Flame Structure And Combustion Characteristics Of CH₄/Air Premixed V-jet Flame With Sidewall

Flame wall interaction（FWI）is a common phenomenon in closed combustion system.The existence of wall affects the flow,thermodynamics and reaction kinetics of flame significantly.The trend of miniaturization of combustion device further enlarges the importance of FWI.Therefore,in order to better organize the combustion process of combustion system,it is urgent to explore the FWI process.In this paper,the structure and combustion characteristics of CH₄/Air premixed v-jet flame with sidewall were conducted through a combination of experiments and numerical calculations.The research contents and innovations are as follows:（1）The experimental platform of the interaction between the sidewall and premixed jet flame was built.A two-dimensional numerical model of methane/air premixed combustion process coupled with chemical reaction mechanism was established,and the model was verified by comparing with the experimental data.（2）Experiments and numerical simulations were carried out to obtain the characteristics of methane/air premixed V-shaped flame with or without sidewall.The results show that the sidewall will make the gas temperature and velocity fields incline to the right side of the wall.The flammability limit,peak temperature,peak velocity and cold flow stability under the action of the sidewall are improved,but the flame stability becomes worse.With the increase of Reynolds number,the effect of sidewall on restraining the left branch of V-shaped flame from stretching downstream is enhanced,and the equivalence ratio range of V-shaped flame is widened continuously.（3）Experiments and numerical simulations were carried out by changing the sloping angle of the sidewall,and the characteristics of methane/air premixed V-shaped flame with different sloping sidewall angles were obtained.The results show that during the process of reducing the sloping sidewall angle from 90°to 60°,the flame shape remains V-shaped,the flammability limit of V-shaped flame and its amplitude increase continuously,and the equivalence ratio range of V-shaped flame shrinks significantly.With the decrease of the sloping sidewall angle,the area of the highest temperature region of the gas decreases,the peak velocity increases,the flame stability becomes poor,and the quenching height reaches the maximum at 80°.The peak temperature,heat flux on gas-solid interface and net reaction rate of CH₄,CO and CO₂ near the wall reach the peak value when the wall inclination angle is 70°.When the sloping sidewall angle is the same,the peak co mass fraction in the FWI decreases continuously and the branch of CO oxidation moves to the low temperature.At the same position,when the sloping sidewall angle decreases,the CO oxidation branch moves to the low temperature.（4）The influence of sidewall temperature on the characteristics of methane/air V-shaped flame is analyzed by numerical calculation.The results show that during the rise of sidewall temperature,the flame shape remains V-shaped,the quenching height of V-shaped flame decreases.With the increase of the sidewall temperature,the inclination angle of the gas temperature field and velocity field to the right side of the wall decreases significantly,the low temperature zone and low velocity zone near the wall above the quenching height contract significantly,the peak heat flux on the gas-solid interface increases continuously,and the corresponding longitudinal distance is always closely aligned with the quenching height.The peak values of the net reaction rates of CH₄,CO and CO₂ near the wall increase significantly with the increase of the sidewall temperature.Near quenching height,the oxidation branch of CO moves to high temperature with the increase of sidewall temperature;When the sidewall is cooled,the transverse distance corresponding to the peak CO mass fraction is close to the sidewall,and when the sidewall is heated,the transverse distance corresponding to the peak CO mass fraction is far away from the sidewall.