Gravity effects on the dynamics of evaporating droplets in a heated jet

Abstract

Dispersion and vaporization behavior of liquid fuel droplets in a heated axisymmetric jet is studied using detailed flow visualization based on numerical simulations. Results show that the gravity has a strong effect on the dynamics of jet shear layer and droplets. The presence of gravity introduces the buoyancy-induced hydrodynamic instability, causing the large vortical structures to appear without any external perturbation. The droplet dispersion and vaporization behavior is influenced by both the vortex structures and the gravity. Three regimes, distinguished by the Stokes number St and the ratio of droplet terminal velocity to characteristic gas velocity Vr, are identified to characterize the effects of vortex structures and gravity on droplet dispersion. At low S/ and Vr, the droplets behave like gas particles. In the second regime, 0.1 < St < 0.64 and 0.04 < Vr < 0.3, due to the centrifugal action of the vortex structures the droplets are dispersed more than the gas particles. At the lower end of the third regime, the droplet motion is affected by both the vortex structures and the gravity, whereas at the higher end it is affected more by gravity. The effect of vaporization is to shift the Stokes number range for the three regimes.

Advanced models of fuel droplet heating and evaporation

“…(102) is used with fZ1/Le (see, e.g. [170][171][172]), which cannot be justified unless c pv Zc pg . This difference in the presentation of these equations can be traced to the form of energy conservation Eq.…”

Heat and mass transfer in evaporating turbulent drop-laden flow

“…Several models (e.g. Renksizbulut and Yuen [1] and Park et al [2]) are based on the correlation model of Ranz and Marshall [3] and have been developed to model the parameters. The evaporation rate model of Abramzon and Sirignano [4] considers additionally the latent heat flux of the evaporated liquid leaving the droplet.…”

Comparative study of Euler/Euler and Euler/Lagrange approaches simulating evaporation in a turbulent gas–liquid flow

“…The corresponding turbulent diffusion coefficients C t and D t are defined in Equations (20) and (72), respectively. The necessary kinetic energy of turbulence k C , its viscous dissipation rate ε C , kinetic energy of turbulence k D (the corresponding turbulent diffusion coefficient K D t is given in Equation (73)) and velocity covariance q are to be determined by solving Equations (75), (76), (70) and (71), respectively.…”

“…Several models, e.g. [19,20], based on the correlation model of Ranz and Marschall [21], have been developed to model these parameters. The evaporation rate model of Abramzon and Sirignano [22] considers additionally the latent heat flux of the evaporated liquid leaving the droplet.…”