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Introduction to Emulsified Fuel

Background

Emulsified fuel in simple term means a mixture of water in fuel oil in such a way that small particles of water are formed in the fuel oil to produce a stable water‐in‐fuel emulsion. The main purpose of doping fuel oil with small quantities of water is to improve combustion efficiency and thus achieve better specific fuel consumption of marine diesel engines.

For decades, the focus of improving fuel combustion efficiency of diesel engine has been to improve the mixing of the fuel and air inside the combustion chamber so that a more complete combustion can take place. This have been achieved, among many innovative ideas, largely by better fuel injection techniques, better air flow dynamics and allowing more time for combustion through longer engine strokes etc. There is a finite limit to the improvement of the mixing of fuel and air in the combustion chamber due to physical limitations to the fuel injector design, dynamic air flow and time available for combustion. Nevertheless, emulsified fuel offers a practical method to further improve this mixing of fuel and air without any modifications to the diesel engine.

Brief history of Emulsified Fuel

Burning emulsified fuel is not totally a new application. Emulsified fuel had been burnt decades ago in boilers primarily for the purpose of washing down the furnace. Although the benefits of burning emulsified fuel were apparent in the reported cleanness of the furnace, they were neither identified nor quantified.

In the early 1970’s, with the sudden and rising trend in the price of fuel oil, interests in burning emulsified fuel were rekindled and efforts were directed at studying the feasibility of burning emulsified fuel in marine diesel engines with the aim of achieving fuel saving.  Most of the studies made in emulsified fuel have been with diesel engines. One of the pioneers is R.V Thompson and his team from University of Newcastle Upon Tyne. They conducted detailed and extensive research work in water-in-fuel emulsion for several years with breakthrough results. Dr.  Jerry Ng Kok Loon, the founder of Blue Ocean Solutions, was one of the key persons of the team.

 

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Secondary atomization effect of emulsified fuel

Smaller fuel droplets will achieve better fuel-air mixture as more fuel-air surface will be available for combustion. Therefore, the key to achieve better combustion is to create a secondary atomization effect by adding water into the fuel. The secondary atomization effect creates even smaller fuel droplets after injection.

The microscopic water particles in the fuel are superheated to about 130°C under pressure to prevent the water from boiling off. When the water-in-fuel emulsion is injected into the combustion chamber, the water particles flash off immediately causing a secondary atomization effect creating finer fuel mist and better fuel-air mixture for combustion.

Through extensive and comprehensive research, the optimum water content and particle sizes for maximum fuel saving on marine diesel engines was established: water content of 10% and particle sizes of 2-8 micron.