The effect of ozone addition on the combustion characteristics of hydrogen-jet fuel

Abstract

Ozone (O3) addition combustion is a trending technique to enhance the ignition characteristics of hydrocarbon fuel. In this study, the spray ignition characteristics of jet fuel along with hydrogen (H2) and O3 seeding were experimentally investigated and numerically simulated with an updated chemical kinetic model. The ignition delay (ID) period of jet propellant 5 (JP-5) with H2/O3 addition was measured using a constant volume combustion chamber (CVCC) at 600 K to 818 k, the pressure of 15 bar, equivalence ratio of 0.5. The intake manifold was added with air, H2 (10%, and 20% volume fraction), and 2000 ppm ozone (O3). In general, pure JP-5 has a shorter ID than those obtained with H2 addition. At 600 K, with 10% and 20% H2 to JP-5, the ID was increased by 18.49%, and 35.12% respectively. When O3 was added, the ID of JP-5 was shortened by 10%, while for 10% and 20% H2 addition, the ID was shortened by 19.25% and 22.5%, respectively. An existing jet fuel mechanism was chosen and validated with the previous and the present study experimental ID. The model was in agreement with the practical ID. The H2-mechanism rate constants were updated with the recently optimized values available in the literature to reflect the newly obtained experimental data at low temperatures. An existing sub-mechanism of O3 was adopted and combined with the JP-5 model. The updated model was validated with the present study ID data. Good predictions were noticed between the model and JP-5 experimental ID. However, a small deviation of 5.01% and 0.71% was found for 10%, and 20% H2 ID at 600 K. The reaction H2 + OH = H2O + H and HO2 + HO2 = H2O2 + O2 were found to be the critical reactions responsible to reduce the systems reactivity and makes the fuels ID to become longer. The O-atom from O3 was decomposed through the reaction O3 + N2 = O2 + O + N2, and O3 + O2 = O2 + O + O2 at an early stage of combustion. Due to H2 addition to O3 and air, the early formation of OH radicals is due to O3 + H = O2 + OH, which further accelerates the oxidation of the fuel, resulting in a shorter ID.