A turbocharger unsteady performance model for the GT -Power internal combustion engine simulation

Turbochargers are utilized in a wide variety of applications, including heavy duty diesel engines involved in over-the-road transportation. Historically, turbocharger design has relied heavily on steady and quasi-steady flow design principles to determine performance and sizing. With the wide spread usage of pulse turbochargers, these steady and quasi-steady methods have been shown to be invalid due to the large fluctuations in exhaust gas properties entering the turbine portion of the turbocharger. Models created to determine unsteady turbocharger performance have relied heavily on steady performance maps, or have simplified the problem to the extent that the driving physics behind the unsteady flow has been adversely affected. To address the need for an accurate unsteady prediction tool for turbocharger performance and design, the unsteady Euler equations will be utilized to create a model which includes the effects of fluid inertia. The model creates a series of 1-D problems linked together to simulate the various components that comprise the turbocharger. For rotating components, the governing equations are transformed into the rotating reference frame to preserve the 1-D character of the model, while still allowing the full unsteady representation of the flow. The Euler equations are solved using an upwinded explicit finite volume method, with a 4th order Runge-Kutta time integration algorithm. Losses are included in the model, but are determined based on the steady performance values since the inviscid model cannot determine actual operating losses. The resulting model will be incorporated into the GT-Power engine simulation code to predict on-engine performance