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 (T c = 627–733 K), low-to-moderate pressures (p c = 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 (T c = 675 K) than the JP-5 fuel (T c = 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 p c = 5 bar and ϕ = 1.0, but outside of this region, the disparity was often 2-fold or greater.