Numerical Investigation of Two-Stage Turbocharging Systems Performance

Abstract

In regulated two-stage sequential turbocharging systems, a smaller, high pressure (HP), and a larger, low pressure (LP), turbocharger are sequentially positioned to recover the energy available in the exhaust gases and deliver acceptable level of boost to the intake of an internal combustion engine. Due to the different sizes of the turbochargers, by-pass valves are placed in the system to control operations. Due to the turbocharging system layout, it is clear that the air pressurized by the LP compressor enters non-uniformly the HP compressor. This is caused by the rotating radial compressor and the interconnecting bends which cause swirl and velocity to scatter, respectively. Furthermore, the heat transfer in the two turbochargers may have an effect on the apparent efficiencies. For these reasons, the standard mapping approach for turbochargers is not able to take into account the effect of non-uniform flow and heat transfer. In this paper, a novel approach for mapping the two-stage turbocharging system is proposed and performed into a mono-dimensional simulation code. Although, flow non-uniformity and turbochargers heat transfer effects on the performance of the turbocharging system are not considered, at this present time, the study centralizes on the investigation and the validation of the mapping approach. In fact, a two-stage sequential turbocharging system has been considered for the study and a simulation code to investigate the mapping technique has been implemented.

Design of an Advanced Air Path Test Stand for Steady and Transient Evaluation

“…A settling tank was specified based on the 1D gas dynamic modeling work done with an already validated 2.2 l engine model (discussed in [27]). The 1D modeling involved studying the flow dampening effect for six different cylinder volumes as shown in Figure 3: .…”