Experimental investigation on the effect of pulsations on exhaust manifold-related flows aiming at improved efficiency

Abstract

The gas flowing through the exhaust manifold of the internal combustion engine to the inlet of the turbine side of a turbocharger is highly pulsating and turbulent. The gas enters the turbine after travelling through a complex curved and branched pipe system where the effect of centrifugal (from the acute curvature), inertia and viscous forces result in a three-dimensional, non-symmetric flow field. Additionally, vortical structures are being formed and dissolved due to the co-existence of these forces that change in magnitude under a pulse period. This complex flow field, typical for the inflow condition to the turbine, is the focus of the present study. Instantaneous mass flow rate and pressure measurements that provide information on changes in the turbine map when a sharp bend is mounted at the inlet of the turbine are performed and complemented with time-resolved stereoscopic particle image velocimetry measurements of the pulsating turbulent flow downstream a 90° pipe bend. The results indicate, that the time-averaged operation point in a turbine map is only marginally affected by the inflow conditions and the pulsation frequency. The hysteresis loops, on the other hand, exhibit differences not only for different pulsation frequencies, but also for different inflow conditions as a comparison between a straight and a curved pipe section upstream the turbine shows.