WinGD targets mixed-fuel combustion in 2016

The development – which will allow the simultaneous burning of gas and diesel at any ratio, without any modifications to engine hardware – will be particularly beneficial for LNG carriers, enabling them to achieve their desired speed even with a limited amount of natural boil-off gas, without the need to force boil-off.

However the flexibility may also be welcomed by other vessel types. For example, compliance with MARPOL fuel sulphur limits could be achieved either through the burning of pure marine diesel oil, or through a combination of LNG with an amount (determined by sulphur content) of heavy fuel oil.

The X-DF engines, which are compliant with IMO Tier III NOx limits in pure gas mode, will be tuned for Tier II compliance in mixed mode, given the significant component of diffusive diesel combustion.

Marcel Ott, general manager of dual-fuel technology research and development at WinGD, told The Motorship that the main technical challenges in developing mixed-mode operation were related to combustion control, which requires more complex tuning requirements.

“The fuel-sharing ratio is an additional degree of freedom which needs to be reflected in the engine control system for emissions compliance and consumption optimisation,” he said. “The feature is currently under development with the target to get it released within this year.”

As reported, the X-DF concept – which features a low-pressure gas admission system – passed type approval tests in December last year. Orders have already been received for 33 engines.

WinGD, a joint venture between Wärtsilä and China State Shipbuilding Corp, designs Wärtsilä’s two-stroke engine portfolio.