NEW EXPERIMENTAL APPROACHES TO THE STUDY  OF COMBUSTION OF DROPLETS OF WATER-FUEL EMULSIONS

doi:10.26565/2222-5617-2025-43-05

M. O. Ivanov Odesa National I. I. Mechnikov University, 2 V. Zmienka Str., Odesa 65082, Ukraine https://orcid.org/0009-0006-1547-4067
O. S. Chernenko Odesa National I. I. Mechnikov University, 2 V. Zmienka Str., Odesa 65082, Ukraine https://orcid.org/0000-0002-3722-0694

DOI: https://doi.org/10.26565/2222-5617-2025-43-05

Keywords: evaporation, combustion, droplets, water-fuel emulsions, pulsations

Abstract

The based on a review of existing methods for studying droplet combustion, it is concluded that the combustion of emulsions is accompanied by the phenomenon of micro-explosions: the division of the primary droplet into secondary droplets. Depending on the intensity of heat input, both a small material ejection and complete droplet destruction can occur. The use of emulsions is important in reducing nitrogen oxide emissions and increasing the combustion efficiency of liquid fuels. The aim of this work is to review the authors' methods for studying the combustion of emulsion droplets, which have several advantages.

A new method for rapid analysis of the combustion rate of a liquid is described in the porous ball method. A ball soaked in a flammable liquid is placed on a special stand on a balance. The mass of the ball is measured over time, and a linear section of the mass vs. time curve defines the combustion rate of the liquid. Compared to existing methods, the advantage of this method is its speed, repeatability, low liquid consumption, and the ability to quickly compare different compositions, including emulsions.

An original method involves the use of high-frequency electrical discharge as an electric trigger for micro-explosion initiation. Even a small thermal power of the streamer is sufficient to observe the pulsations of the droplet diameter over time. The behavior of an emulsion droplet of water-diesel fuel (50%/50%) was studied, where water has a significantly lower boiling point than diesel fuel. The streamer passing near the droplet on a thermocouple does not fully heat the entire droplet initially. As a result, a steam bubble forms near the thermocouple joint, which expands, moves away from the joint, and bursts near the droplet's outer surface, leading to the emission of emulsion material (pulse period of 10–25 ms). As the entire droplet heats up, multiple bubbles expand and burst simultaneously, resulting in more mini-pulsations (2–3 ms).

In the stationary droplet method, continuous emulsion feeding through a needle to a porous metal particle is implemented. The visualization of micro-explosion formation on the droplet surface during combustion is demonstrated. The possibility of using high-frequency electrical discharge in the combustion of emulsions with a high water content (up to 60%) is also indicated.

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