2013
EMSS 2013 Proceeding
Experimental and numerical analysis of the knocking phenomenon in a GDI engine
Authors: Michela Costa, Ugo Sorge, Bianca Maria Vaglieco, Paolo Sementa, Francesco Catapano
Abstract
The in-cylinder auto-ignition process leading to knocking in a GDI (gasoline direct injection) engine equipped with a high-pressure injector is numerically simulated. The turbocharged engine, 4-stroke, 4- cylinder, is also experimentally characterized at the test bench under stoichiometric conditions by varying the time of spark advance so to promote the occurrence of the knocking phenomenon. This last is numerically investigated by resorting to the Shell model, that allows reproducing within the combustion chamber the chemical activity of the mixture at low temperature in the end-gas zone. The simultaneous use of an Extended Coherent Flamelet Model (ECFM) for the combustion initiated by the spark plug allows calculating the pressure cycle, as well as the amount of CO produced under each considered operating condition. The link between the knocking occurrence and the CO amount at the exhaust is analyzed, together with the role of an intermediate species of the Shell model in localizing both spatially and temporally the occurrence of an undesired auto-ignition.
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