What Is Water-in-Fuel Emulsion?
For many people in the marine industry, the idea of adding water to fuel immediately raises concerns.
Traditionally, water contamination in fuel is associated with:
- corrosion
- unstable combustion
- fuel system damage
- poor engine performance
A controlled water-in-fuel emulsion (WFE) is fundamentally different.
Instead of uncontrolled free water inside the fuel system, a WFE system injects a carefully controlled amount of clean water into the fuel under stable operating conditions. The fuel and water are then mechanically homogenized into microscopic droplets before combustion.
The purpose is not simply “adding water,” but improving the combustion process itself.
Why Water-in-Fuel Technology Was Sometimes Misunderstood
Historically, many water-in-fuel systems focused primarily on achieving maximum NOx reduction.
In some applications, this resulted in very high water percentages — sometimes 15% to 30% water content. While such high water ratios can significantly reduce NOx emissions, they may also negatively affect combustion efficiency and Specific Fuel Oil Consumption (SFOC).
This created a lasting industry perception that:
“Water in fuel always increases fuel consumption.”
In practice, the situation is more nuanced.
Modern marine applications increasingly focus on lower and controlled water percentages, typically optimized for the specific engine, fuel type and operating profile.
At moderate water ratios, the combustion improvements from better atomization and cleaner combustion can partially offset — or in some cases outweigh — the energy displacement caused by the added water.
The objective is therefore not maximum water addition, but balanced combustion optimization.
The Role of Fuel Droplet Size
Efficient combustion depends heavily on fuel droplet size and distribution.
Conventional heavy fuel oil injection often produces fuel droplets with a wide size distribution. Larger droplets require more time and oxygen to burn completely. This can lead to:
- incomplete combustion
- soot formation
- smoke
- localized high-temperature zones
- carbon deposits
IPCO Power homogenizer technology mechanically conditions the fuel before combustion by reducing and equalizing droplet size.
Smaller and more uniform fuel droplets:
- evaporate faster
- mix more efficiently with oxygen
- burn more completely
- produce cleaner combustion
This principle already provides combustion benefits, even without water addition.
What Happens During Combustion?
When a stable water-in-fuel emulsion enters the combustion chamber, several processes occur simultaneously.
Step 1 — Fuel Injection
The fuel enters the cylinder or boiler burner as a homogenized mixture containing microscopic water droplets evenly distributed throughout the fuel.
Step 2 — Heating and Compression
As temperature and pressure increase during combustion, the microscopic water droplets begin to evaporate rapidly.
Step 3 — Micro-Explosion and Secondary Atomization
The water rapidly expands into steam.
This expansion disrupts the surrounding fuel droplets and breaks them into many smaller droplets — a process often referred to as:
- micro-explosion
- secondary atomization
This significantly increases the effective fuel surface area exposed to oxygen.
Step 4 — Improved Combustion
The smaller atomized fuel droplets mix more efficiently with air and oxygen.
This may contribute to:
- cleaner combustion
- lower visible smoke
- reduced soot formation
- lower particulate emissions
- improved combustion stability
At the same time, the evaporation of water can reduce local peak flame temperatures, helping reduce thermal NOx formation.
Why Lower Water Ratios Matter
The relationship between water percentage and fuel efficiency is important.
Very high water percentages:
- maximize NOx reduction
- but can negatively affect combustion efficiency and SFOC
Lower controlled water percentages often provide a more balanced result:
- cleaner combustion
- reduced soot and smoke
- lower NOx
- while maintaining good combustion efficiency
Benefits in Boilers
Water-in-fuel technology is not limited to diesel engines.
In marine boilers, improved atomization and combustion quality may help reduce soot deposits and fouling on boiler walls and heat transfer surfaces.
In practice, operators may observe:
- cleaner boiler walls
- less soot accumulation
- cleaner exhaust gas paths
- more stable flame patterns
Cleaner heat transfer surfaces may also help maintain boiler efficiency over longer operating periods.
The Role of the Homogenizer
The homogenizer is the core of the IPCO Power system.
Using high-shear rotor/stator technology, the homogenizer:
- reduces droplet size
- disperses water uniformly
- stabilizes the emulsion
- conditions the fuel before combustion
The result is not simply “fuel mixed with water,” but a controlled and engineered fuel conditioning process.
Learn More About the IPCO Power FID Injector
The IPCO Power FID Injector combines controlled water dosing with high-shear homogenizer technology to create a stable water-in-fuel emulsion for marine engines and boilers.
The system is designed for:
- HFO applications
- ULSFO/VLSFO applications
- cleaner combustion
- soot and smoke reduction
- NOx reduction support
- fuel conditioning before combustion
More information about the system, specifications and applications can be found here: