This study experimentally investigated various spraying modes in electrospraying, an atomization method in which a high voltage is applied to the auxiliary device at the tip of the nozzle. The spraying modes were generated depending on the experimental parameters (voltage, current, and flow rate) and characteristics of two test solutions (S and C), which were a mixture of ethanol, glycerol, citric acid, and water. Solution C had a higher electrical conductivity than solution S. Eleven spray modes were identified in the study. From a comparison of the spray modes, a maximum Sauter mean diameter (SMD) of the cone jet of solution S was 1. 7 times that of solution S. The standard deviation of SMD for the unstable, rotating-jet, and pulsed-jet modes were more than two times that for the cone-jet mode. With an increase in flow rate in the cone jet, the SMD and SMD standard deviation of solution C increased linearly, and the SMD value of solution C was ~5% lower than that of solution B. The SMD standard deviations for both S and C solutions were small at low flow rates, and the standard deviation for solution C (with high conductivity) was smaller than that of solution S. For a given SMD, the current associated with solution C was higher than that associated with solution S. The study presented the comprehensive data for SMD, SMD standard deviation, and current in an electrospray system for the two fluids of different electrical conductivities under various experimental conditions.

Electrospray is an atomization method which produces monodisperse and fine droplets by applying a high potential difference between a nozzle and a counter electrode. Therefore liquid meniscus shows different behaviors when flow rate or applied voltage varies in the electrospray method. Here we report experimental study of these modes based on observation of the liquid meniscus shape emitted from the nozzle. The formation of different modes is reported and forces acting on the meniscus in each mode is discussed. In this work classification of electrospray modes is reviewed for a wide range of flow rates, between0- 80ml/h, and voltage, between 0-8.5kV. Electrospraying of ethanol is studied as a promising clean fuel for a wide range of voltages and flow rates. Formation of dripping, sibling, spindle, micro spindle, intermittent cone jet, oscillating jet, precession, cone-jet, multi jet, simple jet and ramified jet modes are observed. It should be noted that throughout this study such as identification of mode shapes has been done based on taking photos of electrospray phenomenon using the method of shadowgraphy, and this method has been done by using a high speed and a high resolution camera. In present configuration, for all flow rates, the dripping and sibling mode is utilized for all of voltages which are lower than 3kV, for voltages between 3-4kV the spindle mode will be seen and for the voltages which are more than 5.5kV the multi jet mode will be observed. There are the other mode shapes for voltages between 4-5.5kV.

Atomization is a process by which a volume of liquid is converted spray. This process includes the breakup of the liquid jet or the liquid sheet exiting the injector. This paper has experimentally investigated the models and mechanisms for the breakup of the liquid jet and the liquid sheet formed by the jets impingement in a still environment and in an environment with counter flow, coflow, and cross flow. Also, the effects of the impingement angle, injector diameter, and jet length before impingement on the formation of the liquid sheet have been explored. Imaging has been employed to investigate different patterns formed by these interactions. To produce water jets, injectors with 0.4 and 0.9 mm diameters at a velocity range of 1-33 m/s and in accordance with Reynolds numbers between 3,000 and 30,000 have been used. It was found that in the low flow speed range, the water jet breaks up by the Riley’s breakup model. While in high speed range, the breakup model is the firstwind - induced breakup model. The measured breakup length has a very good agreement with the result of Sallam’s equation. In investigating the breakup of liquid jets in cross flow, six breakup models were observed, including Rayleigh-like, turbulent, column, bag, multimode and shear breakup models. Also, in paper, an equation has been presented for the penetration of water jet into an air counter flow. Through a qualitative comparison of the images taken from the impingement of two water jets, velocity and Reynolds number ranges of the closed rim, alternating drops, open rim, and fully-developed models were determined. It was observed that, by increasing pre- impingement length of a jet, the instabilities on the liquid sheet increase.

The interplay between lateral airflow and liquid jet is extensively utilized in many engineering scenarios, including steam-power gas catapult systems. It is of paramount engineering interest for the fragmentation phenomena of jet in crossflow. This study establishes a jet test system and observes the flow characteristics resulting from water jet and crossflow interaction by utilizing the Schlieren method. The effects of inflow and outflow parameters on water jet penetration depth are extensively examined by evaluating parameters such as the gas-to-liquid momentum ratio, nozzle dimensions, and temperature. This study focuses on jet trajectory patterns and establishes mathematical correlations through penetration depth measurements that yield predictive equations for jet behavior.

This paper investigates the effects of swirling air stream on a viscous hollow cone spray atomization with sinuous instabilities. The dimensionless dispersion equation of wave growth rate was derived with linear stability analysis. The dispersion equation is solved by numerical method and swirling air stream effect on maximum growth rate and its corresponding unstable wave number is investigated. The results show that the maximum growth rate of a swirling liquid sheet subjected to purely outer axial air is more pronounced compared to its counterpart subjected to purely inner axial air. In swirling air stream, swirling of outer air has more effect compared to inner air on maximum growth rate and improves the atomization. The combination of inner and outer air stream swirling has the highest effect on wave growth rate. The growth rate can be related to the breakup length of the liquid sheet and when the growth rate increases, breakup length is shorter. The drop diameter is dependent to the wave number and decreases with the increase of the wave number that can afford improvement of combustion and decrease the specific fuel consumption.

A computational study of turbulent evaporating and combustion sprays is reported. The major focus is to develop a solution procedure and to examine the detailed effects of fuel atomisers with and without swirl on droplet behavior and spray characteristics in reacting and non-reacting flows. A hybrid Eulerian-Lagrangian method is employed to model the reactive and isothermal flow-field of the combustor. The equations governing the gas are solved by a control-volume based semi-implicit iterative procedure and the sets of time-dependent differential equations for each of the drop sizes are integrated by a semianalytic method. The calculation procedure is applied to the case of spray combustion in an axisymmetric combustor and the results are compared with experimental data. Computational results show the detailed effects of fuel atomiser design parameters (such as nozzle angle and swirl) on evaporation rate and combustor performance. The calculations show that the droplet trajectory and vaporization characteristics are strongly influenced by the atomization technique. The results also indicate that swirl atomizers have the ability to burn "difficult" fuels (e.g. fuels with low calorific value or high boiling point).

In the present work, a model was proposed to predict the thermal history during rapid solidification (RS) of metal droplets in the gas atomization process. The classical theory of heterogeneous nucleation was based on Newtonian heat flow and enthalpy method. Solving the governing numerical equations by the finite difference method (FDM) gave up the opportunity of analyzing the temperature-time history of the droplets during cooling in the RS process. Here, cooling in the liquid state, nucleation and recalescence, segregated solidification, eutectic solidification and cooling in the solid state were considered. To verify the model, the gas atomization of Al-4.5% Cu alloy was studied and the results were compared with the Shukla's model [1]. Convincing agreement was obtained between the predicted undercoolings and the experimental results reported previously.