组合桨微波反应釜内流动混合特性数值模拟
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摘要
针对微波反应釜搅拌混合均匀性问题,设计具有不同桨型组合的双层搅拌结构微波反应釜,其组合方式上下桨为推进式搅拌桨A100(A1)、上桨A200下桨A100(A2)和上桨A100下桨A200(A3)。基于计算流体力学CFD(Computational Fluid Dynamics)方法,采用层流模型、组分扩散模型和多重参考系方法对微波反应釜内醇油混合液的流动混合特性进行数值模拟,获得了具有3种不同组合桨反应釜内混合液的流动特性和不同加料位置下的混合时间特征。结果表明:组合桨A1釜内上下桨间存在一个轴向速度趋近于零的环流面,该面影响了釜内混合液的轴向流动混合;而组合桨A2、A3,改善了该环流面上的轴向速度分布,其最大轴向速度分别是组合桨A1的1.22,2.28倍,增强了上下桨间混合液的轴向迁移能力;加料点的位置会影响反应釜内混合液的混合时间,在理想加料点B加料时,组合桨A3的混合时间最短。
In order to investigate mixing uniformity in microwave reactor,the microwave reactors with dual stirring structure were designed,combined by the upper and lower impellers A100(A1),the upper impeller A200 and lower impeller A100(A2),and the upper impeller A100 and lower impeller A200(A3). Based on Computational Fluid Dynamics(CFD)method,laminar model,component diffusion model and multi-reference frame method(MRF)were used to simulate flow mixing characteristics of the alcohol-oil mixture in these microwave reactors.The flow characteristics of the alcohol-oil mixture and mixing time characteristics at different feeding positions in these microwave reactors were obtained.The results showed that there was a circulation flow surface with axial velocity approaching zero between the upper and lower impellers in microwave reactor with combined impeller A1,which affected the axial flow mixing of the mixture.The combined impeller A2 and A3 improved the axial velocity distribution on circulation flow surface,with the maximum axial velocity 1.22 times and 2.28 times of the combined impeller A1,respectively.Meanwhile it enhanced the axial migration capability of mixture between the upper and lower impeller.The position of the feeding point could affect the mixing time of mixture in microwave reactor.The combined impeller A3 obtains the shortest mixing time at the ideal feeding point B.The study provided a practical theoretical reference for the design,selection and application of the microwave reactor combined impellers.
In order to investigate mixing uniformity in microwave reactor,the microwave reactors with dual stirring structure were designed,combined by the upper and lower impellers A100(A1),the upper impeller A200 and lower impeller A100(A2),and the upper impeller A100 and lower impeller A200(A3). Based on Computational Fluid Dynamics(CFD)method,laminar model,component diffusion model and multi-reference frame method(MRF)were used to simulate flow mixing characteristics of the alcohol-oil mixture in these microwave reactors.The flow characteristics of the alcohol-oil mixture and mixing time characteristics at different feeding positions in these microwave reactors were obtained.The results showed that there was a circulation flow surface with axial velocity approaching zero between the upper and lower impellers in microwave reactor with combined impeller A1,which affected the axial flow mixing of the mixture.The combined impeller A2 and A3 improved the axial velocity distribution on circulation flow surface,with the maximum axial velocity 1.22 times and 2.28 times of the combined impeller A1,respectively.Meanwhile it enhanced the axial migration capability of mixture between the upper and lower impeller.The position of the feeding point could affect the mixing time of mixture in microwave reactor.The combined impeller A3 obtains the shortest mixing time at the ideal feeding point B.The study provided a practical theoretical reference for the design,selection and application of the microwave reactor combined impellers.
引文
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[3]孙培永,张利雄,姚志龙,等.新型反应器和过程强化技术在生物柴油制备中的应用研究进展[J].石油学报:石油加工,2008,24(1):1-8.
[4]曹湘琪,姚斌,郑勤红,等.凹弧面内筒壁对微波反应器加热效率及均匀性的影响[J].现代制造工程,2016(9):13-16.
[5]钟汝能,姚斌,向泰,等.腔体内壁脊形凹槽对微波反应器加热效率及均匀性的影响[J].食品与机械,2017,33(4):81-85.
[6]杨继孔,郑勤红,曹湘琪,等.高功率矩形微波反应器加载圆柱形负载的仿真优化[J].云南师范大学学报:自然科学版,2014,34(6):14-18.
[7]DOMINGUEZ T E,PLAZA G P,DIAZMORCILLO A,et al.Optimisation of electric field uniformity in microwave heating systems by means of multi-feeding and genetic algorithms[J].International Journal of Materials and Product Technology,2007,29(1):149-162.
[8]ROMANO V R,MARRA F,TAMMARO U.Modelling of microwave heating of foodstuff:study on the influence of sample dimensions with a FEM approach[J].Journal of Food Engineering,2005,71(3):233-241.
[9]贺强.钨矿机械活化碱煮设备性能仿真分析[D].赣州:江西理工大学,2013:1-9.
[10]ZHANG Jin-jin,GAO Zheng-ming,CAI Ya-ting,et al.Power consumption and mass transfer in a gas-liquid-solid stirred tank reactor with various triple-impeller combinations[J].Chemical Engineering Science,2017,170:464-475.
[11]CHENG Dang,FENG Xin,CHENG Jing-cai,et al.Experimental study on the dispersed phase macro-mixing in an immiscible liquid-liquid stirred reactor[J].Chemical Engineering Science,2015,126(APR):196-203.
[12]ZHU Hua-cheng,YE Jing-hua,GULATI T,et al.Dynamic analysis of continuous-flow microwave reactor with a screw propeller[J].Applied Thermal Engineering,2017,123:1 456-1 461.
[14]周俊超,车圆圆,吴可君,等.基于CFD模拟的强放热反应釜盘管空间排布的优化设计[J].高校化学工程学报,2015(1):27-34.
[15]汪博恺,金光远,崔政伟,等.微波反应器的搅拌叶轮性能数值分析及对比[J].热能动力工程,2017(s1):91-96.
[16]梁瑛娜,高殿荣,拜亮.双层桨搅拌槽内层流流场与混合时间的数值模拟[J].机械工程学报,2015,51(16):185-195.
[17]梁瑛娜,高殿荣,拜亮.偏心组合桨搅拌槽内层流混合过程的数值模拟[J].化工进展,2014,33(12):3 203-3 209.
[18]方德明,陈涛,杨象岳,等.基于CFD流场分析的反应釜搅拌器结构改进[J].轻工机械,2014,32(2):95-98.