With the adoption of strategic goals for GHG emission reductions in international shipping, methanol and other alternative fuels are being considered widely and rapidly as future fuel options. In addition, while public attention is shifting away from the TTP approach to the WTP approach, green methanol, which is produced through renewable methanol synthesis, has been gaining greater popularity as a carbon neutral fuel. The design of the ME-LGIM model, a methanol-fueled MAN-ES engine, has already been completed, and we will be able to provide a stable supply of ME-LGIM engines in the commercial shipping market based on our abundant marketing experience.

  The Japanese government has set the goal of achieving net zero GHG emissions by 2050 and aims to reduce GHG emissions by 46% from the 2013 level by 2030 as an interim target. Natural gas is one of the low carbon fuels with potential to reduce GHG emissions, and development of technology that utilizes natural gas is important to achieve this interim target.

  When natural gas is used in large bore marine engines, a pilot fuel ignition system is employed to take advantage of multi-point ignition to avoid a long combustion duration caused by a longer flame propagation distance. However, ignition delays of pilot fuel are affected by natural gas/air mixture concentration, making it difficult to operate an engine under high load variation. Given this, it is all the more important to develop injection strategies for a high efficiency natural gas engine in order to achieve the interim target. In this study, the authors conducted a test using tridecane as a high ignitability pilot fuel and heptane as a low ignitability pilot fuel in methane/air mixture together with a rapid compression machine. The test was designed to clarify the influence of the ignition characteristics of the pilot fuels in methane/air mixture. The results indicated that pilot fuel injection strategies affect pilot fuel ignitability. Especially, it was shown that combustion duration can be shortened by controlling an ignition position with the help of injection strategies and the use of the ignition characteristics of the pilot fuels.