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T. Lauer, M. Heiß:
"Analysis of Pre-ignition Initiation Mechanisms using a Multi-Cycle CFD-Simulation";
Talk: International Multidimensional Engine Modeling User's Group Meeting, Detroit, USA (invited); 2014-04-07; in: "International Multidimensional Engine Modeling User's Group Meeting", https://imem.cray.com/agenda.html, (2014), 5 pages.

For downsized SI-engines at high loads and particularly at low engine speeds spontaneous auto-ignitions randomly occur before the regular spark timing leading to severe engine damage. These pre-ignitions
are limiting the fuel efficient combustion process and the underlying mechanisms must be understood.
Therefore, experimental and numerical investigations were carried out at the Institute for Powertrains and Automotive Technology at the Vienna University of Technology. An optical access was installed
on the test engine to enable high-speed imaging. CFD-simulations were carried out in order to evaluate droplet impingement and wall film formation on the piston and liner. Virtual particles emanated from
wetted areas on the piston crown close to the liner showed a good correlation with the location of the recorded light emissions initiating pre-ignitions.
Additionally, the detachment of soot particles from the combustion chamber walls caused by the highfrequency pressure oscillations during a pre-igniting cycle was modelled in CFD with respect to the
video observations. Particles that remained in the combustion chamber after gas exchange heated up during the following regular combustion cycle and therefore become critical for follow-up pre-ignition
events in the next cycle.
Thus, the initiation for pre-ignitions by droplets and particles could be confirmed.