Research On Combustion Characteristics Of Twin Annular Premixing Swirler Combustor

Twin annular premixing swirler combustor uses the way of three-swirl and central staged combustion,which has the characteristics of lean premixing prevaporizing and lean direct injection,with some advantages including good fuel atomization effect,high combustion efficiency and low pollutant emission.It has been used in the development and research of LEAP engine.In this paper,based on the empirical formula of conventional combustor design,the twin annular premixing swirler combustor was designed and calculated.The Pro/E software is used to establish the three-dimensional geometric model of the combustor.The ANSYS ICEM CFD software is used to mesh the calculation area of the combustor.The mathematical model of the computational domain is solved by the CFD software FLUENT.Then,the numerical simulation study was carried out on the internal flow,combustion and pollutant emission characteristics of the twin annular premixing swirler combustor affected by the parameters such as the swirl number at each level,fuel classification ratio and equivalent ratio.Firstly,the FLUENT software was used to study the cold flow field and the combustion reaction flow field of the combustor with different swirl number at each stage.The research result showed that:the change of the swirl number of the two-stage axial swirler has little effect on the cold flow field,while the swirl number of the main combustion stage radial swirler has a great influence on the airflow structure of the combubstor.With the increase of the swirl number of the swirler,the temperature distribution at the outlet of the combustor is more average,and the pollutant emissions are reduced,however the performance of the combustor is reduced when the swirl number is too large.The performance of the combustor is improved by properly increasing the swirl number of the swirler.Secondly,select the combustor of the first-stage swirler with a swirl number of 0.454,the second-stage swirler with a swirl number of 1.024,and the radial swirler with a swirl number of 1.237.The effect of fuel classification ratio on the performance of the combustor was studied,the result showed that:with the increase of fuel ratio of the main combustion stage,the high temperature area in the combustor is significantly reduced,the outlet temperature distribution is more uniform,and the pollutant emissions are reduced.Therefore,under the premise of ensuring stable combustion,the fuel quantity of the main combustion stage should be as large as possible.Finally,under the condition that the ratio of main fuel to duty fuel is 9:1,the effect of the equivalence ratio on the performance of the combustor was studied.The result showed that:the average temperature of the combustor outlet is increased with the larger equivalence ratio,however the emission of pollutants is also increased.