Study On Flame Stabilization And Pollutant Emission Reduction With A Slitted Bluff Body

In recent years, an increasingly prominent problem of energy shortage and growingenvironmental pollution has become a focus of global attention. As a developing country,the energy and environmental problem of China is particularly prominent. The use of lowcalorific value gas is an efficient way to solve the energy shortage in our country, but lowcalorific value gas is unable to burn in a stable condition, at the same time, the emissions ofnitrogen oxides has become increasingly in China. Therefore, low calorific value gasstable-combustion technology and reduce NOx emissions technology for shortage of energyresources and environmental pollution problem in our country has extremely importantsignificance.In this paper, the premixed methane-air turbulent combustion were simulated with abluff body or a slitted bluff body in a free space, by using the commercial softwareFLUENT, and detailed chemical reaction mechanism of methane/air mixture, the velocityfields, temperature fields and concentration fields of the bluff body burner and the slittedbluff body buner were compared in the free space. In this paper, the effect on flamestruction and NO formation in methane-air premixed flame with steam addition in the freespace was studied. By comparing the simulation results, we draw the followingconclusions:(1) When the velocity of inlet is20m/s, the velocity field of the bluff body appear tothe phenomenon of karman vortex street flow in free space, but the downstream wake ofslitted bluff body speed smoothly, this is conducive to keep fluid flow steady. Therecirculation zone average turbulence intensity of slitted bluff body is stronger than thebluff body, this is beneficial to heat exchange and mass transfer between high temperatureburned gases and fresh premixed gases.(2) The slitted bluff body burner of free space, introducing a small amount of gas andair directly into the gap of slitted bluff body, the fresh premixed gases can be ignitedquickly because of the high temperature and low speed conditions of recirculation region,then establishing duty flame,so the combustion performance of slitted bluff body burner of free space is better than bluff body burner, the flame area of slitted bluff body is muchwider, exothermic area is larger, the temperature of high temperature reaction zone is higher,the heat release is much more, all this will be conducive to the stability of flame. Becauseof the methane-air premixed combustion with slitted bluff body in free space producehigher flame temperature, but the thermal NOx productions are associated with temperature,so the emission level of NOx increased, this is not conducive to the protection of theenvironment.(3) Simulation found that water vapor added to decrease the highest temperature of theflame, it makes the flame area become smaller, the high temperature reaction zone becomelong and narrow, it also decreases the stability of the flame. What’s more,The addition ofwater vapor also reduces the concentrations of OH radicals and O radicals, inhibiting thegeneration of NO, so as to achieve the purpose to reduce NO emissions.