JP‑5 and HRJ‑5 Autoignition Characteristics and Surrogate Modeling

A heated
rapid compression machine has been used to investigate the autoignition
behavior of JP-5 and camelina-based hydrotreated renewable jet (HRJ-5)
fuels. Testing was conducted at low temperatures (Tc = 627–733 K), low-to-moderate pressures (pc = 5, 10, and 20 bar), and lean (ϕ =
0.25 and 0.50) and stoichiometric mixtures in air. The HRJ-5 fuel,
which is 99% paraffinic, exhibited greater reactivity than the JP-5
fuel in the form of shorter ignition delays. The HRJ-5 fuel also exhibited
transition into the negative temperature coefficient region at a lower
compressed temperature (Tc = 675 K) than
the JP-5 fuel (Tc = 700 K). Two surrogate
fuel blends and kinetic models intended for Jet-A and kerosene-type
fuels are evaluated for their ability to predict JP-5 ignition delay
times because JP-5 and Jet-A ignition delay times showed close resemblance.
The models reproduced the qualitative trend in the data, including
an accurate representation of when the negative temperature coefficient
behavior appears. The best agreement between the data and predictions
was obtained at pc = 5 bar and ϕ
= 1.0, but outside of this region, the disparity was often 2-fold
or greater.