skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Effects of iso-octane/ethanol blend ratios on the observance of negative temperature coefficient behavior within the Ignition Quality Tester

Abstract

Here, an ignition delay study investigating the reduction in low temperature heat release (LTHR) and negative temperature coefficient (NTC) region with increasing ethanol concentration in binary blends of ethanol/isooctane was conducted in the Ignition Quality Tester (IQT). The IQT is advantageous for studying multi-component fuels such as iso-octane/ethanol which are difficult to study at lower temperatures covering the NTC region in traditional systems (e.g., shock tubes, rapid compression machines, etc.). The high octane numbers and concomitant long ignition delay times of ethanol and iso-octane are ideal for study in the IQT allowing the system to reach a quasi-homogeneous mixture; allowing the effect of fuel chemistry on ignition delay to be investigated with minimal impact from the fuel spray due to the relatively long ignition times. NTC behavior from iso-octane/ethanol blends was observed for the first time using an IQT. Temperature sweeps of iso-octane/ethanol volumetric blends (100/0, 90/10, 80/20, 50/50, and 0/100) were conducted from 623 to 993 K at 0.5, 1.0 and 1.5 MPa and global equivalence ratios ranging from 0.7 to 1.0. Ignition of the iso-octane/ethanol blends in the IQT was also modeled using a 0-D homogeneous batch reactor model. Significant observations include: (1) NTC behavior was observed formore » ethanol/ iso-octane fuel blends up to 20% ethanol. (2) Ethanol produced shorter ignition delay times than iso-octane in the high temperature region. (3) The initial increase in ethanol from 0% to 10% had a lesser impact on ignition delay than increasing ethanol from 10% to 20%. (4) The 0-D model predicts that at 0.5 and 1.0 MPa ethanol produces the shortest ignition time in the high-temperature regime, as seen experimentally.« less

Authors:
 [1];  [2];  [2];  [1];  [2]
  1. Colorado School of Mines, Golden, CO (United States)
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Bioenergy Technologies Office (EE-3B)
OSTI Identifier:
1329461
Report Number(s):
NREL/JA-5400-66816
Journal ID: ISSN 0016-2361
Grant/Contract Number:
AC36-08GO28308; AC36-08-GO28308
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Fuel
Additional Journal Information:
Journal Volume: 186; Journal ID: ISSN 0016-2361
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; IQT; iso-octane; ethanol; ignition; NTC; fuel blends

Citation Formats

Bogin, Jr., Gregory E., Luecke, Jon, Ratcliff, Matthew A., Osecky, Eric, and Zigler, Bradley T. Effects of iso-octane/ethanol blend ratios on the observance of negative temperature coefficient behavior within the Ignition Quality Tester. United States: N. p., 2016. Web. doi:10.1016/j.fuel.2016.08.021.
Bogin, Jr., Gregory E., Luecke, Jon, Ratcliff, Matthew A., Osecky, Eric, & Zigler, Bradley T. Effects of iso-octane/ethanol blend ratios on the observance of negative temperature coefficient behavior within the Ignition Quality Tester. United States. doi:10.1016/j.fuel.2016.08.021.
Bogin, Jr., Gregory E., Luecke, Jon, Ratcliff, Matthew A., Osecky, Eric, and Zigler, Bradley T. 2016. "Effects of iso-octane/ethanol blend ratios on the observance of negative temperature coefficient behavior within the Ignition Quality Tester". United States. doi:10.1016/j.fuel.2016.08.021. https://www.osti.gov/servlets/purl/1329461.
@article{osti_1329461,
title = {Effects of iso-octane/ethanol blend ratios on the observance of negative temperature coefficient behavior within the Ignition Quality Tester},
author = {Bogin, Jr., Gregory E. and Luecke, Jon and Ratcliff, Matthew A. and Osecky, Eric and Zigler, Bradley T.},
abstractNote = {Here, an ignition delay study investigating the reduction in low temperature heat release (LTHR) and negative temperature coefficient (NTC) region with increasing ethanol concentration in binary blends of ethanol/isooctane was conducted in the Ignition Quality Tester (IQT). The IQT is advantageous for studying multi-component fuels such as iso-octane/ethanol which are difficult to study at lower temperatures covering the NTC region in traditional systems (e.g., shock tubes, rapid compression machines, etc.). The high octane numbers and concomitant long ignition delay times of ethanol and iso-octane are ideal for study in the IQT allowing the system to reach a quasi-homogeneous mixture; allowing the effect of fuel chemistry on ignition delay to be investigated with minimal impact from the fuel spray due to the relatively long ignition times. NTC behavior from iso-octane/ethanol blends was observed for the first time using an IQT. Temperature sweeps of iso-octane/ethanol volumetric blends (100/0, 90/10, 80/20, 50/50, and 0/100) were conducted from 623 to 993 K at 0.5, 1.0 and 1.5 MPa and global equivalence ratios ranging from 0.7 to 1.0. Ignition of the iso-octane/ethanol blends in the IQT was also modeled using a 0-D homogeneous batch reactor model. Significant observations include: (1) NTC behavior was observed for ethanol/iso-octane fuel blends up to 20% ethanol. (2) Ethanol produced shorter ignition delay times than iso-octane in the high temperature region. (3) The initial increase in ethanol from 0% to 10% had a lesser impact on ignition delay than increasing ethanol from 10% to 20%. (4) The 0-D model predicts that at 0.5 and 1.0 MPa ethanol produces the shortest ignition time in the high-temperature regime, as seen experimentally.},
doi = {10.1016/j.fuel.2016.08.021},
journal = {Fuel},
number = ,
volume = 186,
place = {United States},
year = 2016,
month = 8
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Citation Metrics:
Cited by: 2works
Citation information provided by
Web of Science

Save / Share:
  • 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,more » 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 (> ~30 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