Recently published chemical kinetic mechanisms are used to evaluate autoignition characteristics for conventional and alternative hydrotreated renewable jet (HRJ) fuels at low temperature and under lean combustion conditions. These kinetic models are examined for their predictive capabilities of ignition delay times compared against previously obtained experimental results from direct test chamber rapid compression machine (RCM) tests. Cases were evaluated at Pc = 20 bar in the low temperature (Tc = 630-730 K) and lean mixture (ø = 0.25 and 0.50) operating limits. The Ranzi mechanism was used for further simulation analysis in this work, where two-component jet fuel blends were developed to model camelina-based hydrotreated renewable jet fuels (HRJ-5 and HRJ-8), and the published conventional jet fuel surrogate of the Ranzi mechanism was used to represent both JP-5 and JP-8 jet fuels. Modeling results generally agree with RCM test results, indicating greater reactivity for the mostly paraffinic HRJ fuels at both mixture conditions. The kinetic models accurately capture the unique, multistage ignition observed in experimental results for the extra lean (ø = 0.25) case. Further analysis suggests several reactions potentially responsible for this unique ignition trend, namely, CO oxidation through the CO + OH → CO2 + H and CO + HO2 → CO2 + OH reactions, resulting in a mild third stage ignition for ø = 0.25 conditions. Additional examination of H2 production and destruction reactions reveals similar reactions occurring in conventional and alternative jet fuels with CO-H2-O2 kinetics dominating the final stage oxidation kinetics.
ASJC Scopus subject areas
- Chemical Engineering(all)
- Fuel Technology
- Energy Engineering and Power Technology