Characteristics of turbulent premixed oxy-fuel combustion - a DNS study

A 3D DNS numerical study with detail chemistry mechanism has been carried out to investigate turbulent premixed combustion with oxyfuel mixtures under similar operating conditions as happened in spark ignition Internal Combustion Engine (ICE). H2O and CO2 are adopted as the dilution in oxy-fuel combustion. The temperature profiles of oxy-H2O and oxy-CO2 combustion are consistent with those of air-fired conditions in laminar premixed flame when the molar fraction of H2O and CO2 are 73% and 66% in oxidizer, respectively. 79%, 67% molar fraction of H2O and 79%, 56% molar fraction of CO2 are also conducted to learn the effects of the dilution molar fraction on the process of flame propagation. With the molar fraction of dilution increases, the mass of C2H2 increases the flame propagation speed and the mass of CO does an opposite influence. With the investigation for effects of turbulent intensity under conditions of 73% H2O and 66% CO2 with the initial u′ of 0.8, 1.6 and 2.4 m/s, respectively, results show that the turbulent intensity has little effect on the formation of CO. It is also demonstrated that for oxy-fuel combustion, due to the disparity in laminar flame speed, an appropriate u′ is necessary to keep consistent with the flame propagation speed meanwhile to maintain suitable temperature profiles.