Combined effects of engine speed, excess air ratio and nozzle diameter on characteristics of an SI engine with passive pre-chamber
Year: 2026
Type: article
Abstract: Turbulent jet ignition (TJI) offers a promising approach to extending the lean-burn limit of spark-ignition (SI) engines by enhancing ignition and accelerating combustion. However, further research, particularly on passive TJI configurations, is needed to facilitate their practical implementation in commercial SI engines, bridging the gap between experimental insights and real-world applications. This study examines combined effects of engine speed, excess air ratio (λ) and nozzle diameter on combustion characteristics, performance, and emission behavior of a commercial SI engine equipped with passive pre-chamber TJI (PTJI) systems. Experimental investigations were conducted using three pre-chamber configurations, each incorporating six nozzles with diameters of 1.00, 1.25, and 1.50 mm. Tests were performed using commercial gasoline at λ values ranging from 0.9 to 1.7 and engine speeds of 2500, 3000, and 3500 rpm. Experimental results showed that stable combustion, defined by a coefficient of variation of indicated mean effective pressure (COV IMEP ) below 5 %, was maintained up to λ = 1.3 across all engine speeds and pre-chamber configurations. Beyond λ = 1.3, further mixture leaning resulted in progressively deteriorating combustion stability, depending on the engine speed and the nozzle diameter. For λ ≤ 1.3, the 1.00 mm nozzle configuration generally outperformed the other pre-chamber configurations across the tested engine speeds. The highest indicated thermal efficiency (ITE) and lowest indicated specific fuel consumption (ISFC) were consistently obtained at λ = 1.3, with an ITE of approximately 45 % and an ISFC of approximately 190 g/kWh at 2500 rpm with the 1.00 mm nozzle diameter. Although ITE decreased and ISFC increased with further mixture leaning, the 1.25 mm nozzle configuration generally provided better performance than the 1.00 and 1.50 mm nozzle configurations at λ = 1.4 under stable combustion conditions across all engine speeds. The detailed results obtained in this study provide a comprehensive dataset that offers valuable guidance for researchers and engine manufacturers in the design and integration of PTJI systems, while also serving as useful benchmark data for the development and validation of numerical models.
Institution: Pamukkale University
Language: English
Subfield: Fluid Flow and Transfer Processes
Field: Chemical Engineering
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,800
OpenAlex ID: W7213743045