| The central-staged combustor is based on theory of aerodynamic staged and fuel staged combustion,which consists of two combustion modes: diffusion combustion and lean premixed combustion.Its structural characteristics are generally as follows: The head is divided into two stages,the central one is pilot stage,in which combustion is diffusion combustion,The periphery is the primary stage,in which lean premixed combustion mode is adopted,and two-stage coaxial arrangement is adopted.By applying staged supply fuel and zoning combustion the working range of the engine can be broadened while the emission can be greatly reduced.Therefore,it is of great significance to study cold flow field and fuel spary field of central-staged combustor.In this paper,the flow field and fuel spray field in central-staged combustor are studied.The research contents in this paper mainly consist of the following three aspects:1)The cold flow fields of a central-staged combustor model with head case A and its simplified model are numerically simulated.The numerical results show that:(1)There is a low-speed primary recirculation zone in central-staged combustor,which provides a stable ingnition source for lean fuel combustion.The radial width of the primary recirculation zone increases first and then decreases with the increase of axial distance.(2)The velocity of the throat area of the pliot stage's Venturi tube is high,and two swirls in the inner baffle have strong turbulent flow,which has a positive atomization and mixing effect on the primary stage's fuel spray.(3)The observation window has an obvious influence on structure of cold flow field in the section with the window,while its influence on cold flow field in the section without the window is not obvious.2)The cold flow fields of each head under different working conditions are studied by Particle Image Velocimetry(PIV).The baffle expansion angle and height of head case A are less than that of head case B.The experiment results show that:(1)With the increase of inlet air massflow,the velocity of air flow in combustor increases gradually,and the component velocity of air flow also increases.However,the shape and trend of velocity distribution are basically the same,and the structure of flow field is unchanged.(2)The velocity of cold flow field in case A is similar to that in case B,and the variation law is also the same.Changing the expansion angle and height of the baffle will reduce the radial width of the front part of primary recirculation zone.3)The fuel atomization characteristics of different head cases under different operating conditions are studied by PIV measurement technology and Image post-processing technology.The experiment results show that:(1)With the increase of inlet air massflow,the SMD spatial distribution in central-staged combustor is gradually uniform,and the average SMD decreases gradually.(2)Under various working conditions,the fuel droplets with particle size of 50-100 ?m occupy a larger volume fraction.With the increase of inlet air massflow,the volume fraction of fuel droplets with diameter less than 100 ?m increases gradually.(3)The distribution structures of fuel spary field in jet area are similar for head A and B,The number of each fuel droplet size in case A is smaller than that in case B,and the average SMD of the whole field is smaller.The above research results can provide technical support for the design and optimization of central-staged combustor... |
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