جستجوی مقالات مرتبط با کلیدواژه « Gas Turbine » در نشریات گروه « مکانیک »

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.

Today, global demand for energy has increased due to economic and population growth. Turbines play an important role in generating power in order to generate electricity. This industry is one of the important factors in the global economy and has experienced continuous growth from the early years. To achieve higher thermodynamic efficiency in turbines from higher inlet temperature and pressure, advanced aerodynamics, efficient blade cooling systems, advanced alloys with higher temperature tolerance, heat treatment and metal and thermal barrier ceramic coatings is used. Under turbine operating conditions, some damage may occur that will decrease its life. In present study, mechanical and metallurgical aspects of turbine blade destruction and the development of materials to overcome it have been analyzed. Failure mechanisms must be identified to estimate blade life. The combination of different variables causes stress and complex damage mechanisms such as creep and fatigue are created by changing mechanical and heat stresses. In addition to the above, the importance of coating on gas turbine blades is mentioned. After investigation of various aspects of damage to clarify the issue, some case studies of failure during operation are briefly described.

Nowadays, due to the extensive application of renewable-based co-generation systems and also the economic and the environmental necessities, their design and thermodynamic analysis has been conducted by many scientists.In this way, a novel, simple, and practical combined power and hydrogen cogeneration unit has been designed in the present study in which there are gas turbine, gasifier, trans critical Rankine cycle, and proton exchange membrane electrolyzer.This system has been analyzed from first and second laws of thermodynamics by engineering equation solver(EES).The proposed system is able to generate power and hydrogen simultaneously for users.The power and hydrogen production capacities of the system are 3.92 MW and 608.8 cubic meter per hour, respectively which consumes biomass about 1.155 kg/s. The energy utilization factor and second law efficiency ofthe system are 34.71 % and 29.44 %, respectively. It can be seen that the overall exergy destruction of the system is 11854 kW in which gasifier, gas turbine, and combustion chamber have the highest irreversibilities. In addition, it can be concluded that the exergy efficiency of condenser and heat exchanger 3 are the lowest ones among other equipments.According to the parametric studies,it was found that the increasing the inlet temperature ofthe gas turbine has a positive effect and the increasing the maximum pressure ofthe TCO2 cycle has a negative effect on the EUF and the second law efficiency ofthe system.