Blade Excitation in Pulse-Charged Mixed-Flow Turbocharger Turbines

In this article, a fully three-dimensional computational modeling approach in the time and frequency domain is presented which allows to accurately predicting fluid-structure interactions (FSI) in pulse-charged mixed-flow turbocharger turbines. As part of the approach, a transient computational fluid mechanics analysis is performed based on the compressible inviscid Euler equations covering an entire engine cycle. The resulting harmonic orders of aerodynamic excitation are imposed in a forced response analysis of the respective eigenvector to determine effective stress amplitudes. The modeling approach is validated with experimental results based on various mixed-flow turbine designs. It is shown that the numerical results accurately predict the measured stress levels. The numerical approach can be used in the turbine design and optimization process. Aerodynamic excitation forces are the main reason for high cycle fatigue in turbocharger turbines and therefore, a fundamental understanding is of key importance.