Emissions and dynamic stability of the flameless combustion regime using hydrogen blends with natural gas

• Published in: International journal of hydrogen energy 2021-01, Vol.46 (1), p.1246-1258
• Main Authors: Cano Ardila, Fabián E., Obando Arbeláez, Julian E., Amell Arrieta, Andrés A.
• Format: Article
• Language: English
• Subjects: Dynamic instabilities; Flameless combustion; Hydrogen; Transient NOx
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2020.09.236

Flameless combustion regime has been considered one of the most promising types of combustion in the 21st century. Different studies have been conducted to evaluate its behavior with hydrogen content mixtures, some of them are in atmospheric pressure and high pressure but nothing has been done in sub-atmospheric conditions and measuring the instability level inside the combustion chamber. In this study we evaluate a furnace operating under the flameless combustion regime using hydrogen blends with natural gas (NG), varying from 0% to 45% H2 (in volume). The experiments were carried out under sub-atmospheric conditions of 0.850 bar; we measure NO emissions along with the pressure fluctuations inside the combustion chamber of the furnace. Transient tests were also performed to evaluate the stability of the regime varying the air-to-fuel ratio from n = 1.17 to n = 2.0 and the maximum air-to-fuel ratio based on NO emission just before the destruction of flameless combustion regime was found to be around n = 1.66 for several H2/NG mixtures. We also find that the addition of hydrogen to the mixture increases the operating stability of the flameless regime by reducing the dynamic instability level by 7.4% when going from 0% H2 to 45% H2. •Maximum air -to-fuel ratio based on NOx emission for several H2/natural gas mixtures.•Hydrogen content decreases dynamic instability level in the combustion chamber..•Transient tests variating aeration factor were performed using lean mixtures.•Flameless regime under sub-atmospheric conditions was obtained, 0% - 45%H2.•Flameless regime was obtained without preheating of combustion air, 0% - 45%H2.