新型混炼单螺杆植物蛋白挤出机的仿真分析与参数优化

Simulation analysis and parameter optimization of new mixing single screw vegetable protein extruder

为了提高单螺杆挤出机中花生蛋白的挤出品质,基于拉伸应力的破碎效应,以传统单螺杆挤出机为参照,利用有限元软件CFX计算了花生蛋白在流场中的运动情况,通过压力场、速度流线场以及应变速率场,分析新型混炼单螺杆挤出机的特性,并以拉伸流变学理论对设计原理进行验证,同时采用响应面法对新型混炼单螺杆挤出机的工艺参数进行优化。结果表明:新型混炼单螺杆挤出机中混炼元件的分流作用使得沿挤出方向产生了压力降,物料发生回流,导致建压性能降低,从而延长了停留时间,此处因回流效果产生的局部高压也有利于压延,物料在流经抛物线曲面时既能经历周向拉伸,又能经历径向拉伸,分散混合效果更好;经模拟计算,发现新型混炼单螺杆挤出机的平均应变速率相较于传统单螺杆挤出机提高了16.5%,使得挤出产品质量更优;各因素对花生蛋白平均应变速率的影响顺序依次为螺杆转速、收敛比、分割棱厚度,新型混炼单螺杆挤出机最优工艺参数为螺杆转速128 r/min、收敛比6.6、分割棱厚度3.1 mm,在此条件下花生蛋白的理论平均应变速率为50.945 s^(-1)。综上,新型混炼单螺杆挤出机中由于拉伸流场的形成,有效提高了花生蛋白的挤出品质。

In order to improve the extrusion quality of peanut protein in single screw extruder,based on the crushing effect of tensile stress,the traditional single screw extruder was used as a reference,the finite element software CFX was used to calculate the movement of peanut protein in the flow field,the characteristics of the new mixing single screw extruder was analyzed through the pressure field,velocity streamline field and strain rate field,the design principle with tensile rheological theory was verified,and the process parameters of the new extruder were optimized by response surface methodology.The results showed that the diversion effect of the mixing element in the new extruder made the pressure drop along the extrusion direction,and the material flows back,resulting in reduced pressure building performance,thereby prolonging the residence time,and the local high pressure generated by the reflux effect here was also conducive to calendering,the material could experience both circumferential stretching and radial stretching when flowing through the parabolic surface,and the dispersion mixing effect was better.After simulation calculation,it was found that the average strain rate of the new extruder was 16.5%higher than that of the traditional extruder,which made the quality of extrusion product better.The order of influence of each factor on the average strain rate of peanut protein was screw speed,convergence ratio,segmentation prism thickness,and the optimal process parameters of the new single screw extruder were screw speed 128 r/min,convergence ratio 6.6,and segmentation prism thickness 3.1 mm.Under the optimal conditions,the theoretical average strain rate of peanut protein was 50.945 s^(-1).In conclusion,the extrusion quality of peanut protein is effectively improved due to the formation of tensile flow field in the new mixing single screw extruder.