为准确描述下降管反应器内生物质颗粒与高温陶瓷球之间的瞬态传热与热解行为,该研究提出了一种基于分布活化能模型(distributed activation energy model,DAEM)的多物理场耦合数值模型。该模型在颗粒能量平衡框架下,引入接触导热、气膜...为准确描述下降管反应器内生物质颗粒与高温陶瓷球之间的瞬态传热与热解行为,该研究提出了一种基于分布活化能模型(distributed activation energy model,DAEM)的多物理场耦合数值模型。该模型在颗粒能量平衡框架下,引入接触导热、气膜导热、对流与辐射多种传热机制,并与质量转化过程和活化能分布特征相耦合,建立了用于描述生物质快速热解过程的常微分方程模型。基于热重分析试验数据,对高斯、洛伦兹及逻辑斯谛3种活化能分布函数进行了参数反演与对比分析。结果表明,洛伦兹分布能够更准确地再现试验热重曲线,其平均绝对误差(mean absolute error,MAE)和均方根误差(root mean square error,RMSE)分别为0.0116和0.0138。数值模拟结果显示,生物质颗粒在初始阶段经历了极高的升温速率(峰值达到2.14×10^(3)℃/s),但热解反应相对于温度演化存在明显的动力学滞后特征。传热机制分析表明,对流与导热在整个热解过程中占主导地位,而在高温阶段辐射传热的贡献不可忽略。参数敏感性分析进一步揭示,陶瓷球温度和生物质颗粒粒径对热解效率具有显著影响,反应焓和颗粒碰撞概率次之,而辐射视角因子的影响相对有限。研究结果表明,在传热条件充分的快速热解工况下,过程控制机理由传热受限逐渐转变为化学反应动力学受限。研究为深入理解下降管反应器内多物理场耦合热解行为特征及反应器结构与工艺参数优化提供了理论依据和数据支持。展开更多
To achieve efficient and refined thermal environment simulations for single-phase and two-phase flows in aircraft cabins,we propose an integrated analysis method.This approach enables rapid coupled heat transfer calcu...To achieve efficient and refined thermal environment simulations for single-phase and two-phase flows in aircraft cabins,we propose an integrated analysis method.This approach enables rapid coupled heat transfer calculations among single-phase flow,two-phase flow,and solids within a single time step.For single-phase fluid and solid equipment,a fast numerical algorithm for natural convection is developed using a loosely coupled strategy,dividing the single-phase flow into developmental stages for efficient temperature field computation.For two-phase flow and the fuel tank wall,a transient heat transfer model is constructed at the gas-liquid-solid boundary,facilitating fast thermal analysis.These methods are unified for integrated simulation of the cabin’s thermal environment.Validation based on two-dimensional models demonstrates a speedup by a factor of 7.9,while maintaining an average temperature error of less than 1%at two-phase nodes.The method’s robustness is confirmed under various high-temperature boundary conditions.展开更多
大规模双馈风电场作为实现我国“双碳”目标的陆上风电主力,其高比例电力电子设备的接入对电力系统电磁暂态高精度仿真技术提出日益严苛的要求,面向上百台发电单元的双馈场站全拓扑精细化微秒级仿真研究仍相对空白。基于现场可编程门阵...大规模双馈风电场作为实现我国“双碳”目标的陆上风电主力,其高比例电力电子设备的接入对电力系统电磁暂态高精度仿真技术提出日益严苛的要求,面向上百台发电单元的双馈场站全拓扑精细化微秒级仿真研究仍相对空白。基于现场可编程门阵列(field programmable gate array,FPGA)微秒级小步长并行仿真能力,提出一种面向双馈风电场站的发电单元FPGA并行仿真方法。首先,进行双馈感应电机微秒级高并行度离散化建模与换流器受控源建模;接着,对节点导纳矩阵分块降维以实现发电单元内部分网并行,并从整体电路解算层面提出单元级并行仿真框架;最后,考虑实时数字仿真器(real time digital simulator,RTDS)与FPGA仿真平台特点,分配发电单元的微秒级小步长仿真任务并搭建联合仿真硬件框架;通过对比RTDS标准模型与RTDS+FPGA联合仿真模型,验证所提并行仿真方法的准确性。展开更多
Drag force is a key parameter in the numerical modeling of gas-particle flow in circulating fluidized beds. The reliability of current drag force correlations over the regime of fast fluidization has, however, not bee...Drag force is a key parameter in the numerical modeling of gas-particle flow in circulating fluidized beds. The reliability of current drag force correlations over the regime of fast fluidization has, however, not been thoroughly investigated. In this article, a drag force correlation accounting for the clustering effects for Geldart A particles is used to simulate the behaviors typical of fast fluidization, including dynamic evolution of clusters as well as time- averaged axial and lateral voidage profiles. Diverse images of clusters are captured and the time-averaged profiles of voidage are shown to be in quantitative agreement with the present empirical correlation. The results based on different constitutive correlations of drag force show the importance of the choice of drag force in modeling fast-fluidized beds. This drag force correlation, based on a simple averaging assumption, could give some basic insights about the magnitude of the drag reduction.展开更多
文摘为准确描述下降管反应器内生物质颗粒与高温陶瓷球之间的瞬态传热与热解行为,该研究提出了一种基于分布活化能模型(distributed activation energy model,DAEM)的多物理场耦合数值模型。该模型在颗粒能量平衡框架下,引入接触导热、气膜导热、对流与辐射多种传热机制,并与质量转化过程和活化能分布特征相耦合,建立了用于描述生物质快速热解过程的常微分方程模型。基于热重分析试验数据,对高斯、洛伦兹及逻辑斯谛3种活化能分布函数进行了参数反演与对比分析。结果表明,洛伦兹分布能够更准确地再现试验热重曲线,其平均绝对误差(mean absolute error,MAE)和均方根误差(root mean square error,RMSE)分别为0.0116和0.0138。数值模拟结果显示,生物质颗粒在初始阶段经历了极高的升温速率(峰值达到2.14×10^(3)℃/s),但热解反应相对于温度演化存在明显的动力学滞后特征。传热机制分析表明,对流与导热在整个热解过程中占主导地位,而在高温阶段辐射传热的贡献不可忽略。参数敏感性分析进一步揭示,陶瓷球温度和生物质颗粒粒径对热解效率具有显著影响,反应焓和颗粒碰撞概率次之,而辐射视角因子的影响相对有限。研究结果表明,在传热条件充分的快速热解工况下,过程控制机理由传热受限逐渐转变为化学反应动力学受限。研究为深入理解下降管反应器内多物理场耦合热解行为特征及反应器结构与工艺参数优化提供了理论依据和数据支持。
文摘To achieve efficient and refined thermal environment simulations for single-phase and two-phase flows in aircraft cabins,we propose an integrated analysis method.This approach enables rapid coupled heat transfer calculations among single-phase flow,two-phase flow,and solids within a single time step.For single-phase fluid and solid equipment,a fast numerical algorithm for natural convection is developed using a loosely coupled strategy,dividing the single-phase flow into developmental stages for efficient temperature field computation.For two-phase flow and the fuel tank wall,a transient heat transfer model is constructed at the gas-liquid-solid boundary,facilitating fast thermal analysis.These methods are unified for integrated simulation of the cabin’s thermal environment.Validation based on two-dimensional models demonstrates a speedup by a factor of 7.9,while maintaining an average temperature error of less than 1%at two-phase nodes.The method’s robustness is confirmed under various high-temperature boundary conditions.
文摘大规模双馈风电场作为实现我国“双碳”目标的陆上风电主力,其高比例电力电子设备的接入对电力系统电磁暂态高精度仿真技术提出日益严苛的要求,面向上百台发电单元的双馈场站全拓扑精细化微秒级仿真研究仍相对空白。基于现场可编程门阵列(field programmable gate array,FPGA)微秒级小步长并行仿真能力,提出一种面向双馈风电场站的发电单元FPGA并行仿真方法。首先,进行双馈感应电机微秒级高并行度离散化建模与换流器受控源建模;接着,对节点导纳矩阵分块降维以实现发电单元内部分网并行,并从整体电路解算层面提出单元级并行仿真框架;最后,考虑实时数字仿真器(real time digital simulator,RTDS)与FPGA仿真平台特点,分配发电单元的微秒级小步长仿真任务并搭建联合仿真硬件框架;通过对比RTDS标准模型与RTDS+FPGA联合仿真模型,验证所提并行仿真方法的准确性。
基金the National Key Technologies R&D Program (2001BA401A03-10).
文摘Drag force is a key parameter in the numerical modeling of gas-particle flow in circulating fluidized beds. The reliability of current drag force correlations over the regime of fast fluidization has, however, not been thoroughly investigated. In this article, a drag force correlation accounting for the clustering effects for Geldart A particles is used to simulate the behaviors typical of fast fluidization, including dynamic evolution of clusters as well as time- averaged axial and lateral voidage profiles. Diverse images of clusters are captured and the time-averaged profiles of voidage are shown to be in quantitative agreement with the present empirical correlation. The results based on different constitutive correlations of drag force show the importance of the choice of drag force in modeling fast-fluidized beds. This drag force correlation, based on a simple averaging assumption, could give some basic insights about the magnitude of the drag reduction.
