Two-Stage Ignition as an Indicator of Low-Temperature Diesel Combustion

Abstract

Two-stage ignition is characterized by an initial cool-flame reaction followed by typical hot ignition. In traditional combustion conditions the ignition is fast such that the cool flame is not observed. By controlling initial conditions (pressure, temperature, and composition) in a rapid compression machine, for example, the creation and duration of the cool-flame event is predictable. This study focuses on linking the results from the rapid compression machine to those of low-temperature combustion behavior in a medium-duty compression ignition diesel engine. A correlation between cool-flame duration, nitric oxide concentration, and engine control settings allows the postulation that a sufficiently long cool-flame reaction results in a combustion event that can be classified as low-temperature combustion. A potential method for identifying low-temperature combustion events using only the rate of heat release profile is theorized which utilizes the cool-flame reaction duration as a metric.

Keywords:

• Diesel combustion
• Low-temperature combustion
• Two-stage ignition

ACKNOWLEDGMENTS

The authors thank those individuals that have helped 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. Any opinions or views expressed in this manuscript are not necessarily those of the sponsoring agency. Mr. Brandon Tompkins and Mr. Hoseok Song are thanked for their assistance in the engine test cell.

Notes

^a Measured by oil displacement.

^a Measured or calculated by Southwest Research Institute (San Antonio, Texas, USA).

Note. No cool-flame duration was observed for the conventional injection timing, nor is the equivalence ratio calculation in a valid range.

^a Out of range of calculation method.