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Study of biomass gasification in an industrial-scale dual circulating fluidized bed(DCFB)using the Eulerian-Lagrangian method

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Particuology 2023年第12期83卷 156-168页

作者： Jiahui Yu Shuai Wang Kun Luo Debo Li jianren fan State Key Laboratory of Clean Energy Utilization Zhejiang UniversityHangzhou310027China Shanghai Institute for Advanced Study of Zhejiang University Shanghai200120China Guangdong Diankeyuan Energy Technology Co. Ltd.Guangzhou510080China

Dual circulating fluidized bed(DCFB)has emerged as an efficient reactor for biomass gasification due to its unique feature of high gas-solid contact efficiency and separated reactions in two reactors,yet the understanding of complex in-furnace phenomena is still lacking.In this study,biomass gasification in an industrial-scale DCFB system was numerically studied using a multiphase particle-in-cell(MP-PIC)method featuring thermochemical sub-models(e.g.,heat transfer,heterogeneous reactions,and homogeneous reactions)under the Eulerian-Lagrangian framework.After model validation,the hydrodynamics and thermochemical characteristics(i.e.,pressure,temperature,and species)in the DCFB are comprehensively investigated.The results show that size-/density-induced segregation makes solid fuels concentrate on the bed surface.Interphase momentum exchange leads to the continuous decrease of the gas pressure axially.In the gasifier and combustor,the lower heating value(LHV)of the gas products is 5.56 MJ/Nm^(3)and 0.2 MJ/Nm^(3)and the combustible gas concentration(CGC)is 65.5%and 1.86%,respectively.The temperature in the combustor is about 100 K higher than that in the gasifier.A higher solid concentration results in a smaller value of particle heat transfer coefficient(HTC).The HTCs range from 50 to 150 W/(m^(2) K)for a solid concentration larger than 0.3 in the combustor while the HTCs range from 100 to 200 W/(m^(2 )K)in the gasifier.The Reynolds number of biomass particles is two orders of magnitude larger than that of the sand particle.The numerical results shed light on the reactor design and process optimization of biomass gasification in DCFBs.

关键词： Dual fluidized bed Biomass gasification Numerical simulation MP-PIC Heat transfer coefficient

Direct Numerical Simulation of Particle Dispersion in the Flow Around a Circular Cylinder

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Journal of Thermal Science 2004年第4期13卷 344-349页

作者： Lan Liu Feng Ji jianren fan Kefa Cen Inst. of Thermal Power Eng. Zhejiang Univ. Hangzhou 310027 China

The major objective of the paper is to use direct numerical simulation method to get the dispersion patterns of different Stokes number particles in cylinder wake at low Reynolds numbers. The gas fluid structure is simulated by a spectral-element method with third-order accuracy. Non-reflecting boundary condition is specified for the outlet downstream boundary. Lagrangian approach is used to trace particle trajectory. The simulation results show factors to be considered to characterize the particle dispersion and find different particle dispersion pattern in a circular cylinder wake and in a plane wake.

关键词： direct numerical simulation wake particle dispersion gas-solid fluid.

Numerical study on three-dimensional CJ detonation waves interacting with isotropic turbulence

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Science Bulletin 2016年第22期61卷 1756-1765页

作者： Tai Jin Kun Luo Qi Dai jianren fan State Key Laboratory of Clean Energy Utilization Zhejiang University

The three-dimensional structures of a cellular detonation wave interacting with different turbulent flows were investigated using a one-step irreversible Arrhenius kinetics model. High-resolution bandwidth-optimized WENO scheme of spatial discretization and total variation diminishing temporal integration are used to solve the three dimensional chemically reactive Navier–Stokes equations.The turbulent vertical and entropic forcing effects on the three dimensional detonation wave structures and dynamics are analyzed, as well as the detonation effects on turbulent vortex structures. It has been found that the turbulence field imposed has created small scale wrinkles embedded in the detonation front, apart from the large scale features of detonation without turbulence. The detonation propagating velocity over the leading shock front varies from 0.8 to 1.6 times of CJ velocity and its probability density function(pdf) skews towards sub-CJ velocity and peaks at about 0.9. The recorded detonation velocity always preferentially decays with time, with very rapid accelerations through triple point interactions. Its pdf also skews to sub-CJ velocity, while its overall shape agrees well with V–3. The reaction zone is greatly influenced by the vortex, much more irregular and elongated for the turbulent cases. Distributed burning pockets are more likely to be found there. The turbulent kinetic energy is amplified across the detonation, and periodically oscillates downstream the detonation. The off-diagonal components of Reynolds stress also show a rapid rise across the detonation and present to be non-zero downstream of detonation. Vortex structures are compound results of theconvected vortex and the generated vortex by the collision of triple points. The convection term and baroclinic generation term in the transport equation of enstrophy are compared in detail.

关键词：指导数字模拟 CJ 爆炸骚乱爆炸结构

Correlation Analysis on the SGS Velocity between Phases in an Isotropic Gasparticle Two-phase Flow with FDF Model

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Journal of Thermal Science 2012年第5期21卷 447-451页

作者： Hanhui Jin Yuhui Chen jianren fan Kun Luo School of Aeronautics and Astronautics Zhejiang University Hangzhou 310027 China State Key Laboratory of Clean Energy Utilization Zhejiang University Hangzhou 310027 China

Correlation of the SGS (sub-grid scale) velocity between the two phases in an isotropic gas-particle two-phase flow was numerically investigated with FDF model. The results show the SGS gas velocity seen by the particles varies with the relative velocities between particle phase and gas phase. The relative velocity between the two phases produces the effect of the anisotropic turbulence on the particles. The variation of Stokes number influences the magnitude of the interaction between the two phases.

关键词：相对速度各向同性 SGS 两相流 FDF 相关性分析 Stokes数中相

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壁面边界层附近高温圆柱绕流的直接数值模拟

工程热物理学报 2024年第6期45卷 1757-1762页

作者：王凯越王海鸥罗坤樊建人浙江大学能源清洁利用国家重点实验室杭州310027

本文使用直接数值模拟对等温和非等温条件下壁面附近的二维圆柱绕流进了研究。在层流条件下,讨论了间隙比G/D(G为圆柱下表面和壁面的距离,D为圆柱直径)以及传热对圆柱周围流场和圆柱受力的影响。当G/D=0.5时,圆柱下表面的涡脱落会受到... 详细信息

本文使用直接数值模拟对等温和非等温条件下壁面附近的二维圆柱绕流进了研究。在层流条件下,讨论了间隙比G/D(G为圆柱下表面和壁面的距离,D为圆柱直径)以及传热对圆柱周围流场和圆柱受力的影响。当G/D=0.5时,圆柱下表面的涡脱落会受到壁面边界层抑制,在壁上形成一个较大的回流区。当G/D=1.0时,壁面回流区减小,圆柱下表面出现了涡脱落。当G/D=3.0时,流动与无壁面约束条件下的圆柱绕流相似。当圆柱温度高于流体温度时,平均升力系数减小,而曳力的振荡幅度有所增加。

关键词：圆柱绕流边界层涡脱落曳力传热

Numerical prediction of indoor airborne particle concentration in a test chamber with drift-flux model

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Journal of Thermal Science 2011年第2期20卷 161-166页

作者： Hanhui Jin Yong Chen Qinping Li jianren fan Kun Luo School of Aeronautics and Astronautics Zheiiang University Hangzhou 310027 China State Key Laboratory of Clean Energy Utilization Zhejiang University Hangzhou 310027 China

The time-dependent variation of airborne particle concentration for different sizes in a test chamber was numerically predicted with drift-flux model. The performance of the drift-flux model for particle transport in different kinds of airflow fields was analyzed. The results show the drift-flux model can predict the transport of indoor fine particles reasonably well. When the air flow field varies slowly, the model can predict both the time-dependent variation ratio of the particle concentration and final stable concentration very well, and the difference for particles with different sizes can be also well predicted. When the air flow varies drastically, the accuracy of the model is decreased due to the neglect of the particles’ independent convective terms in the air flow.

关键词：漂移通量模型颗粒浓度室内空气试验室数值预报数值预测粒子浓度空气流场

DNS analysis of incipient drop impact dynamics using an accurate level set method

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中国化学工程学报：英文版 2017年第1期25卷 1-10页

作者： Min Chai Kun Luo Changxiao Shao Song Chen jianren fan State Key Laboratory of Clean Energy Utilization Zhejiang University Hangzhou 310027 China

A series of 2D direct numerical simulations were performed with an accurate level set method for single drop impacts.The adopted ACLS method was validated to be efficient with perfect mass conservation in both normal and oblique impacts.A square-root correction for neck bases was modified in accuracy as well as scope of applications.In addition,process of jet formation and evolution was studied to reveal internal dynamics in drop impacts.It's found that pressure gradient and vortex are coexisting and completive reasons for jet topology while the inclined angle has a significant effect on them.Mechanisms of jet formation and evolution are different in the front and back necks.With the help of PDF distribution and correction calculation,a compromise in the competition is observed.This work lays a solid foundation for further studies of dynamics in gas-liquid flows.

关键词：冲击动力学水平集方法 DNS 跌落二维数值模拟内部动力学气液两相流质量守恒

On coherent structures in a three-dimensional transitional plane jet

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Science China(Technological Sciences) 2008年第4期51卷 386-396页

作者： Kun Luo&Email:zjulk@*** Jie Yan jianren fan KeFa Cen State Key Laboratory of Clean Energy Utilization Zhejiang University Hangzhou 310027 China

Direct numerical simulation of coherent structures in the three-dimensional transitional jet with a moderate Reynolds number of 5000 was conducted. The finite volume method was used to discretize the governing equations in space and the low-storage, three-order Runge-Kutta scheme was used for time integration. The comparisons between the statistical results of the flow field and the related experimental data were performed to validate the reliability of the present numerical schemes. The emphasis was placed on the study of the spatial evolution of the three-dimensional coherent vortex structures as well as their interactions. It is found that the evolution of the spanwise vortex structures in three-dimensional space is similar to that in two-dimensional jet. The spanwise vortex structures are subject to three-dimensional instability and induce the formation of the streamwise and lateral vortex structures. Going with the breakup and mixing of the spanwise vortex structures, the streamwise and transverse vortex tubes also fall to pieces and the mixing arranged small-scale structures are formed in the flow field. Finally, the arrangement relationship among the spanwise, the streamwise and the lateral vortex structures was analyzed and their interactions were also discussed.

关键词： coherent structures three-dimensional plane jet direct numerical simulation finite volume method interactions

Group　Theory　Analysis　of　Free　Convective　BoundaryLayer　Behavior　at　a　Stretching　Surface

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Journal of Thermal Science 1995年第4期4卷 229-235页

作者： Junmei Shi Xuezi Xu jianren fan Kefa Cen (Department of Energy Engineering, +Department of Mechanics, Zhejiang University, Hangzhou, 310027,China) Department of Energy Engineering Zhejiang University Hangzhou China Department of Mechanics Zhejiang University Hangzhou China

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关键词：拉伸表面边界层对流群论分析