Large-Eddy Simulation and experimental study of cycle-to-cycle variations of stable and unstable operating points in a spark ignition engine

Victor Granet (1) , Olivier Vermorel (1) , Corine Lacour (2) , Benoît Enaux (1) , Vincent Dugué (3) , Thierry Poinsot (4)

1 CERFACS - Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique
2 IFPEN - IFP Energies nouvelles
3 Technocentre Renault [Guyancourt]
4 IMFT - Institut de mécanique des fluides de Toulouse

This article presents a comparison between experiments and Large-Eddy Simulation (LES) of a spark ignition engine on two operating points: a stable one characterized by low cycle-to-cycle variations (CCV) and an unstable one with high CCV. In order to match the experimental cycle sample, 75 full cycles (with combustion) are computed by LES. LES results are compared with experiments by means of pressure signals in the intake and exhaust ducts, in-cylinder pressure, chemiluminescence and OH Planar Laser Induced Fluorescence (PLIF). Results show that LES is able to: (1) reproduce the flame behavior in both cases (low and high CCV) in terms of position, shape and timing; (2) distinguish a stable point from an unstable one; (3) predict quantitatively the CCV levels of the two fired operating points. For the unstable case, part of the observed CCV is due to incomplete combustion. The results are then used to analyze the incomplete combustion phenomenon which occurs for some cycles of the unstable point and propose modification of the spark location to control CCV.

Mots clés: Piston engine; Spark ignition; Cycle-to-cycle variation; Large-Eddy Simulation; Chemiluminescence; OH Planar Laser Induced Fluorescence

Domaines: Mécanique des fluides [physics.class-ph]; Mécanique des fluides [physics.class-ph]

Victor Granet, Olivier Vermorel, Corine Lacour, Benoît Enaux, Vincent Dugué, et al.. Large-Eddy Simulation and experimental study of cycle-to-cycle variations of stable and unstable operating points in a spark ignition engine. Combustion and Flame, 2012, vol. 159, pp.1562-1575. ⟨10.1016/j.combustflame.2011.11.018⟩. ⟨hal-00800941⟩