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The one-dimensional (1D) modeling of a turbocharged engine requires the availability of the turbine and compressor characteristic maps. This leads to two main problems: performance maps of the turbocharger device are usually limited to a reduced number of rotational speeds, pressure ratios and mass flow rates. Extrapolation of maps’ data is commonly required; performance maps are experimentally derived on stationary test benches, while the turbocharger usually operates under unsteady conditions, when coupled to an internal combustion engine (ICE). To overcome the above problems, in the present paper the flow inside a rotating pipe of a centrifugal compressor is simulated within a 1D modeling approach, with the aim of predicting its characteristic map. The main improvement with respect to the employment of a steady experimental map consists in the absence of data extrapolation and in the possibility of fully characterizing the unsteady operation of the component.

A theoretical-experimental analysis of a VVT engine and a methodology for the definition of its optimal control is presented. The analyses are based on the employment of a very accurate 1D simulation model of the engine, developed by the authors. The code is validated by comparison with experimental data collected on a traditionally fixed- and a variable-valve timing engine as well. The model is then linked to an efficient optimization procedure, which is able to select - for each assigned operating condition - the most appropriate values of control parameters (spark advance, intake/exhaust valve opening/closing, and valve lift), with the objective of pursuing part-load BSFC improvements. Various VVT or VVA arrangements are analyzed and compared.