CFD Simulation of Pre-Chamber Spark-Ignition Large Bore CNG Engine: Model Development, Practical Applications, and Experimental Validation

Soo-Jin Jeong (), Seokpan Seo and Seong-Joon Moon
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Soo-Jin Jeong: Alternative Fuel Power System R&D Department, Korea Automotive Technology Institute, 303 Pungse-myeon, Dongnam-gu, Cheonan-si 31214, Republic of Korea
Seokpan Seo: STX Engine Co., Ltd., 36, Gongdan-ro, 474 beon-gil, Seongsan-gu, Changwon-si 51574, Republic of Korea
Seong-Joon Moon: Alternative Fuel Power System R&D Department, Korea Automotive Technology Institute, 303 Pungse-myeon, Dongnam-gu, Cheonan-si 31214, Republic of Korea

Energies, 2025, vol. 18, issue 7, 1-42

Abstract: This study develops and validates a three-dimensional CFD model for a 12 L large-bore active-type pre-chamber spark-ignition (PCSI) engine fueled by natural gas. The model incorporates an advanced Extended Coherent Flamelet Model (ECFM-3Z) with a tuned stretch factor to capture complex turbulence–flame interactions, flame propagation, and pollutant formation under ultra-lean conditions. By systematically varying pre-chamber geometries—specifically the orifice diameter, cone angle, diverging tapered nozzle, and volume—the simulations assess their effects on combustion dynamics, heat release rates, turbulent jet penetration, and emissions (NOx and CO). Model predictions of in-cylinder and pre-chamber pressure profiles, combustion phasing, and emission trends are validated against experimental data. The results demonstrate that optimizing pre-chamber and orifice configurations enhances turbulent mixing, accelerates flame development, and reduces local high-temperature zones, thereby suppressing NOx and CO formation. Although some discrepancies in NOx predictions persist due to limitations in current turbulence–chemistry models, the findings offer valuable insights for the design of high-efficiency, low-emission PCSI engines.

Keywords: natural gas; active pre-chamber; computational fluid dynamics; pre-chamber spark ignition (PCSI); lean, premixed natural gas combustion; turbulent jet ignition; flame speed; exhaust emission (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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