CFD Simulation of a Hyperloop Capsule Inside a Low-Pressure Environment Using an Aerodynamic Compressor as Propulsion and Drag Reduction Method

Abstract

One of the most restrictive conditions in ground transportation at high speeds is aerodynamic drag. This is even more problematic when running inside a tunnel, where compressible phenomena such as wave propagation, shock waves, or flow blocking can happen. Considering Evacuated-Tube Trains (ETTs) or hyperloops, these effects appear during the whole route, as they always operate in a closed environment. Then, one of the concerns is the size of the tunnel, as it directly affects the cost of the infrastructure. When the tube size decreases with a constant section of the vehicle, the power consumption increases exponentially, as the Kantrowitz limit is surpassed. This can be mitigated when adding a compressor to the vehicle as a means of propulsion. The turbomachinery increases the pressure of part of the air faced by the vehicle, thus delaying the critical conditions on surrounding flow. With tunnels using a blockage ratio of 0.5 or higher, the reported reduction in the power consumption is 70%. Additionally, the induced pressure in front of the capsule became a negligible effect. The analysis of the flow shows that the compressor can remove the shock waves downstream and thus allows operation above the Kantrowitz limit. Actually, for a vehicle speed of 700 km/h, the case without a compressor reaches critical conditions at a blockage ratio of 0.18, which is a tunnel even smaller than those used for High-Speed Rails (0.23). When aerodynamic propulsion is used, sonic Mach numbers are reached above a blockage ratio of 0.5. A direct effect is that cases with turbomachinery can operate in tunnels with blockage ratios even 2.8 times higher than the non-compressor cases, enabling a considerable reduction in the size of the tunnel without affecting the performance. This work, after conducting bibliographic research, presents the geometry, mesh, and setup. Later, results for the flow without compressor are shown. Finally, it is discussed how the addition of the compressor improves the flow behavior and power consumption of the case.

Methodology for a Numerical Multidimensional Optimization of a Mixer Coupled to a Compressor for Its Integrationin a Hyperloop Vehicle

“…However, in the context of the present paper, amongst these proposed solutions, the most interesting one is the proposal of using a compressor [20,21]. It shows that by implementing an air bypass system such as a compressor that crosses the pod, the air passing through the area between the pod and the tube will be reduced, and therefore the velocity of the pod could be increased [22,23]. Moreover, the larger the flow that the compressor is able to handle, the greater the drag reduction.…”

“…On the other hand, the axial flow velocity into the compressor can be calculated using the continuity equation. For an operating pressure of 10 kPa [22], the tube density can be calculated, assuming an undisturbed flow from the equation of state. )…”

“…Moreover, the larger the flow that the compressor is able to handle, the greater the drag reduction. However, within the found literature, the problem of the adaptation of a compressor in the internal aerodynamic system has not been addressed, as these works [20][21][22][23] consider the compressor and the nozzle by means of a simple model in which some mass flow is swallowed at the vehicle front and discharged at its rear part. The current work therefore predicts for the first time the flow field in the compressor and the downstream geometry in the framework of a hyperloop system.…”

CFD Simulation on Aerodynamic Performance of Hyperloop Vehicle

“…Zhang et al, [11] outlined a few important problems with evacuated tube transportation systems that need to be taken into account during the design phase. Lluesma-Rodríguez et al, [12] outlined on what would happen in a closed and controlled environment of a ETT which can be written as Evacuated tube train.…”

Numerical Investigation of Aerodynamic Characteristics of Hyperloop System Using Optimized Capsule Design

“…Capsule size consideration got important when Nick and Sato [16] used the Gamma transition model to determine aerodynamics and Fomin and Nalivaychenko [17] tried to estimate the range of possible values of drag force, possible values of lift force, and aerodynamic heating. Wave creation in high-speed transport is a common phenomenon [18]- [20]; following this, Le et al [21] investigated the aerodynamic drag and pressure waves in different Hyperloop systems. Here a twodimensional, axisymmetric, transient, dynamic mesh model was used to simulate waves formed by a high-speed pod moving inside a tunnel.…”