Numerical characterization of a hyperloop propelling nozzle and its adaption to an experimental wind tunnel

Abstract

Hyperloop systems, where a pod travels at high speed within a tube under rarefied conditions, have a maximum speed limit due to the Kantrowitz effect. One solution to overcome this limit is to include a circuit with a fan that can also assist the pod's propulsion through a nozzle at the vehicle's rear. This paper focuses on analyzing the propulsive efficiency of these coaxial jets within a tube at low-pressure conditions. The paper's objective is to use a computational fluid dynamics tool to design an experiment in a wind tunnel with a steady tube and vehicle that could reproduce the actual operation of a stationary tube and a moving vehicle. Several issues are dealt with. First, the effect of the vehicle's front design on the coaxial jets, which resulted be negligible. Additionally, the increase in temperature in the compressor circuit can be neglected, simplifying the experimental arrangement. Third, scaling the wind tunnel prototype shows that the difference in size can be compensated by setting the test pressure at ambient conditions. Finally, considering steadiness in the vehicle in the test leads to a different velocity pattern in the coaxial jets. Several changes in the tube's geometry are proposed and analyzed to address this problem. The results demonstrate that it is possible to replicate the actual coaxial jets in steady conditions with a small tapered section in the tube. Furthermore, this modification can be used over a relatively large range of operating conditions and for different rear pod designs.