Abstract
One of the ultimate goals of chemical kinetic study is to understand and predict autoignition in engines. In this study, utilizing toluene primary reference fuels (TPRF) as a gasoline surrogate and a recently developed multicomponent gasoline kinetic mechanism, we have demonstrated a general approach to analyze autoignition in arbitrary spark-ignition (SI) and advanced compression ignition (ACI) engine conditions by combining thermodynamic pressure-temperature trajectory and the fuel ignition delay iso-contours. This method allows direct evaluation of controlling chemistry, potential involvement of low temperature heat release, and the dependence of autoignition to conventional fuel metrics (research and motor octane rating, i.e., RON and MON, and octane sensitivity OS = RON-MON) and engine operating conditions such as equivalence ratio, exhaust gas recirculation (EGR) ratio and engine intake conditions. Applying the analysis to the pressure-temperature trajectories of the conventional RON and MON tests, as well as those beyond RON and beyond MON, distinct roles of conventional gasoline fuel metrics and engine operating parameters are identified for all representative engine conditions. By comparing the autoignition behavior in ACI and SI engine conditions, the knowledge obtained from SI engine knock cannot be directly transferred to ACI bulk combustion phasing control in general, due to the different mixture equivalence ratios and the associated differences in reactivity and its dependence. This method could be extended to generate an auto-ignition map for arbitrary fuels and arbitrary engine trajectories, and the useful insights and overall evaluations can be used to complement conventional kinetic simulation of engine cycles.
| Original language | English |
|---|---|
| Pages (from-to) | 207-218 |
| Number of pages | 12 |
| Journal | Combustion and Flame |
| Volume | 200 |
| DOIs | |
| State | Published - Feb 2019 |
Funding
This research was conducted as part of the Co-Optimization of Fuels and Engines (Co-Optima) initiative sponsored by the US Department of Energy Office of Energy Efficiency and Renewable Energy and Bioenergy Technologies and Vehicle Technologies Offices , including Co-optimization of Fuels & Engines Program with Award Number DE-EE0007985 . Co-Optima is a collaborative project of multiple national laboratories initiated to simultaneously accelerate the introduction of affordable, scalable, and sustainable biofuels and high-efficiency, low-emission vehicle engines. Special thanks to program managers Trevor Smith, Alicia Lindauer, Kevin Stork, Gurpreet Singh, Leo Breton, and Mike Weismiller. This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE 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 ).
Keywords
- Advanced compression ignition (ACI)
- Autoignition
- Livengood-Wu method
- Octane rating
- Octane sensitivity
- Phi-sensitivity