Fuel flexible gas engine

Liquid natural gas (LNG) has during the past couple of decades gained attraction as a marine fuel in response to regulations on harmful emissions such as NOx, SOx and particulate matters. Thanks to the low emission levels without aftertreatment, solutions using LNG are also economically attractive. Although LNG still is a fossil fuel, it brings the potential to reduce greenhouse gas emissions by up to 25% compared to fuel oil. From decarbonisation perspective, one interesting aspect of installing an LNG-capable solution is the capability of running also on renewable fuels such as liquid biomethane, and liquid methane derived from green hydrogen without further modification. However, with the introduction of alternative fuel sources for an LNG-capable solution comes the question whether the fuel can be switched without any implications. Essentially the fuel can be switched, they all have the methane molecule in common independent of origin. Attention needs to be paid to the other possible components affecting the gas quality, i.e. the methane number, and its impact on the engine operability and efficiency. The essential challenges with varying gas quality in lean burn gas engines is the impact on the combustion behaviour. Controls adapting to the gas quality are needed in order to maintain maximum efficiency, and here both methods utilizing dedicated hardware as well as methods relying on monitoring of the combustion process are reviewed. The report provides background knowledge on the combustion behaviour and the control methods needed to manage the operation of high performing lean burn gas engines. Upcoming work within the CHEK project will focus on the introduction of selected technology, engine testing and test results.