Numerical Simulation Of Flow Field And Combustion Characteristics Of A Gas Burner

With the implementation of the East Gas Popeline project, gasous fuel is widely used for its high gas combustion efficiency and low emission characteristics. As the main equipment, gas combustion burner takes a very important role in the clean use of gas. Current investigations on gas combustion burner are focused on flame control through structure change and combustion control etc. In this paper, strong swirl burner which is common in use and typical side micro jets burner are studied in detail using the methods of the numerical simulation combined with experiment research to explore the combustion-control mechanism and methods, and flame control is achieved by optimization of the geometry and operation condition, thus strengthening the mixture of the gas and air, improving combustion efficiency and reducing emissions.The typical strong swirl burner TECFLAM is simulated, using three kinds of turbulence models (the standardκ-εmodel, RNG modle and the modified RSM model) and three kinds of combustion models (Finite rate/eddy dissipation model, the equilibrium chemical PDF model and the steady flamelet model), respectively, coupled with detail chemical reaction mechanism of methane combustion, the fields of temperature, velocity and concentration of the main combustion products are obtained by simulation, the results show that different models in use can all reflect the the feature of strongly swirling flow field, but great differences exist in the coincidence with the experiment results, the result of RSM model coupling with detail mechanism of chemical reaction agrees well with the experiment data.The cold turbulence jet with circle/square/rectangular structure respectively is simulated using the LES model with the Re of 10000. The results show that jet perturbation increase with different degree, entrainment capacity is enhanced and axial velocity decay accelerates due to the irregular cross section of the square and rectangular structure. However through simple changing the cross section figuration of the nozzle, the jet initial section with poor mixing ability is only able to shorted, but not be eliminated..Through cold and hot flow field simulation of different structure of side micro jet in different flow ratio, the result shows that side micro jet can increase the disturbance, and the axis velocity decay accelerates. When the number of side micro jets decreases and flow ratio of side micro jet increases, the axis velocity decay accelerates. The axis velocity decay is the fastest in the 2 and 3 side micro jets. By comparing the flame structure and concentration distribution of methane with different side micro jets under the flow ratio of 8:2, due to the disturbance of side micro jets, the mixing of fuel/air at near-field region is enhanced and flame becomes shorter. The low temperature region at the initial section is shortened, the high temperature region moves forward and the flame peak temperature is increased. While the amount of air entrainment and turbulence is enhanced. By comparing different side micro jets, it's found that with 2 or 3 side micro jets, the rate of methane combustion is faster, while the flame length and low temperature region at the near field section are shorter and the axis temperature rises faster, and the 6 side micro structure is the worst. For turbulence is enhanced, sub-phenomenon of flame appears in the 4 and 6 side micro jets and flame maintaines a continuous structure in the 2 and 3 side micro jets. By comparing the mass fraction of NOx with different geometries, the amount of NOx formation without side micro jet is more than that with 2,3,6 or 4 side micro jets.Though the cold and hot simulation on the side micro jet, it is found that with the micro-jets, the entrainment mixing capacity is enhanced, the size of central low temperature area is reduced, the high temperature region moves forward, the peak temperature of the flame is also increased, while mixing capacity with 2 or 3 side micro jets is strongest and the flame length is shortest at the certain flow ratio.Finally, the cold experiment of different side micro jets is done, the test results show that the axial velocity decay in the 2 and 3 side micro structure is the fastest. The experimental results agree with the simulation results in a large degree.