Understanding Failure Modes and High Load Operation in CI Engines With Ducted Fuel Injection

This thesis explores the potential of Ducted Fuel Injection (DFI) as a combustion strategy for reducing emissions in compression-ignition (CI) engines. The research investigates the performance, failure modes, and optimization possibilities of DFI through experimental studies conducted in a pressure vessel and an optically accessible engine.

First, a pressure vessel experiment is conducted to examine the impact of duct geometries on DFI performance. The analysis of duct diameter and length provides insights into their influence on combustion behavior. These findings are valuable for optimizing the design and configuration of the ducts. Additionally, a potential failure mode related to soot flare-ups is identified. These flare-ups manifest as sudden and inconsistent increases in soot luminosity.

While combustion vessel experiments allow for flexibility in testing various duct configurations, they cannot fully capture the complexities of engine operation. To address this limitation, a parametric evaluation is carried out in an optical engine using two different duct configurations. The results of this study provide data on emissions, efficiency, and combustion behavior trends for different duct setups. The findings highlight the trade-offs between reducing emissions and improving fuel-conversion efficiency, emphasizing the need for careful selection of duct configuration. Notably, the presence of
soot flare-ups is also observed in the engine, characterized by their occurrence late in the combustion cycle.

The further characterization of late-cycle flare-up behavior in the optical engine identifies distinct combustion modes associated with flare-ups and determines the factors influencing their occurrence. These insights help unravel the mechanisms behind this potential failure mode and guide strategies to mitigate its impact.

This investigation advances the understanding of DFI for CI engines. It provides new data on DFI performance, identifies geometric parameter trends, characterizes failure modes, and offers insights for optimizing DFI implementation. This thesis lays the groundwork for further advancements in DFI technology and its practical application in achieving cleaner and more efficient combustion engines.

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