Abstract The objective of this study was to develop a stochastic model for flow behavior of starchy melts inside an extruder barrel and bubble growth dynamics after exiting the extruder and obtain the variability of the end product characteristics, using the variability of operating conditions (screw speed, water injection) and material properties (consistency coefficient). The model was written in Visual Basic and experimentally validated using pilot-scale twin screw extrusion of corn meal based expanded products. Process and product data was measured at different in-barrel moisture contents (19–28 g/100g dry basis) and screw speeds (250–330 rpm). The variability in input parameters was characterized using a Data Acquisition System and Monte Carlo Simulation was used to incorporate this variability into the model. The coefficient of variation (CV) of expansion ratio obtained from the model (0.24–3.11%) compared well with CV of the experimental expansion ratio (2.54–4.89%). This model was also used to conduct sensitivity analysis for understanding which raw material and process characteristics contribute most to product variability. Sensitivity analysis showed that the relative increase in CV of expansion ratio was affected more by the CV of water added in extruder (160.5%) as compared to screw speed (3.25%) and consistency index coefficient (25%).

中文翻译：

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挤压过程中淀粉熔体膨胀的随机模拟

摘要 本研究的目的是为挤出机机筒内淀粉熔体的流动行为和离开挤出机后气泡生长动力学开发一个随机模型，并利用操作条件（螺杆速度、注水）和材料特性（稠度系数）。该模型是用 Visual Basic 编写的，并使用基于玉米粉的膨胀产品的中试规模双螺杆挤出进行了实验验证。在不同的桶内水分含量（19–28 g/100g 干基）和螺杆速度（250–330 rpm）下测量工艺和产品数据。使用数据采集系统表征输入参数的可变性，并使用蒙特卡罗模拟将这种可变性合并到模型中。从模型中获得的膨胀率变异系数 (CV) (0.24–3.11%) 与实验膨胀率的变异系数 (CV) (2.54–4.89%) 相比较。该模型还用于进行敏感性分析，以了解哪些原材料和工艺特性对产品可变性的贡献最大。敏感性分析表明，与螺杆速度（3.25%）和稠度指数系数（25%）相比，膨胀比CV的相对增加受挤出机中加入水的CV（160.5%）的影响更大。