Study On Numerical Simulation Mechanism Of Taylor Bubble Movement In Stagnation Liquid Hydrogen

High-energy and environmentally friendly liquid hydrogen cryogenic propellant is widely used in rocket launches.Because the gas-liquid two-phase flow of cryogenic fluid is quite different from that of normal temperature fluid,the study of bubble motion in liquid hydrogen is of great significance.Based on the Fluent software,this paper uses the VOF model and the RNG k-? turbulence model to numerically simulate the rising motion of Taylor bubble in static liquid hydrogen under different pipe diameters and inclination angles,and analyzes the ultimate velocity of Taylor bubble,the hydraulic characteristics of the nose and the liquid film area and the change law of wake length.The research results show that:(1)The rise Fr of Taylor bubble in the liquid hydrogen fluid under the vertical pipeline increases first and then stabilizes with the increase of Eo number,but the stable value of Fr is quite different from that of normal temperature fluid.The distance variable Z'/D from the tip of the bubble to the steady flow field at the front end,is less affected by Nf number.The length variable Z*/D from the bubble nose to stable liquid film,increases with the increase of Nf number.And the thickness of the non-dimensional liquid film ?/D increases first and then decreases with the increase of Nf number.The dimensionless value of wall shear stress first increases and then decreases with the increase of Eo number.The length variable Lmin/D from bubble tail to the steady flow field at the end of the bubble,increases with the increase of Eo number.(2)The shape of the nose of the single Taylor bubble in the liquid hydrogen fluid under the inclined pipe increases with the inclination angle,and gradually approaches the wall until it adheres to the wall.The symmetrical vortex structure of the bubble nose and tail streamlines in opposite directions is destroyed,and the final liquid film thickness gradually counter-clock-wise vortex on the increasing side occupies the pipe;the ultimate velocity of bubble rise first increases and then decreases with the inclination of the pipe.When the inclination angle 0=90°,the ultimate velocity of the Taylor bubble rise is zero;the length of the bubble increases with the inclination of the pipe However,in a fluctuating state,the non-dimensional value of the maximum wall shear stress decreases with the increase of the inclination angle,and the pipe wall shear stress at the end of the bubble decreases violently fluctuatingly.(3)During the approach and fusion of the double Taylor bubbles in the stagnant liquid hydrogen fluid,the shape,length and speed of the nose of the leading bubble remain almost unchanged,and the shape,length and speed of the nose of the bubble follow the change.The length of the double Taylor bubble fusion into a stable Taylor bubble increases with the increase of the pipe inclination angle,and the velocity first increases and then decreases with the increase of the pipe inclination angle.As the bubble spacing gradually decreases,the maximum value of the non-dimensional value of the wall shear stress of the leading bubble remains almost unchanged,the non-dimensional value of the wall shear stress at the tail of the leading bubble gradually increases,and the non-dimensional value of the wall shear stress following the bubble The maximum value gradually increases.The research results in this paper are helpful to the study of slug flow patterns in cryogenic gas-liquid two-phase flow,and lay a theoretical foundation for the safe transportation of liquid hydrogen propellant in cryogenic pipelines.