The Research Of High Efficiency Combustion Flow Field Organization In Low Load

Combustion efficiency is an important factor which characterizes the combustion chamber economy.Generally,combustion efficiency is close to 100% in design condition.But it is lower relatively in non-design condition,especially in low load.It means that the engine requires more fuel to compensate for the inefficient combustion.In the combustion chamber,flame tube head structures play a decisive role in combustion performance.So it needs a detailed study for the head of flame tube structures to improve the combustion performance in low load condition.This paper takes a combustor with dual-stage axial swirler as a based model and analyses the head of flame tube structures in low load condition by means of numerical simulation.In numerical simulation,Pro/E software is used to create three-dimensional model and ICEM software is used to mesh the computational domain.When carrying out numerical simulation in Fluent software,Realizable k-? turbulence model and EDC combustion model are employed;CONE injection model is used to simulate the atomization process of the fuel.To include the description of variation process of liquid oil droplets,the Particle trajectory model is activated.For equation discretions,the upwind scheme is utilized.Standard wall function and the SIMPLE algorithm method are used to solve the wall problem and the equations,respectively.The main contents are as follow:1? The anlysis of swirler structures shows that the change of structures will cause the change of velocity field,the recirculation zone size,the intensity of turbulence,the performance of the combustion,such as combustion efficiency,the uniformity of outlet,the pressure loss.2? The structures of the venturi will effect the fuel distribution characteristics and the airflow velocity distribution.It will lead to different combustor performance.Inappropriate outlet diameter values may cause the combustion chamber flameout.3? The form of sleeve outlet and the angle not only affect the velocity distribution of the cold flow field,but also affect the fuel distribution and combustion performance of combustor.Different forms of the sleeve outlet may cause occurrence of local combustion in combustor.4? The influence of these variations in low load condition and design condition are not the same.Above all,dual-stage axial swirler use reverse swirl.First-stage and second-stage vane angles both are 50°.The number of first-stage vane is 14 and the second-stage is 12.Venturi outlet diameter is 24 mm,throat diameter is 22 mm and the distance from the throat to venturi outlet is 8.6mm.The sleeve is in the form of expansion outlet with the angle of 80°.