The newest legislative trends enforce a significant decrease in CO2 emissions for commercial vehicles. For instance, in Europe a drop in fleet consumption of 15% and 30% is set as target by the regulation by 2025 and 2030. The use of carbon-neutral fuels offers possibilities regarding net-zero CO2 emissions - although not yet considered by the rules. Another challenging aspect is the drastic tightening of NOx emissions limits for future legislations, which is approved or being discussed both for the United States and for the EU.
The current work describes the potentials of an innovative fuel, marketed as Gane fuel regarding performance, efficiency and emission behavior. First, the properties of the developed fuel are described: Gane is made from methanol blended with water and is tailored for diffusive combustion. The fuel blending is so defined to fulfill the combustion requirements. With DME the ignition can be initiated and adding water can reduce the combustion temperature to minimize the NOx. The innovative fuel system fumigates the DME into the inlet air and is combined with HPDI injection of the Methanol-Water blend.
As baseline for the experimental investigations, a conventional in-line 6-cylinder HD diesel engine was selected and the fuel system modified. During the extensive engine testing, the complete engine map was calibrated for the Gane fuel without significant drawbacks regarding power density compared to the diesel baseline. The experimental results show that using Gane fuel leads to comparable high brake thermal efficiencies as in case of diesel fuel - even though the engine-out NOx emission level was reduced to under ca. 2 g/kWh compared to the diesel baseline with ca. 7 to 10 g/kWh. In addition, very low soot emissions occur, which makes the tested fuel possibly compliant to EURO VI without DPF. In order to assess the ignition process of the Gane fuel, the intake temperatures and also the mass flow rate of the port-injected DME were varied and the combustion processes compared. As expected, the lower the intake temperatures or the DME mass flow, the higher is the ignition delay.
In order to estimate the effect on the ignition process in a predictive way, a simulation model based on in-cylinder kinetic reaction mechanisms was developed and validated. The results of the simulation model show that the reaction kinetics based modeling approach can simulate the auto-ignition timing accurately, which is presented on the example of an intake temperature variation.