Study on Ion Current Characteristics and Reaction Mechanism of Oxygen-Enriched Ammonia Combustion

To develop a diagnosis of ammonia-hydrogen blended combustion based on ion current detection technology, this study investigates the pressure and ion current waveform characteristics of oxygen-enriched ammonia-hydrogen combustion using a constant volume combustion chamber (CVCC) testing platform. In addition, the formation mechanism of the ion current is revealed through CHEMKIN-PRO combustion simulation. The results demonstrate that the peak values and peak timings of the pressure and ion current signals exhibit highly consistent variation patterns as the equivalence ratio changes. Specifically, under lean/stoichiometric combustion, the dominant cations include NH4+, NO+, and H3O+, while NH4+ predominates under rich combustion. Moreover, the 10% hydrogen-blended condition exhibits similar ion current waveforms and cation concentration variation trends compared with pure ammonia combustion. However, 10% hydrogen blending can significantly enhance the ion current signal intensity, advance the signal peak timing, and promote the chemical ionization of reactants to generate NH4+.