Study On Transverse Jet Atomization And Droplet Microexplosion And Combustion Of Aviation Kerosene Blending With N-butanol/n-pentanol

Because of the high calorific values,the density and viscosity values thatclose to those of aviation kerosene,and the mature preparation processes and the low preparation costs,n-butanol and n-pentanol are potential alternative fuels in aeroengines.In the aeroengine,the breakup of liquid jet,droplet distribution and droplet micro-explosion during the fuel transverse jet process have very important impacts on the combustion process,engine performance and emission characteristics of fuel usage.Therefore,the study of the transverse jet spray process,atomization characteristics and single droplet microexplosion and combustion process of aviation kerosene-n-butanol(or n-pentanol)blended fuel is helpful to evaluate theirapplications in aero engines.A transverse jet spray experimental system was set up.Under a variety of experimental conditions,the transverse jet spray experiment of aviation kerosene n-butanol/n-pentanolblended fuels were carried out.The process of the breakup of liquid jet in the transverse airflow was collected by a Shadow light path and high-speed photography,and the MATLAB program was used for data processing.It was found that there existed column breakup regime and surface breakup regime,while the ratio of liquid to gas momentum q and the Weber numberof crossflow air Weg played leading roles in the transformation of the two regimes.The transition boundary in the Weg-qmap suitable for the transverse jet breakupregime of aviation kerosene-n-butanol/n-pentanol blended fuel was proposed.The results showed that there exists bag breakup mode,multi-mode breakup mode and shear breakup mode in the surface breakup regime.The formulas for predicting the boundary of the upper trajectory,the point of the column breakup and the surfacewave lengthwere constructed,in which the influences of the dimensionless parameters such as the gas Weber number,the liquid gas momentum ratio and the Ohnesorgenumberwere considered.The velocity field and diameter distribution characteristics of the transverse jet of aviation kerosene n-butanol/n-pentanol blended fuels were experimentally studied.The overall velocity fieldcharacteristicsand the influence ofn-butanol/n-pentanol proportion on the velocity field were obtained by PIV experimental data analysis.The velocity direction of droplets gradually changed from vertical to transverse flow direction with the action of transverse air flow.At the liquid-gas interface of transverse jet,the maximum turbulence intensity appeared,and the position of vortex region wasdetermined;with the increment of n-butanol/n-pentanol volume proportion,thevalues of Uxz,Uxy,Ux,Uz and Uy increased first and then decreased.,while thevolume proportion of n-butanol corresponding to the maximum velocity value was different from that of n-pentanol.Through the analysis of Shadow method experimental data,it was found that in aviation kerosene-n-butanol/n-pentanol transverse jet,the droplet diameter,the shape factor Sf and the number density were all dominated by gas Weber number,and the change tendencies were different in different breakup modes;with the increase of n-butanol/n-pentanol volume proportion,in bag breakup mode and multi-mode breakup mode,the droplet diameters and the shape factors both increased first and then decreased,and the maximum droplet diameter in the diameter distribution field of the aviation kerosene-n-pentanol blended fuel was larger than that of the aviation kerosene-n-butanol blended fuel.Ina microexplosion experimental device,the microexplosion and combustion experiments ofsingle droplets of aviation kerosene-n-butanol/n-pentanol fuels were carried out.The experimental results showed that the increase of the volume ratio of n-butanol/n-pentanol led to the appearance of microexplosion of the fuel single dropletduring the heating process,and the microexplosion delay time decreased first and then increased.Compared with the pure aviation kerosene droplet,the blended fuel droplet showed longer ignition delay time and shorter combustion duration time.With the increment of ambient heating temperature,the ignition delay time and the combustion duration time of tested droplet were all shortened.Combining the maximum expansion diameter with the delay time of microexplosion,the microexplosion index was proposed to comprehensively evaluate the microexplosion intensity and difficulty of multi-component fuel droplet;combining the ignition delay time with the combustion duration time,the comprehensive combustion index was proposed to comprehensively evaluate the combustion performance of multi-component fuel droplet.