Numerical Simulation Of Liquid Jet Atomization In Subsonic Crossflow

As a typical droplet atomization method,jet in crossflow is a method that is often used in engine combustion chamber and other systems to inject liquid fuel jet into gaseous transverse flow.The residence time of fuel in the combustion chamber is very short,and the time is in milliseconds.The liquid fuel needs to undergo complex processes such as atomization,mixing,evaporation,and combustion.The efficient mixing of fuel and air flow is a key factor determining the combustion performance,and can correspondingly reduce pollutant emissions.In this paper,large eddy simulation method based on CLSVOF is used to investigate the atomization mechanism of liquid jets and pulsed jets in subsonic crossflow,and the influence of dimensionless parameters involved in jet in crossflow on the jet shape and atomization characteristics is further explored.Firstly,this paper studies the primary atomization process of liquid jet in subsonic crossflow.The spatial shape of the jet is effectively obtained,the physical process of the primary breaking of the jet is expounded,and the primary atomization mechanism of the liquid lateral jet is explored.The results show that the shearing effect of gas-liquid leads to the generation of KH unstable fluctuations,and the KH surface wave dominates the surface fragmentation of the jet column;the squeezing effect of gas-liquid leads to the generation of RT unstable fluctuations,and the RT surface wave dominates the jet column and finally columnar broken.Secondly,the effects of three dimensionless parameters,Weber number,Ohnesorge number and Liquid / gas momentum ratio q,on the atomization morphology and characteristics of transverse jet in subsonic airflow are studied in this paper.It was found that the larger the We number,the greater the shearing effect of the gas-liquid interface,and the columnar fracture dominated by RT instability gradually transformed into the surface fragmentation dominated by KH instability.The fragmentation length Lx and the fragmentation height Ly both decreased with the increase of the We number,the droplet velocity increased significantly with the increase of the We number.The larger the Oh number,the higher the viscosity of the liquid,the more likely the liquid is to aggregate and not be easily broken,the windward surface of the liquid column is smoother,and the surface breakage dominated by KH instability is gradually weakened.The larger the Oh number is,the deeper the jet penetration depth is;the crushing length Lx and the crushing height Ly both increase with the increase of the Oh number.The momentum ratio q is a key parameter affecting the jet penetration depth.The larger the momentum ratio q,the higher the outlet velocity of the liquid jet.The greater the momentum of the liquid jet,the more resistant the liquid column bending and breaking caused by aerodynamic force and penetrate deeper.Finally,a pulsed jet whose incident flow is a small sinusoidal oscillation is studied in this paper.Under the same average mass flow conditions,compared with the steady-state jet,the instability caused by the periodic fluctuation of the pulsed jet velocity will replace the RT instability and lead to the generation of surface waves,and dominate the liquid transverse pulsed jet once atomization.Effectively enhances the primary atomization and crushing degree of the pulsed jet.The larger the St number,the faster the oscillation frequency of the pulsed jet velocity,the more obvious the surface wave on the windward side of the jet column,the more severe the vibration amplitude of the surface wave,the easier the droplets are peeled from the jet column,the more severe the surface breakage,and the shorter the surface wave wavelength.At high St numbers,the penetration depth of the pulsed jet is increased by 12%,enhancing the gas-liquid mixing efficiency.