Effects of pre-spark heat release on engine knock limit

Journal Article · Tue Jan 01 00:00:00 EST 2019 · Proceedings of the Combustion Institute

DOI:https://doi.org/10.1016/j.proci.2018.05.145· OSTI ID:1457510

Splitter, Derek A. ; Gilliam, Arthur; Szybist, James ; Ghandhi, Jaal

It is well known that spark ignited engine efficiency is limited by end gas autoignition, commonly known as knock. This study focuses on a recently discovered phenomena, pre-spark heat release (PSHR) due to low-temperature chemistry, and its impact on knock behavior. Boosted operating conditions are more common as engines are downsizing and downspeeding in efforts to increase fuel economy and prone to PSHR. Experiments were prone at fixed fueling and air fuel ratio for a range of intake temperature that spanned the threshold for PSHR. It was found that when PSHR occurred, the knock-limited combustion phasing was insensitive to intake temperature; higher intake temperatures did not require retarded timings as it is usual. Inspection of the temperature–pressure history overlaid on ignition delay contours allow the results to be explained. The temperature rise from the low-temperature reactions moves the end gas state into the negative temperature coefficient (NTC) region, which terminates the heat release reactions. As a result, the end gas then resides in the long ignition delay peninsula, which inhibits knock.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 1457510
• Alternate ID(s): OSTI ID: 1468233
• Journal Information: Proceedings of the Combustion Institute, Journal Name: Proceedings of the Combustion Institute Vol. 37 Journal Issue: 4; ISSN 1540-7489
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
SI Engines
Knock
Low temperature chemistry
Pre spark heat release
Chemical kinetics