FGM combustion model performance in a simplified naval engine combustion chamber

Present work investigates the performance of the Flamelet Generated Manifold combustion model in a marine-sized combustion chamber within the framework of RANS turbulence modeling using the software OpenFOAM. The dimensions involved, both in terms of nozzles (∼1 mm) and chamber diameter (500 mm), make a tabulated combustion model a convenient choice to keep the computational time low with reliable results. A validation of the mesh is shown, using liquid length and spray penetration of a single-nozzle injector configuration. Then the reacting cases are presented, both in single and multi-nozzle configuration. The results are promising and in good agreement with experiments, in terms of Ignition Delay Time (IDT), Lift-Off Length (LOL) and Ignition Location (IL). However, a shorter IDT is found in both configurations and mainly explained with the surrogate fuel used in simulation (n-Dodecane) being more reacting than the one used in experiments (Diesel). On the other hand, LOL shows good agreement, particularly in the multi-nozzle configuration. IL was available experimentally only for the single nozzle configuration, and the numerical value has shown spot-on results. Eventually, the effectiveness of the specific enthalpy as an additional control variable for the FGM manifold in capturing the cooling effect of the liquid spray injected is assessed. It is found that the larger the nozzle, and consequently the amount of liquid fuel injected, the larger the cooling on the surrounding gas is. Therefore, the introduction of multiple oxidizer temperature levels below the ambient initial temperature is strongly recommended in the tabulated chemistry method.