| Double jet impingement is a common atomization method in the combustion chamber of liquid rocket engine.In this paper,the direct numerical simulation method and piecewise linear interface reconstruction method are used to study the jet structure,fluid surface area,liquid film deflection angle,vortex characteristics,wave characteristics and shear thinning characteristics produced by the impact of shear thinning non Newtonian liquid.It can be divided into the following aspects:1.In this paper,the typical liquid film structure formed by the impact of two jets with medium Weber number is calculated.It is thin in the middle and thick on both sides,and rim flow is formed at the edge of the liquid film.The breaking form belongs to the closed type of liquid film breaking.The surface area of liquid is increasing,but the growth rate is changing.The maximum dimensionless surface area is 1.92.The expansion half angle of the liquid film is constant at 42.38° and the breaking process of the liquid film is accompanied by the direct contraction of the liquid filament into droplets.The vorticity increases gradually from the upstream to the downstream of the jet,and the vorticity is larger in the middle broken area.The rim part of the upwind region downstream of the jet is basically stagnant.The vorticity dissipates gradually along the y-axis as well as in the x-direction,and the viscosity coefficient near the impact point is only 0.7 times of the initial viscosity coefficient.2.Three kinds of flow structures produced by jets impingement are obtained by calculating different Weber numbers:single diagonal jet,typical liquid film structure and open liquid film structure.In general,the jet Weber number determines the atomization mode of jet impingement.When the Weber number is low,the wave produced by the impact is reflected as the wave of the synthetic liquid column,which can be decomposed into the superposition of three sinusoidal functions,and the vortex produced has less influence.At the middle Weber number,no obvious fluctuation is observed on the liquid film surface.The vorticity increases gradually from the upstream to the downstream of the jet.In addition,the vorticity dissipates gradually when it is far away from the liquid surface.At high Weber number,there are many obvious impact waves on the liquid film formed by liquid impact,and the overall wavelength increases with the increase of the distance from the wave to the free edge.The vortices produced by the jet are mainly distributed in the ordered attachment region and the disordered explosion region.Obvious pairs of counter vortices can be observed in the ordered attachment region,while the vortices in the disordered explosion region are mainly irregular.In addition,in these three states,the liquid film is broken to form liquid filaments,the liquid filaments contract to round droplets under aerodynamic force,and the droplets fuse.3.By calculating the two influencing factors of different momentum ratio(MR),i.e.the jet velocity ratio and the jet aperture ratio,it is found that when the momentum ratio is equal to one moment,a thin liquid film structure with thick edge in the middle is formed,which is broken from the inside under the action of surface tension.In different jet velocity ratio,when Mr is not equal to 1,the structure of liquid film and liquid column is formed in the middle of the jet,and the structure of head droplet is formed in the downstream,and bubbles are generated inside the jet.The bubbles gradually develop from slug shape to fine bubble shape.The jet cross-section shape can be divided into four stages:Yuanbao shape,arc shape,Douban shape and ellipse shape.In different jet aperture ratio,when Mr is equal to 2,the droplets in the tail of the liquid film roll up,while the others are basically consistent with the jet velocity ratio.The law of both is that the deflection angle of liquid film increases with the increase of momentum ratio,and the length width ratio of liquid film increases with the increase of momentum ratio.The film spreading angle decreases with the increase of Mr.The decrease of the viscosity coefficient near the impact point decreases gradually with the increase of MR,and the maximum decrease is more than 20%. |
