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Modern pulse-turbocharged systems produce a turbine operating environment that is dominated by unsteady flow. Effective utilization of the unsteady exhaust gas energy content at the turbine inlet is critical to achieving optimum system efficiency. This work presents predictions for turbocharger unsteady performance from a model based on the Euler equations with source terms (EEST). This approach allows the time-accurate performance of the turbine to be determined, allowing comparisons of actual energy utilization and that estimated from steady flow performance maps.

Swirl/tumble are rotational flow inside the combustion chamber. Fluent Computational Fluid Dynamics (CFD) software has been successfully used to simulate engine swirl and tumble flow. Two mesh approaches are possible within Fluent software to calculate transient engine swirl and tumble. One approach uses hybrid mesh with remeshing, while the other approach uses hex/wedge mesh with layering. The hybrid method employs tetrahedral remeshing, and is easier to set up compared to hex/wedge method for which only layering is used. Being easier to use, the hybrid method raises some concerns about result accuracy due to higher numerical diffusion associated with tet elements compared to the corresponding hex/wedge elements used for layering approach. This paper examines the two mesh approaches in terms of result accuracy for two engines, one SI and one diesel. The results are compared with PIV data for the SI engine.