| Liquid-centered swirl coaxial nozzle has been widely used in aero-engine because it has the functions of both pneumatic nozzle and centrifugal nozzle.In this paper,based on the theory of computational fluid dynamics,combined with experimental research and numerical simulation methods,the influence of working parameters and structural parameters on the atomization characteristics of the nozzle is studied,and the nozzle is optimized.The research contents include the following aspects.Firstly,the experimental system for spray measurement is introduced systematically.The introduction of the spray measurement experiment system mainly includes two aspects: one is the composition of the whole system and its corresponding principle;the other is the method of measuring discharge coefficient and atomization cone angle,and the method of obtaining data processing in the later stage.Secondly,the theoretical basis and numerical simulation methods are studied.(1)Combined with the structure of the liquid centered gas-liquid coaxial centrifugal nozzle and the flow situation inside and outside the nozzle,the fluid region of the nozzle was determined,and the three-dimensional modeling and grid generation were carried out by using UG software and CFD software respectively.(2)Based on the theoretical basis of computational fluid dynamics and experimental results,the corresponding turbulence model was selected as Reynolds stress model(RSM),and the multiphase flow model was selected as VOF model to simulate the flow.(3)The internal and external flow characteristics of liquid-centered swirl coaxial nozzle were analyzed,including the flow development in the nozzle under transient condition,the pressure distribution,velocity distribution and fuel volume distribution in the nozzle under steady condition.Thirdly,the influence of working parameters and structural parameters on the atomization characteristics of liquid-centered swirl coaxial nozzle is studied.Based on the single factor control variable method,the relationship between the three working parameters of gas injection pressure drop,fuel injection pressure drop and gas-liquid ratio,the four key structural parameters of nozzle outlet diameter,straight pipe length,expansion section length and expansion angle,and the three atomization characteristic indexes of flow coefficient,liquid film thickness and atomization cone angle were explored.Finally,the multi-variable multi-objective optimization design of the liquid-centered swirl coaxial nozzle is carried out.The optimum parameters are gas-liquid ratio,nozzle outlet diameter,outlet straight pipe length,expansion length and expansion angle,experimental Design of multi-objective atomization performance index based on atomization Cone Angle,liquid film thickness and flow coefficient.By means of range variance analysis,the main influencing factors and the order of the influencing factors are discussed,and by means of regression analysis,the optimal solution of parameters and the optimal target value are obtained. |
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