Study Of Droplet Deformation Research Articles

A study of droplet deformation: The effect of crossflow velocity on jet fuel and biofuel droplets impinging onto a dry smooth surface

The aeronautical sector has been, in the last decade, one of those that most invested in more efficient and ecological solutions in order to reduce significantly greenhouse gas and pollutant emissions. The introduction of biofuels in fuel mixtures for aircraft engines is a promising alternative in this sector. The main objective of this experimental study is understanding the influence of crossflow variation on droplet deformation and consequent impact outcomes. An experimental facility was developed and validated to study the impact of single droplets onto a dry, smooth aluminium impact surface under the influence of several crossflow velocities. Different crossflow velocities of 4,5,6,7 and 8m/s were tested. A combination of conventional jet fuel and a biofuel was considered to understand the behavior of jet fuel and biofuel mixtures, and three fluids were used: 100% jet fuel, 75% jet fuel/25% biofuel and 50% jet fuel/50% biofuel. Several parameters, including velocity components, impact angle and eccentricity, were analysed for the different crossflow velocities, and the spread and splash regimes were also defined for the different fluids. The results display that, for each crossflow velocity, an increase in the droplet impact velocity causes a shift from the spread to the splash regime. The presence of a crossflow induces deformation on the droplet, altering its outcome. Ellipsoidal droplets promote the occurrence of spreading, whereas splashing tends to occur for spherical forms, corresponding to higher and lower eccentricity values, respectively. A substantial increase in the crossflow velocity leads to aerodynamic breakup of the droplet.

The study of droplet deformation and droplet volume fraction in an aero-engine bearing chamber

Inside an aero-engine bearing chamber, the shape, velocity, and temperature of each droplet shed from roller elements keep changing under the actions of the rotating airflow. Research on droplet deformation, droplet motion, and droplet volume fraction is fundamental to the understanding of the complex two-phase flow in an aero-engine bearing chamber. In this paper, the modified Taylor analogy breakup model, equations of temperature and motion are established to obtain the size, temperature, and velocity of a deformed droplet. Subsequently, a method is presented to solve for the droplet volume fraction in a bearing chamber based on the size and motion parameters of deformed droplets. In the end, a simplified bearing chamber experimental setup has been constructed. Comparisons between the experimental results and theoretical calculations show a good match based upon the research analogy used. The research work in this paper can provide theoretical foundations for the analyses of heat exchange and lubrication in bearing chambers. This also has great significance in realizing the rigorous design required for the lubrication system of an aero-engine.

Study of droplet deformation, heat-conduction and solidification using incompressible smoothed particle hydrodynamics method

This paper presents a numerical model based on incompressible smoothed particle hydrodynamics (SPH) method to simulate the deformation, heat-conduction and solidification process of a droplet impinging on a substrate. Continuum, momentum and energy equations of the fluid flow are solved using SPH method, with van der Waals force accounting for the surface tension and Fourier's law for heat conduction. Incompressible smoothed particle hydrodynamics method (ISPH) is used here instead of weakly compressible smoothed particle hydrodynamics method (WSPH), to satisfy the fluid incompressibility. Effects of rough and smooth substrates are also taken into account. Results show that the droplet begins to deform and spread, followed by solidification. Also, the temperature of droplet falls faster in the rough one, and this may attribute to the roughness.

In line study of droplet deformation in polymer blends in channel flow

AbstractWe present in situ measurements of a dilute polymer blend in channel flow using an optical flow cell placed at the exit of a twin screw extruder. At weak shear stress, we find mildly deformed ellipsoidal droplets whereas at moderate sher rtes we find coexistence between large aspect ratio strings and ellipsoidal droplets. In the regime of low to moderate stress, depth resolved optical microscopy reveals that the deformation is a function of local shear stress. At large shear stress, the droplet breakup is suppressed; mildly deformed droplets at high capillary number are observed, in contrast to the Taylor model. Optical light scattering provides complementary morphological information that is averaged over the channel depth and confirms the optical microscopy. We discuss these results in terms of Taylor theory and normal forces.