Using high-speed video recording, we establish the following regimes of hydrodynamic interaction of a biodiesel micro-emulsion fuel droplet with a heated wall: deposition (including drop spreading and receding), drop hydrodynamic breakup, and rebound. Collision regime maps are plotted using a set of dimensionless criteria: Weber number We = 470–1260, Ohnesorge number Oh = 0.146–0.192, and Reynolds number Re = 25–198. The scenarios of droplet hydrodynamic disintegration are studied for transient and film boiling. We also estimate the disintegration characteristics of a biodiesel micro-emulsion droplet (mean diameter of child droplets, their number, and evaporation surface area increase due to breakup). The study establishes the effect of water proportion on the micro-emulsion composition (8–16 vol.%), heating temperature (300–500 °C), droplet size (1.8–2.8 mm), droplet velocity (3–4 m/s), rheological properties of the examined compositions, and emulsifier concentration (10.45 vol.% and 20 vol.%) on the recorded characteristics. The results show that the initial liquid surface area can be increased 2–19 times. The paper analyzes ways to control the process. The hydrodynamic disintegration characteristics of a biodiesel micro-emulsion fuel droplet are compared using 2D and 3D recording.

A method of preparing oil-filled cryogels on the basis of an aqueous solution of poly(vinyl alcohol) (PVA) has been elaborated. The stability of primary oil emulsions and their rheological properties were analyzed for 30 days, as well as the mechanical properties of gel fuel pellets (obtained after 15 cycles of freezing/thawing of oil emulsions) with size of 20 mm for a group of compositions: 100−20 vol % aqueous solution of PVA (5, 10 wt %) + 0−80 vol % oil. The rheological behavior of non-Newtonian oil emulsions is described by the Herschel−Bulkley model. The elastic moduli and the tensile strength of fuel pellets of different component compositions range from 0.7 to 7.6 kPa and from 2.5 to 60 kPa, respectively. The oleophilic properties are more distinct for gel fuel prepared from oil emulsions with a higher content of the dispersed phase and lower concentrations of the polymer in the dispersion medium. The ignition mechanism and combustion characteristics have been established for processes occurring under the conditions of a radiant heat supply. Gel fuels, unlike combustible liquids, are characterized by a longer induction period, but a multicomponent structure of fuel caused microexplosions that enhance the combustion process.

This paper presents an experimental and theoretical study of Newtonian and non-Newtonian (Bingham plastic) emulsion drop impact on a solid non-heated surface. The utilization of different emulsifiers at a constant concentration of continuous and dispersed phases in emulsions allows the considerable variation of the surface tension at the liquid–liquid interface. Our data for the maximum spreading diameter of water, n-decane, and emulsion drops impacting on a surface are compared with that predicted from the existing models for single-phase liquid drops. All selected models underpredict the experimental data. As a result, the importance of considering the capillary effects at the internal interfaces of the emulsion drops and the careful examination of all rheological properties in the case of Bingham plastic fluids is confirmed experimentally and is taken into account theoretically. The models of Pasandideh-Fard et al. [“Capillary effects during droplet impact on a solid surface,” Phys. Fluids 8, 650 (1996)] and Ukiwe and Kwok [“On the maximum spreading diameter of impacting droplets on well-prepared solid surfaces,” Langmuir 21, 666–673 (2005)] are modified and adapted to the emulsion drop by means of including the additional surface energy term at the liquid–liquid interface of the emulsion drop in the energy conservation equation and the non-Newtonian Reynolds number. The predictions of the maximum spreading diameter give good agreement with the measured one. Several constraints and future lines of research that relate to a specific behavior of the compound liquid drops at the impact on a solid surface are highlighted.

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We investigate the properties and phase behavior of the water−diesel fuel−Neonol AF 9-6/2-ethylhexanol system, which is regarded as a promising microemulsion fuel. A pseudoternary diagram of the system has been obtained. In the diesel fuel/ water (DF/W) ratio ranging from 98:2 to 50:50 and the emulsifier concentration of 8−40 vol %, a region of microemulsions has been distinguished, generating particular interest as an alternative fuel. In the region under study, a reverse micellar phase L 2 has existed predominantly. Fish-cut diagrams have been obtained for the DF/W ratios in the emulsifier concentration−temperature coordinates. An increase in the water fraction in microemulsions significantly has narrowed the range of their stability. The critical changes of microemulsion properties have been identified using the fish-cut diagrams. We have established the empirical relationship among the phase inversion temperature, the emulsifier concentration in the phase inversion point, and the water fraction in microemulsions.