Relationship Between Ignition Processes and the Lift-Off Length of Diesel Fuel Jets

Experimental characterization of diesel ignition and lift-off length using a single-hole ECN injector

“…Table 3 shows part of the results from the statistical analysis performed. Concerning the SSI obtained by the broadband chemiluminescence, results show relatively good agreement with the results from Pickett et al [34]. Although small differences appear, the general trend is very close and the high R 2 found is proving the good precision of the tests and the reliability of the results.…”

“…The number of conditions tested and the high value of R 2 obtained allows having a very accurate analytical description of the data obtained over a wide range of test conditions. When compared to coefficients found by Pickett et al [34] an important agreement is still found concerning the effect of ambient temperature, ambient density and oxygen concentration. However, an important difference has been observed in the effect that injection pressure has on LOL.…”

“…Although small differences appear, the general trend is very close and the high R 2 found is proving the good precision of the tests and the reliability of the results. Moreover, the constant A, related to the effect of the ambient temperature, is affected by the fuel employed: Pickett et al [34] used DR2 reference fuel while in the present work the fuel used is pure n-dodecane and therefore some difference in A should be expected. Table 3.…”

“…In these figures it is possible to appreciate the effect that the test conditions have on these parameters and on the related time-dwell. While the effect of oxygen concentration and ambient temperature can be chemically explained (typically higher oxygen concentration and ambient temperature accelerate oxidation reactions as expected theoretically [32] and observed experimentally by other authors [33], [34]) the effect of ambient density and injection pressure is related to fuel-air mixing dynamics. At higher ambient density the spray spreading angle increases significantly [35]: in this condition the volume of air entrained in the spray is higher (and denser), causing therefore a faster heating of the fuel mixture.…”

“…On the other hand, LOL is strongly linked to the spray development and therefore an exponential equation is preferred: Equation (2). Moreover, in other works [15], [34] the same equations have been chosen to perform a similar analysis and therefore the new results obtained in the two cases can be compared. being fuel  the density of the fuel.…”