Abstract
To this date, extensive research has been conducted to understand the low-temperature auto-ignition chemistry of gasoline. The detection of low-temperature chemical reactions under Spark Ignition (SI) combustion cannot be detected, as they are hidden by the flame propagation. Alternatively, Homogeneous Charge Compression Ignition (HCCI) combustion has a two-stage combustion involving low and high-temperature heat release (LTHR and HTHR respectively). Both Knocking SI and HCCI combustion involve auto-ignition and are governed by fuel characteristics and the pressure-temperature (P-T) history. Therefore, HCCI combustion might provide an alternative to understand the knocking behavior and LTHR in modern SI engines. A standard Cooperative Fuel Research (CFR) engine was operated at lean HCCI conditions (lambda 3), as well as SI conditions at stoichiometry. For SI combustion, the CFR engine was operated with RON-like conditions, but at late spark timing to induce LTHR prior to flame propagation. Three RON 90 binary fuel blends were investigated, being composed of n-heptane with isooctane, toluene, or ethanol. This work demonstrated that the CFR engine under stoichiometric SI with late spark timing and HCCI combustion mode can help to detect LTHR which is not possible in the standard RON test. The intake pressure and temperature sweeps showed similar effects on LTHR for both combustion modes. The linking of auto-ignition behavior of SI and HCCI was dependent primarily on intake valve closing (IVC) conditions. The high exhaust temperature in SI lead to high IVC temperatures. In order to match the IVC temperatures and to overlap the P-T trajectories, the intake temperature for HCCI was increased.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 115745 |
| Journal | Fuel |
| Volume | 256 |
| DOIs | |
| State | Published - Aug 14 2019 |
Bibliographical note
KAUST Repository Item: Exported on 2020-10-01Acknowledgements: The author would like to thank both King Abdullah University of Science and Technology and Argonne National Laboratory for their support during the publication of this article. Specifically, the research funds were provided by King Abdullah University of Science and Technology and the experimental facilities by Argonne National Laboratory. The author would also like to thanks Nimal Naser for providing a code used for post-processing the experimental data, Timothy Rutter for his support in the Laboratory and the section manager Doug Longman. The submitted manuscript has been created in part by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under ContractNo. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government. 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 is performed under the auspices of the Office of Energy Efficiency and Renewable Energy, Office of Vehicle Technology, U.S. Department of Energy, under contract number DE-AC02-06CH11357, as part of the Co-Optimization of Fuels & Engines (Co-Optima).