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.