Integrated energy systems(lESs)represent a promising energy supply model within the energy internet.However,multi-energy flow coupling in the optimal configuration of IES results in a series of simplifications in the ...Integrated energy systems(lESs)represent a promising energy supply model within the energy internet.However,multi-energy flow coupling in the optimal configuration of IES results in a series of simplifications in the preliminary planning,affecting the cost,efficiency,and environmental performance of IES.A novel optimal planning method that considers the part-load characteristics and spatio-temporal synergistic effects of IES components is proposed to enable a rational design of the structure and size of IES.An extended energy hub model is introduced based on the“node of energy hub”concept by decomposing the IES into different types of energy equipment.Subsequently,a planning method is applied as a two-level optimization framework-the upper level is used to identify the type and size of the component,while the bottom level is used to optimize the operation strategy based on a typical day analysis method.The planning problem is solved using a two-stage evolutionary algorithm,combing the multiple-mutations adaptive genetic algorithm with an interior point optimization solver,to minimize the lifetime cost of the IES.Finally,the feasibility of the proposed planning method is demonstrated using a case study.The life cycle costs of the IES with and without consideration of the part-load characteristics of the components were$4.26 million and$4.15 million,respectively,in the case study.Moreover,ignoring the variation in component characteristics in the design stage resulted in an additional 11.57%expenditure due to an energy efficiency reduction under the off-design conditions.展开更多
The internal flow fields in a compact return diffuser under strong part-load conditions are investigated both numerically and experimentally.For numerical simulation,three-dimensional unsteady Reynolds-Averaged Navier...The internal flow fields in a compact return diffuser under strong part-load conditions are investigated both numerically and experimentally.For numerical simulation,three-dimensional unsteady Reynolds-Averaged Navier–Stokes equations are solved on high-quality structured grids in conjunction with the shear stress transport k–turbulence model by employing the computational fluid dynamics(CFD)software ANSYS-Fluent 14.5.For flow field measurements,a special test rig is designed and the two-dimensional particle image velocimetry(PIV)measurements are conducted in the diffuser midplane to capture the complex flow field and for validation of the CFD results.The analysis of the results has been focused on the flow structure in the diffuser,especially under part-load conditions.The detailed comparison between CFD and PIV results is performed.Vortical flow and recirculation flow patterns in the diffuser are captured and analyzed.Large flow separation and backflow appear under the part-load flow conditions.This paper provides a good data set for developing as well as evaluating the accuracy of various CFD models for capturing the complex flow field in a compact return diffuser used with multistage pumps.展开更多
Owing to the part-load operations for the enhancement of grid flexibility, the Francis turbine often suffers from severe low-frequency and large-amplitude hydraulic instability, which is mostly pertinent to the highly...Owing to the part-load operations for the enhancement of grid flexibility, the Francis turbine often suffers from severe low-frequency and large-amplitude hydraulic instability, which is mostly pertinent to the highly unsteady swirling vortex rope in the draft tube. The influence of disturbances in the upstream（e.g., large-scale vortex structures in the spiral casing） on the draft-tube vortex flow is not well understood yet. In the present paper, the influence of the upstream disturbances on the vortical flow in the draft tube is studied based on the vortex identification method and the analysis of several important parameters（e.g., the swirl number and the velocity profile）. For a small guide vane opening（representing the part-load condition）, the vortices triggered in the spiral casing propagate downstream and significantly affect the swirling vortex-rope precession in the draft tube, leading to the changes of the intensity and the processional frequency of the swirling vortex rope. When the guide vane opening approaches the optimum one（representing the full-load condition）, the upstream disturbance becomes weaker and thus its influences on the downstream flow are very limited.展开更多
Providing stable combustion of lean-burn natural gas engines was always a bigchallenge, particularly during a low load operation. In transient sea conditions, there is an additional concern due to irregular time-varyi...Providing stable combustion of lean-burn natural gas engines was always a bigchallenge, particularly during a low load operation. In transient sea conditions, there is an additional concern due to irregular time-varying loads. Therefore, this study aimed at investigatingthe part-load operation of a marine spark-ignition lean-burn natural gas engine by simulatingthe entire engine. The engine’s essential components are modeled, including air manifold,intake valves, fuel system, controllers, combustion chamber, exhaust valves, exhaust manifoldand turbocharger.In steady-state, the results of emission compounds from modeling have been compared tomeasured data from 25% to 100% loads. For transient conditions, for the sample time of about50 min, the fuel flow and turbocharger output are selected from the vessel logged data andcompared with the simulation results. The model has shown the great potential of predictingthe engine response throughout the steady-state and transient conditions. Simulating the engineat part-load transient condition showed that the unburned hydrocarbon formation, known asmethane slip in lean-burn gas engines, is more than the part-load steady-state. This increaseof methane slip is due to the combustion instability in lower loads and flame extinguishingin such transient conditions. The engine measured data shows a double amount of methane slipin a 25% load than the 100% load in steady-state. However, the simulation output in the transient conditions confirms an increase in methane slip over four times than equivalentsteady-state load. Moreover, the lean-burn gas engine releases less NOX in part-load operationin a steady-state due to lower in-cylinder temperature. In transient conditions, there is remarkable instability in excess air ratio. Due to this instability, there is a rich mixture in instantaneoustime steps during loads up. Therefore, it will result in an unusually high amount of NOX, andmore than two times in comparison with the equivalent steady-state output.展开更多
A novel adjusting method for improving gas turbine(GT)efficiency and surge margin(SM)under partload conditions is proposed.This method adopts the inlet air heating technology,which uses the waste heat of lowgrade heat...A novel adjusting method for improving gas turbine(GT)efficiency and surge margin(SM)under partload conditions is proposed.This method adopts the inlet air heating technology,which uses the waste heat of lowgrade heat source and the inlet guide vane(IGV)opening adjustment.Moreover,the regulation rules of the compressor inlet air temperature and the IGV opening are studied comprehensively to optimize GT performance.A model and calculation method for an equilibrium running line is adopted based on the characteristic curves of the compressor and turbine.The equilibrium running lines calculated through the calculation method involve three part-load conditions and three IGVopenings with different inlet air temperatures.The results show that there is an optimal matching relationship between IGV opening and inlet air temperature.For the best GT performance of a given load,the IGV could be adjusted according to inlet air temperature.In addition,inlet air heating has a considerable potential for the improvement of part-load performance of GT due to the increase in compressor efficiency,combustion efficiency,and turbine efficiency as well as turbine inlet temperature,when inlet air temperature is lower than the optimal value with different IGV openings.Further,when the IGV is in a full opening state and an optimal inlet air temperature is achieved by using the inlet air heating technology,GT efficiency and SM can be obviously higher than other IGVopenings.The IGV can be left unadjusted,even when the load is as low as 50%.These findings indicate that inlet air heating has a great potential to replace the IGV to regulate load because GT efficiency and SM can be remarkably improved,which is different from the traditional viewpoints.展开更多
The purpose of this study is to compare the part-load performance of a lean burn catalytic combustion gas turbine (LBCCGT) system in three different control modes: varying fuel, bleeding off the fuel mixture flow afte...The purpose of this study is to compare the part-load performance of a lean burn catalytic combustion gas turbine (LBCCGT) system in three different control modes: varying fuel, bleeding off the fuel mixture flow after the compressor and varying rotational speed. The conversions of methane species for chemical process are considered. A 1D heterogeneous plug flow model was utilized to analyze the system performance. The actual turbomachinery components were designed and predicted performance maps were applied to system performance research. The part-load characteristics under three control strategies were numerically investigated. The main results show that: the combustor inlet temperature is a significant factor that can significantly affect the part-load characteristics of the LBCCGT system; the rotational speed control mode can provide the best performance characteristics for part-load operations; the operation range of the bleed off mode is narrower than that of the speed control mode and wider than that of the fuel only mode; with reduced power, methane does not achieve full conversion over the reactor at the fuel only control mode, which will not warrant stable operation of the turbine system; the thermal efficiency of the LBCCGT system at fuel only control strategy is higher than that at bleed off control strategy within the operation range.展开更多
Exhaust gas recirculation control(EGRC),an inlet air heating technology,can be utilized in combination with inlet/variable guide vane control(IGV/VGVC) and fuel flow control(FFC) to regulate the load,thereby effective...Exhaust gas recirculation control(EGRC),an inlet air heating technology,can be utilized in combination with inlet/variable guide vane control(IGV/VGVC) and fuel flow control(FFC) to regulate the load,thereby effectively improving the part-load(i.e.,off-design) performance of the gas turbine combined cycle(GTCC).In this study,the E-,F-,and H-Class EGR-GTCC design and off-design system models were established and validated to perform a comparative analysis of the part-load performance under the EGR-IGV-FFC and conventional IGV-FFC strategies in the E/F/H-Class GTCC.Results show that EGR-IGV-FFC has considerable potential for the part-load performance enhancement and can show a higher combined cycle efficiency than IGV-FFC in the E-,F-,and H-Class GTCCs.However,the part-load performance improvement in the corresponding GTCC was weakened for the higher class of the gas turbine because of the narrower load range of EGR action and the deterioration of the gas turbine performance.Furthermore,EGR-IGV-FFC was inferior to IGV-FFC in improving the performance at loads below 50% for the H-Class GTCC.The results obtained in this paper could help guide the application of EGR-IGV-FFC to enhance the part-load performance of various classes of GTCC systems.展开更多
基金the National Natural Science Foundation of China(Grant No.51821004)supported by the Major Program of the National Natural Science Foundation of China(Grant No.52090062)The author Chengzhou Li also thank the China Scholarship Council(CSC)for the financial support.
文摘Integrated energy systems(lESs)represent a promising energy supply model within the energy internet.However,multi-energy flow coupling in the optimal configuration of IES results in a series of simplifications in the preliminary planning,affecting the cost,efficiency,and environmental performance of IES.A novel optimal planning method that considers the part-load characteristics and spatio-temporal synergistic effects of IES components is proposed to enable a rational design of the structure and size of IES.An extended energy hub model is introduced based on the“node of energy hub”concept by decomposing the IES into different types of energy equipment.Subsequently,a planning method is applied as a two-level optimization framework-the upper level is used to identify the type and size of the component,while the bottom level is used to optimize the operation strategy based on a typical day analysis method.The planning problem is solved using a two-stage evolutionary algorithm,combing the multiple-mutations adaptive genetic algorithm with an interior point optimization solver,to minimize the lifetime cost of the IES.Finally,the feasibility of the proposed planning method is demonstrated using a case study.The life cycle costs of the IES with and without consideration of the part-load characteristics of the components were$4.26 million and$4.15 million,respectively,in the case study.Moreover,ignoring the variation in component characteristics in the design stage resulted in an additional 11.57%expenditure due to an energy efficiency reduction under the off-design conditions.
基金supported by the National Natural Science Foundation of China(Grant No.51279069)the Natural Science Foundation of Jiangsu Province(Grant No.BK20131256)
文摘The internal flow fields in a compact return diffuser under strong part-load conditions are investigated both numerically and experimentally.For numerical simulation,three-dimensional unsteady Reynolds-Averaged Navier–Stokes equations are solved on high-quality structured grids in conjunction with the shear stress transport k–turbulence model by employing the computational fluid dynamics(CFD)software ANSYS-Fluent 14.5.For flow field measurements,a special test rig is designed and the two-dimensional particle image velocimetry(PIV)measurements are conducted in the diffuser midplane to capture the complex flow field and for validation of the CFD results.The analysis of the results has been focused on the flow structure in the diffuser,especially under part-load conditions.The detailed comparison between CFD and PIV results is performed.Vortical flow and recirculation flow patterns in the diffuser are captured and analyzed.Large flow separation and backflow appear under the part-load flow conditions.This paper provides a good data set for developing as well as evaluating the accuracy of various CFD models for capturing the complex flow field in a compact return diffuser used with multistage pumps.
基金Project supported by the National Natural Science Foundation of China(Grant No.51506051)
文摘Owing to the part-load operations for the enhancement of grid flexibility, the Francis turbine often suffers from severe low-frequency and large-amplitude hydraulic instability, which is mostly pertinent to the highly unsteady swirling vortex rope in the draft tube. The influence of disturbances in the upstream（e.g., large-scale vortex structures in the spiral casing） on the draft-tube vortex flow is not well understood yet. In the present paper, the influence of the upstream disturbances on the vortical flow in the draft tube is studied based on the vortex identification method and the analysis of several important parameters（e.g., the swirl number and the velocity profile）. For a small guide vane opening（representing the part-load condition）, the vortices triggered in the spiral casing propagate downstream and significantly affect the swirling vortex-rope precession in the draft tube, leading to the changes of the intensity and the processional frequency of the swirling vortex rope. When the guide vane opening approaches the optimum one（representing the full-load condition）, the upstream disturbance becomes weaker and thus its influences on the downstream flow are very limited.
文摘Providing stable combustion of lean-burn natural gas engines was always a bigchallenge, particularly during a low load operation. In transient sea conditions, there is an additional concern due to irregular time-varying loads. Therefore, this study aimed at investigatingthe part-load operation of a marine spark-ignition lean-burn natural gas engine by simulatingthe entire engine. The engine’s essential components are modeled, including air manifold,intake valves, fuel system, controllers, combustion chamber, exhaust valves, exhaust manifoldand turbocharger.In steady-state, the results of emission compounds from modeling have been compared tomeasured data from 25% to 100% loads. For transient conditions, for the sample time of about50 min, the fuel flow and turbocharger output are selected from the vessel logged data andcompared with the simulation results. The model has shown the great potential of predictingthe engine response throughout the steady-state and transient conditions. Simulating the engineat part-load transient condition showed that the unburned hydrocarbon formation, known asmethane slip in lean-burn gas engines, is more than the part-load steady-state. This increaseof methane slip is due to the combustion instability in lower loads and flame extinguishingin such transient conditions. The engine measured data shows a double amount of methane slipin a 25% load than the 100% load in steady-state. However, the simulation output in the transient conditions confirms an increase in methane slip over four times than equivalentsteady-state load. Moreover, the lean-burn gas engine releases less NOX in part-load operationin a steady-state due to lower in-cylinder temperature. In transient conditions, there is remarkable instability in excess air ratio. Due to this instability, there is a rich mixture in instantaneoustime steps during loads up. Therefore, it will result in an unusually high amount of NOX, andmore than two times in comparison with the equivalent steady-state output.
基金supported by Project 2017-II-0007-0021 of the National Science and Technology Major Project of China.
文摘A novel adjusting method for improving gas turbine(GT)efficiency and surge margin(SM)under partload conditions is proposed.This method adopts the inlet air heating technology,which uses the waste heat of lowgrade heat source and the inlet guide vane(IGV)opening adjustment.Moreover,the regulation rules of the compressor inlet air temperature and the IGV opening are studied comprehensively to optimize GT performance.A model and calculation method for an equilibrium running line is adopted based on the characteristic curves of the compressor and turbine.The equilibrium running lines calculated through the calculation method involve three part-load conditions and three IGVopenings with different inlet air temperatures.The results show that there is an optimal matching relationship between IGV opening and inlet air temperature.For the best GT performance of a given load,the IGV could be adjusted according to inlet air temperature.In addition,inlet air heating has a considerable potential for the improvement of part-load performance of GT due to the increase in compressor efficiency,combustion efficiency,and turbine efficiency as well as turbine inlet temperature,when inlet air temperature is lower than the optimal value with different IGV openings.Further,when the IGV is in a full opening state and an optimal inlet air temperature is achieved by using the inlet air heating technology,GT efficiency and SM can be obviously higher than other IGVopenings.The IGV can be left unadjusted,even when the load is as low as 50%.These findings indicate that inlet air heating has a great potential to replace the IGV to regulate load because GT efficiency and SM can be remarkably improved,which is different from the traditional viewpoints.
基金supported by the National Natural Science Foundation of China(Grant No.51206160)
文摘The purpose of this study is to compare the part-load performance of a lean burn catalytic combustion gas turbine (LBCCGT) system in three different control modes: varying fuel, bleeding off the fuel mixture flow after the compressor and varying rotational speed. The conversions of methane species for chemical process are considered. A 1D heterogeneous plug flow model was utilized to analyze the system performance. The actual turbomachinery components were designed and predicted performance maps were applied to system performance research. The part-load characteristics under three control strategies were numerically investigated. The main results show that: the combustor inlet temperature is a significant factor that can significantly affect the part-load characteristics of the LBCCGT system; the rotational speed control mode can provide the best performance characteristics for part-load operations; the operation range of the bleed off mode is narrower than that of the speed control mode and wider than that of the fuel only mode; with reduced power, methane does not achieve full conversion over the reactor at the fuel only control mode, which will not warrant stable operation of the turbine system; the thermal efficiency of the LBCCGT system at fuel only control strategy is higher than that at bleed off control strategy within the operation range.
基金financial support from the Fundamental Research Project in the Chinese National Sciences and Technology Major Project (Grant No.2017-1-0002-0002)。
文摘Exhaust gas recirculation control(EGRC),an inlet air heating technology,can be utilized in combination with inlet/variable guide vane control(IGV/VGVC) and fuel flow control(FFC) to regulate the load,thereby effectively improving the part-load(i.e.,off-design) performance of the gas turbine combined cycle(GTCC).In this study,the E-,F-,and H-Class EGR-GTCC design and off-design system models were established and validated to perform a comparative analysis of the part-load performance under the EGR-IGV-FFC and conventional IGV-FFC strategies in the E/F/H-Class GTCC.Results show that EGR-IGV-FFC has considerable potential for the part-load performance enhancement and can show a higher combined cycle efficiency than IGV-FFC in the E-,F-,and H-Class GTCCs.However,the part-load performance improvement in the corresponding GTCC was weakened for the higher class of the gas turbine because of the narrower load range of EGR action and the deterioration of the gas turbine performance.Furthermore,EGR-IGV-FFC was inferior to IGV-FFC in improving the performance at loads below 50% for the H-Class GTCC.The results obtained in this paper could help guide the application of EGR-IGV-FFC to enhance the part-load performance of various classes of GTCC systems.
