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The aim of this article is to compare a direct hybrid system of gas turbine and solid oxide fuel cell with an indirect system from thermodynamic and exergy viewpoints. According to importance of fuel cell role in hybrid cycles and providing further proportion of produced power, discrete and complete thermodynamic, electrochemical and thermal analyses have been done. Calculation of working temperature which has an impact on system performance is one of the most significant works that is done in this article. In addition, by parametric study of this hybrid system, the influence of inlet air rate and compression ratio on efficiency, power and exergy destruction rate has been perused and eventually an optimized state for system will be offered. Results indicate that a direct hybrid system is more efficient in comparison with an indirect system. Higher efficiency, less irreversibility, higher power, and less pollution are the most important advantages of direct hybrid systems.

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The purpose of this study is thermo-economic analysis of a combined fuel cell and micro gas turbine power plant cycle for using in small scale CHP systems. Since the fuel cell is the main source of power generation in hybrid systems, in this study, complete electrochemical, thermal and thermodynamic calculations are performed to obtain more accurate results; and unlike most studies, the cell temperature is not assumed constant. The performance analysis of the hybrid system shows that increasing the pressure and air to fuel ratio, causes to loss of electrical efficiency and increase in the electricity price because of reduction in cell and turbine inlet gas temperatures. The other results of this study show that considering the economic life of the system, making use of this type of hybrid systems is economical and generates less electricity price in comparison with micro gas turbine.

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The present paper discussed about the technique that can be used to vector the exhaust flow in the pitch directions with using Double Throat nozzle (DTN). Compressible and supersonic gas flow inside a Double Throat nozzle and its exhaust plume at specific nozzle pressure ratios have been numerically studied with several turbulence models. The numerical results reveal that, the SST k–ω model gave the best results compared with other models in time and accuracy. In the present research, effects of changes in injection area of secondary flow and percent of secondary mass flow rate, on performance of Double Throat nozzle and thrust vectoring system have been investigated. The predicted results show that by decreasing the value of secondary flow injection area in a case with 7% secondary injection, the thrust vector angle increase 18º to 21º and thrust vectoring efficiency will increase. But by decreasing the value of secondary flow injection area, the thrust and discharge coefficient will decrease. Also when secondary mass flow rate increases, the discharge coefficient will decrease. So that in the design of fluidic thrust vectoring with double throat nozzle, the value of secondary mass flow rate should be low.

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Because of various applications of UAVs, research in this field has been developed increasingly in recent years. Propeller has considerable importance as a key factor in producing propulsion in such vehicles. Having information about a propeller’s performance variations in different operational conditions is very important in order to choose a suitable propeller for a predefined mission of the flying vehicle. For this aim, in this research a test stand was designed and fabricated to evaluate the static performance of electromotor driven propellers with application in UAVs. After collecting data by performing experimental tests, the results were compared to those obtained from the numerical and analytical techniques. In order to verify the results, a propeller was modeled and a computational method was applied based on k-ε, RNG turbulence model. The comparison of experimental, analytical and computational results shows an acceptable agreement between them. According to the results, the difference between analytical and empirical results is 0.4%, the difference between computational and empirical results is 0.3% and the difference between analytical and computational results is about 1.23%. Also in the range of the rotational speed of the propeller, the difference between computational and empirical results became less than 10% in most cases, implying the validity of the applied computational method and correctness of experimental test procedure.

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Solid oxide fuel cells competence in combination with gas turbine cycle has caused the obtained synthetic system to become as a new power production system in consideration of different researchers. One of the important applications of this type of hybrid systems is to use them in UAV propulsion systems and in airliners as an APU. The main purpose of this research is design of a hybrid APU equipped to solid oxide fuel cell that would be one of the basic requirements for electric power generation in larger aircrafts in the future. Design parameters and decision-making variables in analysis of this system are the compressor pressure ratio, gas temperatures entrance to turbine and the number of selected cells. The results show that the system’s increasing pressure causes decrease in the temperature of outlet gases from the turbine and the cell’s operating temperature; and this problem severely affects the productivity and efficiency of the electrical system. At 1000 ° C for entrance gases to the turbine, electrical efficiency of system is about 49 percent. Also, the maximum electrical efficiency of the system in fuel cell is estimated to be about 55 percent. The obtained result shows that in case of controlling the generated heat in the cell and effective usage of it, the overall system efficiency will be augmentable about 84 percent. On the other hand, increasing the number of cells will cause increasing electrical efficiency and reducing the overall efficiency of the fuel cell hybrid system.

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The present paper introduces a new electro-hydro mechanical fuel metering and control system for a turbojet engine. The developed metering system uses a new direct drive rotary proportional metering valve, which is coupled to a servomotor. The aim of this new design is to modify and optimize the mission of a constant speed turbojet engine. The main innovations in the present design include: the rotary actuating mechanism, rotary metering valve configuration, direct drive rotary metering valve configuration and the special metering flow geometry. Due to rotary direct drive metering section design, the parts count, manufacturing cost and system weight is decreased with respect to usual methods. Another benefit of the innovated valve is improvement of the control resolution. The fuel metering area in the present developed system consists of a triangular shape on sleeve and a rectangular shape on plunger. Mathematical modeling and system simulations are applied to acquire design parameters for different working conditions. After manufacturing a prototype, rig testing is done. The results of simulations and experimental measurements are compared in the last section of the paper.

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In the current study a combined heat and power (CHP) system based on diesel engines is studied. A CHP system is investigated parametrically according to first and second laws of thermodynamics. In this investigation instead of modeling the air standard cycle, the fuel air standard cycle and fuel combustion are simulated, which leads to more accurate results. Since a standard cycle has many differences with an actual cycle, the exhaust gas from combustion chamber of a diesel engine is also used to simulate the CHP system, and the heat exchanger of the CHP is investigated from exergetic and economic viewpoints. It was seen that applying the pre-described system, it is possible to warm up 0.17Kg/s water from 25°C to 68.64°C. This enhances the overall efficiency of the system about 20%, raising it up to 80%. Exergy destruction in heat exchanger is almost high which is due to heat transfer process and high temperature difference in the heat exchanger.

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The present study was undertaken to design and analyze three different configurations of SOFC (solid oxide fuel cell) and MGT (micro-gas turbine) hybrid system. The first presented configuration is a hybrid system with one fuel cell which considered as a basic mode. Two other configurations are considered with two fuel cells that mounted upstream of the turbine in series and parallel forms. The aim of the current study was thermodynamic analyze of designed hybrid systems and achieving the optimum fuel consumption factor for fuel cells that used in hybrid systems. Therefore, other performance parameters such as turbine inlet temperature, compressor pressure ratio and the number of cells, which play an important role in implementation of SOFC and gas-turbine, were parametrically analyzed and the obtained optimum values were used in analyzes. In this regard, the parameters associated with electrochemical processes within cells considered as a function of their chemical and thermodynamic conditions, and their modeling code combined with the modeling code of micro gas turbine cycle. The results of this study revealed that fuel utilization factor has direct impact on the SOFC/MGT hybrid system performance. Also we demonstrate that the optimal fuel utilization factor for basic mode hybrid system was 0.85, hybrid system with 2 series fuel cells were obtained 0.7 and 0.8 respectively and hybrid system with two parallel fuel cells were calculated to be 0.85. Moreover, the SOFC/MGT hybrid system with two series fuel cells account for the highest electrical efficiency and was selected as the most efficient configuration.