Effect of ammonia addition on combustion characteristics of hydrogen/air using passive turbulent jet ignition

Abstract

Hydrogen (H2) and ammonia (NH3) are ideal carbon-free fuels, and the application of NH3/H2 in internal combustion engines offers the potential to reduce carbon emissions. And turbulent jet ignition (TJI) is an advanced ignition strategy that can effectively enhance the combustion. This work aims to experimentally investigate the effect of NH3 addition on the combustion characteristics of H2/air mixtures under passive TJI conditions. Combustion images and instantaneous pressure were collected for processing and analysis. The effect of NH3 substitution and equivalence ratio were investigated. The results indicate that the peak combustion pressure decreases with the addition of NH3, accompanied by longer combustion duration and ignition delay, as well as lower jet velocity and flame area growth rate. The hot jet will be quenched by the strong heat transfer, causing the change in the ignition mechanism as the NH3 substitution ratio increases. In addition, compared to lean conditions, the combustion appears to be less sensitive to the equivalence ratio on the rich side and always shows high jet velocity and flame propagation speed. However, a relatively small amount of NH3 addition changes the ignition mechanism on the rich combustion side compared with lean conditions, resulting in a longer ignition delay.