Wärtsilä Engine Achieves Emissions Certification

Picture of the Wärtsilä 26 engine

Wärtsilä has achieved Tier 2 marine certification under the emissions control legislation of the US EPA (United States Environmental Protection Agency) for the Wärtsilä 26, in-line marine diesel engine type. This is the latest step in Wärtsilä’s continuing, proactive development of its engines for lower exhaust emissions and reduced environmental impact. The Wärtsilä 26 engine is a four-stroke heavy-duty marine engine of 260 mm cylinder bore by 320 mm piston stroke built in in-line and Vee-form configurations. It covers a power range of 1950–5440 kW (2650-7393 bhp), and is popular in a wide range of marine applications. More than 800 engines have been delivered since the introduction in 1996 and there are engines with more than 60,000 running hours. With a swept volume of 17 liters per cylinder the Wärtsilä 26 is classified by the EPA as a category 2 engine. Since 1 January, 2007 US-flag vessels powered by category 2 engines are required to meet the Tier 2 requirements.

For in-line engines the US EPA Tier 2, category 2, required emission levels for total hydrocarbons and nitrogen oxides (NOx) are less than 8.7 g/kWh. This is a reduction of NOx emissions of more than 30% compared with the IMO limit in Annex VI of the MARPOL 73/78 convention. In addition, the US EPA legislations set limits for carbon monoxide (CO) of 5.0 g/kWh and particulate matter (PM) of 0.5 g/kWh. Testing of Wärtsilä 26 engines for compliance with the US EPA Tier 2 legislation was successfully performed in the Trieste engine laboratory in Italy with fuels meeting the EPA requirements. The emission levels have been lowered largely by reducing the maximum combustion temperatures. This has involved a combination of measures: Miller timing, optimization of the combustion chamber, and optimization of the fuel injection equipment. In this way, the emissions been reduced with a marginal decrease in efficiency.