Papers by Keyword: Gas Turbine

Abstract: In order to improve the cooling effectiveness of the film, a numerical study was conducted to study the effects of different film-cooled angles on surface heat transfer. In this work CFD simulation has revealed the difference of injection angles ranging from 35°,45°,55°,65° and 90° with different blowing, where the low blowing ratios are represented by M = 0.5, and the high blowing ratios by M = 1.0 and 1.5. And the turbulence closure is done with the help of the k - ω shear stress transport (SST) turbulence model. It is found that the stream-wise variations in the angles of the holes do not really provide a significant change in the adiabatic film cooling effectiveness results. On the other hand, the results indicate that the hole of angles 35°and 45° improved the centerline and laterally averaged adiabatic effectiveness, and the effectiveness decrease particularly at high blowing ratios.

Abstract: Wet compression process has been widely accepted as a measure of increasing the performance of industrial gas turbine, in the present work, in-depth analysis on the principle aspects of wet compression, more specifically, the influence of injected water droplets diameter, surface temperature, and their effects on the behavior of axial flow transonic compressor and gas turbine performance were analyzed using computational fluid dynamic. Injected water droplets and gas flow phase change was most intense in the area adjacent to shockwaves and were the slip velocity of the droplet is highest. Water injection in to the compressor rotor is a little perturbation to the flow field due to the formation of flow separation, evaporation rate, increasing weber number, reduction in the inlet temperature, and velocity vortex pattern relatively different from that of the dry case. The effects of water droplets on the rotor region at injection rate of 1%, shows decrease in the inlet temperature of 11%, outlet temperature 5% and uplift the efficiency to 1.5%.

Abstract: Since 2004, Mitsubishi has been pursuing a 1,700°C gas turbine as part of the Japanese National Project [1][2]. One of the most important key technologies for the target is thermal barrier coatings (TBCs) which are capable of improving cooling efficiency of hot parts. With increasing the turbine inlet temperature, TBCs surface temperature is also rising up. In addition, the temperature gradient through TBCs thickness must steepen as a result of keeping metal temperature. Both have a significant effect on durability such as spallation and erosion of TBCs. To evaluate these issues, thermal cycle test and hot erosion test were introduced. After the screening of those component tests, the advanced TBCs coated in the first unit of M501J were verified at our pilot plant called T-point. Sound condition for row 1 blades and vanes had been confirmed after over 3 year operation.

Abstract: All thermal power plants including gas turbine (GT) of Tokyo electric company are located along Tokyo bay. If Mt. Fuji is exploded, volcanic ash is fallen down in Kanto area. If volcanic ash is inhaled into GTs, the ash would be firstly impacted and deposited onto thermal barrier coating (TBC) of the blades. Such deposition of the volcanic ash causes the delamination of the ceramic coating. In this study, TBC delamination mechanisms due to the volcanic ash deposition is discussed based upon thermal stress evaluated by a laser monitoring measurement system.

Abstract: The more and more restrictive environment requirements in the field of pollutant emissions of co-generative plants are imposing researches related to the more efficient work of those related to the post combustion facility. The paper presents the results of a post combustion burner achieved on a test bench, when it idling operates on natural gas mixed with air or with burned gases of a gas turbine. The modeling of the measured emissions, led to NO_x concentrations in ambient air that are below the limits imposed by the in force regulations related to air quality and are correlated to the real time measured data.

Abstract: Lubricated bearings are usually used to support and guide the shafts in gas turbines, exhaust gas turbochargers and other turbomachines. The lubricant is also used for cooling the hot parts such as the turbine side of the rotor. The high temperature condition effects a contamination of the compressed air by evaporating the lubricant. In special applications an oil-free operation has to be guaranteed. In other applications an oil lubricated bearing system prevents an immediate engine stop. The use of air foil bearings eliminates the disadvantages of the oil lubricated bearings. An air foil bearing works self-adjusting the necessary gap which depends on relative speed of the rotor and the stator surfaces and on the viscosity of the lubricating fluid. A low rotor speed requires a small bearing gap, whereas the gap must be enlarged for high speed at constant viscosity of the lubricant. An air foil bearing works contact-free in a wide speed range even at small rotation speed depending on design. On an experimental basis an air foil bearing system was developed and tested for a standard automotive exhaust gas turbocharger. The developed bearings need no infrastructure for supplying with lubricant and its cooling and filtering. The air foil bearings was calculated and designed based on the estimated bearing loads. For the manufacturing of the radial wave springs a procedure was developed. A test facility was set up for the experiments. The modified rotor works at the standard rotation speed of 80000 rpm. The bearings support and guide the shaft contact-free (without wear) in a range of a few thousands of revolutions per minute up to the standard rotation speed.

Abstract: In this paper, experiment investigation is conducted on the machinability when ball milling A880 gas turbine blade profile. Cutting force spectrum acquired online is used to optimize the cutting parameters. The results indicate that cutting force signal in time domain and frequency domain can reveal the cutting stability, which provides an experimental guideline for gas turbine blades manufacturing.

Abstract: Hot gas path component consists of components designed to burn air-fuel mixture in combustion section and provide hot gasses to the turbine section where mechanical power is produced. The aim of this research project is expected to improve the current practices of managing degradation of hot gas path components. Understanding the damage mechanisms is of great interest in reducing the damage and failure risk. In this research, a study was conducted on F-Class type gas turbine hot gas path components assembly. It involved extensive examination and testing of the components which had been in operations for 24,000 hours since the last shutdown. Various factors such as installation, operating conditions, hardness and material of constructions were also investigated. This paper reports the initial findings of the study of hot gas path components degradation. It describes the damage observed on the affected areas of the components and proposes the factors that contribute to the damage processes. Potential solutions for mitigating the damages are also discussed.

Abstract: This study is to develop mathematical models and evaluate the performance of a gas turbine with variable geometry compressor working in a CHP plant. A single shaft gas turbine plant can maintain the exhaust gas temperature if the load is not below 50 % of the full load by simultaneously regulating the compressor variable vanes position and fuel flow. For load less than 50% the engine is running to meet the power demand. This is achieved by controlling the fuel flow and air bleed at the downstream of the compressor to avoid surge formation while variable vanes are opened fully. To accommodate change of compressor parameters during variable vanes re-stagger correction coefficients are introduced. A behavior of a 4.2 MW gas turbine performance was evaluated. The effect of variation of load and ambient temperature on the gas turbine specific fuel consumption, temperature, pressure ratio, variable vanes opening and efficiency were examined. Comparison between the field data and simulation results demonstrate good agreement. The off-design calculation was done by in-house developed program in MATLAB environment.

Abstract: The importance of a land-based gas turbine has been increased in order to maintain energy security in Japan. Since our country has been always exposed to a natural disaster, it is necessary to consider about influence of air intake of volcanic ash spouted from a volcanic explosion on high-temperature components in gas turbine as well as vibration by an earthquake event. In this study, a high-temperature exposure tests were conducted for 8YZ/CoNiCrAlY/IN-738LC sample on which volcanic ash was deposited. Here, we selected the natural ash picked up from Shin-moe mountain where had been exploded in 2011. As a result, it was found that the top coating was peeled completely off at the exposure condition 1273 K for 100 hours, which means that volcanic ash deposition brings about some acceleration for the delamination life of TBC. The microstructure observation after the exposure tests revealed that Si and Ca contents involved in the volcanic ash was detected inside open-pores. Thus, it was identified that those ashes infiltrated into open pores along splat boundaries under a high-temperature exposure environment. The damage model for explaining degradation induced by volcanic ash deposition was developed based upon micromechanics. The formulae for constitutive equation of TBC was done by considering about influence of both crystal distortion by tetragonal to monoclinic phase transformation and thermal shrinking by temperature drop in the heat exposure treatment. Residual stress and interfacial energy were evaluated using the proposed constitutive equation in order to clarify degradation mechanisms for ash attack to TBC.