Water-In-Fuel Emulsion Monitoring for Marine NOx Reduction
Real-time measurement of the water-to-fuel ratio in WIFE systems. Maintain the optimal emulsion for IMO Tier II/III compliance without over-diluting fuel.
The Challenge
Water-in-fuel emulsion (WIFE) is an established technique for reducing nitrogen oxide (NOx) emissions from marine diesel engines. By emulsifying a controlled amount of fresh water into the fuel oil before combustion, peak flame temperatures in the cylinder are reduced. Since NOx formation is exponentially dependent on combustion temperature, even a moderate reduction in peak temperature yields a significant drop in NOx output — typically 30–60% reduction with 15–30% water addition, sufficient to meet IMO Tier II requirements and contribute to Tier III compliance strategies.
Ratio Control
The water-to-fuel ratio must be maintained within a narrow band. Too little water and NOx reduction is insufficient. Too much water and combustion quality degrades — misfiring, increased particulates, and power loss.
Emulsion Stability
The emulsion must be stable and homogeneous when it reaches the injectors. Water droplet size and distribution directly affect combustion performance. The ratio must be verified after the emulsifier, not just at the water injection point.
Variable Operating Conditions
Engine load, fuel viscosity, and water supply pressure all vary during operation. The emulsion system must adapt, and the measurement must track the actual ratio in real time — not rely on pump speed calculations alone.
Compliance Documentation
IMO NOx Technical Code requires demonstration that emission control systems operate correctly. Continuous measurement of the water-fuel ratio provides the auditable data needed for port state control and flag state verification.
How Zelentech Solves It
The ZT-100 WIFE Monitor is installed inline on the emulsified fuel line between the emulsifier and the engine fuel inlet. It measures the water-to-fuel ratio of the emulsion continuously, providing a real-time feedback signal for the emulsion control system.
Unlike flow-meter-based ratio calculations that infer the ratio from separate water and fuel flow measurements, the ZT-100 WIFE measures the actual composition of the emulsified mixture after blending. This captures any imbalance from pump drift, pressure variations, or incomplete mixing that flow-based methods miss.
The 4–20mA output feeds directly into the WIFE control system as a process variable for closed-loop ratio control. The 1-second update rate enables tight control even during rapid load changes when the water injection rate must adjust quickly.
Direct Composition Measurement
Measures the actual water-fuel ratio in the emulsion — not a calculation from separate flow meters. Catches mixing errors and pump drift.
Closed-Loop Control
1-second update rate enables the WIFE system to maintain tight ratio control through engine load changes and fuel switches.
Compliance Record
Continuous logged measurement of the water-fuel ratio provides auditable data for IMO NOx Technical Code compliance verification.
Maersk Safemarin Chambal — WIFE Emulsion Control
Aboard the container vessel Safemarin Chambal, the ZT100 WIFE monitor continuously measures the water-in-fuel emulsion ratio in the heavy fuel oil supply. Real-time feedback keeps the emulsion within the target range for effective NOx reduction and stable combustion, while the control panel gives engine crew instant visibility of system performance.
Key Specifications
| Medium | Water-in-fuel emulsion (HFO + water, MDO + water) |
| Measurement Range | 0–50% water in fuel (typical operating range 15–30%) |
| Measurement | Water-to-fuel ratio (volume %) |
| Response Time | 1 second |
| Power | 24 VDC, loop powered |
| Output | 4–20mA (for WIFE control loop) + HART |
| Installation | Inline on emulsified fuel line, after emulsifier, before engine |
| NOx Reduction | Typically 30–60% with 15–30% water addition (engine dependent) |
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