Supercritical CO_(2)(SCO_(2))Brayton cycle has received more and more attention in the field of power generation due to its high cycle efficiency and compact structure.SCO_(2) compressor is the core component of the c...Supercritical CO_(2)(SCO_(2))Brayton cycle has received more and more attention in the field of power generation due to its high cycle efficiency and compact structure.SCO_(2) compressor is the core component of the cycle,and the improvement of its performance is the key to improving the efficiency of the entire cycle.However,the operation of the SCO_(2) compressor near the critical point has brought many design and operation problems.Based on the Reynolds Averaged Navier-Stokes(RANS)model,the performance and flow field of SCO_(2) centrifugal compressors based on different CO_(2) working fluid models are numerically investigated in this paper.The stability and convergence of the compressor steady-state simulation are also discussed.The results show that the fluid based on the Span-Wanger(SW)equation can obtain a more ideal compressor performance curve and capture a more accurate flow field structure,while the CO_(2) ideal gas is not suitable for the calculation of SCO_(2) centrifugal compressors.But its flow field can be used as the initial flow field for numerical calculation of centrifugal compressor based on CO_(2) real gas.展开更多
Supercritical carbon dioxide(SCO_(2))centrifugal compressor is a key component of a closed Brayton cycle system based on SCO_(2).A comprehensive understanding of the loss mechanism within the compressor is vital for i...Supercritical carbon dioxide(SCO_(2))centrifugal compressor is a key component of a closed Brayton cycle system based on SCO_(2).A comprehensive understanding of the loss mechanism within the compressor is vital for its optimized design.However,the physical properties of SCO_(2) are highly nonlinear near the critical point,and the internal flow of the compressor is closely related to its properties,which inevitably influences the generation of aerodynamic losses within the compressor.This paper presents a comprehensive investigation of the compressor's loss mechanism with an experimentally validated numerical method.The real gas model of CO_(2) embodied in the Reynolds-Averaged Navier-Stokes(RANS)model was used for the study.Firstly,the numerical simulation method was validated against the experimental results of Sandia SCO_(2) compressor.Secondly,performance and loss distribution of the compressor were compared among three fluids including SCO_(2),ideal CO_(2)(ICO_(2))and ideal air(IAir).The results showed that the performance of SCO_(2) was comparable to IAir under low flow coefficient,however markedly inferior to the other two fluids at near choke condition.Loss distribution among the three fluids was distinctive.In the impeller,SCO_(2) was the most inefficient,followed by ICO_(2) and IAir.The discrepancies were magnified as the flow coefficient increased.This is due to a stronger Blade-to-Blade pressure gradient that intensifies boundary layer accumulation on walls of the shroud/hub.Furthermore,owing to the reduced sonic speed of SCO_(2),a shock wave appears earlier at the throat region and SCO_(2) encounters more intenseboundarylayerseparation.展开更多
文摘Supercritical CO_(2)(SCO_(2))Brayton cycle has received more and more attention in the field of power generation due to its high cycle efficiency and compact structure.SCO_(2) compressor is the core component of the cycle,and the improvement of its performance is the key to improving the efficiency of the entire cycle.However,the operation of the SCO_(2) compressor near the critical point has brought many design and operation problems.Based on the Reynolds Averaged Navier-Stokes(RANS)model,the performance and flow field of SCO_(2) centrifugal compressors based on different CO_(2) working fluid models are numerically investigated in this paper.The stability and convergence of the compressor steady-state simulation are also discussed.The results show that the fluid based on the Span-Wanger(SW)equation can obtain a more ideal compressor performance curve and capture a more accurate flow field structure,while the CO_(2) ideal gas is not suitable for the calculation of SCO_(2) centrifugal compressors.But its flow field can be used as the initial flow field for numerical calculation of centrifugal compressor based on CO_(2) real gas.
基金supported by the National Natural Science Foundation of China(Grant No.52076130)。
文摘Supercritical carbon dioxide(SCO_(2))centrifugal compressor is a key component of a closed Brayton cycle system based on SCO_(2).A comprehensive understanding of the loss mechanism within the compressor is vital for its optimized design.However,the physical properties of SCO_(2) are highly nonlinear near the critical point,and the internal flow of the compressor is closely related to its properties,which inevitably influences the generation of aerodynamic losses within the compressor.This paper presents a comprehensive investigation of the compressor's loss mechanism with an experimentally validated numerical method.The real gas model of CO_(2) embodied in the Reynolds-Averaged Navier-Stokes(RANS)model was used for the study.Firstly,the numerical simulation method was validated against the experimental results of Sandia SCO_(2) compressor.Secondly,performance and loss distribution of the compressor were compared among three fluids including SCO_(2),ideal CO_(2)(ICO_(2))and ideal air(IAir).The results showed that the performance of SCO_(2) was comparable to IAir under low flow coefficient,however markedly inferior to the other two fluids at near choke condition.Loss distribution among the three fluids was distinctive.In the impeller,SCO_(2) was the most inefficient,followed by ICO_(2) and IAir.The discrepancies were magnified as the flow coefficient increased.This is due to a stronger Blade-to-Blade pressure gradient that intensifies boundary layer accumulation on walls of the shroud/hub.Furthermore,owing to the reduced sonic speed of SCO_(2),a shock wave appears earlier at the throat region and SCO_(2) encounters more intenseboundarylayerseparation.
