Visualization and Statistical Analysis of Passive Pre-chamber Knock in a Constant-volume Optical Engine

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Authors Abstract
Content
This study investigates the behavior of pre-chamber knock in comparison to traditional spark ignition engine knock, using a modified constant-volume gasoline engine with an optically accessible piston. The aim is to provide a deeper understanding of pre-chamber knock combustion and its potential for mitigating knock. Five passive pre-chambers with different nozzle diameters, volumes, and nozzle numbers were tested, and nitrogen dilution was varied from 0% to 10%. The stochastic nature of knock behavior necessitates the use of statistical methods, leading to the proposal of a high-frequency band-pass filter (37–43 kHz) as an alternative pre-chamber knock metric. Pre-chamber knock combustion was found to exhibit fewer strong knock cycles compared to SI engines, indicating its potential for mitigating knock intensity. High-speed images revealed pre-chamber knock primarily occurs near the liner, where end-gas knock is typically exhibited. The study identified that increasing pre-chamber nozzle diameter resulted in a larger dispersion of knock cycles and more severe knock intensity, likely due to shorter jet penetration depth requiring more time for end-gas consumption. Strategies for mitigating knock in pre-chamber combustion systems include reducing the pre-chamber volume for a fixed A/V ratio and increasing dilution level. The results of this study offer valuable insights for developing effective knock mitigation approaches in pre-chamber combustion systems, contributing to the advancement of more efficient and reliable engines.
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DOI
https://doi.org/10.4271/03-17-03-0020
Pages
18
Citation
Lee, D., Yu, X., Baur, A., and Qiao, L., "Visualization and Statistical Analysis of Passive Pre-chamber Knock in a Constant-volume Optical Engine,"https://doi.org/10.4271/03-17-03-0020.
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Publisher
Published
Oct 20, 2023
Product Code
03-17-03-0020
Content Type
Journal Article
Language
English