Biofuel Emulsifier Using High-Velocity Impinging Flows and Singularities in Microchannels

Abstract

The objective of this experimental work is to design an original microfluidic mixer for continuous emulsification of small fractions of water in a lipid phase. This system is aimed to be integrated on-line in the process so as to avoid the use of a surfactant. The currently targeted application is a better combustion of water-supplemented alternative biofuels in boilers, turbines, or internal combustion engines in general. Therefore, mean size of droplets of water in the emulsion should be 5–10 μm, and the water content should not exceed ∼20%. Microsystems developed in this work are designed so as to enhance different flow perturbations that are favorable for the emulsification process. The microchannels for the fluids admittance have different sections: 300 × 300 μm2 and 600 × 600 μm2. As a consequence, an impinging flow is developed at the crossing of the inlet microchannels of the two phases which has for effect a significant stretching of the fluids. Then, depending on the continuous phase, Rayleigh instabilities can be developed in the straight parts of the outlet channels (600 × 600 μm2) and/or the enhancement of fluid splitting is obtained; thanks to a singularity (bend) located in the same outlet channels. Two different continuous phases are tested (gasoil and sun flower oil) for which the flow rate is about (65–100 ml/min). The water fraction is varied in the range 7–24%. It is shown that the length of the outlet microchannels is a crucial parameter. Considering an oil phase with low viscosity, such as gasoil, a too long channel can promote coalescence. On the opposite, longer outlet channels are needed with more viscous fluids (like sunflower oil) in order to develop Rayleigh instabilities which is, in this case, the more efficient way to obtain emulsions in this kind of microsystem. On a general point of view, concerning the size of the water droplets, dispersion of water is much more efficient with this microsystem using gasoil rather than vegetable oil as the continuous phase. Considering the targeted application, emulsions with an average size of water droplets of about 10 μm were obtained with gasoil as the continuous phase.

Experimental investigation on single drop breakage in two-stream impinging microchannels

“…The finely dispersed droplets in W/O emulsion are consequently produced in the emulsion. Further modifications were made by placing 90° bend at outlet channels (Belkadi et al 2018) or arranging two impinging microsystems in series (Belkadi et al 2016) in order to produce emulsified biofuel with finer water dispersed droplets. Most recently, Ji et al (2020) reported oil-in-water emulsification process in this microsystem by characterizing the flow patterns and droplet size, emphasizing the advantage of two jets impinging configuration in the microchannel on transporting great kinetic energy to disrupt dispersed phase fluids.…”

Effect of cross-slot configuration in microfluidics on o/w emulsification at high throughput

“…2(d). These bends are intended to enhance the breaking-up of droplets (Belkadi et al 2018). It has to be noted that previous works have led to the current design of the asymmetric system.…”

“…It has to be noted that previous works have led to the current design of the asymmetric system. For example, the effect of the number of bends (Bellettre et al 2017) and the length of the outlet channels (Belkadi et al 2018) have been studied. It has been observed that the length of the outlet channels should be selected depending on the viscosity ratio of the fluids.…”

Electrokinetic peristaltic bioconvective Jeffrey nanofluid flow with activation energy for binary chemical reaction, radiation and variable fluid properties

“…Micro-channels transport phenomena are used in a wide spectrum of design modern energy systems and applications by chemical engineers, such as biofuels emulsifying agents [1], exchangers of heat [2], thermoelectric power technology [3], collectors of solar energy [4], processing of polymers [5], design of the condensers [6], the propulsion systems of the rocket [7]. Other utilizes include naphtha redesigning and the systems of sustainable hydrogen fuel.…”