Numerical and Experimental Investigation of a Pre-chamber Igniter for Enhanced Low Load Stability in Internal Combustion Engines

Developing innovative technologies offers a crucial opportunity to improve Internal Combustion Engines’ performance while significantly reducing harmful emissions, contributing to a more sustainable future. The replacement of the standard spark plug in externally ignited engines for passenger vehicles with a prechamber igniter is a well-known combustion accelerator, facilitating the increase of engine efficiency especially at high loads. However, prechamber ignition technology has not yet been widely adopted in the market, primarily due to the difficulty of achieving stable operation at lower engine loads. The gas exchange in the passive prechamber was studied using a combination of numerical modelling and experimental methods. A better understanding of the flow and mixture conditions is needed to improve stability of the prechamber igniter in low load operation points. Accessing those parameters experimentally comes with high efforts for the test bench design and operation. To overcome the requirement for those elaborated test bench designs, robust and accurate numerical models, which are validated with available experimental data, should be used. A modelling approach was developed based on measurement data from a single cylinder engine over a wide range of engine loads and injection timings, where it was employed to predict the flow and mixture characteristics inside the pre-chamber volume. The physical phenomena which dictate the operation limits measured in the experimental campaign can be identified through the numerical results, removing the limitations of experimental measuring. Furthermore, this study delves into the variation of the intake valve actuation and its effects on the pre-chamber gas exchange and combustion process.