###### Abstract
[21] used a three-dimensional and a compressible turbulence model to investigate the pressure waves generated while two trains were passing each other in a tunnel. [PERSON] and [PERSON] [22] reported that the pressure waves of a high-speed train in a tunnel show complicated variations due to their propagation and superposition. [PERSON] et al. [23] did some research about the wave phenomena produced by an evacuated-tube maglev train running at a super high speed. Finally, [PERSON] et al. [24] analyzed the formation and evolution mechanism of aerodynamic heating in the tube. Other studies were performed for the Hyperloop Pod Competition [25] held by SpaceX and The Boring Company since 2016 in Los Angeles, California. For the competition, several university teams studied the effects of the shape of the capsule inside the low-pressure environment. One of the most relevant studies from these teams is the one from [PERSON] et al. [26] for Purdue University. They designed a kind of hyperloop capsule that could generate lower drag force and effective lift force inside the evacuated tube. They conducted three-dimensional computational simulations of a hyperloop system with varying capsule shapes and found that drag could be reduced by a maximum of 69% compared with the optimized lift design. Another important study was conducted by [PERSON] et al. [27] for MIT, who predicted flow separation and transition on the capsule. However, none of the previous studies, apart from the Hyperloop Alpha, considered the use of a compressor inside the evacuated tube, which is one of the main purposes of the present work. [PERSON] et al. [28] presented in 2015 an overall system of the hyperloop concept and quantified the choking risk, which is determined by the minimum section between the capsule and the inner tube wall. Furthermore, the low-pressure operation leads to low Reynolds numbers, which enhances the risk of early separation of a laminar boundary layer in the rear part of the vehicle. To overcome the choking problem, known as the Kantrowitz limit, they proposed adding a compressor to the vehicle. Then, part of the mass flow passes through the capsule itself, increasing the maximum achievable speed. This was the first time that a study of the performance of an ETT with aerodynamic propulsion was conducted. However, no CFD was performed, and only a 0D analysis was done to compute the energy consumption. They reported a difference of 0.16 on the Mach just by adding a compressor. It is important to remark that [PERSON] in [5] considered the compressor only for levitating purposes. This study aims to compare the performance of a hyperloop that uses aerodynamic propulsion operating at a certain pressure level and one that does not. This comparison is conducted at different blockage ratios and different train speeds, and it is mainly focused on evaluating the power required to maintain the speed in both cases. Moreover, from the parametric study for the blockage ratio is obtained the equivalent tunnel size that matches the same performance for both cases. The aim is to quantify the tunnel size reduction when having aerodynamic propulsion on the vehicle, as proposed by [PERSON] [5] and [PERSON] et al. [28]. For this analysis, a simplified geometric model is employed. As it has been assumed that axisymmetry on the case to reduce the computational cost, the model does not reproduce the real geometry of a maglev train. Actually, purely cylindrical shapes are used for the tube and the vehicle, the latter was perfectly placed in the middle of the former. For research purposes, this simplification is still useful to compare cases in which the capsule has or does not have the compressor installed, especially when using the blockage ratio as an independent variable, instead of absolute areas. In any case, the model is based on the Transrapid Maglev train used in [12], whose maximum speed is 505 km/h [29].