Temperature rise is one of the limiting factors in generator design. Bearings and windings failure are the two most prominent cause of generator failure in the wind turbine application. The generator is mostly converter-fed in the wind turbine application, and operation with converter brings specific challenges. Insulation of generator system should be designed in such a way to withstand these challenges. Two immediate problems with converter-fed wind generators are winding temperature rise due to harmonic losses and voltage peaks. Voltage peaks generated by converter can create a winding hotspot and eventually destroy the insulation system of generator winding, which leads to reducing the lifetime of the insulation system. Turbine availability study from a commercial point of view is presented. For selecting the winding insulation system, it is essential to know the environment generator is going to operate. Specific voltage peaks from different converter systems can damage windings insulation. Damage insulation brings the downtime of the turbine, which affects the LCOE and AEP of the wind turbine. The electrical voltage between motor terminals and ground can be generated due to the different converter output circuit, longer feeder cables (when converter being placed on the basement and not in the nacelle) on the and unfavorable grounding conditions. Paper discusses voltage peaks due to operation with converter and make a recommendation for the winding insulation system, for a particular case. A better selection procedure for a generator winding insulation system is recommended.
{"title":"The Impact of the Converter on the Reliability of a Wind Turbine Generator","authors":"Gopal Singh, S. Lentijo, K. Sundaram","doi":"10.1115/power2019-1966","DOIUrl":"https://doi.org/10.1115/power2019-1966","url":null,"abstract":"\u0000 Temperature rise is one of the limiting factors in generator design. Bearings and windings failure are the two most prominent cause of generator failure in the wind turbine application. The generator is mostly converter-fed in the wind turbine application, and operation with converter brings specific challenges. Insulation of generator system should be designed in such a way to withstand these challenges. Two immediate problems with converter-fed wind generators are winding temperature rise due to harmonic losses and voltage peaks. Voltage peaks generated by converter can create a winding hotspot and eventually destroy the insulation system of generator winding, which leads to reducing the lifetime of the insulation system. Turbine availability study from a commercial point of view is presented. For selecting the winding insulation system, it is essential to know the environment generator is going to operate. Specific voltage peaks from different converter systems can damage windings insulation. Damage insulation brings the downtime of the turbine, which affects the LCOE and AEP of the wind turbine. The electrical voltage between motor terminals and ground can be generated due to the different converter output circuit, longer feeder cables (when converter being placed on the basement and not in the nacelle) on the and unfavorable grounding conditions. Paper discusses voltage peaks due to operation with converter and make a recommendation for the winding insulation system, for a particular case. A better selection procedure for a generator winding insulation system is recommended.","PeriodicalId":315864,"journal":{"name":"ASME 2019 Power Conference","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115344123","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The efficiency of ground source heating and cooling can be improved during installation by utilizing non-uniform properties of the soil. This paper presents a transient analysis of a computed optimal distribution of heterogeneous soils with varying thermal conductivities. This optimal configuration was computed via a gradient descent approach. The numerically simulated case studies demonstrate an improved performance when utilizing this approach to maximize the overall efficiency. The focus of this study is optimization of the soil heterogeneity surrounding the ground heat exchanger composed of pipes buried 2 meters underground. Finite element mathematics is used for the optimization algorithm. The finite element cells are treated as isotropic material voxels. The variation of material thermal conductivity in individual cells is employed as the optimizing variable. The updated conductivities are verified to ensure they are within the design domain. This method computes the sensitivities for the search direction (i.e. the gradient descent direction) utilizing the equations employed in the finite element mathematics. The optimization solution commences with the finite element model and applied boundary conditions. An initial guess is made of the elements’ conductivity. Based on these conductivities, the initial temperature is computed and later implemented to estimate the gradient. The global geometric conductivity matrix is assembled once in this process from the element geometric conductivity matrices. The objective function presented in this work maximizes the temperature at the critical locations. For this study, the critical locations are the location of the pipes. A three-dimensional, transient thermal simulation is developed based upon the optimized configuration for the soil. The monthly mean diurnal ambient air temperature variations for the months in the Northeast United States representing winter and summer are implemented in this study along with typical solar loading for each season. The results are presented for both a baseline homogeneous soil configuration and the optimized configuration. The results illustrate the benefits of an optimized soil configuration to maximize performance.
{"title":"Transient Response of Gradient-Based Optimization for Ground Source Heat Exchangers","authors":"A. DiCarlo, R. A. Caldwell","doi":"10.1115/power2019-1922","DOIUrl":"https://doi.org/10.1115/power2019-1922","url":null,"abstract":"\u0000 The efficiency of ground source heating and cooling can be improved during installation by utilizing non-uniform properties of the soil. This paper presents a transient analysis of a computed optimal distribution of heterogeneous soils with varying thermal conductivities. This optimal configuration was computed via a gradient descent approach. The numerically simulated case studies demonstrate an improved performance when utilizing this approach to maximize the overall efficiency.\u0000 The focus of this study is optimization of the soil heterogeneity surrounding the ground heat exchanger composed of pipes buried 2 meters underground. Finite element mathematics is used for the optimization algorithm. The finite element cells are treated as isotropic material voxels. The variation of material thermal conductivity in individual cells is employed as the optimizing variable. The updated conductivities are verified to ensure they are within the design domain. This method computes the sensitivities for the search direction (i.e. the gradient descent direction) utilizing the equations employed in the finite element mathematics. The optimization solution commences with the finite element model and applied boundary conditions. An initial guess is made of the elements’ conductivity. Based on these conductivities, the initial temperature is computed and later implemented to estimate the gradient. The global geometric conductivity matrix is assembled once in this process from the element geometric conductivity matrices. The objective function presented in this work maximizes the temperature at the critical locations. For this study, the critical locations are the location of the pipes.\u0000 A three-dimensional, transient thermal simulation is developed based upon the optimized configuration for the soil. The monthly mean diurnal ambient air temperature variations for the months in the Northeast United States representing winter and summer are implemented in this study along with typical solar loading for each season. The results are presented for both a baseline homogeneous soil configuration and the optimized configuration. The results illustrate the benefits of an optimized soil configuration to maximize performance.","PeriodicalId":315864,"journal":{"name":"ASME 2019 Power Conference","volume":"151 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128434103","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper utilizes numerical modeling to address the effects of two parameters on natural draft cooling tower performance, namely the radial hot water distribution and flue gas injection. Predictions show that cold water temperature leaving the tower can be slightly decreased by increasing the weighting of the radial hot water distribution towards the tower periphery. The injection of scrubbed flue gas into the tower chimney can have either a positive or a negative effect on tower cooling performance, depending on the temperature of the flue gas relative to the temperature of moist air in the chimney. The temperature of the scrubbed flue gas is the primary variable affecting cooling tower performance, associated with flue gas injection. This paper investigates using the radial distribution of hot water to optimize the tower cooling performance when injecting scrubbed flue gas into the chimney, both for conditions when the flue gas is warmer and cooler than the temperature of moist air in the chimney. Predictions with no flue gas injection show that optimizing hot water distribution produced 0.4 °C reduction in cooled water temperature. With relatively cold (32.2 °C) and relatively hot (65.6 °C) flue gas injection, optimizing hot water distribution produced slightly more than 0.2 °C reduction in cooled water temperature.
{"title":"Investigating the Effects of Flue Gas Injection and Hot Water Distribution and Their Interaction on Natural Draft Wet Cooling Tower Performance","authors":"T. Eldredge, J. M. Stapleton","doi":"10.1115/power2019-1962","DOIUrl":"https://doi.org/10.1115/power2019-1962","url":null,"abstract":"\u0000 This paper utilizes numerical modeling to address the effects of two parameters on natural draft cooling tower performance, namely the radial hot water distribution and flue gas injection. Predictions show that cold water temperature leaving the tower can be slightly decreased by increasing the weighting of the radial hot water distribution towards the tower periphery. The injection of scrubbed flue gas into the tower chimney can have either a positive or a negative effect on tower cooling performance, depending on the temperature of the flue gas relative to the temperature of moist air in the chimney. The temperature of the scrubbed flue gas is the primary variable affecting cooling tower performance, associated with flue gas injection. This paper investigates using the radial distribution of hot water to optimize the tower cooling performance when injecting scrubbed flue gas into the chimney, both for conditions when the flue gas is warmer and cooler than the temperature of moist air in the chimney. Predictions with no flue gas injection show that optimizing hot water distribution produced 0.4 °C reduction in cooled water temperature. With relatively cold (32.2 °C) and relatively hot (65.6 °C) flue gas injection, optimizing hot water distribution produced slightly more than 0.2 °C reduction in cooled water temperature.","PeriodicalId":315864,"journal":{"name":"ASME 2019 Power Conference","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128574277","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The present work introduces an indirect supercritical CO2–air driven concentrated solar plant with a packed bed thermal energy storage. The proposed plant design enables a supercritical CO2 turbine inlet temperature of 800°C, overcoming the temperature limits imposed by the use of solar molten salts as primary heat transfer fluid. Furthermore, the packed bed thermal energy storage permits the decoupling between thermal power collection from the sun and electricity generation. Besides, the thermal energy storage unit grants operational flexibility and enlarges the plant capacity factor, making it as available as a conventional coal facility. A transient thermodynamic model of the integrated concentrating solar plant, including receiver, thermal energy storage, intermediate heat exchangers and supercritical CO2 power cycle has been developed. This same model has been used to evaluate the thermodynamic performance of the proposed plant design over a complete year. A similar model has been implemented to simulate a supercritical CO2 plant driven by a more traditional solar molten salt loop. A comparison of the thermodynamic performance of the two plant designs has been performed. A complete economic model has been developed in order to evaluate the economic viability of the proposed plant. Furthermore, a multi-objective optimization have been executed in order to assess the influence of the thermal energy storage size, supercritical CO2 turbine inlet temperature and plant solar multiple on the key performance indicators. Results show that the proposed indirect supercritical CO2–air driven with a packed bed thermal energy storage concentrated solar plant leads to improved thermo-economic performance with respect to the molten salts driven design. Enhancements in the power cycle efficiency and in the overall electricity production can be achieved, with a consequent reduction in the levelized cost of electricity. Particularly, for a design net electrical power production of 10MWe a minimum levelized cost of electricity has been calculated at 89.4 $/MWh for a thermal energy storage capacity of 13.9 hours at full load and a plant solar multiple of 2.47 corresponding to a capital investment of about 73.4 M$.
{"title":"Supercritical CO2 Brayton Power Cycle for CSP With Packed Bed TES Integration and Cost Benchmark Evaluation","authors":"S. Trevisan, R. Guédez, Björn Laumert","doi":"10.1115/power2019-1903","DOIUrl":"https://doi.org/10.1115/power2019-1903","url":null,"abstract":"\u0000 The present work introduces an indirect supercritical CO2–air driven concentrated solar plant with a packed bed thermal energy storage. The proposed plant design enables a supercritical CO2 turbine inlet temperature of 800°C, overcoming the temperature limits imposed by the use of solar molten salts as primary heat transfer fluid. Furthermore, the packed bed thermal energy storage permits the decoupling between thermal power collection from the sun and electricity generation. Besides, the thermal energy storage unit grants operational flexibility and enlarges the plant capacity factor, making it as available as a conventional coal facility. A transient thermodynamic model of the integrated concentrating solar plant, including receiver, thermal energy storage, intermediate heat exchangers and supercritical CO2 power cycle has been developed. This same model has been used to evaluate the thermodynamic performance of the proposed plant design over a complete year. A similar model has been implemented to simulate a supercritical CO2 plant driven by a more traditional solar molten salt loop. A comparison of the thermodynamic performance of the two plant designs has been performed. A complete economic model has been developed in order to evaluate the economic viability of the proposed plant. Furthermore, a multi-objective optimization have been executed in order to assess the influence of the thermal energy storage size, supercritical CO2 turbine inlet temperature and plant solar multiple on the key performance indicators. Results show that the proposed indirect supercritical CO2–air driven with a packed bed thermal energy storage concentrated solar plant leads to improved thermo-economic performance with respect to the molten salts driven design. Enhancements in the power cycle efficiency and in the overall electricity production can be achieved, with a consequent reduction in the levelized cost of electricity. Particularly, for a design net electrical power production of 10MWe a minimum levelized cost of electricity has been calculated at 89.4 $/MWh for a thermal energy storage capacity of 13.9 hours at full load and a plant solar multiple of 2.47 corresponding to a capital investment of about 73.4 M$.","PeriodicalId":315864,"journal":{"name":"ASME 2019 Power Conference","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125258191","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
O. Olatunji, S. Akinlabi, N. Madushele, P. Adedeji, S. Fatoba
This article applied a hybridized, adaptive neuro-fuzzy inference system ANFIS-genetic algorithm (GA-ANFIS) and ANFIS -Particle swarm optimization (PSO-ANFIS) to predict the HHV of biomass. The minimum input parameter for the prediction model is based on the proximate values of biomass which are fixed carbon (FC), ash content (A) and volatile matter (VM). The 214 data which cover a wide range of biomass classes were extracted from reliable literature for the training and testing of the models. The optimal results obtained based on each modelling algorithm were compared. The proposed algorithms were evaluated by statistical indices which are the Coefficient of Correlation (CC), Root Mean Squared Error (RMSE), Mean Absolute Percentage Error (MAPE), Mean Absolute Deviation (MAD) estimated at 0.9189, 1.2369,7.4575 and 1.3560 respectively for PSO-ANFIS and 0.9088, 1.1200, 6.3960, 0.8895 respectively for GA-ANFIS. The GA showed exceptional ability to generalize in term of MAPE though at the expense of lesser CC which is obtained in the case of PSO. The reported indices showed that PSO-ANFIS and GA-ANFIS could be applied as an approach to the prediction of HHV based on proximate analysis instead of lengthy experiment procedures.
{"title":"Comparative Analysis of the Heating Values of Biomass Based on GA-ANFIS and PSO-ANFIS Models","authors":"O. Olatunji, S. Akinlabi, N. Madushele, P. Adedeji, S. Fatoba","doi":"10.1115/power2019-1825","DOIUrl":"https://doi.org/10.1115/power2019-1825","url":null,"abstract":"\u0000 This article applied a hybridized, adaptive neuro-fuzzy inference system ANFIS-genetic algorithm (GA-ANFIS) and ANFIS -Particle swarm optimization (PSO-ANFIS) to predict the HHV of biomass. The minimum input parameter for the prediction model is based on the proximate values of biomass which are fixed carbon (FC), ash content (A) and volatile matter (VM). The 214 data which cover a wide range of biomass classes were extracted from reliable literature for the training and testing of the models. The optimal results obtained based on each modelling algorithm were compared. The proposed algorithms were evaluated by statistical indices which are the Coefficient of Correlation (CC), Root Mean Squared Error (RMSE), Mean Absolute Percentage Error (MAPE), Mean Absolute Deviation (MAD) estimated at 0.9189, 1.2369,7.4575 and 1.3560 respectively for PSO-ANFIS and 0.9088, 1.1200, 6.3960, 0.8895 respectively for GA-ANFIS. The GA showed exceptional ability to generalize in term of MAPE though at the expense of lesser CC which is obtained in the case of PSO. The reported indices showed that PSO-ANFIS and GA-ANFIS could be applied as an approach to the prediction of HHV based on proximate analysis instead of lengthy experiment procedures.","PeriodicalId":315864,"journal":{"name":"ASME 2019 Power Conference","volume":"97 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127103688","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Energy storage systems provide a variety of benefits, including taking better advantage of renewable electricity when available and smoothing demand by shifting demand peaks to times when electricity prices and demand are lower. When low electricity demand occurs during the nighttime, system wide advantages also occur. These lower nighttime ambient temperatures lead to efficiency improvements throughout the grid, including power generators, transmission and distribution systems, chillers, etc. An analysis of ice thermal energy storage carried out by T. Deetjen et al. in 2018 analyzed fuel consumption of the power generation fleet for meeting cooling demand in buildings as a function of ambient temperature, relative humidity, transmission and distribution current, and baseline power plant efficiency. Their results showed that the effective round trip efficiency for ice thermal energy storage could exceed 100% due to the efficiency gains of nighttime operation. However, their analysis was performed on a case study in Dallas, where relatively high humidities lead to a relatively small diurnal temperature variation during the cooling season. In order to expand on this limitation, our study extends this analysis to a mountain west climate, using northern Arizona as a case study. The climate of the mountain west has several key differences from that of the Dallas case study in the previous work, including lower relative humidity, higher diurnal temperature variation, and near- and below-freezing nighttime temperatures during shoulder seasons that also exhibit cooling demand in buildings. To address these differences, this paper updates the models of Deetjen et al. to consider generator fleet efficiency and chiller/icemaking COP for local weather characteristics relevant to the mountain west, as well as considering the differences between fuel mixes of the generator fleet in nighttime and daytime. Compared to Dallas, the larger temperature variation of northern Arizona leads to higher round trip efficiencies (RTE) over the course of the year in most days of the year (e.g. 313 days of the year in northern Arizona in comparison with 182 days in Dallas), demonstrating frequent achievement of over 100% effective round trip efficiency. The presence of a mature commercial market and the possibility of gaining over 100% effective round trip efficiency create a strong case for cooling thermal energy storage as an energy storage approach. Future work will investigate emissions impacts as well as extend the analysis to additional western climates, including the hot dry and marine climates.
{"title":"Analysis of Round Trip Efficiency of Thermal Energy Storage in Northern Arizona","authors":"Amin Sepehri, Brent A. Nelson","doi":"10.1115/power2019-1860","DOIUrl":"https://doi.org/10.1115/power2019-1860","url":null,"abstract":"\u0000 Energy storage systems provide a variety of benefits, including taking better advantage of renewable electricity when available and smoothing demand by shifting demand peaks to times when electricity prices and demand are lower. When low electricity demand occurs during the nighttime, system wide advantages also occur. These lower nighttime ambient temperatures lead to efficiency improvements throughout the grid, including power generators, transmission and distribution systems, chillers, etc. An analysis of ice thermal energy storage carried out by T. Deetjen et al. in 2018 analyzed fuel consumption of the power generation fleet for meeting cooling demand in buildings as a function of ambient temperature, relative humidity, transmission and distribution current, and baseline power plant efficiency. Their results showed that the effective round trip efficiency for ice thermal energy storage could exceed 100% due to the efficiency gains of nighttime operation. However, their analysis was performed on a case study in Dallas, where relatively high humidities lead to a relatively small diurnal temperature variation during the cooling season. In order to expand on this limitation, our study extends this analysis to a mountain west climate, using northern Arizona as a case study. The climate of the mountain west has several key differences from that of the Dallas case study in the previous work, including lower relative humidity, higher diurnal temperature variation, and near- and below-freezing nighttime temperatures during shoulder seasons that also exhibit cooling demand in buildings. To address these differences, this paper updates the models of Deetjen et al. to consider generator fleet efficiency and chiller/icemaking COP for local weather characteristics relevant to the mountain west, as well as considering the differences between fuel mixes of the generator fleet in nighttime and daytime. Compared to Dallas, the larger temperature variation of northern Arizona leads to higher round trip efficiencies (RTE) over the course of the year in most days of the year (e.g. 313 days of the year in northern Arizona in comparison with 182 days in Dallas), demonstrating frequent achievement of over 100% effective round trip efficiency. The presence of a mature commercial market and the possibility of gaining over 100% effective round trip efficiency create a strong case for cooling thermal energy storage as an energy storage approach. Future work will investigate emissions impacts as well as extend the analysis to additional western climates, including the hot dry and marine climates.","PeriodicalId":315864,"journal":{"name":"ASME 2019 Power Conference","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129112386","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Eric Kjolsing, R. James, Keith Kubischta, D. Parker
Nuclear power plants around the world are nearing the end of their designed service life. Sufficient structural capacity must be demonstrated to extend each plant’s operating license when accounting for concrete creep, shrinkage, and tendon relaxation past the original design life. This may take the form of in-situ values which meet the design allowable or, as outlined in this paper, analysis models which demonstrate capacity. This paper presents an analysis methodology for a concrete containment structure utilizing grouted post-tensioned tendons representative of a non-US design. The methodology is intended to demonstrate that a structure can still meet established design requirements while accounting for creep, shrinkage, and tendon relaxation. The analysis effort is performed in multiple stages. First, design parameters feeding into post-tensioning loss calculations are identified and assigned statistical distributions. Probabilistic estimates of the post-tensioning losses are developed using both a variational and Monte Carlo approach. Second, a finite element model of a representative containment structure is developed with tendons and reinforcement explicitly modeled. Lastly, the finite element model is used in example analyses to demonstrate future performance and pressure capacity accounting for projected tendon losses.
{"title":"Assessing Prestress Losses in a Nuclear Containment Structure for License Renewal","authors":"Eric Kjolsing, R. James, Keith Kubischta, D. Parker","doi":"10.1115/power2019-1842","DOIUrl":"https://doi.org/10.1115/power2019-1842","url":null,"abstract":"\u0000 Nuclear power plants around the world are nearing the end of their designed service life. Sufficient structural capacity must be demonstrated to extend each plant’s operating license when accounting for concrete creep, shrinkage, and tendon relaxation past the original design life. This may take the form of in-situ values which meet the design allowable or, as outlined in this paper, analysis models which demonstrate capacity.\u0000 This paper presents an analysis methodology for a concrete containment structure utilizing grouted post-tensioned tendons representative of a non-US design. The methodology is intended to demonstrate that a structure can still meet established design requirements while accounting for creep, shrinkage, and tendon relaxation. The analysis effort is performed in multiple stages. First, design parameters feeding into post-tensioning loss calculations are identified and assigned statistical distributions. Probabilistic estimates of the post-tensioning losses are developed using both a variational and Monte Carlo approach. Second, a finite element model of a representative containment structure is developed with tendons and reinforcement explicitly modeled. Lastly, the finite element model is used in example analyses to demonstrate future performance and pressure capacity accounting for projected tendon losses.","PeriodicalId":315864,"journal":{"name":"ASME 2019 Power Conference","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124415876","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In recent years, the aircraft industry is heading towards the concept of the More Electric Airplane (MEA). Previous research has investigated the possibility of integrating Dual Chamber Solid Oxide Fuel Cells (DC-SOFC) with the auxiliary power unit (APU) of the aircraft. This paper evaluates the merits of integrating the recently proposed Flame-assisted Fuel Cells (FFCs) with the APU gas turbine system. The syngas composition for fuel-rich combustion is studied using chemical equilibrium analysis of Jet-A/air at 8 Bar and 1073 K. The results show the potential for reforming Jet-A fuel to 22% Carbon Monoxide and 18% Hydrogen in the exhaust at an equivalence ratio of 2.4. The paper also reports how the efficiency of power generation changes when FFCs are placed in the combustor of a turbine in the APU. The maximum theoretical electrical efficiency of the FFC/combustor and the area and weight of the fuel cell required to generate the design power is calculated. The FFC offers a viable substitute for the DC-SOFC to be integrated with the APU.
近年来，飞机工业正朝着更电动飞机(MEA)的概念发展。之前的研究已经研究了将双室固体氧化物燃料电池(DC-SOFC)与飞机的辅助动力装置(APU)集成的可能性。本文评价了最近提出的火焰辅助燃料电池(FFCs)与APU燃气轮机系统集成的优点。利用喷气- a /空气在8 Bar和1073 K下的化学平衡分析，研究了富燃料燃烧合成气的组成。结果表明，以2.4的当量比将Jet-A燃料转化为排气中22%的一氧化碳和18%的氢气。本文还报道了在APU的涡轮燃烧室中放置FFCs时发电效率的变化。计算了FFC/燃烧室的最大理论电效率以及产生设计功率所需的燃料电池的面积和重量。FFC为与APU集成的DC-SOFC提供了一个可行的替代品。
{"title":"Integration of Flame-Assisted Fuel Cells With a Gas Turbine Running Jet-A As Fuel","authors":"R. Ghotkar, R. Milcarek","doi":"10.1115/power2019-1852","DOIUrl":"https://doi.org/10.1115/power2019-1852","url":null,"abstract":"\u0000 In recent years, the aircraft industry is heading towards the concept of the More Electric Airplane (MEA). Previous research has investigated the possibility of integrating Dual Chamber Solid Oxide Fuel Cells (DC-SOFC) with the auxiliary power unit (APU) of the aircraft. This paper evaluates the merits of integrating the recently proposed Flame-assisted Fuel Cells (FFCs) with the APU gas turbine system. The syngas composition for fuel-rich combustion is studied using chemical equilibrium analysis of Jet-A/air at 8 Bar and 1073 K. The results show the potential for reforming Jet-A fuel to 22% Carbon Monoxide and 18% Hydrogen in the exhaust at an equivalence ratio of 2.4. The paper also reports how the efficiency of power generation changes when FFCs are placed in the combustor of a turbine in the APU. The maximum theoretical electrical efficiency of the FFC/combustor and the area and weight of the fuel cell required to generate the design power is calculated. The FFC offers a viable substitute for the DC-SOFC to be integrated with the APU.","PeriodicalId":315864,"journal":{"name":"ASME 2019 Power Conference","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115630367","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
As the electricity market has evolved with the addition of renewables to the generation mix, Heat Recovery Steam Generators (HRSGs) that were originally designed for base load conditions are now frequently forced to operate in a cycling and/or low-load regime. This can lead to front end tube-to header fatigue, creep or creep-fatigue failures, often induced by Gas Turbine (GT) flow imbalances causing locally-elevated tube temperatures and/or bending stresses on joints due to large temperature differences between tube rows. This paper focuses on the use of Computational Fluid Dynamics (CFD) as a tool to analyze the risks of shifting operation mode. Exhaust gas flow profiles were analyzed for various low load conditions in two power plants with differing vertical designs. One of the plants had already moved into cycling mode and suffered tube failures that were directly related to low-load (and start-up) exhaust flow patterns, the other plant is projected to operate in a frequent cycling mode in the near future. The contribution of CFD to identifying the conditions that lead to failure for the first plant is presented, along with projections on the potential impact of lowload operation on the second plant design in terms of risk of hotend tube failures. Mechanisms to reduce the failure risk, such as addition of flow-conditioning devices, are also investigated.
{"title":"On the Use of Computational Fluid Dynamics (CFD) to Assess the Impact of Low-Load Operations on Heat Recovery Steam Generator (HRSG) Tube Module Integrity","authors":"A. Fabricius, D. Moelling, J. Rusaas","doi":"10.1115/power2019-1805","DOIUrl":"https://doi.org/10.1115/power2019-1805","url":null,"abstract":"\u0000 As the electricity market has evolved with the addition of renewables to the generation mix, Heat Recovery Steam Generators (HRSGs) that were originally designed for base load conditions are now frequently forced to operate in a cycling and/or low-load regime. This can lead to front end tube-to header fatigue, creep or creep-fatigue failures, often induced by Gas Turbine (GT) flow imbalances causing locally-elevated tube temperatures and/or bending stresses on joints due to large temperature differences between tube rows. This paper focuses on the use of Computational Fluid Dynamics (CFD) as a tool to analyze the risks of shifting operation mode. Exhaust gas flow profiles were analyzed for various low load conditions in two power plants with differing vertical designs. One of the plants had already moved into cycling mode and suffered tube failures that were directly related to low-load (and start-up) exhaust flow patterns, the other plant is projected to operate in a frequent cycling mode in the near future. The contribution of CFD to identifying the conditions that lead to failure for the first plant is presented, along with projections on the potential impact of lowload operation on the second plant design in terms of risk of hotend tube failures. Mechanisms to reduce the failure risk, such as addition of flow-conditioning devices, are also investigated.","PeriodicalId":315864,"journal":{"name":"ASME 2019 Power Conference","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121796680","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Spray ponds offer significant advantages over mechanical draft cooling towers (MDCT) including superior simplicity and operability, lower preferred power requirements, and lower capital and maintenance costs. Unlike a conventional spray pond in which spray nozzles are arranged in a flat bed and water is sprayed upward, the Oriented Spray Cooling System (OSCS) is an evolutionary spray pond design in which nozzles are mounted on spray trees arranged in a circle and are tilted at an angle oriented towards the center of the circle. As a result, each nozzle is exposed to essentially ambient air as water droplets drag air into the spray region while the warm air concentrated in the center of the circle rises. Both of these effects work together to increase air flow through the spray region. Increased air flow reduces the local wet-bulb temperature (LWBT) of the air in the spray pattern, promoting heat transfer and more efficient cooling. The authors have developed analytical models to predict the thermal performance of the OSCS that are based on classical heat and mass transfer and kinetic vector relationships for spherical water droplets that rely only on generic experimental thermal performance data. Therefore, the model is not limited in application with regard to spray pressure or nozzle spacing or orientation and is not limited by droplet size considerations. This paper describes specific details such as nozzle type, orientation, and drop spectrum and details on the analytical model never before published that are used to predict the OSCS performance. The paper compares the predicted performance of the OSCS with the rigorous full-scale field test results that were measured in compliance with Nuclear Regulatory Commission requirements at the Columbia Generating Station (CGS) where the ultimate heat sink (UHS) is two OSCS.
{"title":"The Oriented Spray Cooling System for Heat Rejection and Evaporation","authors":"C. Bowman, Robert Taylor, J. D. Hubble","doi":"10.1115/power2019-1803","DOIUrl":"https://doi.org/10.1115/power2019-1803","url":null,"abstract":"\u0000 Spray ponds offer significant advantages over mechanical draft cooling towers (MDCT) including superior simplicity and operability, lower preferred power requirements, and lower capital and maintenance costs. Unlike a conventional spray pond in which spray nozzles are arranged in a flat bed and water is sprayed upward, the Oriented Spray Cooling System (OSCS) is an evolutionary spray pond design in which nozzles are mounted on spray trees arranged in a circle and are tilted at an angle oriented towards the center of the circle. As a result, each nozzle is exposed to essentially ambient air as water droplets drag air into the spray region while the warm air concentrated in the center of the circle rises. Both of these effects work together to increase air flow through the spray region. Increased air flow reduces the local wet-bulb temperature (LWBT) of the air in the spray pattern, promoting heat transfer and more efficient cooling. The authors have developed analytical models to predict the thermal performance of the OSCS that are based on classical heat and mass transfer and kinetic vector relationships for spherical water droplets that rely only on generic experimental thermal performance data. Therefore, the model is not limited in application with regard to spray pressure or nozzle spacing or orientation and is not limited by droplet size considerations. This paper describes specific details such as nozzle type, orientation, and drop spectrum and details on the analytical model never before published that are used to predict the OSCS performance. The paper compares the predicted performance of the OSCS with the rigorous full-scale field test results that were measured in compliance with Nuclear Regulatory Commission requirements at the Columbia Generating Station (CGS) where the ultimate heat sink (UHS) is two OSCS.","PeriodicalId":315864,"journal":{"name":"ASME 2019 Power Conference","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121695500","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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