, the heat output from the compression refrigeration cycle is used for preheating and the waste heat of the Brayton cycle is used to produce steam in the Rankine cycle. Air, water, and R134a are the working fluids in the Brayton, Rankine, and refrigeration cycles. Mass flow rates of 5, 10 and 20 kg/s are considered for water, R134a refrigerant and air, respectively. The effect of the working fluid rate on the thermal efficiency of the combined cycle is investigated. By energy analysis, the thermal efficiency of the Brayton cycle was 49.29%, the Rankine cycle was 27.68%, the coefficient of performance of the refrigeration cycle was 4.38%, and the thermal efficiency of the combined cycle was 48.84%. The results show that with increasing air flow rate, the thermal efficiency of the combined cycle increases, but with increasing R134a refrigerant flow rate and water vapor, the combined cycle efficiency decreases

In hot seasons of year, due to increase in inlet temperature to compressor, production power of gas turbines decreases. Gas turbine inlet air cooling is a technology that improves gas turbine performance, in which gas turbine power per kilowatt is increased by spending less. In this study, three gas turbine inlet air cooling methods including fog, media and absorption chiller have been technically and economically evaluated in order to improve performance of Kashan combined cycle power plant. In this article, by using multicriteria technique according to decision criteria, prioritization of inlet air cooling method for use in Kashan power plant has been done and prioritization of methods has been determined using TOPSIS1 methods. Considering technical and economic conditions and environmental conditions of Kashan region, using multi-criteria techniques, Media cooling system is selected and introduced as a suitable system to improve performance in this power plant. By using media system in Kashan power plant, net power output from power plant increases by 5.166%, energy efficiency and exergy of gas cycle increases by 2.26% and 2.25%, respectively.

Nowadays, due to scarcity of water resources, water recycling and extraction have been given more attention. Among sources of water is water vapor in combustion products. In this research, as an example, amount of water vapor in exhaust smoke of Kashan combined cycle power plant unit was predicted in different seasons and conditions, which is a significant amount of 22.6 liters per second in winter season. Then, conventional systems of separation of gas streams, solid and liquid surface absorption, condensation cooling, cryogenic separation and membrane process were investigated for feasibility of extracting water from smoke and were evaluated technically and economically. In this case, water quality parameters, energy saving, investment cost, operation cost and technology evolution were considered as evaluation parameters. Result of comparison showed superiority of ceramic membrane system of porous nano filter. Assuming 40% extraction of water in smoke flow, membrane system has a much lower investment cost than other systems and based on data of Kashan power plant, extraction of 9.32 liters of water per second can be expected.

Functionally graded materials (FGM) are a group of engineered materials that are designed and manufactured continuously and discontinuously in two forms, thin film and bulk. With the expansion and easier access of advanced, more precise and controlled methods of manufacturing parts such as additive manufacturing, the potential of using these materials has also increased. In this report, with an overview of the basic definitions and common methods of gradient materials manufacturing, the possibility of produce these materials using additive manufacturing has been investigated, and the characteristics of each method have been mentioned by reviewing the studies conducted. In the end, considering the importance of using this category of materials in sensitive applications such as the turbine industry, two examples of case studies of the use of these materials based on the additive manufacturing method in the rotary system (gas turbine) have been introduced. In these studies, both the thin film in the form of gradient coating and the bulk and integrated form have been used to make the part used in the gas turbine.

In this article, a combined cycle for multiple production of power, steam and fresh water is proposed and its outputs are compared with a basic cycle. The main fuel of both systems is biomass, which burns in the gas turbine cycle and produces power. Then the waste heat of this cycle is recycled by an organic Rankine cycle. A solar cycle with the flat plate collectors is used to preheat the organic fluid before entering the ORC’s evaporator. Also, the proposed cycle has a geothermal cycle which, in addition to reheating the organic Rankine cycle, is used to generate steam in a steam generator and run a steam turbine. Both the proposed and basic systems are equipped with a reverse osmosis desalination unit, whose high-pressure pump power is supplied from organic and steam turbines, respectively. The designs have been analyzed and simulated in term of exergy. Compared to the basic system, the proposed system has 34%, 131%, 100%, and 49.32% more output power, purified water, steam, and exergy efficiency, respectively.

In this research، a combined heating and electricity cooling system is proposed and a complete thermodynamic analysis is presented. This system consists of a gas turbine، a thermal cooling system، a cogeneration system and a hot water heat exchanger. The excess heat in the gas turbine is initially produced by the cogeneration system and converted into power through an ammonia steam turbine. Will be then،  the output steam of the ammonia steam turbine is used in a single-effect water absorption refrigeration system to produce cooling energy. Effective use of produced surplus energy can reduce natural gas consumption compared to independent power systems، cooling and heating. The energy and exergy efficiency of the studied system is 20 and 21 %، respevtively، wich is a resonable value. The results of economic analysis show that the produced system has a high economic efficiency with a total cost of 93.56 dollars per second and a total investment and maintenace cost of 1732 dollars per second. This work will provide a new method to increase efficiency and effectiveness of the thermodynamic performance of cogeneration systems.

Due to the very high importance of gas turbine in electricity production and also its increasing development in the electricity industry, one of the most important methods to increase the efficiency of gas turbine blades is to add thermal barrier coating to their outer surface. These coatings improve the cooling of gas turbine blades, but they also have disadvantages such as roughness of their surface cause to the separation of the hot fluid flow around the turbine blades. The rough surfaces of thermal barrier coatings should be used optimally and purposefully. In this research, using commercial software of Fluent, this type of coating has been investigated and analyzed in order to find the most optimal possible mode for its use. The influence of surface parameters such as roughness, thickness and material of thermal barrier coatings have been investigated. The most optimal state for the mentioned parameters are: 0.1 mm, 0.38 mm and 2.7 W/m.K respectively.

Due to the complexity of the processes governing the flow in the gas turbine, it is necessary to perform experimental tests to ensure the performance, but creating the conditions governing the components in the operational conditions is very complex. most of the combustion chamber tests are performed in atmospheric conditions and then the results are generalized to the operational conditions. This work, along with the lack of test stands with real operational conditions, has been developed based on the fact that most of the processes governing the behavior of the chamber have not undergone significant changes with the change of operating pressure, and especially if the shape of the flame does not change, it is possible to study the behavior of the chamber even at low pressure. In the present research, this issue has been numerically investigated for a real combustion chamber and it has been observed that changes are characterized by increasing pressure. Also, NOx pollutant increases at higher pressures. The overall flow structures were not affected by the pressure increase, but the pressure loss rate increased. The current results show that in the desired combustion chamber, the atmospheric test can provide acceptable results and can be generalized to high pressure conditions.

In this study, the effect of failure of a screw in the coupling connecting two compressor shafts on the dynamic behavior of the rotor in The Rolls Roys gas turbine has been investigated. For this purpose, the geometric model of the compressor shaft was designed and Modal analysis was performed by finite element method by ANSYS and Campbell diagram were designed separately. Experiential Modal analysis and its comparison with numerical Modal analysis have been used to validate and confirm the designed model. It used the harmonic analysis of the shaft without blades and discs, as well as the shafts with blades and discs for the frequency response of velocity and displacement due to the failure of the screw connecting the two shafts at the edge and medial connection separately and synchronous. The results showed that the frequency response of the compressor shaft velocity in the coupling screw failure at the edge of the screw failure location is about 30% higher than the medial screw failure mode, indicating that the coupling screw failure in the edge has a greater effect on the shaft and rotor behavior in terms of velocity and displacement compared to the medial screw.

In this research, the internal flow of open-end pressure-swirl atomizer, which has many applications in gas turbine engines and space propulsion, is investigated numerically. A multi-phase fluid volume model is used to simulate the internal flow of the atomizer. Also, due to the nature of the rotational flow inside the atomizer, the RNG k-ε turbulence model was used. Structured mesh has been used to achieve better results. In this research, spray parameters such as liquid film thickness, spray cone angle, discharge coefficient and velocity and pressure distribution contours have been studied. Simulation of an open-end atomizer with an L⁄D = 5 ratio, as well as the use of a structured mesh and the inclusion of kerosene fuel to create conditions close to the operation of a gas turbine, are among the things that differentiate the present study from other studies. The results also show that at a pressure of 0.5 MPa, the time required to reach the fuel in the atomizer used is less than 1.5 milliseconds and the failure of the to spray cone and turn into larger droplets can be observed. The spray angle and discharge coefficient for the studied atomizer were 74.8 and 0.17, respectively.