Papers by Keyword: Gas Turbine

Abstract: Improving the energy efficiency of thermal power plants through the thermodynamic analysis of their operational parameters in real time is a major issue in order to ensure rational and sustainable operation. An in-depth analysis has been conducted on the thermodynamic efficiency of three gas turbines in a gas/steam combined cycle power plant using real-time operational data. The presented work is part of the research that deals with operational parameters in order to maintain the performance of thermal power plants at the highest possible value. A combination of the first and second laws of thermodynamics has been developed to provide a model able of predicting the thermal efficiency of gas turbines in different operating modes in real-time. The results of our study indicate that each turbine demonstrated a thermal efficiency of around 33.5%. Additionally, the turbines produced an output power of 284 MW and had a specific fuel consumption rate of roughly 206 kg/MWh. The analysis not only verifies the durability of the turbines under various operating conditions, but also presents a verified method to monitor and improve energy efficiency in real time, which is crucial to optimize the power plant operations. Furthermore, this thermodynamic model can be used as a calculation program to be integrated into the display panel which will be used to provide operating indicators in real time. Keywords: Steam/Gas combined cycle, Gas turbine, Thermal performance, Energy conversion.

Abstract: In a hot and dry climate country, performance of a gas turbine power cycle is low. Incorporation of a regenerator in the cycle and a spray cooler before compression of inlet air enhances its performance. Accordingly, this study focuses on the effect of regeneration and cooling of the inlet air on performance of an open cycle gas turbine plant, which mainly includes improvement in its thermal efficiency and reduction in specific fuel consumption. In this context, a suitable mathematical model is developed on the basis of fundamental understanding of thermodynamics and gas turbine relations. This model is then used in simulations by developing a code on Java platform where ambient temperature, pressure ratio and regenerator effectiveness are considered as major system parameters. In the simulation, a comparison among a simple Brayton cycle, a regenerative cycle and a regenerative cycle with spray cooler is considered under different system parameters. It is predicted that there is a significant increase in thermal efficiency and a significant decrease in specific fuel consumption on incorporation of regenerator and spray cooler to the cycle. However, addition of a spray cooler is applicable above an optimal pressure ratio (≈6) and in the high temperature environmental condition. As an example, 12.89% increase in thermal efficiency is found at a regenerator effectiveness of 0.85 on addition of spray cooler before compression of inlet air at an ambient temperature of 328K, and subsequent reduction in specific fuel consumption is found as 2.85% at pressure ratio of 10.

Abstract: One of the thermophysical characteristics of metals and alloys is the specific heat capacity. It is measured, as a rule, experimentally, which determines the high cost and labor intensity of this approach. A model has been developed for calculating the specific heat capacity of chemical elements and their compounds. The calculation results are in satisfactory agreement with the experimental data of other authors (reference data). The simulation results are used to calculate the thermal state of gas turbine parts. It can also be used in alloy design.

Abstract: MoSi₂/Mo₅Si₃ eutectic composites have been considered as one of the promising candidates for ultra-high temperature structural applications owing to their high melting point, good oxidation resistance, and low mass density. Their mechanical properties can be improved by controlling the eutectic structure (i.e. script lamellar structure) in directional solidification. It is important to elucidate the dominant factors underlining the unique pattern formation. We conducted a comprehensive phase field study to examine the influence of various factors on the MoSi₂/Mo₅Si₃ eutectic microstructure with complicated morphology. First, the inclined lamellae have been attributed to the minimization of elastic strain energy due to the lattice mismatch between MoSi₂ and Mo₅Si₃, which are partially relaxed by forming semi-coherent phase boundaries. Second, the maze-like pattern on the horizontal cross-section appeared when a two-fold anisotropy of interfacial energy is superimposed on the MoSi₂/Mo₅Si₃ boundary. Third, the random and intersected lamellae have been obtained by assuming the instability of the solid-liquid interface and introducing successive nucleation of Mo₅Si₃ phase. These findings provide guidance for manipulating the eutectic structure and act as footsteps for further theoretical investigation.

Abstract: In order to reduce the operating costs of the engine, turbine designers must also increase the life of their components. However, high gas temperatures throughout the engine require more cooling air or better cooling efficiency to protect the parts from thermal damage. This study presents numerical research on cooling holes. Research focused on aerodynamics and thermal aspects of shallow whole angle. The numerical simulation is performed based on Reynolds Averaged Navier-Stokes (RANS) equations with SST turbulence model by using CFX. A modification has been done in the normal injection hole of 35°, by injecting the cold fluid at different blowing ratio, providing a significant change in the shape of holes which later we found in our numerical investigation giving good quality of film cooling effectiveness.

Abstract: CMAS attack is known to occur owing to the deposition of volcanic ash onto thermal barrier coating (TBC) surface at a high-temperature environment. The serious problem is TBC spallation resulting from the infiltration of molten volcanic ash into the porous microstructure of TBC. The infiltration induces inner stress and phase transformation, which directly results in those serious problems. In this study, the diffusional equation for expressing the infiltrating process of the molten ash into the porous structure of TBC and the associated constitutive equation considered regarding phase transformation are formulated. The equations are installed into commercial finite element (FE) code (MARC) using the user subroutine. The numerical simulation results are compared with the cross-sectional SEM observation for the volcanic-ash-deposited TBC sample exposed at a high-temperature to confirm verification of the model proposed herein.

Abstract: Thermal barrier coating (TBC) is deposited onto the gas turbine blade surface in order to protect the substrate from high-temperature combustion gas. Cracks and delamination of the ceramic coating which come from high heat flux loading are serious problem in TBC. In this study, the rapid thermal cycling device utilizing laser irradiation was developed. It was then investigated how the damage progresses in the ceramic coating exposed to cyclic rapid thermal loading. As a result, a sintering layer was formed in the surface of the ceramic coating, although such phenomenon was not recognized in TBC sample tested by the conventional thermal cycling test using an electric furnace. It was also revealed from the cross-sectional observation that the vertical crack was initiated at the surface of TBC and propagated into sintering layer. Finally, mechanical factors of those damages from finite element analysis using the TBC model including sintering progress was discussed

Abstract: TBCs (Thermal Barrier Coatings) is deposited on gas turbine blades to protect the substrate from a combustion gas flow. One of the serious problems occurred in gas turbine is TBC delamination which is caused by startup, steady and stop operation in service. TBC delamination results from subjecting to both cyclic thermal stress and evolution of internal stress due to thermally grown oxide (TGO). In this study, the finite element code which can simulate thermal and internal stress fields generated in TBC was developed. The developed code involves the follows: inelastic constitutive equation for ceramic coating, bilinear-type constitutive equation for bond coating and Chaboche-type inelastic constitutive equation for the substrate, and mass transfer equation in consideration of oxygen diffusion and chemical reaction with aluminum. Thermal cycling simulation was conducted using the developed code. It was confirmed that maximum stress and its location in the ceramic coating/bond coating interface were matched with the associated experimental results.

Abstract: CMCs have been developed in the 80th for the shuttle programs and commercialized as brake discs from 2000 till today. Since 2017 CMCs are used also in components of flight gas turbines. This application requires highest levels of process and material development and performance. Therefore the knowledge of any process on material damage is of highest importance.The presented work will show a method how to evaluate the quality of edges and surfaces of CMCs created by a special diamond machining operation. The objective is to develop a machining process for CMCs in gas turbine applications and a method for quality assessment for future production.

Abstract: A finite element analysis code was developed to accurately predict stress and damage fields in thermal barrier coatings (TBCs) systems subjected to thermo-mechanical loadings. An inelastic constitutive equation for TBCs, and a Chaboche-type viscoplastic constitutive equation for Ni-based super alloys (IN738LC) were employed to simulate high temperature creep and cyclic deformation. Simulations of the TBC/IN738LC system subjected to two types of loading, namely, a triangle-wave loading and a GT-operation loading, were performed using the developed analysis code. The results confirmed that the stress and damage fields in the TBC/IN738LC system could be simulated accurately, and provided us with credible results regarding the crack occurrence. Additionally, the analysis under the GT-operation loading conditions revealed that a peak stress generated during the start-up operation would lead to delamination of the TBC, while a peak stress at the shut-down would lead to cracking in the substrate.