Lift-off in reacting diesel jets is of interest because soot concentration in the jet has a suggested correlation with it. It has been suggested that larger lift-off height enables greater fuel/air mixing upstream of the lift-off height which, in turn, leads to reduced formation rates of soot. In this work, computations of reacting diesel jets, including soot and NO, are carried out for a wide range of conditions by employing a RANS model in which an unsteady flamelet progress variable (UFPV) submodel is employed to represent turbulence/chemistry interactions. The conditions selected reflect changes in injection pressure, chamber temperature, oxygen concentration, and density, and orifice diameter. As reported in prior work, the UFPV model predicts the ignition delay and flame lift-off height within about 25% of reported measurements. The flame is found to stabilize at the location where the ignition scalar dissipation rate is equal to the local scalar dissipation rate at the stoichiometric mixture fraction. For all cases, except the cases with different orifice diameter and ambient density the soot concentration is found to correlate with the lift-off height. Analysis of the entrained mass upstream of the lift-off height confirms that this correlation arises from variation in entrained mass.
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