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

Developing innovative ignition technologies offers a crucial opportunity to improve the performance of internal combustion engines while significantly reducing harmful emissions, contributing to a more sustainable future. The replacement of the standard spark plug with a pre-chamber igniter is a well-known combustion accelerator for externally ignited engines for passenger vehicles. An increase in engine efficiency, especially at high loads, can be realized. However, pre-chamber ignition technology has not yet been widely adopted in the market, primarily due to the difficulty of achieving stable operation at lower engine loads. A better understanding of the flow and mixture conditions is needed to improve the combustion stability with the pre-chamber igniter in low-load operating conditions. The gas exchange in the passive pre-chamber was studied using a combination of numerical modelling and experimental methods. Accessing those parameters experimentally requires a high effort in test bench design and operation. To overcome the requirement for such elaborate 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 that dictate the operation limits measured in the experimental campaign can be identified through the numerical results, removing the limitations of experimental measurement. Furthermore, this study delves into the variation of the intake valve actuation and its effects on the pre-chamber gas exchange and combustion process under low engine load.