Title: Investigation of Iso-octane Ignition and Validation of a Multizone Modeling Method in an Ignition Quality Tester

Abstract

An ignition quality tester was used to characterize the autoignition delay times of iso-octane. The experimental data were characterized between temperatures of 653 and 996 K, pressures of 1.0 and 1.5 MPa, and global equivalence ratios of 0.7 and 1.05. A clear negative temperature coefficient behavior was seen at both pressures in the experimental data. These data were used to characterize the effectiveness of three modeling methods: a single-zone homogeneous batch reactor, a multizone engine model, and a three-dimensional computational fluid dynamics (CFD) model. A detailed 874 species iso-octane ignition mechanism (Mehl, M.; Curran, H. J.; Pitz, W. J.; Westbrook, C. K.Chemical kinetic modeling of component mixtures relevant to gasoline. Proceedings of the European Combustion Meeting; Vienna, Austria, April 14-17, 2009) was reduced to 89 species for use in these models, and the predictions of the reduced mechanism were consistent with ignition delay times predicted by the detailed chemical mechanism across a broad range of temperatures, pressures, and equivalence ratios. The CFD model was also run without chemistry to characterize the extent of mixing of fuel and air in the chamber. The calculations predicted that the main part of the combustion chamber was fairly well-mixed at longer times (> ~30more » ms), suggesting that the simpler models might be applicable in this quasi-homogeneous region. The multizone predictions, where the combustion chamber was divided into 20 zones of temperature and equivalence ratio, were quite close to the coupled CFD-kinetics results, but the calculation time was ~11 times faster than the coupled CFD-kinetics model. Although the coupled CFD-kinetics model captured the observed negative temperature coefficient behavior and pressure dependence, discrepancies remain between the predictions and the observed ignition time delays, suggesting improvements are still needed in the kinetic mechanism and/or the CFD model. This approach suggests a combined modeling approach, wherein the CFD calculations (without chemistry) can be used to examine the sensitivity of various model inputs to in-cylinder temperature and equivalence ratios. In conclusion, these values can be used as inputs to the multizone model to examine the impact on ignition delay. Additionally, the speed of the multizone model also makes it feasible to quickly test more detailed kinetic mechanisms for comparison to experimental data and sensitivity analysis.« less

Authors:

Osecky, Eric M. ^[1]; Bogin, Gregory E. ^[1]; Villano, Stephanie M. ^[1]; Ratcliff, Matthew A. ^[2]; Luecke, Jon ^[2]; Zigler, Bradley T. ^[2]; Dean, Anthony M. ^[1]

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+ Show Author Affiliations

1. Colorado School of Mines, Golden, CO (United States)
2. National Renewable Energy Lab. (NREL), Golden, CO (United States)

Publication Date:

Thu Aug 18 00:00:00 EDT 2016

Research Org.:

National Renewable Energy Laboratory (NREL), Golden, CO (United States)

Sponsoring Org.:

USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V)

OSTI Identifier:

1333413

Report Number(s):

NREL/JA-5400-66890
Journal ID: ISSN 0887-0624

Grant/Contract Number:  

AC36-08GO28308

Resource Type:

Accepted Manuscript

Journal Name:

Energy and Fuels

Additional Journal Information:

Journal Volume: 30; Journal Issue: 11; Journal ID: ISSN 0887-0624

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

33 ADVANCED PROPULSION SYSTEMS; iso-octane; ignition quality; validation