Study of Combustion Characteristics of a Two-stroke Opposed Piston Engine using Low-octane Fuels

Various fuels are being considered as the next generation of carbon neutral fuels, including methanol, ethanol, and SAF. These have widely different ignition properties. Methanol and ethanol are high-octane fuels, so there are no major problems with their use in gasoline engines. However, SAF is a hydrocarbon with a large molecular weight, so it has a fundamentally low octane rating and is not easy to use in SI engines. In order to put carbon-neutral fuels of various properties into practical use, it is effective to develop a technology that allows fuels with low octane to be operated in SI engines. Therefore, in this study, basic research was conducted on the combustion of fuels with low octane using PRF fuel in opposed-piston engines. Opposed piston engines are characterized by their light weight due to the absence of a cylinder head, low S/V ratio due to the ultra-long stroke, reduced cooling loss due to the long stroke, and reduced vibration due to the offsetting of the reciprocating inertial forces of the left and right pistons, resulting in high efficiency and output. In addition, one of the disadvantages of low-octane fuel is that it tends to auto-ignite, but combustion under high residual gas conditions has the effect of suppressing fuel auto-ignition, and by using a 2-stroke engine with a high percentage and high concentration of residual gas and locally high temperatures, auto-ignition is suppressed and low The use of two-stroke engines with high residual gas content and high concentration and high local temperatures can be expected to suppress auto-ignition and allow the use of low-octane fuels.