Effect of Operational Pressure Reduction on Axial Compressor Performance by Means of 3D CFD Modeling at Nominal Operating Speeds

Abstract The hyperloop system constitutes one of the most promising alternative means of transportation for the next years. Nevertheless, there are still some challenges to face, such as the blockage of the air surrounding the pod inside the tube. To solve that, one proposal consists of including a compressor that helps to relieve the pressure conditions between the pod and the tube. Thus, this work makes, for the first time in this context application, a numerical analysis with CFD tools of the performance of the compressor under low Reynolds conditions by decreasing the pressure of the system until hyperloop operation values. By doing so, it is observed how the compressor performance slightly decreases with the pressure. From this point, the efficiency is severely affected until the point where the compressor is totally lost. The flow analysis supported this idea. Initially, at high Reynolds, the flow behaved completely turbulent, and almost no separation was observed in the boundary layer. Later, some separation started to appear, but the turbulent nature of the boundary layer allowed the reattachment of it. Eventually, it was observed how the laminar conditions of the boundary layer at low Reynolds constitute the main reason for the huge detachments that appear. Other aspects were also explored, such as the interstitial losses at the tip, which seemed to work in the opposite direction, that is, decreasing with the lower pressures, but being globally way less important than the losses generated by the flow detachment. Therefore, this work suggests that decreasing the pressure could have a big impact on the propulsive system of a hyperloop vehicle, even opening the door to develop an ad hoc turbomachine for its purpose.