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

Abstract

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.

Conventional and Bio-Derived Jet Fuel Surrogate Modeling in Low Temperature and Lean Combustion

“…These surrogates were used to represent both JP-8 and JP-5 because of the similarities seen in low temperature ignition between Jet-A and conventional military fuels in studies we have conducted previously. 6 Figure 3 shows the results of each surrogate in comparison to the measured experimental trace, indicating closest agreement to experimental results for both the Dooley and Ranzi mechanisms. The Aachen mechanism fails to show ignition within the time frame for both ϕ = 0.25 and 0.5 cases.…”

“…Another recent study by Allen et al focused on USN jet fuel, JP-5, and camelina-based USN fuel equivalent, HRJ-5. The lean, low temperature rapid compression machine (RCM) test conditions confirmed the enhanced reactivity of the paraffinic HRJ fuels as seen in prior studies . Kinetic models from the Aachen group, developed by Honnet et al, and Princeton, by Dooley et al, were used to examine model agreement with observed experimental results.…”

“…The lean, low temperature rapid compression machine (RCM) test conditions confirmed the enhanced reactivity of the paraffinic HRJ fuels as seen in prior studies. 6 Kinetic models from the Aachen group, developed by Honnet et al, 7 and Princeton, by Dooley et al, 8 were used to examine model agreement with observed experimental results. The models most accurately captured combustion features at stoichiometric and low pressure conditions, reproducing the general ignition trends but lacking accuracy in predicting actual ignition delay times.…”

Autoignition behavior of synthetic alternative jet fuels: An examination of chemical composition effects on ignition delays at low to intermediate temperatures

“…Overall, the shock tube and RCM data correlate favorably, with the exception of HRJ-5 and LINPAR 1416V where the RCM predicts faster ignition than the shock tube. This phenomenon has been previously noted [3,4], where ignition delays measured in RCMs can be shorter than observed in shock tubes for ignition delay times less than $8 ms due to preignition chemistry occurring prior to TDC, particularly for highly reactive n-paraffinic fuels such as HRJ-5 and LINPAR 1416V.…”

“…Understanding of the chemical kinetic behavior of alternative fuels, for example macroscopically exemplified through ignition delay, flame speed, and extinction limits, is needed for combustion model development. Kinetic targets for fuel characterization and model development have only become recently available in the literature for complex multi-component fuels, including autoignition studies for conventional, HRJ, and FT fuels [3][4][5][6][7]; however, little work has been performed regarding blends of conventional and alternative fuels. Additionally, the influence of fuel composition/structure on autoignition is sparse in the literature, particularly at lean conditions, that are becoming increasingly attractive for achieving reductions in production of harmful emissions.…”