Investigation On Combustion Mechanism Of High Temperature Air Combustion And Heat Transfer Characteristics Of Regenerator

With the increase of global energy consumption and environmental damage caused by pollutant emission,people are increasingly concerned about how to improve the efficiency of traditional combustion methods to save energy and how to reduce the emission of pollutants to protect environment.Although preheated air combustion can achieve higher efficiency than traditional diffusion flame,it will cause a large increase in the emission of nitrogen oxides and other pollutants,which accelerate the destruction of the environment.The High Temperature Air Combustion(HiTAC)is to preheat the air to more than 800 K and achieve the atmosphere of high temperature and low oxygen in the reaction zone,which makes the peak flame temperature decrease sharply.The distribution of flame temperature is more uniform,the emission of nitrogen oxides and other pollutants is obviously reduced.In order to apply the High Temperature Air Combustion to all kinds of combustion equipment,it is necessary to study the flame characteristics and chemical reaction mechanism,and provide more theoretical and experimental investigation on the energy saving and emission reduction of combustion.In this paper,the combustion mechanism and nitrogen oxide emission characteristics of the High Temperature Air Combustion are studied by two ways of experimental research and numerical simulation.Numerical simulation of heat transfer of regenerator is also studied.The experimental setup consists of a coflow burner,gas supply system,measurement instruments and data processing system.Liftoff behivor and stabilizaiton mechanism of turbulent jet diffusion flame for methane and propane under different coflow conditions are investigated.The influence of oxygen concentration and temperature of the coflow on the lifted height of flame is also studied.By analyzing the evolution trend of the lifted height,it is revealed that the auto-ignition of the jet fuel replaced the traditional diffusion flame propagation mechanism to become the main factor affecting the stability of the flame in the atmosphere of high temperature and low oxygen,while the stabilization mechanism of the free jet diffusion flame is still dominated by the traditional flame propagation mechanism.The flame temperature is measured by primary spectrum pyrometry and the temperature distribution characteristics of the flame under different coflow conditions are analyzed.Three different combustion modes are divided into traditional combustion,High Temperature Air Combustion and the transition mode between them.A prediction model of lifted height which is influenced by the non adiabatic ignition delay time the initial mass fraction of fuel is proposed to explain the stabilization mechanism of High Temperature Air Combustion.Eddy Dissipation Concept(EDC)model combined with GRI-Mech 3.0 and USC-Mech II detailed reaction mechanism for methane and propane respectively is proposed for simulating the combustion characteristics and NO_x emission characteristics of the jet flame under different coflow conditions.Standard k-ε turbulence model and NO_x model are considered.The comparison of the calculated results with the experimental data shows that the error of the model can meet the requirements of the study.The results show that the High Temperature Air Combustion is featured with more uniform temperature distribution and lower emission of nitrogen oxide.The lower flame peak temperature can also prevent local high temperature from damaging the material and structure of the combustion equipment.The heat transfer of regenerator in high temperature air combustion system is numerically simulated.Based on the mass conservation and energy conservation,a single channel heat transfer model of a glass furnace regenerator is established.Periodic boundary conditions and heat loss of the system are considered.Heat resistance factor is introduced to improve the accuracy of the model.The effects of different flow inlet speed,cycle time,brick material and wall thickness of regenerator brick on heat transfer of regenerator are studied.The results agree well with the experimental data and can help improve the heat transfer and optimize the structure design of the regenerator.