On-Engine Turbocharger Turbine Inlet Flow Characterization

Increased power and fuel efficiency requirements ofmodern vehicle diesel engines have lead to wide pread use of turbocharging to increase engine power-to-weight ratio. Typically, these systems employ pulse-turbocharging where an increase in exhaust gas transport efficiency is achieved at the expense of creating a highly unsteady flow through the turbine. This imposed unsteadiness is known to have a significant effect on turbine performance. To date, research performed to quantify the effects of exhaust pulsations on the performance of radial turbocharger turbines has been performed in off-engine facilities which simulate the engine manifold conditions. However, to better gauge the applicability of these data, a detailed investigation into the actual on-engine turbocharger operating environment is required.

Research at Purdue University is focused on the characterization of the nature of the on-engine turbine operating environment and how it relates to turbocharger performance. As part of this effort, measurements at the turbine inlet in an in-line six cylinder Cummins B-series diesel engine have been made to characterize the nature of the turbine inlet waveform and its relation to exhaust valve events. Measurements of the instantaneous velocity with Particle Image Velocimetry, in addition to unsteady stagnation pressure, static pressure, and static temperature measurements have been made with a goal of understanding the relevant mechanisms of energy transport from the engine cylinder to the turbine inlet durin. the exhaust valve event. Observation of the periodic crank-ensemble-averaged component of these signals indicates that both convective and acoustic time scales are important in energy transport to the turbine inlet such that this transport can not be accurately modeled as either a simple convection or a simple acoustic propagation.