Relationship of the combustion characteristics of natural gas-hydrogen/carbon dioxide mixtures with the ion current and pressure parameters

Abstract

The characteristics of the ionization current, pressure, and flame schlieren photos during the combustion process of natural gas-hydrogen/CO2 blends were studied using high-speed schlieren data acquisition technology and flame ionization analysis methods. According to the ion current waveform, pressure waveform, and flame propagation photos, the relationship of the characteristic parameters between the ion current and pressure were analysed using available experimental data. The ionization current waveform can reflect not only the entire combustion process (including ignition phase, the front flame phase and the post flame phase) but also the effect of the initial pressure, equivalence ratios, hydrogen fraction and CO2 dilution ratios on the combustion process.This results of this study show that the amplitude and characteristic timing of the ion current can be used to predict the change of the chamber pressure. The ion current and pressure will increase with the increase of the initial pressure, equivalence ratio and hydrogen fractions, but the parameters will decrease with the increase of the CO2 dilution ratio. The characteristic timing of the ion current and pressure peaks is advanced with the increase of the equivalence ratio and hydrogen fractions; however, the peaks are postponed by the increase in the initial pressure and CO2 dilution ratio. The corresponding relationship of the characteristic timing between the ion current and pressure is basically unchanged. The results of this study provide a new approach for exactly controlling the combustion process.