More than 10 years after it was unveiled to the market, the Wärtsilä 20DF four-stroke, dual-fuel engine has received a makeover, delivering increased power output and lower fuel consumption, while cutting methane slip by 40%
Introduced in 2009 as the dual-fuel version of the Wärtsilä 20 engine platform introduced in the 1990s, the multi-fuel Wartsilä 20DF – also known as the W20DF - can operate on natural gas, marine fuel oil or heavy fuel oil.
Well-suited for small coastal vessel, ferry and tug main propulsion applications, Wärtsilä 20DF has been modified to further increase its fuel flexibility, allowing a much wider gas quality span, down to methane number (MN) 65, while still delivering full output, said the engine builder.
Wärtsilä Marine Power Solutions product manager for Wärtsilä 20, 20DF and 26 Johan Kålax tells Marine Propulsion, “The fuel consumption benefit is around 3% at 85% load” in the new 20DF.
In addition, Mr Kålax, said, “LNG usually contains a portion of hydrogen and we have limited this to 15% (blend or not). There isn´t any technical issues, when operating at or below this limit, but the Methane number of the gas must be followed as de-rating might be needed. The limit for the methane number is 65 on the new 20DF.”
The Wärtsilä 20DF operates on the lean burn principle: the mixture of air and gas in the cylinder contains more air than is needed for complete combustion. Lean combustion reduces peak temperatures, reducing NOx emissions. In gas mode, the engine is already compliant with IMO Tier III regulations without any secondary exhaust gas purification systems
As a result of the upgrade, the engine’s power per cylinder is increased from 185 to 195 kW. Additionally, Wärtsilä replaced the Wärtsilä 20DF control system with the latest Wärtsilä UNIC all-inclusive automation system.
The new Wärtsilä 20DF engine is better suited for variable speed applications with mechanical propulsion.
For genset applications, the engine now incorporates skip-firing technology combining torque control with cylinder deactivation to optimise fuel consumption at low engine load. Energy consumption is reduced by 3%, said Wärtsilä.
“The focus at Wärtsilä is on making every effort to support our customers by improving efficiencies, lowering operating costs, and lessening the carbon footprint of operations,” said Wärtsilä Marine Power director, product management & sales support Lars Anderson.
“This latest version of the Wärtsilä 20DF achieves all these ambitions and is a positive move towards reducing greenhouse gas emissions,” he added.
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