Influence of the Pre-chamber Gas Composition on the Ignition Process of an Active Pre-chamber

Wittmann F, Schönhofer F, Clemente Mallada R, Kowis C, Rieß S, Wensing M (2026)

Publication Language: English

Publication Type: Conference contribution, Conference Contribution

Publication year: 2026

Publisher: Narr Francke Attempto Verlag GmbH + Co. KG

City/Town: Tübingen

Pages Range: 309 - 325

Conference Proceedings Title: IAV SPARK26 – IAV Symposium on Pre-Ignition, Auto-Ignition, Reactivity, and Knock

Event location: Berlin

ISBN: 978-3-381-16861-3

DOI: 10.24053/9783381168620

Abstract

An actively fueled single-hole pre-chamber ignition system is studied to investigate how the gas composition inside the pre-chamber influences the emerging jets and the transition between flame ignition and jet ignition. The pre-chamber is fueled with a homogeneously premixed methane-air mixture with equivalence ratios ϕ =0.9, 1.0, 1.2 and 1.5. Methane and air are mixed using two mass flow controllers and supplied to the pre-chamber using a DI-injector. The mixture inside the pre-chamber is ignited by a spark plug. Additionally, the oxygen content of the air is varied to investigate different residual gas fractions inside the pre-chamber prior to ignition. Therefore, experiments with an oxygen content of 21 %, 18 % and 15 % have been conducted in order to mimic the real operating conditions of a pre-chamber engine with 0 %, 14.29 % and 28.57 % residual gas remaining inside the pre-chamber while running. The pre chamber is mounted to a continuously scavenged constant flow chamber (CFC) with high optical accessibility. The CFC enables highly controlled the modynamic conditions, with the purge gas temperature maintained at a constant 573 K and the pressure regulated to 1 MPa. The CFC is purged either with nitrogen or air. The pre-chamber is equipped with a miniature piezoelectric pressure sensor, providing information about the pressure rise caused by the ignition and combustion inside the pre-chamber. High-speed Schlieren imaging was used to visualize the penetration of the hot gas jet exiting the pre-chamber. Additional
OH* chemiluminescence imaging was used to identify if the emerging jet contains active radicals and, if so, to provide insight into the position of the reaction zone. Together, the jet penetration speed in the main chamber and the pressure trace inside the pre-chamber serve as indicators of the pre-chamber heat-release rate and the resulting blowdowndriven jet momentum. The jet penetration and pressure trace are evaluated and compared for different oxygen contents showing that ignition stability is influenced by the available oxygen. The OH* signal is only detected for rich mixtures and when using air instead of nitrogen as purge gas in the CFC, leading to the conclusion that the equivalence ratio and available oxygen are important factors when distinguishing
between flame ignition and jet ignition. The experiments highlight the central influence of gas composition on jet formation and ignition mode for pre-chamber ignition systems.

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How to cite

APA:

Wittmann, F., Schönhofer, F., Clemente Mallada, R., Kowis, C., Rieß, S., & Wensing, M. (2026). Influence of the Pre-chamber Gas Composition on the Ignition Process of an Active Pre-chamber. In Marc Sens (Eds.), IAV SPARK26 – IAV Symposium on Pre-Ignition, Auto-Ignition, Reactivity, and Knock (pp. 309 - 325). Berlin, DE: Tübingen: Narr Francke Attempto Verlag GmbH + Co. KG.

MLA:

Wittmann, Frank, et al. "Influence of the Pre-chamber Gas Composition on the Ignition Process of an Active Pre-chamber." Proceedings of the IAV SPARK26 - IAV Symposium on Pre-Ignition, Auto-Ignition, Reactivity, and Knock, Berlin Ed. Marc Sens, Tübingen: Narr Francke Attempto Verlag GmbH + Co. KG, 2026. 309 - 325.

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