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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).