Optimization of the Injection Strategy to Enhance Mixture Formation in a 4-Cylinder Methanol Engine by means of a 3D-CFD Virtual Engine Test Bench

Emissions reduction and carbon neutrality are two obligations to fulfil in order to ensure a clean and bearable planet for the future. The diversification of energy carriers is one of the keys to achieving a concrete and time-effective solution and methanol can be one of the possible ways to reach carbon neutrality, showing many positive characteristics to be used as fuel for internal combustion engines. Using Methanol as a fuel or in a blend can greatly reduce exhaust emissions, with a great impact on CO2 emissions. Nevertheless, some challenges have to be overcome to exploit the whole potential of methanol as a fuel. The aim of this work is to investigate which aspects can improve the mixture formation using a 4-cylinder gasoline engine fuelled with Methanol. The study was conducted numerically, by means of a virtual engine test bench, considering two different operating points, the former at high engine speed and load, the latter in a lower load region of the engine map. As the first step, the injection model has been validated with experimental data acquired employing methanol spray analysis which has included spray geometrical features and droplet size measurements. 3D-CFD simulations analysis of different injection methods have been conducted, to understand which parameters affect more Methanol mixture formation. Two different injector temperatures are used, showing considerable differences in terms of combustion efficiency and knocking onset. As a second step, a PFI injector mounted in the intake channel has been considered, as a replacement of the direct injector, to exploit methanol intake charge cooling power and increase volumetric and indicated efficiency. The results of these analyses are presented in this work, discussing Methanol performances compared to a commercial SP98 gasoline, showing how an optimized methanol injection strategy can improve efficiency and enlarge the range for lean operations.