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Experimental and Numerical Low-Speed Pre-ignition Analysis and Mechanism Synthesis on a Turbocharged Gasoline Engine with Direct Injection
- Thorsten Schweizer - Karlsruhe Institute of Technology, Institute of Internal Combustion Engines, Germany ,
- Norbert Zöbinger - TU Wien, Institute of Powertrains and Automotive Technology, Austria ,
- Heiko Kubach - Karlsruhe Institute of Technology, Institute of Internal Combustion Engines, Germany ,
- Thomas Lauer - TU Wien, Institute of Powertrains and Automotive Technology, Austria ,
- Thomas Koch - Karlsruhe Institute of Technology, Institute of Internal Combustion Engines, Germany
Journal Article
03-16-03-0018
ISSN: 1946-3936, e-ISSN: 1946-3944
Sector:
Topic:
Citation:
Schweizer, T., Zöbinger, N., Kubach, H., Lauer, T. et al., "Experimental and Numerical Low-Speed Pre-ignition Analysis and Mechanism Synthesis on a Turbocharged Gasoline Engine with Direct Injection," SAE Int. J. Engines 16(3):305-333, 2023, https://doi.org/10.4271/03-16-03-0018.
Language:
English
Abstract:
The concept of downsizing is a successful approach to improve efficiency for
passenger car spark-ignition (SI) engines. This leads to highly charged gasoline
engines with direct injection and high specific power densities, promoting a
combustion anomaly known as low-speed pre-ignition (LSPI). This unpredictable
occurring and multi-cycle phenomenon is not yet fully understood and thus limits
the achievable in-cylinder pressure and further efficiency gains. To achieve a
comprehensive understanding of the entire PI initiating mechanism, thermodynamic
and optical experiments were conducted, as well as accompanying numerical
investigations. For this purpose, the influence of various engine parameters is
investigated on the testbed in a modern three-cylinder gasoline engine. In
particular, an increased spray/liner interaction was found to promote PI
frequencies vigorously. Based on these results, optical characterization of the
emerging premature ignitions is performed by utilizing a minimally invasive
endoscopic high-speed imaging testbed setup. It could be observed that visibly
glowing flying objects and deposits at specific regions initiate premature
ignitions. The use of a computational fluid dynamics (CFD) engine model
incorporating a multicomponent fuel surrogate revealed that those deposit-prone
regions coincide with areas of strong fuel wall wetting on the liner and the
piston crevice region. This observation could be validated experimentally by
in-cylinder recordings of fluorescence tracer-doped fuel. Based on the optical
results, a numerical study on the thermal behavior of detached inert particles
over three consecutive combustion cycles is performed. A stochastic particle
release from deposition hotspots could reveal that inert particles do not reach
a sufficiently high surface temperature to initiate a premature ignition.
Advanced ex-situ analysis of naturally and artificially generated combustion
chamber deposits showed that inorganic substances originating from lubricating
oil enhance oxidation reactivity and enable deposits to ignite the surrounding
mixture. Through a final synthesis step of all results, a multidimensional
reactive particle-driven LSPI mechanism is established.