Nitrogen Oxides Emissions from Fuel-Sensitized Detonations for a Synthetic Biofuel

Fuel-sensitization is one of the possible techniques that ensure the operation of a detonation-based combustor near its limits without the risk of failure or attenuation of a detonation wave. The primary effect of fuel sensitization is to alter the ignition chemistry of the fuel–air mixture without affecting the other thermodynamic and gas dynamic properties of gaseous detonation. The chemical kinetics of biofuels is relatively slow for their application in detonation-based engines. Ignition promoters like ozone and hydrogen peroxide could improve the ignition and combustion kinetics of synthetic biofuels tremendously for applications in ramjets and detonation-based engines. However, ignition promoters are strong oxidizing agents and could lead to larger NOx emissions. Therefore, the effect of fuel-sensitization on NOx emissions from a synthetic biofuel under detonation conditions is investigated in the present study. In the present study, one-dimensional ZND calculations are carried out for C1-air detonations with ozone and hydrogen peroxide as ignition promoters, where C1 is an alcohol-to-jet synthetic biofuel. The effect of ignition promoters on the emission characteristics and the critical detonation parameters is studied over a range of equivalence ratios. It is observed that while ozone is a better ignition promoter and reduces the length and time scales drastically, it leads to larger NOx emissions when compared to hydrogen peroxide. Hydrogen peroxide exhibits a dual behavior. It acts both as an ignition promoter and a NOx mitigating agent. The dual favorable nature of hydrogen peroxide can be harnessed for its practical application in detonation-based combustors. The results from the present study are promising and can be used as a starting point to efficiently utilize synthetic biofuels for detonation-based combustors.