On the Relationship Between Fuel Injection Pressure and Two-Stage Ignition Behavior of Low Temperature Diesel Combustion

In previous work, it is reported that increased dilution at mid-range injection pressures produces longer first stage combustion (cool-flame) duration. There is also corresponding decreases in nitric oxide concentrations and smoke number with respect to a reference conventional combustion mode. Continuing this effort, the objective of this study is to investigate the effect of injection pressure on the cool-flame duration under low temperature combustion conditions. A sweep of injection pressure is performed and the resulting heat release profiles are examined. The ignition delay behavior is expected based on changing injection pressure, but the cool-flame duration does not follow expected trends based on initial literature review. It is postulated that the influence of injection pressure on the local equivalence ratios is causing the observed behavior. The appropriate measurement and analysis tools are not available to the authors to confirm this postulation. A literature review of work investigating ignition conditions in low temperature combustion modes is used to support the postulation made in this study.