The characteristics of Dutch natural gas (DNG) have been quantified by measuring the laminar flame speed of a premixed Bunsen flame over a range of equivalence ratios ϕ, varied from ϕ=0.80 to ϕ=1.55. The laminar flame speed has been calculated from the OH* chemiluminescence images recorded with a high speed camera with an acquisition rate of 1 kHz. Both the semi-cone angle method and mass conservation method were used in deriving the magnitude of the laminar burning velocity. From the data it was shown that the laminar flame speed of DNG is consistently lower compared to natural gas from Pittsburgh, Abu Dhabi and Indonesia. Moreover the data has been compared using the laminar flame speed of methane mixtures to validate the experimental setup. This showed that the laminar flame speed of DNG was marginally lower than the laminar flame speed of methane. The uncertainty within the measurements has been quantified by deriving the probability density function of the data. Advisors/Committee Members: Bohlin, Alexis (mentor), Delft University of Technology (degree granting institution).

[EN] In the current work, the characterization of the combustion process inside a stratified pre-chamber spark ignition (PCSI) system is performed. An extensive bibliographical review about the pre-chamber systems developed from the second half of the 20th century until modern times is presented. The review shows that the latest generation systems have the potential to accomplish the emissions limits while providing high performance and low fuel consumption. Nevertheless, many efforts of the scientific community are still needed to allow the large-scale application of the technology. Indeed, based on the outstanding challenges observed, the investigation plan is developed including both experimental and numerical parts. All experiments were performed by means of the rapid compressionexpansion machine (RCEM) in the CMT-Motores Térmicos laboratory. The original cylinder head layout was modified to allow the housing of the prechamber itself, fuel injectors, spark plug, pressure transducers in both chamber, and a thermocouple. The test methodology involved the acquisition of the pressure evolution in both main chamber and pre-chamber, the piston position (used to compute the instantaneous cylinder volume), the duration of the auxiliary injection, and the spark ignition point. These are used as input for the zero-dimensional thermodynamic model which simulates the fundamental parameters aims to characterize the PCSI system working cycle. Therefore, a deeper knowledge of the mass interchanged process, induced turbulence field, heat release rate, combustion speed, and flame regime is generated. Subsequently, to calibrate the zero-dimensional model coefficients under motoring conditions, several 3D CFD simulations were carried out by means of Converge software. Hence, the results of the simulations in terms of interchanged mass and pre-chamber turbulent kinetic energy have been used to calibrate the nozzle discharge coefficient and the turbulence sub-model coefficients for all the pre-chamber geometries. Furthermore, the 3D CFD simulations outputs are analysed to fully understand the flow field structure and the local effect induced by the different nozzles at the spark activation time. The turbulent kinetic energy in terms of intensity and orientation is investigated over several relevant pre-chamber sections. The results reveal a clear relationship between the turbulence developed within the pre-chamber and the orifices structure. Straight orifices or perpendicular jets impact, promote more intense local turbulence due to direct collision while tilted orifices guarantee more homogeneity due to the swirling motion. Additionally, increase the orifice numbers shows benefits on the fluid dynamic homogeneity. Thus, preceding the experimental campaign several fundamental aspects of the system are evaluated. The cycle-to-cycle dispersion is explored by means of the statistical assessment showing low pressure peak deviation. The auxiliary injection pressure and timing are optimized for avoiding wall wetting phenomena while… Advisors/Committee Members: Morena Borja, Joaquín de la (advisor).