Optical Spray Investigations on OME3-5 in a Constant Volume High Pressure Chamber 2019-24-0234

Oxygenated fuels such as polyoxymethylene dimethyl ethers (OME) offer a chance to significantly decrease emissions while switching to renewable fuels. However, compared to conventional diesel fuel, they have lower heating values and different evaporation behaviors which lead to differences in spray, mixture formation as well as ignition delay. In order to determine the mixture formation characteristics and the combustion behavior of neat OME_3-5, optical investigations have been carried out in a high-pressure-chamber using shadowgraphy, mie-scatterlight and OH-radiation recordings. Liquid penetration length, gaseous penetration length, lift off length, spray cone angle and ignition delay have been determined and compared to those measured with diesel-fuel over a variety of pressures, temperatures, rail pressures and injection durations. Liquid penetration lengths for OME_3-5-sprays were found to be shorter than that of diesel-fuel analogues, while lift-off-lengths were generally observed to be longer for OME_3-5, resulting in longer gaseous mixing lengths. As the cetane numbers suggested, ignition delay was found to be shorter for OME_3-5. Spray cone angles were reduced at low temperature and wider at high temperature, while gaseous penetration length was equivalent. These results serve as a valuable basis for enabling the optimum design of the combustion process parameters for the application of OME_3-5, allowing the validation of spray- and combustion simulations, thus enabling a full optimization of the combustion system.