MAN develops cylinder bypass for gas engines

MAN's ME-GI engines will soon be able to bypass misfiring cylinders running on gas, rather than switching to diesel mode MAN's ME-GI engines will soon be able to bypass misfiring cylinders running on gas, rather than switching to diesel mode

MAN Diesel & Turbo's new cylinder bypass function will enable ME-GI engines to run on LNG even when a cylinder misfires.

At present, if a cylinder burning LNG misfires, the safety system switches the entire engine to burn fuel oil. This can increase fuel costs, particularly for gas carriers which use boil-off LNG to power their engines but purchase their own fuel oil.

The new concept allows the faulty cylinders to be bypassed while the rest of the engine continues to run on gas. MAN engines have featured cylinder bypass previously, but this is the first time the function has been offered in gas mode.

The company has been developing the system over the past six months and will be studying it on a test engine this year. René Sejer Laursen, ME-GI promotion manager, MAN Diesel & Turbo, told The Motorship that the company hopes to deliver an engine with the new safety concept in the first half of 2019.

Meanwhile, MAN is also set to begin testing a new atomiser that could further reduce the amount of pilot fuel burned by ME-GI engines in gas mode. The new injection module, which employs smaller outlets to spray less pilot fuel, has already been tested on a test engine.

Laursen said that the new atomiser design could reduce pilot fuel consumption to around 1.5% or lower. It will gain its first at-sea reference on a newbuild LNG carrier that will shortly take delivery of an ME-GI engine.

The company has accumulated around 6,000 hours of operation on its current injection valve design, which was reworked after the original nozzle developed cracks because of rapid pressure and temperature changes. The new nozzle design has been moved further into the cylinder cover to protect it from the highest temperatures of the combustion zone.

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