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Exhaust Gas Recirculation (EGR) is employed widely in compression-ignited engines and currently under consideration for being implemented into spark-ignited engines. EGR cylinder-to-cylinder dispersion is one of the features of such engines that developers are challenged to abate, because low EGR rates increase NOx emissions and excessive EGR rates can produce a significant amount of particulate matter. Taking into account the complex geometries of some automotive manifolds, the treatment of this topic through 3D computational fluid-dynamics (CFD) simulations seems mandatory to study the transport phenomena in a proper way. The main objective of this work is the analysis of the influence of the numerical setup main parameters (mesh, time-step size, turbulence modeling) in a CFD URANS simulation of an automotive engine intake manifold in the EGR distribution.

Turbocharging has become the favored approach for downsizing internal combustion engines to reduce fuel consumption and CO2 emissions, without sacrificing performance. Matching a turbocharger to an engine requires a balance of various design variables in order to meet the desired performance. Once an initial selection of potential compressor and turbine options is made, corresponding performance maps are evaluated in 1D engine cycle simulations to down-select the best combination. This is the conventional matching procedure used in industry and is ‘passive’ since it relies on measured maps, thus only existing designs may be evaluated. In other words, turbine characteristics cannot be changed during matching so as to explore the effect of design adjustments. Instead, this paper presents an ‘adaptive’ matching methodology for the turbocharger turbine.

The downsizing of spark ignition engines should be an issue to decrease the consumption and to fulfil the ACEA commitment, i.e. 140 g CO2/km in 2008 and maybe 120 g/km in 2012. To achieve very low specific fuel consumption, the use of very downsized engines should be a solution. However, it is well known that one problem with such engines, that means very small turbocharged engines with high specific power (up to 100 kW/l), will be the turbo lag [5-6]. Different ways are possible to avoid it: some changes in intake layout, exhaust manifolds, turbo inertia, valve timings can be considered, or more sophisticated systems (such as electrically assisted compressor [3], volumetric compressor …) can be envisaged. To classify the interest of such solutions, it is very useful to compute their transient behaviour and, thus, to have accurate models to predict their impact under transient conditions like tip-in at constant speed but also tip-in on a vehicle (varying speed conditions).

0D-1D codes allow researchers to obtain a prediction of the behavior of internal combustion engines with little computational effort. One of the submodels of such codes is devoted to the centrifugal compressor. This model is often based on the compressor performance maps, therefore requiring the extrapolation of the maps so that all possible operating conditions are covered. Particularly, a suitable extrapolation of isentropic efficiency map is sought. This work first examines different available methods for compressor efficiency extrapolation into off-design conditions. No method is found to provide satisfactory results at all extrapolated regions: low and high compressor speeds and low compression ratio at measured speeds. Hence, a new method is proposed and its accuracy is assessed with the aid of compressor off-design measurements.