Investigation of the LTC fuel performance index for oxygenated reference fuel blends Public Deposited

Downloadable Content

Download PDF


Attribute NameValues
  • A new metric for ranking the suitability of fuels in LTC engines was recently introduced, based on the fraction of potential fuel savings achieved in the FTP-75 light-duty vehicle driving cycle. In the current study, this LTC fuel performance index was calculated computationally and analyzed for a number of fuel blends comprised of n-heptane, isooctane, toluene, and ethanol in various combinations and ratios corresponding to octane numbers from 0 to 100. In order to calculate the LTC index for each fuel, computational driving cycle simulations were first performed using a typical light-duty passenger vehicle, providing pairs of engine speed and load points. Separately, for each fuel blend considered, single-zone naturally aspirated HCCI engine simulations with a compression ratio of 9.5 were performed in order to determine the operating envelopes. These results were combined to determine the varying improvement in fuel economy offered by fuels, forming the basis for the LTC fuel index. The resulting fuel performance indices ranged from 36.4 for neat n-heptane (PRF0) to 9.20 for a three-component blend of n-heptane, isooctane, and ethanol (ERF1). For the chosen engine and chosen conditions, in general lower-octane fuels performed better, resulting in higher LTC fuel index values; however, the fuel performance index correlated poorly with octane rating for less-reactive, higher-octane fuels.
Resource Type
Date Available
Date Issued
  • Niemeyer, K. E., Daly, S. R., Cannella, W. J., & Hagen, C. L. (2015). Investigation of the LTC fuel performance index for oxygenated reference fuel blends. Fuel, 155, 14-24. doi:10.1016/j.fuel.2015.04.010
Journal Title
Journal Volume
  • 155
Rights Statement
Funding Statement (additional comments about funding)
  • The authors gratefully acknowledge the Chevron Energy Technology Company for supporting this research.
Peer Reviewed



This work has no parents.