Effect Of Variable Conditions On Flame Characteristics Of Partially Premixed Combustion

In recent years,with the rapid development of gas-steam combined cycle technology and gas turbine technology,the requirement of gas turbine technology is getting higher and higher.Combustor is an indispensable core component of gas turbine,so the research on it is more and more urgent.The working process in combustion chamber is much more complicated than other parts.It involves a series of complex processes such as heat transfer,mass transfer,flow and chemical reaction of gas.Therefore,it is a trend to study the design method of combustor by computer numerical simulation,and it is also the most commonly used way to summarize the empirical formula of combustor design method based on a large number of experimental data.In this thesis,the combustion characteristics of partially premixed swirl flame of methane are studied based on the research of premixed combustion at home and abroad.Firstly,a gas turbine combustion test-bed is built and relevant experiments are carried out.Then,the corresponding three-dimensional model of the model combustor is established by using Gambit,a three-dimensional pre-processing software.Then,the combustion characteristics of the model combustor are simulated by using Fluent,the combustion chamber is calculated under different operating conditions,and the temperature and velocity fields of the combustor are analyzed in detail.Finally,the prediction results of different theoretical models are compared with the experimental results,which reveals the accuracy of the existing theoretical models.Based on the experimental data,a new prediction model is proposed,and some basic rules of partial premixed combustion of methane in combustion chamber are summarized.The work carried out in this paper and the results obtained are as follows:The results of temperature field obtained from the experimental and numerical simulation are basically the same:under the same pressure conditions,the flame length Lf increases with the increase of fuel flow mF,and the experimental value is about 0.8 times of the simulation value.The flame area increases with the increase of fuel flow rate,the experimental value decreases slightly with the increase of pressure,and the simulation value does not change much.On the whole,the experimental value is about 0.75 times of the simulated value.The flame area increases especially fast from 10 g/min to 12 g/min.The distribution of velocity field under three kinds of fuel flow is approximately the same.The larger the fuel flow rate,the larger the area of a certain velocity range correspondingly.At the bottom of the combustor,the velocity at both sides of the flame and at the outlet of the cyclone shows a minimum negative value.Because of the viscous force between the gas and the wall,the velocity of the air flow decreases,and the velocity at the wall is also relatively small.The predicted results of theoretical models:Fr number,Frf number and dimensionless heat release rate Q*all accurately predicted the variation trend of flame length.Their predicted values were 1.2,1.7 and 1.3 times higher than the experimental values,respectively.At the same time,based on these three models,the experimental data are fitted to get a new correlation.Finally,a prediction method based on Re is proposed.