Study Of Flame Characteristics Of N-alkanes Under High CO₂Concentration Atmospheres

The most significant feature of Oxy-fuel combustion is the persence of high CO₂concentration in combustion atmosphere.As the physical and chemical properties of CO₂and N2are very different,the flame characteristics of fuels under O₂/CO₂atmosphere arequite different from that under conventional air atmosphere.At present,the variation offlame characteristics of n-alkanes and the internal reaction mechanisms under O₂/CO₂atmosphere are unclear,which is need to carry out systematic and in-depth study.In this paper,laminar flame speed,ignition delay time and adiabatic flame temperatureof C1-C7n-alkanes are calculated by detailed chemical kinectic models. The influences ofatmospheres,equivalence ratios,CO₂concentration and O₂concentration on the flamecharacteristics are revealed.In further study,the combustion progress of methane in gasturbine conbustion chamber are simulated by CFD method to study the influence ofturbulent flow on combustion progress.For the same O₂concentration, flame speed and adiabatic flame temperature underO₂/CO₂atmosphere are lower than that under O₂/N2atmosphere,while ignition delay timesare higher than that under O₂/N2atmosphere.As the equivalence ratio increases, flamespeed and adiabatic flame temperature increase firstly and then decrease,while the ignitiondelay time continuously increase. Flame speed and adiabatic temperature are graduallyredued,while the ignition delay time are gradually increased,as the CO₂concentrationincreases in the initial atmosphere.Flame speed and adiabatic flame temperature areinceasing as the O₂concentration increases in the initial atmosphere.In CFD simulationresults, the flow field characteristics,temperature distribution characteristics,speciecsconcentration distribution characteristics are familiar under O₂/CO₂atmosphere and airatmosphere.The NOXemissions increase firstly and then decrease as the equivalence ratioincreases, while CO emissions increase.