Methanol is a promising renewable energy source. It can be produced from hydrogen and CO2 at reasonable cost and offers simple logistics with good volumetric energy density for international energy trading. The potential recovery of emitted CO2 enables the establishment of a sustainable circular economy.
Current research projects on the use of methanol focus on component and process optimization in SI combustion processes with intake manifold or direct injection. This project is part of a so-called “Cluster of Methanol-CI Research Ideas.” The aim of the overall project is to investigate various ignition processes that enable the use of methanol in diesel-like (CI) engine combustion processes.
Due to its advantageous chemical composition and good combustion properties (higher octane rating, wider ignition limits than gasoline, and very high evaporation enthalpy), high thermal efficiencies and low pollutant emissions can be achieved, especially in SI processes, but also in CI combustion processes.
The use of a diesel engine combustion process with methanol offers further potential for increasing efficiency compared to the gasoline engine combustion process: On the one hand, the geometric compression ratio can be further increased, and on the other hand, increased charge dilution leads to lower wall heat losses and advantages in terms of combustion gas properties. Due to the molecular structure of the fuel, methanol burns almost soot-free and is therefore particularly suitable for diffusive combustion processes. However, ignition of the mixture poses a challenge due to the ignition energy required and the low tendency to self-ignite.
Compared to the current state of the art, in which methanol is ignited in dual-fuel engines via a separate pilot injector, this is the first time that stratified injection has been used, in which pilot fuel and methanol are introduced sequentially through a single injector. This concept adapts proven approaches from diesel-water stratified injection for NOₓ reduction and is now to be transferred to the injection of pilot fuel into the methanol engine. Due to the lower calorific value and usually lower pressures, the injector system for methanol must provide larger nozzle cross-sections. Using 0D/1D methods, the spray hole diameters are dimensioned to suit both the pilot and main fuels. The fuel stratification within the injector resulting from the design adaptation is evaluated using 3D CFD calculations.
The aim of the project is to validate stratified injection technology for methanol, thereby laying the foundation for diesel-like methanol CI engines with high efficiency and low emissions.