Investigation Into the Use of Ignition Delay as an Indicator of Low-Temperature Diesel Combustion Attainment

Abstract

The authors evaluated the attainment of low-temperature diesel combustion in a medium-duty diesel engine apparatus. Attainment of low temperature combustion is determined by the simultaneous and substantial decreases in nitric oxide (NO) and smoke concentrations. The extreme low-temperature combustion condition results in greater than 50% reductions in both NO and smoke concentrations relative to a baseline conventional combustion mode. Combustion development occurs at a low speed (1400 rev/min) and nominally light load (nominally 68 N-m torque, or 1.9 bar brake mean effective pressure). The authors conclude that determination of low-temperature combustion attainment is not universally possible using phenomenologically based ignition delay calculations. Evaluations of two methods to determine start of combustion, which render a definition for ignition delay and for engine ignition delay, reveal that neither provides a consistent metric to determine low-temperature combustion attainment.

Keywords:

• Diesel combustion
• Ignition delay
• Low-temperature combustion
• Nitric oxide
• Smoke

ACKNOWLEDGMENTS

The authors wish to thank several contributors who have helped to make this work possible. The preparation of this report is based on work funded by the State of Texas through a grant from the Texas Environmental Research Consortium with funding provided by the Texas Commission on Environmental Quality. Mr. Jason Esquivel and Mr. Brad Williams are thanked for their assistance in the engine test cell.