The wake effect is the biggest challenge when locating downwind turbines in wind farms which imposes large separation distances between turbines. In the present work, CFD simulations are presented to study possible configurations of wind farms of Savonius wind turbines. The farm is composed by in steps, starting from two-turbine configuration, adding one turbine until reaching a cluster of closely set ten rotors with an average power coefficient of 0.225. This value is very close to the single rotor’s power coefficient. The power density of the cluster is 7.55 W/m2 which is much higher than similar ten turbines located far apart to avoid wake effect. The maximum Cp of a downstream rotor in the cluster reached 0.323 which is about 40% higher than the single rotor. The adopted philosophy for placing downstream rotors is locating the rotor’s returning bucket in the low velocity region of the wake of the upstream rotor to get the least negative torque while the advancing bucket is located at the high velocity region getting higher positive torque which increases the performance. After that, two crosswind clusters are added to increase the power generated. The predicted average power coefficient for the 30 rotors farm is 0.246 which is higher than a similar isolated turbine. The increase of the Cp occurs due to the positive interactions between the clusters. The highest Cp in the farm rotors is found to be 0.411 which is higher than the single rotor’s Cp by 78%. The farm also provides a high power-density of 4.65 W/m2 which is 5 times higher than a farm with the same number of turbines located far apart.
{"title":"Investigating Efficient Clusters of Savonius Wind Turbines","authors":"A. Ibrahim, A. Elbaz","doi":"10.1115/GT2018-75405","DOIUrl":"https://doi.org/10.1115/GT2018-75405","url":null,"abstract":"The wake effect is the biggest challenge when locating downwind turbines in wind farms which imposes large separation distances between turbines. In the present work, CFD simulations are presented to study possible configurations of wind farms of Savonius wind turbines. The farm is composed by in steps, starting from two-turbine configuration, adding one turbine until reaching a cluster of closely set ten rotors with an average power coefficient of 0.225. This value is very close to the single rotor’s power coefficient. The power density of the cluster is 7.55 W/m2 which is much higher than similar ten turbines located far apart to avoid wake effect. The maximum Cp of a downstream rotor in the cluster reached 0.323 which is about 40% higher than the single rotor. The adopted philosophy for placing downstream rotors is locating the rotor’s returning bucket in the low velocity region of the wake of the upstream rotor to get the least negative torque while the advancing bucket is located at the high velocity region getting higher positive torque which increases the performance. After that, two crosswind clusters are added to increase the power generated. The predicted average power coefficient for the 30 rotors farm is 0.246 which is higher than a similar isolated turbine. The increase of the Cp occurs due to the positive interactions between the clusters. The highest Cp in the farm rotors is found to be 0.411 which is higher than the single rotor’s Cp by 78%. The farm also provides a high power-density of 4.65 W/m2 which is 5 times higher than a farm with the same number of turbines located far apart.","PeriodicalId":412490,"journal":{"name":"Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114889724","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}
Sebastian Pérez-Becker, Joseph Saverin, D. Marten, J. Alber, G. Pechlivanoglou, C. Paschereit
This paper presents the results of a fatigue load evaluation from aeroelastic simulations of a multi-megawatt wind turbine. Both the Blade Element Momentum (BEM) and the Lifting Line Free Vortex Wake (LLFVW) methods were used to compute the aerodynamic forces. The loads in selected turbine components, calculated from NREL’s FAST v8 using the aerodynamic solver AeroDyn, are compared to the loads obtained using the LLFVW aerodynamics formulation in QBlade. The DTU 10 MW Reference Wind Turbine is simulated in power production load cases at several wind speeds under idealized conditions. The aerodynamic forces and turbine loads are evaluated in detail, showing very good agreement between both codes. Additionally, the turbine is simulated under realistic conditions according to the current design standards. Fatigue loads derived from load calculations using both codes are compared when the turbine is controlled with a basic pitch and torque controller. It is found that the simulations performed with the BEM method generally predict higher fatigue loading in the turbine components. A higher pitch activity is also predicted with the BEM simulations. The differences are larger for wind speeds around rated wind speed. Furthermore, the fatigue reduction potential of the individual pitch control (IPC) strategy is examined and compared when using the two different codes. The IPC strategy shows a higher load reduction of the out-of-plane blade root bending moments when simulated with the LLFVW method. This is accompanied with higher pitch activity at the actuation frequency of the IPC strategy.
{"title":"Investigations on the Fatigue Load Reduction Potential of Advanced Control Strategies for Multi-MW Wind Turbines Using a Free Vortex Wake Model","authors":"Sebastian Pérez-Becker, Joseph Saverin, D. Marten, J. Alber, G. Pechlivanoglou, C. Paschereit","doi":"10.1115/GT2018-76078","DOIUrl":"https://doi.org/10.1115/GT2018-76078","url":null,"abstract":"This paper presents the results of a fatigue load evaluation from aeroelastic simulations of a multi-megawatt wind turbine. Both the Blade Element Momentum (BEM) and the Lifting Line Free Vortex Wake (LLFVW) methods were used to compute the aerodynamic forces. The loads in selected turbine components, calculated from NREL’s FAST v8 using the aerodynamic solver AeroDyn, are compared to the loads obtained using the LLFVW aerodynamics formulation in QBlade.\u0000 The DTU 10 MW Reference Wind Turbine is simulated in power production load cases at several wind speeds under idealized conditions. The aerodynamic forces and turbine loads are evaluated in detail, showing very good agreement between both codes. Additionally, the turbine is simulated under realistic conditions according to the current design standards. Fatigue loads derived from load calculations using both codes are compared when the turbine is controlled with a basic pitch and torque controller. It is found that the simulations performed with the BEM method generally predict higher fatigue loading in the turbine components. A higher pitch activity is also predicted with the BEM simulations. The differences are larger for wind speeds around rated wind speed. Furthermore, the fatigue reduction potential of the individual pitch control (IPC) strategy is examined and compared when using the two different codes. The IPC strategy shows a higher load reduction of the out-of-plane blade root bending moments when simulated with the LLFVW method. This is accompanied with higher pitch activity at the actuation frequency of the IPC strategy.","PeriodicalId":412490,"journal":{"name":"Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132008839","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}
S. Schuster, D. Brillert, V. Hermes, Atti̇lla Yildiz, F. Benra
Wet compression or evaporative cooling is used during the compression of gases. Evaporative cooling reduces the power demand and keeps the discharge temperature in a suitable range. The cooling effect can be used before the impeller as well as within the impeller. The latter is more challenging and the focus of this research is on it. This paper looks into evaporative cooling in radial impellers from a general perspective in order not to limit the scope. Therefore, a mean line calculation program is applied. The program takes into account the entropy production due to the irreversible heat exchange between gas and liquid. This paper focuses on the thermodynamic aspects and shows how to analyse them. The paper highlights the necessity to consider the additional entropy production during the design and analysis process.
{"title":"Thermodynamic Modelling Aspects of Wet Compression in Radial Compressors","authors":"S. Schuster, D. Brillert, V. Hermes, Atti̇lla Yildiz, F. Benra","doi":"10.1115/GT2018-76429","DOIUrl":"https://doi.org/10.1115/GT2018-76429","url":null,"abstract":"Wet compression or evaporative cooling is used during the compression of gases. Evaporative cooling reduces the power demand and keeps the discharge temperature in a suitable range. The cooling effect can be used before the impeller as well as within the impeller. The latter is more challenging and the focus of this research is on it. This paper looks into evaporative cooling in radial impellers from a general perspective in order not to limit the scope. Therefore, a mean line calculation program is applied. The program takes into account the entropy production due to the irreversible heat exchange between gas and liquid. This paper focuses on the thermodynamic aspects and shows how to analyse them. The paper highlights the necessity to consider the additional entropy production during the design and analysis process.","PeriodicalId":412490,"journal":{"name":"Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy","volume":"134 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127551352","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}
Changjiang Huo, Jinju Sun, Shanxiu Sun, Peng Song, G. Zhao, B. Pan
The paper focuses on an operational gas expander being used in a natural gas plant for over 10 years, whose recent realtime monitoring shows that the impeller back-side gap pressure is excessively low. To ensure the safe operation, an insight into the complex internal flow of the expander is demanded. The reverse engineering is firstly conducted to reconstruct the flow passage data from the used impeller and nozzle. The physical model includes the main flow domain components (nozzle ring, impeller, and diffuser duct), and the leakages and seal chambers (the impeller front and back-side toothed gaps, shaft seal chamber, and seal gas inlet). Two-phase flow simulation is conducted with the homogeneous multiphase mixture equilibrium model, which is used to allow for the phase change in terms of condensation. Flow analysis is performed based on the obtained numerical results. At the concerned operating point, the expander outlet wetness fraction is about 16.0%, and evident condensation is encountered in the main flow domain and its back-side gap around the pressure tap, which is thought to be responsible for the abnormal pressure reading. The condensed small droplets may grow to block the pressure tap leading to a lower gauge reading. At the operating speed and different flow rates, the flow simulation is conducted for the expander: condensation in the expander is encountered locally at all flow rates and the overall isentropic efficiency closely associated with the overall wetness fraction.
{"title":"Flow Analysis of an Operational Natural Gas Turbo Expander","authors":"Changjiang Huo, Jinju Sun, Shanxiu Sun, Peng Song, G. Zhao, B. Pan","doi":"10.1115/GT2018-75211","DOIUrl":"https://doi.org/10.1115/GT2018-75211","url":null,"abstract":"The paper focuses on an operational gas expander being used in a natural gas plant for over 10 years, whose recent realtime monitoring shows that the impeller back-side gap pressure is excessively low. To ensure the safe operation, an insight into the complex internal flow of the expander is demanded. The reverse engineering is firstly conducted to reconstruct the flow passage data from the used impeller and nozzle. The physical model includes the main flow domain components (nozzle ring, impeller, and diffuser duct), and the leakages and seal chambers (the impeller front and back-side toothed gaps, shaft seal chamber, and seal gas inlet). Two-phase flow simulation is conducted with the homogeneous multiphase mixture equilibrium model, which is used to allow for the phase change in terms of condensation. Flow analysis is performed based on the obtained numerical results. At the concerned operating point, the expander outlet wetness fraction is about 16.0%, and evident condensation is encountered in the main flow domain and its back-side gap around the pressure tap, which is thought to be responsible for the abnormal pressure reading. The condensed small droplets may grow to block the pressure tap leading to a lower gauge reading. At the operating speed and different flow rates, the flow simulation is conducted for the expander: condensation in the expander is encountered locally at all flow rates and the overall isentropic efficiency closely associated with the overall wetness fraction.","PeriodicalId":412490,"journal":{"name":"Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy","volume":"187 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117276201","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}
Wind industry experiences a tremendous growth during the last few decades. As of the end of 2016, the worldwide total installed electricity generation capacity from wind power amounted to 486,790 MW, presenting an increase of 12.5% compared to the previous year. Nowadays wind turbine manufacturers tend to adopt new business models proposing total health monitoring services and solutions, using regular inspections or even embedding sensors and health monitoring systems within each unit. Regularly planned or permanent monitoring ensures a continuous power generation and reduce maintenance costs, prompting specific actions when necessary. The core of wind turbine drivetrain is usually a complicated planetary gearbox. One of the main gearbox components which are commonly responsible for the machinery breakdowns are rolling element bearings. The failure signs of an early bearing damage are usually weak compared to other sources of excitation (e.g. gears). Focusing towards the accurate and early bearing fault detection, a plethora of signal processing methods have been proposed including spectral analysis, synchronous averaging and enveloping. Envelope analysis is based on the extraction of the envelope of the signal, after filtering around a frequency band excited by impacts due to the bearing faults. Kurtogram has been proposed and widely used as an automatic methodology for the selection of the filtering band, being on the other hand sensible in outliers. Recently an emerging interest has been focused on modelling rotating machinery signals as cyclostationary, which is a particular class of non-stationary stochastic processes. Cyclic Spectral Correlation and Cyclic Spectral Coherence have been presented as powerful tools for condition monitoring of rolling element bearings, exploiting their cyclostationary behaviour. In this work a new diagnostic tool is introduced based on the integration of the Cyclic Spectral Coherence along a frequency band that contains the diagnostic information. A special procedure is proposed in order to automatically select the filtering band, maximizing the corresponding fault indicators. The effectiveness of the methodology is validated using the National Renewable Energy Laboratory (NREL) wind turbine gearbox vibration condition monitoring benchmarking dataset which includes various faults with different levels of diagnostic complexity.
{"title":"Vibration Based Condition Monitoring of Wind Turbine Gearboxes Based on Cyclostationary Analysis","authors":"Alexandre Mauricio, Junyu Qi, K. Gryllias","doi":"10.1115/gt2018-76993","DOIUrl":"https://doi.org/10.1115/gt2018-76993","url":null,"abstract":"Wind industry experiences a tremendous growth during the last few decades. As of the end of 2016, the worldwide total installed electricity generation capacity from wind power amounted to 486,790 MW, presenting an increase of 12.5% compared to the previous year. Nowadays wind turbine manufacturers tend to adopt new business models proposing total health monitoring services and solutions, using regular inspections or even embedding sensors and health monitoring systems within each unit. Regularly planned or permanent monitoring ensures a continuous power generation and reduce maintenance costs, prompting specific actions when necessary. The core of wind turbine drivetrain is usually a complicated planetary gearbox. One of the main gearbox components which are commonly responsible for the machinery breakdowns are rolling element bearings. The failure signs of an early bearing damage are usually weak compared to other sources of excitation (e.g. gears). Focusing towards the accurate and early bearing fault detection, a plethora of signal processing methods have been proposed including spectral analysis, synchronous averaging and enveloping. Envelope analysis is based on the extraction of the envelope of the signal, after filtering around a frequency band excited by impacts due to the bearing faults. Kurtogram has been proposed and widely used as an automatic methodology for the selection of the filtering band, being on the other hand sensible in outliers. Recently an emerging interest has been focused on modelling rotating machinery signals as cyclostationary, which is a particular class of non-stationary stochastic processes. Cyclic Spectral Correlation and Cyclic Spectral Coherence have been presented as powerful tools for condition monitoring of rolling element bearings, exploiting their cyclostationary behaviour. In this work a new diagnostic tool is introduced based on the integration of the Cyclic Spectral Coherence along a frequency band that contains the diagnostic information. A special procedure is proposed in order to automatically select the filtering band, maximizing the corresponding fault indicators. The effectiveness of the methodology is validated using the National Renewable Energy Laboratory (NREL) wind turbine gearbox vibration condition monitoring benchmarking dataset which includes various faults with different levels of diagnostic complexity.","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":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122686104","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}
M. A. Ancona, M. Bianchi, L. Branchini, A. D. Pascale, F. Melino, S. Ottaviano, A. Peretto, L. Scarponi
In the last years, the increased demand of the energy market has led to the increasing penetration of renewable energies in order to achieve the primary energy supply. However, natural gas is expected to still play a key role in the energy market, since its environmental impact is lower than other fossil fuels. It is mainly employed as gaseous fuel for stationary energy generation, but also as liquefied fuel, as an alternative to the diesel fuel, in vehicular applications. Liquefied Natural Gas is currently produced mainly in large plants directly located at the extraction sites and transported by ships or tracks to the final users. In order to avoid costs and environmental related impact, in previous studies Authors developed a new plant configuration for liquefied natural gas production directly at filling stations. One of the main issues of the process is that in various sections the working fluid needs to be cooled by external fluids (such as air for compressor inter and after-cooling or chilling fluids), in order to increase the global performances. As a consequence, an important amount of heat could be potentially recovered from this Liquefied Natural Gas production process. Thus, based on the obtained results, in this study the integration between the liquefaction process and an organic Rankine cycle is proposed. In fact, the heat recovered from the Liquefied Natural Gas production process can be used as hot source within the organic Rankine cycle. The aim of the work is the identification of the optimal integrated configuration, in order to maximize the heat recovery and, as a consequence, to optimize the process efficiency. With this purpose, in this study different configurations — in terms of considered organic fluid, architecture and origin of the recovered heat — have been defined and analyzed by means of a commercial software. This software is able to thermodynamically evaluate the proposed process and had allowed to define the optimal solution.
{"title":"Heat Recovery From a Liquefied Natural Gas Production Process by Means of an Organic Rankine Cycle","authors":"M. A. Ancona, M. Bianchi, L. Branchini, A. D. Pascale, F. Melino, S. Ottaviano, A. Peretto, L. Scarponi","doi":"10.1115/GT2018-75370","DOIUrl":"https://doi.org/10.1115/GT2018-75370","url":null,"abstract":"In the last years, the increased demand of the energy market has led to the increasing penetration of renewable energies in order to achieve the primary energy supply. However, natural gas is expected to still play a key role in the energy market, since its environmental impact is lower than other fossil fuels. It is mainly employed as gaseous fuel for stationary energy generation, but also as liquefied fuel, as an alternative to the diesel fuel, in vehicular applications.\u0000 Liquefied Natural Gas is currently produced mainly in large plants directly located at the extraction sites and transported by ships or tracks to the final users. In order to avoid costs and environmental related impact, in previous studies Authors developed a new plant configuration for liquefied natural gas production directly at filling stations. One of the main issues of the process is that in various sections the working fluid needs to be cooled by external fluids (such as air for compressor inter and after-cooling or chilling fluids), in order to increase the global performances. As a consequence, an important amount of heat could be potentially recovered from this Liquefied Natural Gas production process. Thus, based on the obtained results, in this study the integration between the liquefaction process and an organic Rankine cycle is proposed. In fact, the heat recovered from the Liquefied Natural Gas production process can be used as hot source within the organic Rankine cycle.\u0000 The aim of the work is the identification of the optimal integrated configuration, in order to maximize the heat recovery and, as a consequence, to optimize the process efficiency. With this purpose, in this study different configurations — in terms of considered organic fluid, architecture and origin of the recovered heat — have been defined and analyzed by means of a commercial software. This software is able to thermodynamically evaluate the proposed process and had allowed to define the optimal solution.","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":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125431965","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}
A. Hosangadi, T. Weathers, Z. Liu, V. Ahuja, J. Busby
An advanced real-fluid numerical framework for transcritical CO2 spanning both the supercritical and sub-critical regime near the critical point is presented. The numerical algorithm is specifically designed to faithfully model sharp variations of thermodynamic derivatives near the critical point. Numerical results for compressor performance in the Sandia test loop [1] at near critical inlet conditions have been presented over a range of flow rates from the choke point to the stall line. The analysis identifies the shift in the flow losses from the impeller to the diffuser as the flow rate increases from the stall to choke limit. The simulations have been compared with both the Sandia performance curves as well as raw data from Barber Nichols Inc. (BNI); the results compare well with the raw data and provide good qualitative comparisons with Sandia’s performance curves [1]. The numerical framework has also been extended to sub-critical conditions by solving for separate transport equations for each phase. Methodology for NIST table lookup at sub-critical conditions to identify liquid and vapor properties has been developed. Phase change is triggered when local conditions go sub-critical and do not require the phase to be specified a priori. Calculations at both near critical inlet temperatures as well as a two-phase inlet condition at lower temperatures were modeled. Significant difference in the phase change characteristics at these two conditions have been identified and discussed in the paper.
提出了一种先进的跨临界CO2的实流体数值框架，该框架可跨越超临界和亚临界区域，靠近临界点。数值算法是专门设计的，以忠实地模拟热力学导数在临界点附近的急剧变化。在接近临界进口条件下，桑迪亚测试回路[1]中压缩机性能的数值结果已经在从阻塞点到失速线的流量范围内给出。分析表明，当流速从失速增加到节流极限时，流动损失从叶轮转移到扩散器。模拟结果与Sandia的性能曲线以及Barber Nichols Inc. (BNI)的原始数据进行了比较;结果与原始数据比较良好，并与Sandia的性能曲线进行了很好的定性比较[1]。通过求解每个相的单独输运方程，将数值框架扩展到亚临界条件。在亚临界条件下用于识别液体和蒸汽性质的NIST表查找方法已经开发。当局部条件达到亚临界且不需要预先指定相位时，就会触发相变。在接近临界进口温度和较低温度下的两相进口条件下进行了计算。本文发现并讨论了这两种条件下相变特性的显著差异。
{"title":"Numerical Simulations of CO2 Compressors at Near-Critical and Sub-Critical Inlet Conditions","authors":"A. Hosangadi, T. Weathers, Z. Liu, V. Ahuja, J. Busby","doi":"10.1115/GT2018-75102","DOIUrl":"https://doi.org/10.1115/GT2018-75102","url":null,"abstract":"An advanced real-fluid numerical framework for transcritical CO2 spanning both the supercritical and sub-critical regime near the critical point is presented. The numerical algorithm is specifically designed to faithfully model sharp variations of thermodynamic derivatives near the critical point. Numerical results for compressor performance in the Sandia test loop [1] at near critical inlet conditions have been presented over a range of flow rates from the choke point to the stall line. The analysis identifies the shift in the flow losses from the impeller to the diffuser as the flow rate increases from the stall to choke limit. The simulations have been compared with both the Sandia performance curves as well as raw data from Barber Nichols Inc. (BNI); the results compare well with the raw data and provide good qualitative comparisons with Sandia’s performance curves [1].\u0000 The numerical framework has also been extended to sub-critical conditions by solving for separate transport equations for each phase. Methodology for NIST table lookup at sub-critical conditions to identify liquid and vapor properties has been developed. Phase change is triggered when local conditions go sub-critical and do not require the phase to be specified a priori. Calculations at both near critical inlet temperatures as well as a two-phase inlet condition at lower temperatures were modeled. Significant difference in the phase change characteristics at these two conditions have been identified and discussed in the paper.","PeriodicalId":412490,"journal":{"name":"Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125564005","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}
Jongjae Cho, Hyungki Shin, Junhyun Cho, Y. Baik, Bongsu Choi, C. Roh, H. Ra, Y. Kang, J. Huh
The development of a 60-kWe turbo generator that uses supercritical carbon dioxide (sCO2) cycle technology at the lab scale is described herein. The design concept for the turbo generator involved using commercially available components to reduce the developmental time and to increase the reliability of the machine. The developed supercritical partial-admission CO2 turbine has a single-stage axial-type design with a 73-mm rotor mean diameter. The design of the sCO2 turbine uses impulse and partial admission to reduce the axial force and rotational speed. We simulated the flow of the designed sCO2 turbine. To increase the simulation accuracy, a real gas property table is coupled with the flow solver. The turbine performance test apparatus and test results are described; then, the turbine is continuously operated for 44 min. The maximum turbine power is 25.4 kW, and the maximum electric power is 10.3 kWe.
{"title":"Design, Flow Simulation, and Performance Test for a Partial-Admission Axial Turbine Under Supercritical CO2 Condition","authors":"Jongjae Cho, Hyungki Shin, Junhyun Cho, Y. Baik, Bongsu Choi, C. Roh, H. Ra, Y. Kang, J. Huh","doi":"10.1115/GT2018-76508","DOIUrl":"https://doi.org/10.1115/GT2018-76508","url":null,"abstract":"The development of a 60-kWe turbo generator that uses supercritical carbon dioxide (sCO2) cycle technology at the lab scale is described herein. The design concept for the turbo generator involved using commercially available components to reduce the developmental time and to increase the reliability of the machine. The developed supercritical partial-admission CO2 turbine has a single-stage axial-type design with a 73-mm rotor mean diameter. The design of the sCO2 turbine uses impulse and partial admission to reduce the axial force and rotational speed. We simulated the flow of the designed sCO2 turbine. To increase the simulation accuracy, a real gas property table is coupled with the flow solver. The turbine performance test apparatus and test results are described; then, the turbine is continuously operated for 44 min. The maximum turbine power is 25.4 kW, and the maximum electric power is 10.3 kWe.","PeriodicalId":412490,"journal":{"name":"Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127164424","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}
Roman Zamotorin, R. Kurz, Zhang Donghui, Matt Lubomirsky, K. Brun
Many gas compressor stations use multiple gas turbine driven centrifugal compressors. In many instances, the units are not identical. The challenge is to control the units such, that certain operational parameters, for example fuel consumption, are optimized. The control system has to rely on measurable parameters. The system has to be reliable even if parameters that are not directly measured change during operation. For practical use, the two methods available are to control all compressors for the same turndown, or to control all gas turbines for the same load. This methodology can be derived and discussed for the case of identical machines, and will be expanded for the case where the compressors and their drivers are not identical. The paper describes a variety of optimization methods, starting with a simple algorithm, then comparing equalization methods, and finally illustration the capability of methods that combine turbomachinery optimization and the optimization of pipeline hydraulics.
{"title":"Control Optimization for Multiple Gas Turbine Driven Compressors","authors":"Roman Zamotorin, R. Kurz, Zhang Donghui, Matt Lubomirsky, K. Brun","doi":"10.1115/GT2018-75002","DOIUrl":"https://doi.org/10.1115/GT2018-75002","url":null,"abstract":"Many gas compressor stations use multiple gas turbine driven centrifugal compressors. In many instances, the units are not identical. The challenge is to control the units such, that certain operational parameters, for example fuel consumption, are optimized. The control system has to rely on measurable parameters. The system has to be reliable even if parameters that are not directly measured change during operation.\u0000 For practical use, the two methods available are to control all compressors for the same turndown, or to control all gas turbines for the same load. This methodology can be derived and discussed for the case of identical machines, and will be expanded for the case where the compressors and their drivers are not identical.\u0000 The paper describes a variety of optimization methods, starting with a simple algorithm, then comparing equalization methods, and finally illustration the capability of methods that combine turbomachinery optimization and the optimization of pipeline hydraulics.","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":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132080291","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}
A new concept of power generator using two oscillating foils in parallel configuration to extract energy from fluid is proposed and numerically tested in the present study. The theoretical performance of the turbine in this form is investigated through unsteady two-dimensional laminar-flow Navier-Stokes simulations. The effect of the interaction between the two foils is studied at different pitching amplitudes and phase differences between the two foils. The energy extraction performance, instantaneous force coefficients and flow details are compared between single foil and dual foils, and thus the mechanism of performance improvement by wing-in-ground effect is revealed. Two different kinds of asymmetric sinusoidal motions are utilized to further improve the performance of the turbine. Numerical results indicate that anti-phase mode can achieve higher power coefficient than the in-phase mode. The contracted passage under anti-phase mode helps produce larger lift force and power coefficient. The maximum power coefficient per foil for anti-phase dual foils is 1.4% higher than that of single foil. The asymmetric sinusoidal pitching motion in phase can improve the synchronization between plunging velocity and lift force and thus further enhance the energy extraction performance by 1.3%. Besides, the pitching motion with asymmetric amplitude also can increase the power coefficient somehow, but the improvement is very limited.
{"title":"Numerical Investigation Into the Energy Extraction Characteristics of Parallel Dual-Foil Turbine","authors":"W. Jiang, Yulu Wang, Yonghui Xie, Di Zhang","doi":"10.1115/GT2018-76664","DOIUrl":"https://doi.org/10.1115/GT2018-76664","url":null,"abstract":"A new concept of power generator using two oscillating foils in parallel configuration to extract energy from fluid is proposed and numerically tested in the present study. The theoretical performance of the turbine in this form is investigated through unsteady two-dimensional laminar-flow Navier-Stokes simulations. The effect of the interaction between the two foils is studied at different pitching amplitudes and phase differences between the two foils. The energy extraction performance, instantaneous force coefficients and flow details are compared between single foil and dual foils, and thus the mechanism of performance improvement by wing-in-ground effect is revealed. Two different kinds of asymmetric sinusoidal motions are utilized to further improve the performance of the turbine. Numerical results indicate that anti-phase mode can achieve higher power coefficient than the in-phase mode. The contracted passage under anti-phase mode helps produce larger lift force and power coefficient. The maximum power coefficient per foil for anti-phase dual foils is 1.4% higher than that of single foil. The asymmetric sinusoidal pitching motion in phase can improve the synchronization between plunging velocity and lift force and thus further enhance the energy extraction performance by 1.3%. Besides, the pitching motion with asymmetric amplitude also can increase the power coefficient somehow, but the improvement is very limited.","PeriodicalId":412490,"journal":{"name":"Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy","volume":"52 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132481982","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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