曳力模型及镜面系数对鼓泡床气固流场的影响
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摘要
为获悉曳力模型和镜面系数(ψ)对鼓泡床内流动特性的影响规律,利用颗粒动力学理论和欧拉双流体模型对鼓泡床内气固流场进行了数值模拟,考察了床层膨胀率、压降以及颗粒速度特性。实验结果表明,De Felice模型对于床层压降预测效果最好,Wen-Yu模型的固含率径向分布和颗粒速度矢量预测与实验值误差较大,Gidaspow与De Felice模型床层膨胀量接近,而De Felice模型的径向速率分布与实验值最接近;随着鼓泡床内表观气速的增加,De Felice模型对床层膨胀率的预测愈加接近实验值;随着ψ增大,壁面附近固含率较高,曲线波动梯度增大;当ψ=0.1时,固含率分布与实验值最接近,表明颗粒与壁面动量互换效果最好。
To get the in?uence rule of the drag models and the specularity coef?cients(ψ) on the ?ow characteristics in the bubbling bed,the particle dynamics theory and the two ?uid Eulerian-Eulerian model were used to simulate the gas-solid ?ow ?eld in the bubbling bed. The bed expansion ratio,pressure drop and particle velocity characteristics were investigated. The results showed that the De Felice model had the best prediction effect on the bed pressure drop. The radial distribution of the solid content of the Wen-Yu model,and the prediction of the particle velocity vectors had a large error and the amounts of the bed expansions of the Gidaspow and De Felice models were closer. The radial velocities distribution of the De Felice model was closest to the experimental values. As the super?cial gas velocity increased in the bubbling bed,the De Felice model predicted the bed expansion ratio closer to the experimental values;as ψ increased,the solid content rate near the wall was higher and the ?uctuation gradient of the curve also increased. When ψ was 0.1,the solid content distribution was closest to the experimental value,indicating that the particle and wall momentum exchange effect was best.
To get the in?uence rule of the drag models and the specularity coef?cients(ψ) on the ?ow characteristics in the bubbling bed,the particle dynamics theory and the two ?uid Eulerian-Eulerian model were used to simulate the gas-solid ?ow ?eld in the bubbling bed. The bed expansion ratio,pressure drop and particle velocity characteristics were investigated. The results showed that the De Felice model had the best prediction effect on the bed pressure drop. The radial distribution of the solid content of the Wen-Yu model,and the prediction of the particle velocity vectors had a large error and the amounts of the bed expansions of the Gidaspow and De Felice models were closer. The radial velocities distribution of the De Felice model was closest to the experimental values. As the super?cial gas velocity increased in the bubbling bed,the De Felice model predicted the bed expansion ratio closer to the experimental values;as ψ increased,the solid content rate near the wall was higher and the ?uctuation gradient of the curve also increased. When ψ was 0.1,the solid content distribution was closest to the experimental value,indicating that the particle and wall momentum exchange effect was best.
引文
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[2]Jia Dening,Bi Xiaotao,Jim L C,et al.Heat transfer in a pulsed fluidized bed of biomass particles[J].Ind Chem Res,2017,56:3740-3756.
[3]Wang Xiao,Si Hui.Conveying characteristics of dual pneumatic feeder used for biomass pyrolysis[J].Bioresour J Citation Rep,2017,12(3):5970-5983.
[4]Mittal A,Mallick S S,Wypych P W.An investigation into flow mode transition and pressure fluctuations for fluidized dense-phase pneumatic conveying of fine powders[J].Particuology,2014,7(5):187-195.
[6]Papari S,Hawboldt K.A review on the pyrolysis of woody biomass to bio-oil:Focus on kinetic models[J].Renew Sustain Energy Rev,2015,19(2):1580-1595.
[6]宋宁宁,唐晓津,侯栓弟.鼓泡床流体力学特性研究[J].石油炼制与化工,2017,48(2):89-92.
[7]刘学冰.双流化床锅炉和双流态高效洁净燃烧工艺[J].洁净煤技术,2016,22(3):84-89.
[8]李竞岌,杨欣华,杨海瑞,等.鼓泡床焦炭型氮氧化物生成的试验与模型研究[J].煤炭学报,2016,41(6):1546-1553.
[9]Sasithorn S,Benjapon C,Pornpote P.Artificial neural network model for the prediction of kinetic parametersof biomass pyrolysis from its constituents[J].Fuel,2017,193(4):142-158.
[10]张佳宝,崔丽杰,杨宁.曳力模型和湍流模型对内环流反应器数值模拟的影响[J].化工学报,2018,69(1):389-395.
[11]郑晓野.鼓泡流化床曳力模型及气固流动特性数值研究[D].南京:南京航空航天大学,2016.
[12]Johnson P C,Jackson R.Frictional-collisional constitutive relations for granular materials with application to plane slearing[J].J Fluid Mech,2006,176:67-93.
[13]袁竹林,朱立平,耿凡,等.气固两相流与数值模拟[M].南京:东南大学出版社,2013:160-168.
[14]Fronk B M,Garimella S.In-tube condensation of zeotropic fluid mixtures:A review[J].Int J Ref,2013,36(2):534-561.
[15]Allen E E,Zhu C P,James S,et al.Multicomponent condensation reactions via ortho-quinone methides[J].Org Lett,2017,19(7):1878-1881.
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