X-DF – How it works

X-DF – How it works

The technology behind shipping’s leading low-pressure dual-fuel LNG engines

X-DF engines set the standard for low-pressure, dual-fuel LNG technology in two-stroke marine engines.

Designed for efficiency and delivering exceptional operational control, compliance capability and cost advantages, X-DF engines have achieved millions of running hours since their introduction in 2016. But what is the technology behind the widely deployed series? 

Simplicity and efficiency

X-DF technology requires a simple gas supply system, reducing system complexity and auxiliary power consumption compared to high-pressure concepts. Since LNG is mixed with the scavenge air before compression, the required gas pressure is maximum 13 bar or lower when operating at lower loads. As a result, the fuel supply system is relatively simple, reliable and well-proven. 

The pre-chamber technology and design for the gas admission valve in X-DF engines offers the highest level of combustion stability and reduced emissions, well below IMO Tier III level. This stability in dual-fuel operation allows for greater load flexibility while improving port-to-port operations and manoeuvrability at low speeds, ensuring operational control at all times. 

When the X-DF engine runs in gas mode a trip to diesel mode is available at any engine power; it is instantaneously without any loss of engine power and speed. The trip to diesel mode happens automatically when a safety alarm occurs. 

When the X-DF engine runs in diesel mode, transfer to gas mode is available on request at engine powers below 85 % without any loss of power and speed. During the changeover procedure from gas to diesel, the cylinder lubricating oil shall be changed from the low BN to the high BN as recommended in the X-DF operating manual. 

X-DF2.0 – Building on excellence

WinGD has extended the benefits of the original X-DF concept with a second-generation of technology enhancements, X-DF2.0. Intelligent Control by Exhaust Recycling (iCER) improves combustion control to enable further fuel and emission reductions, including Tier III NOx compliance in diesel mode without the need for exhaust aftertreatment. Variable Compression Ratio (VCR) technology eliminates any compromise in diesel mode efficiency and dynamically optimises combustion depending on the running fuel and engine load.