Methanol cold start procedure for a serial hybrid powertrain

Abstract Green methanol is a renewable fuel with many advantages when used in a spark ignition combustion process. Methanol has a comparatively high enthalpy of vaporization, leading to lower combustion temperatures (compared to gasoline combustion) and, hence, lower wall heat losses as well as a reduced tendency to pre-ignition. Therefore, a brake efficiency of more than 40% and, furthermore, minimal emissions are possible. The serial combination of a combustion engine with an electric powertrain provides a disconnection of the load demand of the powertrain and the operating point of the combustion engine. In this case, a high volumetric and gravimetric power density, easy energy storage, and a very cost effective already existing infrastructure of fuel distribution is combined with electric driving, high efficiencies, minimal emissions and a closed carbon cycle for the energy provision. Nevertheless, the high flash point of methanol at 11 °C indicates a challenging cold start. Heating the fuel or intake air or blending lightly boiling components are feasible solutions, but are related to additional expenses regarding packaging and cost. The described procedure enables the cold start of pure methanol down to −20 °C, without the necessity for additional engine components, when using a serial hybrid propulsion system. Besides, a serial hybrid powertrain offers the possibility of preheating the exhaust aftertreatment in addition to a reliable methanol cold start, while the vehicle is already running on its electric power train.