Abstract A cryogenic twin-screw extruder for plasma fuelling is under development at Institute for Plasma Research (IPR), India. The fuel for Indian tokamaks SST-1 and Aditya-Upgrade is injected in the form of frozen hydrogen pellets; the current injector design has a pipe gun based concept, cooled by a GM-cryocooler. An advanced fuelling system will produce hydrogen pellets continuously using a twin-screw extruder, cooled by a GM-cryocooler. The viscous dissipation is one of the critical design parameters for the extruder system which determines the screw torque as well as the required cryocooler heat load. The performance of an extruder is assessed by measuring the pressure development for different throughput. In the current investigation, CFD model has been developed using ANSYS POLYFLOW under cryogenic temperature. A computational model for non-Newtonian isothermal solid hydrogen flow in the screw channel was developed and used to calculate extruder efficiency and viscous dissipation rate. The shear-rate-dependent viscosity law was applied in the present analysis for shear stress modelling of solid hydrogen in the temperature interval from 10 to 13 K. The effect of screw rotation speeds (5-20 rpm) on the viscous dissipation rate and pressure development at required throughput was also examined. As the screw rotation speed reduces, the viscous dissipation rate reduces. The results show that as temperature increases, the viscous dissipation rate and pressure development reduces. The analysis also revealed that the operating point of extruder-die system is highly sensitive to the screw rotation speed.

中文翻译：

---

用于 Cryogenics 双螺杆氢气挤出机系统分析的 CFD 模型的开发

摘要 印度等离子研究所 (IPR) 正在开发一种用于等离子燃料的低温双螺杆挤出机。印度托卡马克SST-1和Aditya-Upgrade的燃料以冷冻氢颗粒的形式注入；当前的喷射器设计具有基于管枪的概念，由 GM 低温冷却器冷却。先进的燃料系统将使用双螺杆挤出机连续生产氢颗粒，由 GM 低温冷却器冷却。粘性耗散是挤出机系统的关键设计参数之一，它决定了螺杆扭矩以及所需的低温冷却器热负荷。通过测量不同产量的压力发展来评估挤出机的性能。在目前的调查中，CFD 模型已在低温下使用 ANSYS POLYFLOW 开发。开发了螺杆通道中非牛顿等温固体氢流动的计算模型，并用于计算挤出机效率和粘性耗散率。剪切速率相关的粘度定律应用于当前分析中固体氢在 10 到 13 K 温度区间的剪切应力建模。 螺杆转速 (5-20 rpm) 对粘性耗散率和压力的影响还检查了在所需吞吐量下的开发。随着螺杆转速降低，粘性耗散率降低。结果表明，随着温度的升高，粘性耗散率和压力发展降低。分析还表明，挤出机-模具系统的工作点对螺杆转速高度敏感。