Influence of methanol reformate injection strategy on performance, available exhaust gas enthalpy and emissions of a direct-injection spark ignition engine

This paper presents experimental study results of a direct injection engine fed with methanol steam reforming products and devised to work with a high-pressure thermochemical recuperation system. The influence of injection pressure and timing on heat release rate, fuel mass fraction burned, cycle-to-cycle variation, pollutant emissions, efficiency and exhaust gas energy available for methanol reforming is investigated and analyzed. Effect of injector flow area on the required injection pressure is discussed. End-of-injection (EOI) timing is shown to be the main influencing factor on engine efficiency and pollutant emissions. The obtained results indicate that there is a range of EOI timing where indicated efficiency is almost constant and NO_x emissions drop by a factor of 2.5. Particle number emissions can be reduced in this range by a factor of 4. We showed that engine exhaust gas possesses enough energy to sustain endothermic reforming reactions up to excess air ratio of 2.5.