Predicting Fuel Performance for Future HCCI Engines

Abstract

The purpose of this research is to investigate the impact of fuel composition on auto-ignition in homogeneous charge compression ignition (HCCI) engines in order to develop a future metric for predicting fuel performance in future HCCI engine technology. A single-cylinder, variable compression ratio engine operating as an HCCI engine was used to test reference fuels and gasoline blends with octane numbers (ON) ranging from 60 to 88. Correlations between fuel composition, ON, and two existing methods for predicting fuel auto-ignition in HCCI engines (Kalghatgi's octane index and Shibata and Urushihara's HCCI index) are investigated. Results show that octane index and HCCI index poorly predict the impact of fuel composition on auto-ignition for fuels with the same ON. The effect of ethanol in delaying auto-ignition depends on the composition of the original gasoline blend; the same is true for the addition of naphthenes. Low-temperature heat release (LTHR) correlates well with auto-ignition for gasoline fuels exhibiting LTHR.

Keywords:

• Auto-ignition
• Fuel composition
• Homogenous charge compression-ignition (HCCI)

ACKNOWLEDGMENTS

Research conducted at the University of California, Berkeley, was supported by the Chevron Corporation. The authors also acknowledge the assistance of T. Dillstrom, A. Van Blarigan, and M. Wissink in conducting experimental measurements.

Notes

^a RON and MON were calculated using method described by Morgan et al. (2010).

^b RON and MON were calculated using bRON and bMON values from Anderson et al. (2010). RON and MON of remaining fuels were assumed.

Note. N/A not available.

^a RON or MON was estimated.

^b RON or MON was provided by Chevron.