Numerical Study On Premixed Combustion Of Methane In A High Pressure Combustor

With the increasing pollution problems and the gradual strengthening of human environmental awareness,problems of pollutants emissions become a topic of common concern.Low-emission technology is the main goal of gas turbine research all over the world.Thus,Optimization of the low NOx emission combustion technology,and improvement of the combustion efficiency while taking into account the combustion stability and restrction of pollutants in the combustion process became of great importance.Based on the research of different low NOx combutsion technologies at home and abroad,this paper uses the numerical simulation software Fluent to simulate the combustion characteristics of dry low-emission combustor,and sums up some basic rules about methane premixed combustion,which lays the foundation for the development of low pollution combustion technology.The work of this paper is mainly from the following aspects:1.By using Gambit,a dry low-emission model combustion chamber is modeled and divided with grid.In order to verify the model,the rationality of the model was tested in two aspects: the verification of grid independence and comparison of simulation results and experimental data.After testing,the model with four hundred and seventy thousand grids has better grid independence.And the simulation results are in good agreement with the experimental data.2.The differences of simulation result using FR-EDM model and EDC model are studied using the Fluent software.The temperature distribution and NOx formation are analyzed to ensure the accuracy of the mathematical model and applicability.3.The temperature,the flow field,the flow field,velocity distribution,NOx formation,NOx concentration at the outlet of the combustion chamber,and temperature uniformity were compared.The predicted results show that,with an increase of equivalent ratio,the flow field barely changes.Bulk radical velocity increases slightly,while the range of the recirculation areas barely changes.The temperature field changes a lot.The area of high temperature expands significantly,and bulk temperature rises clearly.The formation rate and exit concentration of NOx both shows an obvious increase.4.Finally,the effects of intake air temperature on combustion and pollutant generation in the model combustion chamber are studied.The results show that with an increase of intake air temperature,the flow field in the combustion chamber rarely changes.The axial velocity increases slightly.The whole temperature field changes greatly.The area of high temperature extends towards upstream and the central recirculation zone temperature rises obviously.The concentration of NOx increases significantly.The total mole fraction of NOx increases significantly.Some basic rules of high-pressure premixed combustion of natural gas are concluded,which provides a theoretical basis for the combustion stability and low NOx emission combustion technologies,which is of great practical significance.