Experimental evaluation of different pre-chamber geometric characteristics in a single-cylinder SI engine

The adoption of passive pre-chamber spark plugs (PCSP), for Turbulent Jet Ignition (TJI) implementation, is increasing in gasoline engines due to their ability to improve combustion efficiency and reduce emissions. This technology enhances combustion by igniting a small air-fuel mixture in a separate volume (pre-chamber), generating hot jets that promote faster and more uniform combustion in the main chamber. As a result, it improves air-fuel mixing, increases thermal efficiency, and reduces pollutants such as carbon monoxide (CO) and unburned hydrocarbons (HC). This study aims to determine the optimal pre-chamber geometry for a gasoline-fueled spark-ignition (SI) engine under various operating conditions. To achieve this, an experimental campaign was conducted on a single-cylinder spark-ignition (SI) engine across different load and speed conditions, complemented by CFD modeling. Results show that a new prototype, based on the original manufacturer’s design philosophy, has a suitable base geometry that can be slightly modified to achieve similar performance. However, its EGR rate tolerance remains 45% lower at critical low-load conditions, affecting its overall adaptability.