Particle Image Velocimetry Characterization of a Turbocharger Turbine Inlet Flow

Modern diesel engines typically utilize pulse-turbocharging where an increase in exhaust gas transport efficiency is achieved at the expense of creating a highly unsteady flow through the turbine which may have a detrimental effect on turbine performance. As the turbocharger plays a major role in the performance and emissions of the engine system, the characterization of on-engine turbocharger aerodynamics is critical. Thus, this paper is directed at the investigation of the turbocharger turbine volute inlet flowfield on an in-line, six cylinder, diesel engine. Specifically, Particle Image Velocimetry (PIV), a quantitative non-intrusive whole flowfield measurement technique, is used to perform a detailed study of the on-engine pulsating flowfield at the volute inlet of the twin-entry turbocharger turbine. Wall static pressure and PIV measurements on the horizontal center-plane of the turbine volute inlet are obtained to characterized the turbine inlet flowfield during a single typical valve event. The flowfield was found to be comprised of two distinct exhaust flow pulses. The data also indicate uniform flow distributions during the initial flow acceleration at exhaust valve opening, with flow nonuniformities developing during subsequent blowdown and exhaust stroke. Of significant interest are the differences between the measured static pressure and velocity waveforms during the exhaust stroke. These data indicate that both simply convected and potential disturbances make significant contributions to gas transport from the exhaust valve to the turbine volute inlet. As a result, turbine performance estimated in off-engine facilities may not be sufficient to predict the on-engine performance of the turbocharger.