为准确高效地模拟高压CO_(2)管道泄漏的瞬态特性,基于Fluent仿真平台,利用用户自定义真实气体模型(User Defined Real Gas Model,UDRGM)和用户自定义函数(User Defined Function,UDF),结合查表法和双线性插值法建立CO_(2)的真实气体模型...为准确高效地模拟高压CO_(2)管道泄漏的瞬态特性,基于Fluent仿真平台,利用用户自定义真实气体模型(User Defined Real Gas Model,UDRGM)和用户自定义函数(User Defined Function,UDF),结合查表法和双线性插值法建立CO_(2)的真实气体模型,并将压力驱动的Lee模型通过用户自定义函数嵌入Fluent求解器来模拟CO_(2)的非平衡相变过程,建立了高压CO_(2)管道泄漏的非平衡相变数值模型。通过与Botros等的试验数据进行对比分析,验证了该模型的准确性。在此基础上,对比了上述模拟方法与编译S-W(Span-Wagner)状态方程模拟方法的精度和效率,最后使用本模型研究了不同初始压力对高压CO_(2)管道泄漏瞬态特性的影响。结果表明:两种模拟方法精度接近,最大相差为7.37%,但提出的模拟方法效率明显优于编译S-W状态方程的模拟方法,计算时间相较缩短约86.9%;初始压力为11.27 MPa的最大总出口质量流量比4.36 MPa的大7.24 kg/s,而对应的气相CO_(2)出口质量流量却低0.14 kg/s;初始压力为11.27 MPa和4.36 MPa对应的近场最大射流流速分别为155.12 m/s和175.50 m/s;管内初始压力越低,泄漏后到达亚稳态时过热度越大,管内及泄漏口附近相变程度越剧烈,气相出口质量流量越大,近场射流峰值速度越大。这项研究可为工业规模管道泄漏的模拟和管道泄漏的三维模拟提供更高效的方式。展开更多
For the carbon-neutral,a multi-carrier renewable energy system(MRES),driven by the wind,solar and geothermal,was considered as an effective solution to mitigate CO2emissions and reduce energy usage in the building sec...For the carbon-neutral,a multi-carrier renewable energy system(MRES),driven by the wind,solar and geothermal,was considered as an effective solution to mitigate CO2emissions and reduce energy usage in the building sector.A proper sizing method was essential for achieving the desired 100%renewable energy system of resources.This paper presented a bi-objective optimization formulation for sizing the MRES using a constrained genetic algorithm(GA)coupled with the loss of power supply probability(LPSP)method to achieve the minimal cost of the system and the reliability of the system to the load real time requirement.An optimization App has been developed in MATLAB environment to offer a user-friendly interface and output the optimized design parameters when given the load demand.A case study of a swimming pool building was used to demonstrate the process of the proposed design method.Compared to the conventional distributed energy system,the MRES is feasible with a lower annual total cost(ATC).Additionally,the ATC decreases as the power supply reliability of the renewable system decreases.There is a decrease of 24%of the annual total cost when the power supply probability is equal to 8%compared to the baseline case with 0%power supply probability.展开更多
The interaction between the car-body vibration and aerodynamic performance of the train becomes more prominent motivated by the vehicle’s light-weighting design.To address this topic,this study firstly analyzes the p...The interaction between the car-body vibration and aerodynamic performance of the train becomes more prominent motivated by the vehicle’s light-weighting design.To address this topic,this study firstly analyzes the posture characteristics of the car-body based on the previous full-scale test results.And then the aerodynamic performance under different vibration cases(different car-body roll angles)is studied with an improved delayed detached eddy simulation(IDDES).The results revealed that car-body rolling had a significant impact on the aerodynamic behavior of bogies,which significantly increased the lateral force and yaw moment of a bogie and further may have aggravated the operational instability of the train.The unbalanced distribution of the longitudinal pressure on both sides of the bogie caused by the car-body rolling motion was the primary cause for the bogie yaw moment increase.The tail vortex of the train was also affected by the car-body rolling,resulting in vertical jitter.展开更多
文摘为准确高效地模拟高压CO_(2)管道泄漏的瞬态特性,基于Fluent仿真平台,利用用户自定义真实气体模型(User Defined Real Gas Model,UDRGM)和用户自定义函数(User Defined Function,UDF),结合查表法和双线性插值法建立CO_(2)的真实气体模型,并将压力驱动的Lee模型通过用户自定义函数嵌入Fluent求解器来模拟CO_(2)的非平衡相变过程,建立了高压CO_(2)管道泄漏的非平衡相变数值模型。通过与Botros等的试验数据进行对比分析,验证了该模型的准确性。在此基础上,对比了上述模拟方法与编译S-W(Span-Wagner)状态方程模拟方法的精度和效率,最后使用本模型研究了不同初始压力对高压CO_(2)管道泄漏瞬态特性的影响。结果表明:两种模拟方法精度接近,最大相差为7.37%,但提出的模拟方法效率明显优于编译S-W状态方程的模拟方法,计算时间相较缩短约86.9%;初始压力为11.27 MPa的最大总出口质量流量比4.36 MPa的大7.24 kg/s,而对应的气相CO_(2)出口质量流量却低0.14 kg/s;初始压力为11.27 MPa和4.36 MPa对应的近场最大射流流速分别为155.12 m/s和175.50 m/s;管内初始压力越低,泄漏后到达亚稳态时过热度越大,管内及泄漏口附近相变程度越剧烈,气相出口质量流量越大,近场射流峰值速度越大。这项研究可为工业规模管道泄漏的模拟和管道泄漏的三维模拟提供更高效的方式。
基金Project(52108101)supported by the National Natural Science Foundation of ChinaProjects(2020GK4057,2021JJ40759)supported by the Hunan Provincial Science and Technology Department,China。
文摘For the carbon-neutral,a multi-carrier renewable energy system(MRES),driven by the wind,solar and geothermal,was considered as an effective solution to mitigate CO2emissions and reduce energy usage in the building sector.A proper sizing method was essential for achieving the desired 100%renewable energy system of resources.This paper presented a bi-objective optimization formulation for sizing the MRES using a constrained genetic algorithm(GA)coupled with the loss of power supply probability(LPSP)method to achieve the minimal cost of the system and the reliability of the system to the load real time requirement.An optimization App has been developed in MATLAB environment to offer a user-friendly interface and output the optimized design parameters when given the load demand.A case study of a swimming pool building was used to demonstrate the process of the proposed design method.Compared to the conventional distributed energy system,the MRES is feasible with a lower annual total cost(ATC).Additionally,the ATC decreases as the power supply reliability of the renewable system decreases.There is a decrease of 24%of the annual total cost when the power supply probability is equal to 8%compared to the baseline case with 0%power supply probability.
基金Project(BX2021379)supported by the China National Postdoctoral Program for Innovative Talents。
文摘The interaction between the car-body vibration and aerodynamic performance of the train becomes more prominent motivated by the vehicle’s light-weighting design.To address this topic,this study firstly analyzes the posture characteristics of the car-body based on the previous full-scale test results.And then the aerodynamic performance under different vibration cases(different car-body roll angles)is studied with an improved delayed detached eddy simulation(IDDES).The results revealed that car-body rolling had a significant impact on the aerodynamic behavior of bogies,which significantly increased the lateral force and yaw moment of a bogie and further may have aggravated the operational instability of the train.The unbalanced distribution of the longitudinal pressure on both sides of the bogie caused by the car-body rolling motion was the primary cause for the bogie yaw moment increase.The tail vortex of the train was also affected by the car-body rolling,resulting in vertical jitter.
