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Bursting droplets give new insights into making fuels better and less polluting

By studying how individual droplets of fuels, loaded with nanoparticles behave, researchers have found a way to extract more energy from fuels and make them less polluting. This is a significant insight because our fossil fuel resources are depleting, and also our usage of available fuels is adversely affecting environment. The study was carried out by researchers from the Department of Mechanical Engineering, Indian Institute of Science, Bengaluru.

It is known that adding tiny particles of metals to fuel droplets can help us get more out of fuel and make them cleaner. In Western countries, especially Europe, such “energetic fuels” are used in vehicles on an experimental basis, and the results look promising. However, it was not clear how exactly nanoparticles affected the fuel performance.

The IISc research gives some fundamental insights at the droplet level, and opens up the possibility of tailoring fuel performance by controlled addition of nanoparticles. Prof Saptarshi Basu, Associate Professor, Department of Mechanical Engineering, and his PhD student Ankur Miglani studied how a nanoparticle laden fuel droplet would burn and breakup. This has the potential to influence ignition, mixing and combustion efficiency inside an engine or a gas turbine.

They loaded an individual droplet with varying quantities of nanoparticles, and observed how it affected the bursting of the droplet. Bursting is a very important step in combustion, because it makes the whole process efficient through secondary atomization. More bubbles result in vigorous atomization leading to larger surface area, and hence greater is the mixing and combustion efficiency. In fact, inside the gas turbines or engines, the fuel is actually sprayed into the combustion chamber. When a droplet loaded with nanoparticle bursts, it naturally spreads the daughter droplets homogeneously over a larger area, improving the fuel combustion process.

The researchers found that at dilute nanoparticle concentration, the droplet had a greater probability of bursting, and hence spread the nanoparticle-loaded fuel droplets. However, at higher particle concentrations, the droplet was less likely to burst because the particles formed a porous shell inside the droplet. Also, at lower concentration, the frequency of ejection of secondary droplets was also more.

Though the study focussed only on droplets, the implications are quite far reaching. “If successful in model test-engines, this new-class of fuels could well be the future energy carriers that will transform the global energy landscape through better combustion and power generation. It would help give India a competitive edge in this emerging field and position the country as a pioneer in sustainable energy research”, says Prof Saptarshi Basu. According to him, the findings can also help create better thermal coating by controlling nanoparticle agglomerate morphology. In thermal barrier coatings, the nanoparticle laden droplets are vaporized in the flame and deposited on substrates.

Author Information: Prof Saptarshi Basu, Associate Professor, Department of Mechanical Engineering, Indian Institute of Science, Bengaluru. Ankur Miglani is his PhD student.

Contact: Prof Saptarshi Basu can be contacted at sbasu@mecheng.iisc.ernet.in

The paper appeared in the journal Scientific Reports earlier this month. DOi: 10.1038/srep15008