Experimental investigation of the emission behaviour and flame stability of the oxygen and hydrogen enriched methane under acoustic enforcement

The instability changes of oxygen-enriched fuel mixtures under acoustic enforcement in a premixed and swirl supported system were investigated in this study. Different amounts of hydrogen (0%, 10%, 20%) were added to methane used as fuel and oxygen enrichment process (21%, 24%, 26%) was applied in hydrogen-added fuel mixtures. The equivalence ratio was kept constant at 0.7 in experiments conducted under constant burner power and swirl support. Experiments showed that although oxygen enrichment up to 24% ratio increases stability by increasing the laminar flame speed, stability decreases when the oxygen content in the oxidizer was increased to 26%. As a result of increasing both hydrogen ratio in fuel mixture and oxygen enrichment, instabilities grow up with decreasing of Markstein length. In this situation, burning in combustion chamber did not continue under acoustic force. According to the emission values taken during combustion experiments, the addition of oxygen increased NOx emissions due to increased adiabatic temperature and sudden NOx formations, while contributing to the reduction of CO emissions. Although the addition of hydrogen reduces NOx emissions in case of combustion with air (%21 O-2), it has increased the CO emissions from 2 ppm to 13 ppm because it triggers instabilities when combined with oxygen enrichment