Abstract
Vitiation refers to the condition where the oxygen concentration in the air is reduced due to the mix of dilution gas. The vitiation effects on a premixed methane flame were investigated on a swirl-stabilized gas turbine model combustor under atmospheric pressure. The main purpose is to analyze the combustion stability and CO emission performance in vitiated air and compare the results with the flame without vitiation. The N2, CO2, and H2O (steam) were used as the dilution gas. Measurements were conducted in a combustor inlet temperature of 384 K and 484 K. The equivalence ratio was varied from stoichiometric conditions to the LBO (Lean Blowout) limits where the flame was physically blown out from the combustor. The chemical kinetics calculation was performed with Chemkin software to analyze the vitiation effects on the flame reaction zone. Based on the calculation results, the changes in the temperature gradient, CO concentration, and active radicals across the flame reaction zone were identified. The time-averaged CH chemiluminescence images were recorded and the results indicated the features of the flame shape and location. The CH signal intensity provided the information about the heat-release zone in the combustor. The combustion LBO limits were measured and the vitiation of CO2 and H2O were found to have a stronger impact to elevate the LBO limits than N2. Near the LBO limits, the instability of the flame reaction was revealed by the high-speed chemiluminescence imaging and the results were analyzed by FFT (Fast Fourier Transfer). CO emission was measured with a water-cooled probe which is located at the exit of the combustor. The combustion vitiation has been found to have the compression effect on the operation range for low CO emission. However, this compression effect could be compensated by improving the combustor inlet temperature.
Highlights
Due to environmental problems, the low emission combustion technologies have attracted considerable attention
Near the LBO limits, the instability of the flame reaction was revealed by the high-speed chemiluminescence imaging and the results were analyzed by FFT
The vitiation effect of N2 and CO2 on the LBO limits of the methane flame was investigated, and the results showed that CO2 had a stronger effect on the LBO increase [13]
Summary
The low emission combustion technologies have attracted considerable attention. H2 O vitiation was found to have a positive chemical kinetic effect due to its contribution to the increase of H and OH radicals which come from the reaction step O + H2 O ↔ OH + OH [7,8,9] and H2 O ↔ H + OH (the dissociation of the steam under high temperature) [10]. The vitiation effect of N2 and CO2 on the LBO limits of the methane flame was investigated, and the results showed that CO2 had a stronger effect on the LBO increase [13]. The current paper contributes to a better understanding of the vitiated flame on the stable and low CO operation, and the results will bolster the development of environmentally friendly combustion technologies
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
