Abstract
Knock formation and its intensity for a stoichiometric ethanol/air mixture under a representative end-gas auto-ignition condition in IC engines with temperature inhomogeneities are investigated using multidimensional direct numerical simulations (DNS) with a 40-species skeletal mechanism of ethanol. Two- and three-dimensional simulations are performed by systematically varying temperature fluctuations and its most energetic length scale, lT. The volumetric fraction of the mixture regions that have the propensity to detonation development, FD, is proposed as a metric to predict the amplitude of knock intensity. It is found that with increasing lT, FD shows a good agreement with the heat release fraction of the mixture regions with pressure greater than equilibrium pressure, FH. The detonation peninsula is well captured by FD and FH when plotting them as a function of the volume-averaged ?, ?, (? = a/Ssp is the ratio of the acoustic speed, a to the ignition front speed, Ssp). Decreasing lT is found to significantly reduce the super-knock intensity. The results suggest that decreasing lT, as in engines with tumble designs resulting in a smaller turbulence scale, will be effective in mitigating the the super-knock development.
Original language | English |
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Pages (from-to) | 5781-5789 |
Number of pages | 9 |
Journal | Proceedings of the Combustion Institute |
Volume | 38 |
Issue number | 4 |
DOIs | |
State | Published - 2021 |
Event | 38th International Symposium on Combustion, 2021 - Adelaide, Australia Duration: Jan 24 2021 → Jan 29 2021 |
Funding
Notice: This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). This work was sponsored by King Abdullah University of Science and Technology and used the resources of the KAUST Supercomputing Laboratory.
Keywords
- Compression ignition (CI)
- Deflagration to detonation transition (DDT)
- Direct numerical simulation (DNS)
- Ethanol
- Super-knock
- Temperature inhomogeneities