The design of heat exchangers for use in a supercritical carbon dioxide (sCO2) Brayton cycle power converter must provide for acceptable performance for duty cycle events encompassing anticipated transients and postulated accidents. This paper presents the results of a comprehensive analysis of thermal transients for sCO2 cycle heat exchangers, with emphasis on the sodium-to-CO2 heat addition heat exchanger. A range of transients, from normal operation to severe accidents, were simulated with the coupled PDC and SAS4A/SASSYS-1 system level dynamic analysis computer codes. For each transient, the calculated change in the heat exchanger wall temperature is determined as a measure of the thermal loading.
{"title":"Analysis of Thermal Transients for sCO2 Brayton Cycle Heat Exchangers","authors":"A. Moisseytsev, J. Sienicki","doi":"10.1115/gt2019-90374","DOIUrl":"https://doi.org/10.1115/gt2019-90374","url":null,"abstract":"\u0000 The design of heat exchangers for use in a supercritical carbon dioxide (sCO2) Brayton cycle power converter must provide for acceptable performance for duty cycle events encompassing anticipated transients and postulated accidents. This paper presents the results of a comprehensive analysis of thermal transients for sCO2 cycle heat exchangers, with emphasis on the sodium-to-CO2 heat addition heat exchanger. A range of transients, from normal operation to severe accidents, were simulated with the coupled PDC and SAS4A/SASSYS-1 system level dynamic analysis computer codes. For each transient, the calculated change in the heat exchanger wall temperature is determined as a measure of the thermal loading.","PeriodicalId":412490,"journal":{"name":"Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122142154","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}
K. Brinckman, A. Hosangadi, Zisen Liu, T. Weathers
There is increasing interest in supercritical CO2 processes, such as Carbon Capture and Storage, and electric power production, which require compressors to pressurize CO2 above the critical point. For supercritical compressor operation close to the critical point there is a concern that the working fluid could cross into the subcritical regime which could lead to issues with compressor performance if condensation was to occur in regions where the fluid dropped below the saturation point. Presently, the question of whether there is sufficient residence time at subcritical conditions for condensation onset in supercritical CO2 compressors is an unresolved issue. A methodology is presented towards providing a validated simulation capability for predicting condensation in supercritical CO2 compressors. The modeling framework involves the solution of a discrete droplet phase coupled to the continuum gas phase to track droplet nucleation and growth. The model is implemented in the CRUNCH CFD® Computational Fluid Dynamics code that has been extensively validated for simulation at near critical conditions with a real fluid framework for accurate predictions of trans-critical CO2 processes. Results of predictions using classical nucleation theory to model homogeneous nucleation of condensation sites in supersaturated vapor regions are presented. A non-equilibrium phase-change model is applied to predict condensation on the nuclei which grow in a dispersed-phase droplet framework. Model validation is provided against experimental data for condensation of supercritical CO2 in a De Laval nozzle including the Wilson line location. The model is then applied for prediction of condensation in the compressor of the Sandia test loop at mildly supercritical inlet conditions. The results suggest that there is sufficient residence time at the conditions analyzed to form localized nucleation sites, however, droplets are expected to be short lived as the model predicts they will rapidly vaporize.
{"title":"Numerical Simulation of Non-Equilibrium Condensation in Supercritical CO2 Compressors","authors":"K. Brinckman, A. Hosangadi, Zisen Liu, T. Weathers","doi":"10.1115/gt2019-90497","DOIUrl":"https://doi.org/10.1115/gt2019-90497","url":null,"abstract":"\u0000 There is increasing interest in supercritical CO2 processes, such as Carbon Capture and Storage, and electric power production, which require compressors to pressurize CO2 above the critical point. For supercritical compressor operation close to the critical point there is a concern that the working fluid could cross into the subcritical regime which could lead to issues with compressor performance if condensation was to occur in regions where the fluid dropped below the saturation point. Presently, the question of whether there is sufficient residence time at subcritical conditions for condensation onset in supercritical CO2 compressors is an unresolved issue. A methodology is presented towards providing a validated simulation capability for predicting condensation in supercritical CO2 compressors. The modeling framework involves the solution of a discrete droplet phase coupled to the continuum gas phase to track droplet nucleation and growth. The model is implemented in the CRUNCH CFD® Computational Fluid Dynamics code that has been extensively validated for simulation at near critical conditions with a real fluid framework for accurate predictions of trans-critical CO2 processes.\u0000 Results of predictions using classical nucleation theory to model homogeneous nucleation of condensation sites in supersaturated vapor regions are presented. A non-equilibrium phase-change model is applied to predict condensation on the nuclei which grow in a dispersed-phase droplet framework. Model validation is provided against experimental data for condensation of supercritical CO2 in a De Laval nozzle including the Wilson line location. The model is then applied for prediction of condensation in the compressor of the Sandia test loop at mildly supercritical inlet conditions. The results suggest that there is sufficient residence time at the conditions analyzed to form localized nucleation sites, however, droplets are expected to be short lived as the model predicts they will rapidly vaporize.","PeriodicalId":412490,"journal":{"name":"Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131676188","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}
Bongsu Choi, Junhyun Cho, Hyungki Shin, Jongjae Cho, C. Roh, Beomjoon Lee, Gilbong Lee, H. Ra, Y. Baik
The supercritical carbon dioxide (S-CO2) power cycle has been a topic of interest because it exhibits a high efficiency and compact size and is compatible with any heat source. Since 2013, the Korea Institute of Energy Research (KIER) has developed three S-CO2 power cycle experimental test loops for distributed power source applications. Based on this experience, a hundreds of kWe-class dual Brayton test loop with a maximum temperature of 500 °C has been designed and partially fabricated. This cycle consists of two turbines, one compressor, two recuperators, and a flued-gas heater. First, a relatively low-temperature turbine with an inlet temperature of 392 °C was designed and manufactured as an axial impulsetype turbo-generator because of the cost and development time required for construction of a full-cycle test loop. As a preliminary step, the turbo-generator was successfully tested in 2017. Next, it was continuously operated for 4.2 h in 2018. In addition, the following components were designed and manufactured: a centrifugal compressor with a dry gas seal; oil-lubricated tilting-pad bearings; a flued-gas heater, which consists of a burner and a shell-and-tube heat exchanger; and two printed circuit heat exchanger type recuperators. The full cycle is expected to be operational in November 2019.
{"title":"Development of a Hundreds of kWe-Class Supercritical Carbon Dioxide Power Cycle Test Loop in KIER","authors":"Bongsu Choi, Junhyun Cho, Hyungki Shin, Jongjae Cho, C. Roh, Beomjoon Lee, Gilbong Lee, H. Ra, Y. Baik","doi":"10.1115/gt2019-90681","DOIUrl":"https://doi.org/10.1115/gt2019-90681","url":null,"abstract":"\u0000 The supercritical carbon dioxide (S-CO2) power cycle has been a topic of interest because it exhibits a high efficiency and compact size and is compatible with any heat source. Since 2013, the Korea Institute of Energy Research (KIER) has developed three S-CO2 power cycle experimental test loops for distributed power source applications. Based on this experience, a hundreds of kWe-class dual Brayton test loop with a maximum temperature of 500 °C has been designed and partially fabricated. This cycle consists of two turbines, one compressor, two recuperators, and a flued-gas heater. First, a relatively low-temperature turbine with an inlet temperature of 392 °C was designed and manufactured as an axial impulsetype turbo-generator because of the cost and development time required for construction of a full-cycle test loop. As a preliminary step, the turbo-generator was successfully tested in 2017. Next, it was continuously operated for 4.2 h in 2018. In addition, the following components were designed and manufactured: a centrifugal compressor with a dry gas seal; oil-lubricated tilting-pad bearings; a flued-gas heater, which consists of a burner and a shell-and-tube heat exchanger; and two printed circuit heat exchanger type recuperators. The full cycle is expected to be operational in November 2019.","PeriodicalId":412490,"journal":{"name":"Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128781007","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}
Dust may be challenging to the blades of wind turbines deployed in the harsh environment of the Sahara. In this paper, the airfoil sections of a wind turbine have been customized for low sensitivity to surface roughness at the wind conditions prevailing in Hurghada—Egypt to avoid serious power degradation. To this end, a two-dimensional a computational model is developed using ANSYS-FLUENT 15.0 to understand the distinguishing features that govern the specific behavior of NACA-63-215 (root section) and NACA-63-415 airfoils (midspan and tip sections) with respect to dust deposition and sand erosion. Subsequently, a two-objective genetic algorithm is developed in MATLAB 16.0 and used to customize the airfoil geometry, enhancing the lift-to-drag ratio while simultaneously minimizing the deposition and erosion rates. The whole optimization process is realized through coupling MATLAB 16.0 with ANSYS-FLUENT 15.0 via the ICEM meshing tool to predict the optimum blade shape based on its aerodynamic performance in a dust-loaded environment. The optimization process enhanced the aerodynamic performance for the aforementioned airfoils under particle laden conditions with up to 38.34% higher lift-to-drag coefficients ratio in addition to 70 % and 99.267 % drop in dust deposition and sand erosion, repectively.
{"title":"Airfoil Optimization for a Wind Turbine Operating in a Particle-Laden Environment","authors":"A. Diab, A. El-din","doi":"10.1115/gt2019-91044","DOIUrl":"https://doi.org/10.1115/gt2019-91044","url":null,"abstract":"\u0000 Dust may be challenging to the blades of wind turbines deployed in the harsh environment of the Sahara. In this paper, the airfoil sections of a wind turbine have been customized for low sensitivity to surface roughness at the wind conditions prevailing in Hurghada—Egypt to avoid serious power degradation. To this end, a two-dimensional a computational model is developed using ANSYS-FLUENT 15.0 to understand the distinguishing features that govern the specific behavior of NACA-63-215 (root section) and NACA-63-415 airfoils (midspan and tip sections) with respect to dust deposition and sand erosion. Subsequently, a two-objective genetic algorithm is developed in MATLAB 16.0 and used to customize the airfoil geometry, enhancing the lift-to-drag ratio while simultaneously minimizing the deposition and erosion rates. The whole optimization process is realized through coupling MATLAB 16.0 with ANSYS-FLUENT 15.0 via the ICEM meshing tool to predict the optimum blade shape based on its aerodynamic performance in a dust-loaded environment. The optimization process enhanced the aerodynamic performance for the aforementioned airfoils under particle laden conditions with up to 38.34% higher lift-to-drag coefficients ratio in addition to 70 % and 99.267 % drop in dust deposition and sand erosion, repectively.","PeriodicalId":412490,"journal":{"name":"Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129431933","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 many practical applications of thermodynamics, the use of simplified relationships of the ideal-gas model over a more accurate but more complex real gas model, is a critical decision to make. Thermodynamic departure functions provide screening criteria to evaluate whether the ideal-gas model can accurately represent a gas behavior. This paper reports several departure functions to evaluate deviation of a real gas from the ideal-gas model. Included in this paper is the derivation of departure functions based on isothermal compressibility, isobaric expansivity, isochoric change of pressure with temperature, isochoric change of internal energy with pressure, sonic speed, and heat capacities difference. The description of each of these departure functions is accompanied by a numerical example. Departure functions defined in this paper have led to improved representation of deviation from the ideal-gas model across a range of ±2% deviation of the specific volume departure (also known as the compressibility factor, Z) for a typical gas mixture encountered in natural gas processing. The limitations involved in using the compressibility factor, Z, to evaluate departure from the ideal-gas model is highlighted. It is shown that even as the compressibility factor, Z, approaches unity at certain thermodynamic conditions, other departure functions exhibit considerable deviations from the ideal-gas model. It is concluded that the compressibility factor, Z, should not be used as “the only criterion” to evaluate conformance to the ideal-gas model. This paper also explains the physical significance of Schultz compressibility functions X, Y, and L [3] by introducing departure functions based on isothermal compressibility and isobaric expansivity.
{"title":"The Use of Departure Functions to Estimate Deviation of a Real Gas From the Ideal Gas Model","authors":"Matt Taher","doi":"10.1115/gt2019-90112","DOIUrl":"https://doi.org/10.1115/gt2019-90112","url":null,"abstract":"In many practical applications of thermodynamics, the use of simplified relationships of the ideal-gas model over a more accurate but more complex real gas model, is a critical decision to make. Thermodynamic departure functions provide screening criteria to evaluate whether the ideal-gas model can accurately represent a gas behavior. This paper reports several departure functions to evaluate deviation of a real gas from the ideal-gas model.\u0000 Included in this paper is the derivation of departure functions based on isothermal compressibility, isobaric expansivity, isochoric change of pressure with temperature, isochoric change of internal energy with pressure, sonic speed, and heat capacities difference. The description of each of these departure functions is accompanied by a numerical example. Departure functions defined in this paper have led to improved representation of deviation from the ideal-gas model across a range of ±2% deviation of the specific volume departure (also known as the compressibility factor, Z) for a typical gas mixture encountered in natural gas processing.\u0000 The limitations involved in using the compressibility factor, Z, to evaluate departure from the ideal-gas model is highlighted. It is shown that even as the compressibility factor, Z, approaches unity at certain thermodynamic conditions, other departure functions exhibit considerable deviations from the ideal-gas model. It is concluded that the compressibility factor, Z, should not be used as “the only criterion” to evaluate conformance to the ideal-gas model. This paper also explains the physical significance of Schultz compressibility functions X, Y, and L [3] by introducing departure functions based on isothermal compressibility and isobaric expansivity.","PeriodicalId":412490,"journal":{"name":"Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy","volume":" 7","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"113951205","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}
Based on existing reports and databases, most of the installations in highly turbulent sites in fact fail to reach the expected energy yield, resulting in still or underperforming turbines that also give bad press for the technology. A better understanding of the real performance of wind turbines under highly turbulent conditions is then pivotal to ensure the economic viability of new installations. To this end, the possible use of Computational Fluid Dynamics (CFD) techniques could provide notable benefits, reducing the time-to-market and the cost with respect to experiments. On the other hand, it is intrinsically not easy to reproduce properly intense and large-scale turbulence with the techniques of common use for research and industry (e.g. CFD unsteady RANS), while the only methods that are granted to do so (e.g. DNS or LES) are often not computationally affordable. Moving from this background, this study presents the development a numerical strategy to exploit at their maximum level the capabilities of an unsteady Reynolds-Averaged Navier-Stokes (RANS) approach in order to reproduce fields of macro turbulence of use for wind energy applications. The study is made of two main parts. In the first part, the numerical methodology is discussed and assessed based on real wind tunnel data. The benefits and drawbacks are presented also in comparison to other existing methods. In the second part, it has been used to simulate the behavior under turbulence of a H-Darrieus vertical-axis wind turbine, for which unique wind tunnel data were available. The simulations, even if preliminary, showed good matching with experiments (e.g. confirming the increase of power), showing then the potential of the method.
根据现有的报告和数据库，在高湍流地区安装的大多数装置实际上无法达到预期的能量产出，导致涡轮机停滞不前或表现不佳，这也给这项技术带来了负面影响。更好地了解风力涡轮机在高度湍流条件下的真实性能，对于确保新装置的经济可行性至关重要。为此，可能使用计算流体动力学(CFD)技术可以提供显着的好处，减少上市时间和实验成本。另一方面，用研究和工业中常用的技术(例如CFD非定常RANS)来重现适当强度和大规模的湍流本质上是不容易的，而唯一被允许这样做的方法(例如DNS或LES)通常在计算上是负担不起的。从这一背景出发，本研究提出了一种数值策略的发展，以最大限度地利用非定常reynolds - average Navier-Stokes (RANS)方法的能力，以重现用于风能应用的宏观湍流场。本研究主要由两部分组成。第一部分以实际风洞数据为基础，对数值方法进行了讨论和评价。并与其他现有方法进行了比较。在第二部分中，它被用于模拟H-Darrieus垂直轴风力机在湍流下的行为，并获得了独特的风洞数据。虽然是初步的模拟，但与实验结果吻合较好(如证实了功率的增加)，显示了该方法的潜力。
{"title":"Development of a CFD Methodology to Reproduce the Effects of Macro Turbulence on Wind Turbines and its Application to the Particular Case of a VAWT","authors":"F. Balduzzi, Marco Zini, G. Ferrara, A. Bianchini","doi":"10.1115/gt2019-90889","DOIUrl":"https://doi.org/10.1115/gt2019-90889","url":null,"abstract":"\u0000 Based on existing reports and databases, most of the installations in highly turbulent sites in fact fail to reach the expected energy yield, resulting in still or underperforming turbines that also give bad press for the technology. A better understanding of the real performance of wind turbines under highly turbulent conditions is then pivotal to ensure the economic viability of new installations. To this end, the possible use of Computational Fluid Dynamics (CFD) techniques could provide notable benefits, reducing the time-to-market and the cost with respect to experiments. On the other hand, it is intrinsically not easy to reproduce properly intense and large-scale turbulence with the techniques of common use for research and industry (e.g. CFD unsteady RANS), while the only methods that are granted to do so (e.g. DNS or LES) are often not computationally affordable. Moving from this background, this study presents the development a numerical strategy to exploit at their maximum level the capabilities of an unsteady Reynolds-Averaged Navier-Stokes (RANS) approach in order to reproduce fields of macro turbulence of use for wind energy applications. The study is made of two main parts. In the first part, the numerical methodology is discussed and assessed based on real wind tunnel data. The benefits and drawbacks are presented also in comparison to other existing methods. In the second part, it has been used to simulate the behavior under turbulence of a H-Darrieus vertical-axis wind turbine, for which unique wind tunnel data were available. The simulations, even if preliminary, showed good matching with experiments (e.g. confirming the increase of power), showing then the potential of the method.","PeriodicalId":412490,"journal":{"name":"Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy","volume":"78 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131768788","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}
H. Gauch, V. Bisio, S. Rossin, F. Montomoli, V. Tagarielli
In this study we present the application of numerical and analytical models to predict the transient loading of structures by impinging pressure and shock waves in air, which have been recently developed by the authors. Non-dimensional design maps are provided which yield predictions of the maximum loads on structures as a function of the problem parameters. Practical example applications, with reference to typical structures used in turbomachinery packages, are presented. These examples demonstrate the superiority of the new modelling techniques to current industrial design guidelines which are mostly extrapolated from simplified methods developed for shock waves. Finally, conclusions are drawn regarding the nature of the loading exerted on the structure in different regimes of problem parameters.
{"title":"Transient Loading on Turbomachinery Packages due to Pressure Waves Caused by Accidental Deflagration Events","authors":"H. Gauch, V. Bisio, S. Rossin, F. Montomoli, V. Tagarielli","doi":"10.1115/gt2019-90942","DOIUrl":"https://doi.org/10.1115/gt2019-90942","url":null,"abstract":"\u0000 In this study we present the application of numerical and analytical models to predict the transient loading of structures by impinging pressure and shock waves in air, which have been recently developed by the authors. Non-dimensional design maps are provided which yield predictions of the maximum loads on structures as a function of the problem parameters. Practical example applications, with reference to typical structures used in turbomachinery packages, are presented. These examples demonstrate the superiority of the new modelling techniques to current industrial design guidelines which are mostly extrapolated from simplified methods developed for shock waves. Finally, conclusions are drawn regarding the nature of the loading exerted on the structure in different regimes of problem parameters.","PeriodicalId":412490,"journal":{"name":"Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125521448","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 fundamental research and technology development for supercritical CO2 (sCO2) power cycles is gaining worldwide popularity. This is due to their promise of high efficiency, compactness, wide-range-applicability and eco-friendliness. One of the active research areas in the sCO2 power cycle field is to increase cycle efficiency by utilizing a higher turbine inlet temperature. At high temperatures within turbines, radiation may contribute a significant portion of overall heat transfer. The purpose of this paper is to investigate and quantify the effects of radiation heat transfer within a first stage sCO2 turbine linear cascade. This particular topic has not been explored by researchers yet. The correct estimation of radiation heat transfer can prove to be critical for the design of turbine blade cooling system. The aerodynamic and heat transfer analysis of a turbine cascade is carried out using a commercial computational code, STAR-CCM+. Spectral absorption coefficient for CO2 is derived using HITRAN database at required temperature and pressure. Broadening and shifting of intensity lines due to high pressure and temperature are taken into consideration. A second approach utilizes Planck mean absorption coefficient as a function of temperature. Although the data can be extrapolated for the required higher pressure, accuracy of that extrapolated data cannot be verified. Hence the secondary purpose of this study is to encourage researchers to fill the fundamental gaps in the knowledge of CO2 radiation. Findings presented here suggest that radiation can be neglected for cooling system design of the sCO2 turbine stage 1 vane for both inlet temperatures of 1350K and 1775K.
{"title":"Numerical Study of Radiation Heat Transfer for a Supercritical CO2 Turbine Linear Cascade","authors":"Akshay Khadse, Andres Curbelo, J. Kapat","doi":"10.1115/gt2019-91613","DOIUrl":"https://doi.org/10.1115/gt2019-91613","url":null,"abstract":"The fundamental research and technology development for supercritical CO2 (sCO2) power cycles is gaining worldwide popularity. This is due to their promise of high efficiency, compactness, wide-range-applicability and eco-friendliness. One of the active research areas in the sCO2 power cycle field is to increase cycle efficiency by utilizing a higher turbine inlet temperature. At high temperatures within turbines, radiation may contribute a significant portion of overall heat transfer. The purpose of this paper is to investigate and quantify the effects of radiation heat transfer within a first stage sCO2 turbine linear cascade. This particular topic has not been explored by researchers yet. The correct estimation of radiation heat transfer can prove to be critical for the design of turbine blade cooling system. The aerodynamic and heat transfer analysis of a turbine cascade is carried out using a commercial computational code, STAR-CCM+. Spectral absorption coefficient for CO2 is derived using HITRAN database at required temperature and pressure. Broadening and shifting of intensity lines due to high pressure and temperature are taken into consideration. A second approach utilizes Planck mean absorption coefficient as a function of temperature. Although the data can be extrapolated for the required higher pressure, accuracy of that extrapolated data cannot be verified. Hence the secondary purpose of this study is to encourage researchers to fill the fundamental gaps in the knowledge of CO2 radiation. Findings presented here suggest that radiation can be neglected for cooling system design of the sCO2 turbine stage 1 vane for both inlet temperatures of 1350K and 1775K.","PeriodicalId":412490,"journal":{"name":"Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy","volume":"107 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124748388","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}
Existing research has demonstrated the viability of supercritical carbon dioxide as an efficient working fluid with numerous advantages over steam in power cycle applications. Selecting the appropriate power cycle configuration for a given application depends on expected operating conditions and performance goals. This paper presents a comparison for three indirect fired sCO2 cycles: recompression closed Brayton cycle, dual loop cascaded cycle, and partial condensation cycle. Each cycle was modeled in NPSS with an air side heater, given the same baseline assumptions and optimized over a range of conditions. Additionally, limitations on the heater system are discussed.
{"title":"Selecting the Optimum Supercritical CO2 Cycle for Indirect-Fired Applications","authors":"B. Tom, January Smith, Aaron Mcclung","doi":"10.1115/gt2019-91509","DOIUrl":"https://doi.org/10.1115/gt2019-91509","url":null,"abstract":"\u0000 Existing research has demonstrated the viability of supercritical carbon dioxide as an efficient working fluid with numerous advantages over steam in power cycle applications. Selecting the appropriate power cycle configuration for a given application depends on expected operating conditions and performance goals. This paper presents a comparison for three indirect fired sCO2 cycles: recompression closed Brayton cycle, dual loop cascaded cycle, and partial condensation cycle. Each cycle was modeled in NPSS with an air side heater, given the same baseline assumptions and optimized over a range of conditions. Additionally, limitations on the heater system are discussed.","PeriodicalId":412490,"journal":{"name":"Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116497660","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}
D. Holst, F. Balduzzi, A. Bianchini, C. Nayeri, C. Paschereit, G. Ferrara
Wind industry needs high quality airfoil data for a range of the angle of attack (AoA) much wider than that often provided by the technical literature, which often lacks data i.e. in deep- and post-stall region. Especially in case of vertical axis wind turbines (VAWTs), the blades operate at very large AoAs, which exceed the range of typical aviation application. In a previous study, some of the authors analyzed the trend of the lift coefficient of a NACA 0021 airfoil, using the suggestions provided by detailed CFD analyses to correct experimental data at low Reynolds numbers collected in an open-jet tunnel. In the present study, the correction method is extended in order to analyze even the drag and moment coefficients over a wide range of AoAs for two different Reynolds numbers (Re = 140k and Re = 180k) of particular interest for small wind turbines. The utility of these data is again specifically high in case of VAWTs, in which both the drag and the moment coefficient largely contribute to the torque. The investigation involves tunnel data regarding both static polars and dynamic sinusoidal pitching movements at multiple reduced frequencies. Concerning the numerical simulations, two different computational domains were considered, i.e. the full wind tunnel and the open field. Once experimental data have been purged by the influence of the wind tunnel by means of the proposed correction method, they were compared to existing data for similar Reynolds both for the NACA0021 and for similar airfoils. By doing so, some differences in the static stall angle and the extent of the hysteresis cycle are discussed. Overall, the present paper provides the scientific community with detailed analysis of low-Reynolds NACA 0021 data in multiple variations, which may enable, inter alia, a more effective VAWT design in the near future.
{"title":"Static and Dynamic Analysis of a NACA 0021 Airfoil Section at Low Reynolds Numbers: Drag and Moment Coefficients","authors":"D. Holst, F. Balduzzi, A. Bianchini, C. Nayeri, C. Paschereit, G. Ferrara","doi":"10.1115/gt2019-90500","DOIUrl":"https://doi.org/10.1115/gt2019-90500","url":null,"abstract":"\u0000 Wind industry needs high quality airfoil data for a range of the angle of attack (AoA) much wider than that often provided by the technical literature, which often lacks data i.e. in deep- and post-stall region. Especially in case of vertical axis wind turbines (VAWTs), the blades operate at very large AoAs, which exceed the range of typical aviation application. In a previous study, some of the authors analyzed the trend of the lift coefficient of a NACA 0021 airfoil, using the suggestions provided by detailed CFD analyses to correct experimental data at low Reynolds numbers collected in an open-jet tunnel. In the present study, the correction method is extended in order to analyze even the drag and moment coefficients over a wide range of AoAs for two different Reynolds numbers (Re = 140k and Re = 180k) of particular interest for small wind turbines. The utility of these data is again specifically high in case of VAWTs, in which both the drag and the moment coefficient largely contribute to the torque. The investigation involves tunnel data regarding both static polars and dynamic sinusoidal pitching movements at multiple reduced frequencies. Concerning the numerical simulations, two different computational domains were considered, i.e. the full wind tunnel and the open field. Once experimental data have been purged by the influence of the wind tunnel by means of the proposed correction method, they were compared to existing data for similar Reynolds both for the NACA0021 and for similar airfoils. By doing so, some differences in the static stall angle and the extent of the hysteresis cycle are discussed. Overall, the present paper provides the scientific community with detailed analysis of low-Reynolds NACA 0021 data in multiple variations, which may enable, inter alia, a more effective VAWT design in the near future.","PeriodicalId":412490,"journal":{"name":"Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130694340","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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