采用气液两相流模型结合RNG k-ε紊流模型(FLUENT 6.3)对60°弯道内布设丁坝时的水力特性进行了数值模拟,自由液面的捕捉采用VOF(Volume of Fluid)法,速度与压力的耦合方程组利用半隐式SIMPLE(Semiimplicit Method for Pressure-lin...采用气液两相流模型结合RNG k-ε紊流模型(FLUENT 6.3)对60°弯道内布设丁坝时的水力特性进行了数值模拟,自由液面的捕捉采用VOF(Volume of Fluid)法,速度与压力的耦合方程组利用半隐式SIMPLE(Semiimplicit Method for Pressure-linked Equations)算法求解,控制方程采用有限体积法离散。将弯道内布设直丁坝时流速和水位的模拟结果与试验数据进行了比较,两者吻合较好。随后用该模型研究了T型丁坝对弯道水力特性的影响并与直丁坝进行了比较,结果表明:T型丁坝在调整水面横比降、减小坝后回流区长度、改善弯道水流流态等方面较直丁坝有明显优势。展开更多
A hydrodynamic model of liquid-solid circulating fluidized bed is proposed to predict the slip velocity between fluid and solid particles and bed voidage by applying the theory of two-phase flow.The slip velocity can ...A hydrodynamic model of liquid-solid circulating fluidized bed is proposed to predict the slip velocity between fluid and solid particles and bed voidage by applying the theory of two-phase flow.The slip velocity can be represented by the following equation.u s =u-v=(1-ε)(ρ p -ρ f )g+F p -(1-ε)F f /εβ/εExperiments were carried out by using water and ceramic spheres,1.43 and 3.06 mm in mean diameter in a circulating fluidized bed of 31 mm diameter and 1700 mm height.The voidage was from 0.96 to 1,and the ratio between superficial liquid velocity and particle terminal velocity varied from 1.22 to 10.1 in the experiments.The fluid-particle interphase drag coefficient in the model was correlated from experimental data as followsd p βρ f =0.1881(1-ε) 1.0089 UU t -0.8043 d p D t -0.3228 The predicted values by the model proposed agreed with the experimental data well.In the meantime,the variation of slip velocity with superficial liquid velocity,bed voidage and particle diameter was discussed.The results showed that the model in the paper can well predict the hydrodynamics of liquid-solid two-phase flow in circuiating fluidized bed.The model is suitable for liquid-solid circulating fluidized bed under high flow rate and low concentration and can be also used on each tube in liquid-solid circulating fluidized bed heat exchanger.展开更多
文摘采用气液两相流模型结合RNG k-ε紊流模型(FLUENT 6.3)对60°弯道内布设丁坝时的水力特性进行了数值模拟,自由液面的捕捉采用VOF(Volume of Fluid)法,速度与压力的耦合方程组利用半隐式SIMPLE(Semiimplicit Method for Pressure-linked Equations)算法求解,控制方程采用有限体积法离散。将弯道内布设直丁坝时流速和水位的模拟结果与试验数据进行了比较,两者吻合较好。随后用该模型研究了T型丁坝对弯道水力特性的影响并与直丁坝进行了比较,结果表明:T型丁坝在调整水面横比降、减小坝后回流区长度、改善弯道水流流态等方面较直丁坝有明显优势。
文摘A hydrodynamic model of liquid-solid circulating fluidized bed is proposed to predict the slip velocity between fluid and solid particles and bed voidage by applying the theory of two-phase flow.The slip velocity can be represented by the following equation.u s =u-v=(1-ε)(ρ p -ρ f )g+F p -(1-ε)F f /εβ/εExperiments were carried out by using water and ceramic spheres,1.43 and 3.06 mm in mean diameter in a circulating fluidized bed of 31 mm diameter and 1700 mm height.The voidage was from 0.96 to 1,and the ratio between superficial liquid velocity and particle terminal velocity varied from 1.22 to 10.1 in the experiments.The fluid-particle interphase drag coefficient in the model was correlated from experimental data as followsd p βρ f =0.1881(1-ε) 1.0089 UU t -0.8043 d p D t -0.3228 The predicted values by the model proposed agreed with the experimental data well.In the meantime,the variation of slip velocity with superficial liquid velocity,bed voidage and particle diameter was discussed.The results showed that the model in the paper can well predict the hydrodynamics of liquid-solid two-phase flow in circuiating fluidized bed.The model is suitable for liquid-solid circulating fluidized bed under high flow rate and low concentration and can be also used on each tube in liquid-solid circulating fluidized bed heat exchanger.
