Unsteady Behavior in Turbocharger Turbines: Experimental Analysis and Numerical Simulation

The flow in engine turbocharger compressors and turbines is highly unsteady in nature, as it responds to the intake and exhaust manifolds of the internal combustion engine. The optimization of the turbocharger system is therefore a very difficult task, since the devices operate at off-design conditions for most of the engine cycle. Experimental studies allow for improving the understanding on the behavior of the engine components, in particular when tests are performed under real engine operating conditions; however, the experimental tests can be more efficient if they are combined with theoretical simulation tools, which help to select significant engine operating conditions. In this paper, experimental investigations were performed on a flexible component test rig (expressly suited to perform tests on automotive turbochargers) at ICE Laboratory of the University of Genoa (ICEG-DIMSET). Then the test stand configuration and operation were simulated; an approach to model the engine turbocharger working under unsteady operating conditions, implemented in the GASDY N 1D thermo-fluid dynamic code (developed at Politecnico di Milano) is described. The validation of the code against the experimental results is presented.