The investigation focuses on optimizing the length of wind-pipe that transmits acoustic energy from the compression driver to the cavity of twin-fluid atomizers. To accomplish this objective, the primary variable of stability, that is, the breakup length of liquid jet and sheet under acoustic perturbations has been experimentally characterized for a range of wind-pipe length and liquid velocity. The analysis considers liquid phase Weber number in the range of 0.7–8, and the results are compared with primary breakup data without acoustic perturbations. The range of Weber number tested belongs to Rayleigh breakup zone, so that inertia force is negligible compared to surface tension force. It shows the existence of unique stability functions based on dimensionless products up to an optimum wind-pipe length, which extends greater for liquid sheet configuration. The present results may find relevance in atomizer design that utilizes acoustic source to enhance liquid column breakup processes.

The present study focuses on experimental characterization of interfacial instability pertinent to liquid jet and liquid sheet in the first wind-induced zone. To accomplish this objective, the interfacial wave growth rate, critical wave number, and breakup frequency associated with air-assisted atomizer systems were extracted by utilizing high-speed flow visualization techniques. For a range of liquid to gas velocities tested, nondimensionalization with appropriate variables generates the corresponding correlation functions. These functions enable to make an effective comparison between interfacial wave developments for liquid jet and sheet configurations. It exhibits liquid sheets superiority over liquid jets in the breakup processes leading to efficient atomization.

The study focuses on experimental characterization of the primary atomization associated with an effervescent atomizer. Unlike the existing designs available in the literature that inject air perpendicular to the liquid flow direction, the present atomizer design utilizes coflowing air configuration. In doing so, the aerodynamic shear at the liquid–gas interface create instability and enhance the subsequent jet breakup. Both integrated and intrinsic properties of the liquid jet were extracted by utilizing high-speed flow visualization techniques. The integrated property consists of breakup length, while the intrinsic property involves primary and intermediate breakup frequencies. The primary instability is characterized by low-frequency sinusoidal mode, whereas the intermediate instability consists of high-frequency dilatational mode. Dimensionless plots of these parameters with Weber number ratio leads to a better collapse of data, thereby generating appropriate universal functions. The combined diagram of frequencies converge with increasing relative velocity. This may be due to the dominance of energy consuming sinusoidal wave as the aerodynamic shear increases.

Today, the applications of sprays cover a wide range of fields. Their role in internal combustion engines is instrumental in maintaining higher engine efficiency. A deeper understanding of the liquid-gas phase interaction in sprays is crucial to the atomization process. The methods and models used in the simulations have their challenges due to the various discretization schemes and solutions used. To develop and validate the computational models, well defined experimental data is required. In the present work, spray characteristics were studied numerically through OpenFOAM. As the spray characteristics are closely linked with the liquid breakup length, this study focuses on the primary breakup phenomena and the breakup length of the liquid jet emanating from the twin-fluid co-axial flow atomizer. Numerical simulations were performed for a wide range of initial conditions and the breakup length of the spray was validated against the experimental observed by Sivadas et al., [26]. These simulations were carried out using a Eulerian based VOF solver that models the fluid as a continuum. K-Epsilon model was used to predict the turbulent nature of the spray. The air and water velocities were varied between 19.0 to 31.3 m/s and 0.7 to 1.8 m/s respectively. The proposed model was able to predict the computed breakup length within 20% of the experimental values. The present model can be further extended to test for a co-axial swirl injector to predict finer spray formation.

In this paper, Energy, Entropy and Exergy (EEE) analysis of flat plate solar collector is studied through a mathematical model by considering the overall loss coefficient as a non-constant parameter. The overall loss coefficient is calculated by minimizing the top loss coefficient using Lagrange multiplier optimization technique and also by empirical formulas. Further, energy efficiency, entropy generation, exergy destruction and exergy efficiency of the flat plate solar collector are also determined for the both aforesaid overall loss coefficients. The exergy efficiency of the proposed model has been doubled, when compared with the experimental measurements in the earlier literature. Also, comparing the proposed methods, it is observed that exergy efficiency obtained by using the minimal top loss coefficient is reasonably high and it enhances the overall collector’s efficiency.