Wärtsilä has launched its new environmentally advanced Wärtsilä 20DF engine. This compact unit that brings all the advantages of fuel flexibility to auxiliary applications, such as generating sets or as the prime mover in smaller vessels.
The tightening emission regulations under the IMO Tier II & III and ECA zone implementations and volatile fuel prices mean that ship owners and operators are facing serious challenges. Solutions for complying with new environmental rules while maintaining cost-efficient operations vary, but only one – natural gas – appears to fulfill all the requirements.
The Wärtsilä 20DF completes the dual-fuel range
With the launch of the Wärtsilä 20DF, Wärtsilä is extending the benefits of dual-fuel (DF) technology to cover the entire power range. Based on the Wärtsilä 20 diesel engine introduced in the early 1990s, fuel flexibility means the engine can be optimised for constant speed generating sets, as well as variable speed mechanical drives, for main engine applications.
Installed alongside Wärtsilä 34DF or 50DF main propulsion machinery, a Wärtsilä 20DF generating set completes the multi-fuel engine room concept. Compact and light, the Wärtsilä 20DF is intended for use in those vessel types where the Wärtsilä 20 is currently installed.
As well as being an ideal mechanical-drive prime mover in smaller applications, such as small cargo vessels, ferries or tugs, it is also a good choice for harbour generating set applications in a wide range of vessel types.
Keeping emissions under control
When a diesel fuel engine is running in gas mode, carbon dioxide emissions are reduced by approximately 20 percent since natural gas has a lower carbon content than liquid fuels. The lean-burn combustion process employed means that nitrogen oxide emissions are reduced by approximately 80 percent, while sulphur oxide emissions are completely eliminated as natural gas does not contain any sulphur.
The production of particulates is practically non-existent as natural gas has virtually no residuals.
Lean-burn combustion technology results in extremely-low emission values and very-high engine efficiency. In this process, the combustion of a lean air-gas mixture is initiated by injecting a very small amount of MDO as pilot fuel. To obtain the best efficiency and lowest emissions, each cylinder is individually controlled to ensure operation at the correct air-fuel ratio, and with the correct amount and timing of pilot fuel injection.
Wärtsilä has further developed UNIC, a special electronic control system that copes with the demanding task of controlling the combustion in each cylinder, while ensuring optimal performance in terms of efficiency and emissions under all conditions. Stable and well-controlled combustion also contributes to less mechanical and thermal load on the engine components.
In gas mode, Wärtsilä DF engines are already compliant with the forthcoming IMO Tier III regulations without the need for any secondary exhaust gas purification systems. In liquid fuel oil mode, all Wärtsilä DF engines are fully compliant with the IMO Tier II exhaust emission regulations set out in Annex VI of the MARPOL 73/78 convention.
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