Gas Turbine Generator Research Articles

Study on Creep Damage of Ni-Based Superalloy Caused by Variable Load Conditions at Elevated Temperatures.

Higher fatigue and creep resistance at high temperatures are the essential properties for materials such as those used in gas turbines for power generation and aircraft turbines. Therefore, the nickel-based superalloy CMSX-4 was developed through single-crystal casting to satisfy these requirements. In this study, the CMSX-4 creep test results reported by previous researchers were used to mathematically derive an equation to estimate the amount of creep damage occurring under variable load conditions. In addition, low-cycle fatigue tests were performed, and the effect of creep damage occurring during fatigue on material failure was described.

Numerical investigation of heat transfer effects on combustion in a generic gas turbine burner

PurposeThis study aims to methodologically investigate heat transfer effects on reacting flow inside a liquid-fueled, swirl-stabilized burner. Furthermore, particular attention is paid to turbulence modeling and the results of Reynolds-averaged Navier–Stokes and large eddy simulation approaches are compared in terms of velocity field and flame temperature.Design/methodology/approachSimulations consist liquid fuel distribution using Eulerian–Lagrangian approach. Flamelet-Generated Manifold combustion model, which is a mixture fraction-progress variable formulation, is used to obtain reacting flow field. Discrete ordinates method is also added for modeling radiation heat transfer effect inside the burner. As a parametric study, different thermal boundary conditions namely: adiabatic wall, constant temperature and heat transfer coefficient are applied. Because of the fact that the burner is designed for operating with different materials, the effects of burner material on heat transfer and combustion processes are investigated. Additionally, material temperatures have been calculated using 1 D method. Finally, soot particles, which are source of luminous radiation in gas turbine combustors, are calculated using Moss-Brookes model.FindingsThe results show that the flow behavior is obviously different in recirculation region for both turbulence modeling approach, and this difference causes change on flame temperature distribution, particularly in the outer recirculation zone and region close to swirler. In thermal assessment of the burner, it is predicted that material of the burner walls and the applied thermal boundary conditions have significant influence on flame temperature, wall temperature and flow field. The radiation heat transfer also makes a strong impact on combustion inside the burner; however, luminous radiation arising from soot particles is negligible for the current case.Originality/valueThese types of burners are widely used in research of gas turbine combustion, and it can be seen that the heat transfer effects are generally neglected or oversimplified in the literature. This parametric study provides a basic understanding and methodology of the heat transfer effects on combustion to the researchers.

Testing Basic Gradient Turbulent Transport Models for Swirl Burners Using PIV and PLIF

The present paper reports on the combined stereoscopic particle image velocimetry (PIV) and planar laser induced fluorescence (PLIF) measurements of turbulent transport for model swirl burners without combustion. Two flow types were considered, namely the mixing of a free jet with surrounding air for different swirl rates of the jet (Re = 5 × 103) and the mixing of a pilot jet (Re = 2 × 104) with a high-swirl co-flow of a generic gas turbine burner (Re = 3 × 104). The measured spatial distributions of the turbulent Reynolds stresses and fluxes were compared with their predictions by gradient turbulent transport models. The local values of the turbulent viscosity and turbulent diffusivity coefficients were evaluated based on Boussinesq’s and gradient diffusion hypotheses. The studied flows with high swirl were characterized by a vortex core breakdown and intensive coherent flow fluctuations associated with large-scale vortex structures. Therefore, the contribution of the coherent flow fluctuations to the turbulent transport was evaluated based on proper orthogonal decomposition (POD). The turbulent viscosity and diffusion coefficients were also evaluated for the stochastic (residual) component of the velocity fluctuations. The high-swirl flows with vortex breakdown for the free jet and for the combustion chamber were characterized by intensive turbulent fluctuations, which contributed substantially to the local turbulent transport of mass and momentum. Moreover, the high-swirl flows were characterized by counter-gradient transport for one Reynolds shear stress component near the jet axis and in the outer region of the mixing layer.

Recent Combustion Strategies in Gas Turbines for Propulsion and Power Generation toward a Zero-Emissions Future: Fuels, Burners, and Combustion Techniques

The effects of climate change and global warming are arising a new awareness on the impact of our daily life. Power generation for transportation and mobility as well as in industry is the main responsible for the greenhouse gas emissions. Indeed, currently, 80% of the energy is still produced by combustion of fossil fuels; thus, great efforts need to be spent to make combustion greener and safer than in the past. For this reason, a review of the most recent gas turbines combustion strategy with a focus on fuels, combustion techniques, and burners is presented here. A new generation of fuels for gas turbines are currently under investigation by the academic community, with a specific concern about production and storage. Among them, biofuels represent a trustworthy and valuable solution in the next decades during the transition to zero carbon fuels (e.g., hydrogen and ammonia). Promising combustion techniques explored in the past, and then abandoned due to their technological complexity, are now receiving renewed attention (e.g., MILD, PVC), thanks to their effectiveness in improving the efficiency and reducing emissions of standard gas turbine cycles. Finally, many advances are illustrated in terms of new burners, developed for both aviation and power generation. This overview points out promising solutions for the next generation combustion and opens the way to a fast transition toward zero emissions power generation.

Utilising Cold Energy from Liquefied Natural Gas (LNG) to Reduce the Electricity Cost of Data Centres

The Office of the National Broadcasting and Telecommunications Commission has reported that, from 2014 to 2018, Thailand’s internet usage has grown six-fold to 3.3 million terabytes per annum. This market trend highlights one of the policies of Thailand 4.0, with the aim of making Thailand a hub for information transfer in ASEAN. As a result, there will be a massive demand growth for data storage facilities in the near future. Data centres are regarded as the brain and heart of the digital industry and are essential for facilitating businesses in organising, processing, storing and disseminating large amounts of data. As the energy demand for equipment cooling contributes to over 37% of the total energy consumption, the data centres of the world’s leading companies, such as Amazon, Google, Microsoft and Facebook, are generally located in cold climate zones, such as Iceland, in order to reduce operating costs for cooling. Due to this reason, the possibility of data centres in Thailand is limited. Beneficially, PTTLNG, as the first liquified natural gas (LNG) terminal in Thailand, has processed the import, receiving, storage and regasification of LNG. The high abundance of cold energy inherently presented in LNG is normally lost to the surroundings during regasification. Presently, PTTLNG’s LNG receiving terminal utilises a heat exchanger with propane as an intermediate fluid to transfer cold energy from LNG to water. This cold energy, in the form of cold water, is then used in several projects within the LNG receiving terminal: (1) production of electricity via an organic Rankine cycle capacity of 5 MWh; (2) cooling the air inlet of gas turbine generators to increase the generator efficiency; (3) replacing refrigerant heating, ventilation and air conditioning systems within buildings; (4) development of winter plantations with precision agriculture to replace imported products. Therefore, this study focuses on the potential and future use for LNG cold energy by performing a thermodynamic and economic analysis of the use of LNG cold energy as a source to produce cold water at 7 °C, with the total cold energy of 27.77 to 34.15 MW or 7934 t to 9757 t of refrigeration depending on the target pressure of the natural gas to replace the conventional cooling system of data centres. This research has the potential to reduce the cooling operation costs of data centres by more than USD 9.87 million per annum as well as CO2 emissions by 34,772 t per annum. In an economic study, this research could lead to a payback period of 7 years with IRR 13% for the LNG receiving terminal and a payback period of 2.21 years with IRR 45% for digital companies.

전기추진 선박의 연료비용 분석에 따른 최적 발전시스템 구성방안 및 에너지 저장장치 적용의 효용성 분석

This paper presents how to design the configuration of generation system for shipboard power system based on fuel cost analysis. We propose a sophisticated economic analysis method with detailed fuel cost evaluation, which can be obtained from actual specific fuel consumption (SFC) characteristics of the gas-turbine and diesel generators installed in existing ships. Using the proposed method, we analyze economic benefits for optimal configurations of shipboard generation system for both hybrid propulsion ships such as CODLOG (COmbined Diesel-eLectric Or Gas-turbine) and COGLOG (COmbined Gas-turbine eLectric Or Gas-turbine) and full electric propulsion ships. In addition, we analyze the effects of energy storage system (ESS) in shipboard power systems in terms of spinning reserve management and single generator operation mode to meet the reliability and survivability requirement. The effectiveness of the proposed method is verified through multiple case studies with actual measurement data in ships that are currently in operation.

Experimental and numerical study on self-sustaining performance of a 30-kW micro gas turbine generator system during startup process

The safe startup of micro gas turbine (MGT) generator system is the premise of normal operation. The whole start-up process contains motor startup, ignition, speed acceleration, motor switching to generator and power acceleration. Motor switching to generator happens at the self-sustaining state, which is significant to safe start-up process. However, characteristics of MGT generator system at self-sustaining state are hardly to investigate due to the lack of performance maps and complete experiments. Therefore, this work analyzed start-up schedule and presented a theoretical and experimental study on the self-sustaining performance of MGT generator system, based on the self-designed 30 kW MGT generator system built in Jiangjin Turbocharger Plant, China. The self-sustaining speed boundary and fuel consumption area is determined from the aspects of safe startup. A novel principle for determining the self-sustaining point (SSP) is proposed. Results show that the self-sustaining state can be achieved only when speed is over 26,750 rpm, and the SSP is determined at the speed of 30,750 rpm based on the proposed principle. Finally, the self-sustaining TIT and natural gas flow are compared with the experimental data, with two relative errors both almost within 4%. This method is instructive to the MGT generator system startup process.

Analysis on the development of micro gas turbine generation technology

Similar to the structure of small aero engines, the existing micro gas turbines generally apply radial impeller machinery and regenerative cycles to improve efficiency. This paper analyzes the development of micro gas turbine generation technology. After making breakthroughs in basic research fields such as combustion, structural materials and coatings, additive manufacturing, thermal management, and comprehensive simulation and verification experiments, the next-generation micro cogeneration system composed of micro gas turbine and renewable energy power generation equipment will effectively obtain stable power output, improve power energy quality, and overcome difficulty in technology, economy, and application scenarios.

High ambient temperature effects on the performance of a gas turbine-based cogeneration system with supplementary fire in a tropical climate

High ambient temperature negatively affects gas turbine performance, especially in a tropical climate. Cogeneration improves fuel utilization by taking advantage of the energy discharged as waste heat in the exhaust gases. This case study assesses the effects of high ambient temperature on the performance of a natural gas-based cogeneration plant in Barranquilla, Colombia, a location with a hot and humid tropical climate throughout the year with an annual average temperature of 27.4 °C. The cogeneration plant encompasses gas and vapor turbine generation, supplementary fire, waste heat recovery, and process heat exchange. Validated ASPENHYSYS® simulation allows comparing gas-turbine-alone indicators with those at ISO conditions, i.e., 15 °C and 101.3 kPa. Ambient temperature reduces gas turbine power output by up to 22% and decreases thermal efficiency by around 0.06% for every °C rise above ISO conditions. Cogeneration with and without supplementary fire increases power output by 17% and 5% compared to gas-turbine-alone operation. The energy utilization factor increases by 27–37% without supplementary fire and above 37% with supplementary fire. Results give insight into the challenges of cogeneration plants in a tropical climate. Further studies should include the effects of high humidity on power plant performance and the potential benefits of cooling inlet air.

On the Flame Shape in a Premixed Swirl Stabilised Burner and its Dependence on the Laminar Flame Speed

Gas turbines for power generation are optimised to run with fossil fuels but as a response to tighter pollutant regulations and to enable the use of renewable fuels there is a great interest in improving fuel flexibility. One interesting renewable fuel is syngas from biomass gasification but its properties vary depending on the feedstock and gasification principle, and are significantly different from conventional fuels. This paper aims to give an overview of the differences in combustion behaviour by comparing numerical solutions with methane and several different synthesis gas compositions. The TECFLAM swirl burner geometry, which is designed to be representative of common gas turbine burners, was selected for comparison. The advantage with this geometry is that detailed experimental measurements with methane are publicly available. A two-stage approach was employed with development and validation of an advanced CFD model against experimental data for methane combustion followed by simulations with four syngas mixtures. The validated model was used to compare the flame shape and other characteristics of the flow between methane, 40% hydrogen enriched methane and four typical syngas compositions. It was found that the syngas cases experience lower swirl intensity due to high axial velocities that weakens the inner recirculation zone. Moreover, the higher laminar flame speed of the syngas cases has a strong effect on the flame front shape by bending it away from the axial direction, by making it shorter and by increasing the curvature of the flame front. A hypothesis that the flame shape and position is primarily governed by the laminar flame speed is supported by the almost identical flame shapes for bark powder syngas and 40% hydrogen enriched methane. These gas mixtures have almost identical laminar flame speeds for the relevant equivalence ratios but the heating value of the syngas is more than a factor of 3 smaller than that of the hydrogen enriched methane. The syngas compositions used are representative of practical gasification processes and biomass feedstocks. The demonstrated strong correlation between laminar flame speed and flame shape could be used as a rule of thumb to quickly judge whether the flame might come in contact with the structure or in other ways be detrimental to the function of the combustion system.

A novel peak load shaving algorithm for isolated microgrid using hybrid PV-BESS system

A novel peak load shaving algorithm has been proposed in this study for peak shaving application in hybrid PV-BESS connected Isolated Microgrid (IMG) system. This algorithm will help an IMG system to operate its generation systems optimally and economically along with PV generation unit. An IMG model has been developed in MATLAB/Simulink environment with actual load data, conventional Gas Turbine Generator (GTG), Photovoltaic (PV) generation system and Battery Energy Storage System (BESS). The proposed algorithm has been tested with the designed IMG model. To evaluate the effectiveness of the algorithm, simulation case studies have been conducted with actual load data and actual PV generation data. The simulation results demonstrate that the algorithm can minimize the limitations of the existing methods and it can use the PV generation system effectively. Peak shaving service can be found from this algorithm as a simple and forcible way. A comparative analysis has been conducted of the proposed algorithm with the conventional methods. The comparison results can easily reflect that the proposed algorithm can ensure the optimal use of PV generation system and can serve peak shaving service effectively. It can also ensure an economic and environment friendly system where the existing algorithms are limited to serve these. The proposed algorithm can mitigate the available power issues for hybrid PV-BESS connected system and it can also minimize the operating cost by dispatching the generation units optimally.

Influence of operating time on the strength reliability of the gas generator turbine disk of the aircraft drive for the GPA

This paper contains the analysis of characteristics changes of mechanical properties of the EI698-VD alloy depending on the duration of operation of the NK family gas turbine disks working as part of a gas generator turbine for GPA. Their stress-strain state was determined using the finite element method. The strength reserves are defined as characteristics of the disks’ strength reliability at different levels of the operating time.

Power quality considerations for embedded generation integration in Nigeria: A case study of ogba 33 kV injection substation

The deregulation of the Nigerian power sector has resulted in the quest to explore power generation options for power quality improvement. One of such options is the pattern shift from central power generation to embedded power generation. Network integration of embedded generators (EGs) causes several regulatory, technical and economic issues. This research focuses on power quality challenges that may arise as a result of network integration of embedded generation in a weak electricity networks using Ogba 33 kV injection substation as case study. The embedded generators considered comprised of gas turbine and diesel generators. NEPLAN software was used to perform the load flow analysis with and without EGs connection on the network. This was necessary so as to ascertain the healthiness of the existing distribution network for EGs integration. The power quality issues considered in the study were bus voltage profiles and the total line losses. Simulation results showed that EGs connection improved the voltage profile, for example, bus voltage at PTC 11 kV, improved from 0.881 pu to 0.958 pu while the total active power loss was reduced by 78.16%. The results obtained suggest that the grid is healthy enough to accommodate the EGs with no quality issues.

Study of offshore wind power penetration rate in gas turbine generator platform power grid

Because of the energy supply of the offshore oil platforms mainly relies on the supply of gas turbine, the development of renewable energy will become a rich energy supply for offshore oil platforms and a reliable way to improve the stability of the grid of the platforms. This paper developed the simulation model of offshore oil gas turbine platform power grid, simulated the hybrid power grid structure, the energy storage of frequency regulation, high wind power penetration rate, wind power and gas turbine power frequency stability and fault treatment. The method of increasing renewable energy penetration rate was proposed, and the hybrid energy coordinated control strategy of offshore oil platform was also carried out. Based on the weakly connected distributed offshore oil platform power grid project, this paper studied the influence of wind power and turbine power penetration rate on the power grid, in order to explore, determine and verify the limit of high wind power penetration rate under the condition of “large generation machine and small grid”. The simulation experiment of high wind power penetration rate under the condition of different load conditions and different wind speed limits were discussed, on the basis of research the influence degree of the stability of power grid frequency of low wind power swings, as well as to the wind power is given priority to with gas turbine mainly in both cases the advantages and disadvantages of the grid system, and attempt to put forward the corresponding switch control strategy.

Acquisition and Processing Considerations for Infrared Images of Rotating Turbine Blades

Abstract As designers aim to increase efficiency in gas turbines for aircraft propulsion and power generation, spatially resolved experimental measurements are needed to validate computational models and compare improvement gains of new cooling designs. Infrared (IR) thermography is one such method for obtaining spatially resolved temperature measurements. As technological advances in thermal detectors enable faster integration times, surface temperature measurements of rotating turbine blades become possible to capture including the smallest features. This paper outlines opportunities enabled by the latest IR detector technologies for capturing spatially resolved rotating blade temperatures, while also addressing some of the challenges of implementing IR for turbine rigs such as the one in the Steady Thermal Aero Research Turbine (START) Laboratory. This paper documents critical steps in achieving accurate measurements including calibration, integration times, spatial noise, and motion blur. From these results, recommendations are provided for achieving accurate IR measurements collected in a rotating turbine facility to study film cooling.

Toughening Mechanism of Thermal Barrier Coatings

Thermal barrier coatings are applied to the protection of metal components in aircraft thrusters, power generation and ship gas turbine engines, which can make the gas turbine run for a long time in a high-temperature environment. The fracture toughness of the coating characterizes the ability of the material to prevent crack propagation and is one of the most important factors to be taken into consideration to prolong the life of the thermal barrier coating. The current research is mainly through dispersion toughening, the phase transformation toughening, whisker toughening, ferroelastic toughening, and other methods to improve the fracture toughness of ceramic coatings. In this paper, the use of different toughening mechanisms and the addition of unique materials to improve the fracture toughness of thermal barrier coatings are introduced, and the future research direction is put forward.

Performance Optimization of Gas Turbine Generator Based on Operating Conditions Using ANN-GA at Saka Indonesia Pangkah Ltd

Performance Optimization of Gas Turbine Generator Based on Operating Conditions Using ANN-GA at Saka Indonesia Pangkah Ltd

Modeling of an isolated microgrid with hybrid PV-BESS system for peak load shaving simulation

In this paper, a simplified model of an isolated microgrid (IMG) with hybrid photovoltaic (PV)-battery energy storage system (BESS) is discussed. The concept of peak load shaving is also demonstrated. The developed model helps an isolated power system to minimize the demand and maximize the economic benefit. MATLAB/Simulink tool was used to simulate the electrical circuit of the IMG system. The IMG model contains four sub-systems, namely the PV model, time varying load profile model, BESS model and gas turbine generator (GTG) dispatch model. To evaluate the performance of the developed IMG, a simulation case study was conducted under realistic load conditions of Universiti Teknologi PETRONAS (UTP). Results indicated that simulation illustrates the precise situation of the real-time system, as found in the UTP microgrid. Results also revealed that the concept of peak load shaving broadly illustrated in this study. The implementation of the proposed IMG model may bring economic benefit by minimizing peak load demand. © 2021 Md Masud Rana et al.

Numerical investigation of non-uniform flow in twin-silo combustors and impact on axial turbine stage performance

A clear understanding of the flow characteristics in the older generation of industrial gas turbines operating with silo combustors is important for potential upgrades. Non-uniformities in the form of circumferential and radial variations in internal flow properties can have a significant impact on the gas turbine stage performance and durability. This paper presents a comprehensive study of the underlying internal flow features involved in the advent of non-uniformities from twin-silo combustors and their propagation through a single axial turbine stage of the Siemens v94.2 industrial gas turbine. Results indicate the formation of strong vortical structures alongside large temperature, pressure, velocity, and flow angle deviations that are mostly located in the top and bottom sections of the turbine stage caused by the excessive flow turning in the upstream tandem silo combustors. A favorable validation of the simulated exhaust gas temperature (EGT) profile is also achieved via comparison with the measured data. A drop in isentropic efficiency and power output equivalent to 2.28% points and 2.1 MW, respectively is observed at baseload compared to an ideal straight hot gas path reference case. Furthermore, the analysis of internal flow topography identifies the underperforming turbine blading due to the upstream non-uniformities. The findings not only have implications for the turbine aerothermodynamic design, but also the combustor layout from a repowering perspective.

Experimental and numerical investigation of jet impingement cooling onto a concave leading edge of a generic gas turbine blade

This study focuses on an experimental and numerical heat transfer investigation of an impingement jet array with a concave target plate that resembles a turbine blade's leading edge. The array consists of nine circular jets with a diameter of Djet and the target plate has a curvature radius of R=Djet. The target plate also features film cooling holes in a staggered configuration so that each jet is surrounded by three film cooling holes. A Reynolds number of 30,000 is tested, while the separation distance H is altered between H/Djet=2.7 and H/Djet=4. In addition the jets are exposed to a crossflow (cf). The experimental heat transfer data are obtained by using the transient Thermochromic Liquid Crystal (TLC) method. In the Computational Fluid Dynamics (CFD) study 3D steady state Reynolds-Averaged Navier-Stokes (RANS) simulations with the software package OpenFOAM and the kω−shear−stress−transport (SST) turbulence model are performed. The numerical results from OpenFOAM agree well with the experimental data and local flow phenomena are captured correctly. The crossflow decreases the stagnation point heat transfer as well as the overall heat transfer but homogenizes the local heat transfer distribution. A smaller separation distance enhances the crossflow effects and generally increases the heat transfer level.