Wärtsilä’s 34DF tri-fuel engine.

By Keith Henderson at November 23, 2010 09:56
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Wärtsilä has widened its marine propulsion program of medium speed engines with a 34DF model developed from the tried and tested Wärtsilä 32 HFO engine. The DF suffix indicates dual-fuel but in fact it has tri-fuel capabilities, operating on light fuel oil (MDO), heavy fuel oil (HFO) or natural gas. The 340 mm bore and 400 mm stroke marine engine has and output power of 450 kW per cylinder and is offered in six and nine cylinder in-line and 12 and 16 vee cylinder configurations. Engine speed is 750 rpm although for 60Hz generator applications the speed is 720 rpm.

The Wärtsilä 34DF is equipped with a special twin needle injector allowing a lean burn combustion principle to be used whereby the inlet air and gas mixture has a surfiet of air than is needed for complete combustion. Lean combustion reduces peak temperatures and therefore NOx emissions. Ignition of the lean mixture is achieved by compression ignition of a small quantity of MDO that is injected as a pilot fuel which ignites and subsequently causes ignition of the main (lean) charge, be it gas, HFO or MDO fuelled.

To obtain the highest efficiency together with lowest exhaust emissions, a special electronic control system is used to control the pilot injection and main injection quantities and timing of each cylinder individually. Through careful monitoring and automatic adjustments, optimum combustion in each cylinder is achieved. This has the additional benefit of eliminating mechanical and thermal overloading of the engine thereby reducing maintenance and delivering a lower through life cost in operation.


The Wärtsilä 34DF twin-needle injection valve. The larger nozzle is for MDO or HFO.
Pilot fuel runs through the smaller nozzle regardless of the main fuel to ensure
adequate nozzle cooling. Credit:Wärtsilä Corp.



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