Premixed Combustion of Alternative Fuel in Two-stroke Marine Engines

Background
Utilizing the green alternative fuels so called electric fuels is a big step on the way of Decarbonation and sustainable maritime industry. In this context, MAN Energy Solutions is developing a new two-stroke dual fuel methane-diesel marine engine based on new premixed combustion technology. This new technology is expected to be cost effective with lower emission levels. However, premixed combustion is a relatively unknown for marine engines, therefore associated with technical challenges. The main challenges are methane slip in which unburned methane gas ejected out of the engine through the exhaust and combustion stability.

Project
The majority of diesel engines in operation in the maritime sector are equipped with a single fuel nozzle for direct injection of diesel into the combustion chamber. However, in the premixed two-stroke dual fuel methane-diesel marine engine there is another nozzle for methane injection inside the cylinder. The injected methane then mixes with the air to produce a combustible mixture. In the present project, we are trying to numerically study the effect of mixing on combustion to obtain an efficient combustion with the lowest possible methane slip. In addition, the pilot diesel fuel injection parameters will be optimized to minimize the use of diesel pilot fuel and reduce the emission levels.

Expected results
The outcomes of the project are expected to assist in optimizing the performance of two-stroke premixed marine engines, as well as reducing the occurrence of methane slip. Furthermore, the knowledge and insights gained from this project can potentially be extended to help Danish maritime industry for development of new marine engines with different green gaseous alternative fuels, e.g. ammonia which is a topic of interest.