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A Pressure-Oscillation-Based RON Estimation Method for Spark Ignition Fuels beyond RON 100

Robeyn, Tom ; Sileghem, Victor ; Larsson, Tara and Verhelst, Sebastian LU orcid (2024) In Energies 17(6).
Abstract

Knock in spark ignition (SI) engines occurs when the air–fuel mixture in the combustion chamber ignites spontaneously ahead of the flame front, reducing combustion efficiency and possibly leading to engine damage if left unattended. The use of knock sensors to prevent it is common practice in modern engines. Another measure to mitigate knock is the use of higher-octane fuels. The American Society for Testing and Materials’ (ASTM) determination of the Research Octane Number (RON) and Motor Octane Number (MON) of spark ignition fuels has been based on measuring cylinder pressure rise at the onset of knock since its inception in the 1930s. This is achieved through a low-pass filtered pressure signal. Knock detection in contemporary... (More)

Knock in spark ignition (SI) engines occurs when the air–fuel mixture in the combustion chamber ignites spontaneously ahead of the flame front, reducing combustion efficiency and possibly leading to engine damage if left unattended. The use of knock sensors to prevent it is common practice in modern engines. Another measure to mitigate knock is the use of higher-octane fuels. The American Society for Testing and Materials’ (ASTM) determination of the Research Octane Number (RON) and Motor Octane Number (MON) of spark ignition fuels has been based on measuring cylinder pressure rise at the onset of knock since its inception in the 1930s. This is achieved through a low-pass filtered pressure signal. Knock detection in contemporary engines, however, relies on measuring engine vibrations caused by high-frequency pressure oscillations during knock. The difference between conditions in which fuels are evaluated for their octane rating and the conditions that generate a knock intensity signal from the knock sensor suggests a potential difference between octane rating and the knock limit typically identified by a contemporary knock sensor. To address this disparity, a modified RON measurement method has been developed, incorporating pressure oscillation measurements. This test method addresses the historical lack of correlation between RON and high-frequency pressure oscillation intensity during knock. Using toluene standardization fuels (TSFs) as a reference, the obtained results demonstrate excellent high-frequency knock intensity-based RON estimations for gasoline. The method is able to differentiate between two fuels that share the same ASTM RON, associating them with a RON-like metric that is more aligned with their performance in a modern SI engine. This alternative method could potentially serve as a template for an upgrade to the existing ASTM RON method without significantly disrupting the current approach. Additionally, its capability to evaluate fuels beyond RON 100 opens the door to assessing a wider range of fuels for antiknock properties and the intensity of fuel oscillations during knocking combustion.

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Please use this url to cite or link to this publication:
author
; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
knock, knock intensity, octane number, pressure oscillations, spark ignition
in
Energies
volume
17
issue
6
article number
1362
publisher
MDPI AG
external identifiers
  • scopus:85188745165
ISSN
1996-1073
DOI
10.3390/en17061362
language
English
LU publication?
yes
id
bd70a27a-45c7-456c-92b7-fd6dc3bcfc40
date added to LUP
2024-04-19 08:04:50
date last changed
2024-04-19 08:05:33
@article{bd70a27a-45c7-456c-92b7-fd6dc3bcfc40,
  abstract     = {{<p>Knock in spark ignition (SI) engines occurs when the air–fuel mixture in the combustion chamber ignites spontaneously ahead of the flame front, reducing combustion efficiency and possibly leading to engine damage if left unattended. The use of knock sensors to prevent it is common practice in modern engines. Another measure to mitigate knock is the use of higher-octane fuels. The American Society for Testing and Materials’ (ASTM) determination of the Research Octane Number (RON) and Motor Octane Number (MON) of spark ignition fuels has been based on measuring cylinder pressure rise at the onset of knock since its inception in the 1930s. This is achieved through a low-pass filtered pressure signal. Knock detection in contemporary engines, however, relies on measuring engine vibrations caused by high-frequency pressure oscillations during knock. The difference between conditions in which fuels are evaluated for their octane rating and the conditions that generate a knock intensity signal from the knock sensor suggests a potential difference between octane rating and the knock limit typically identified by a contemporary knock sensor. To address this disparity, a modified RON measurement method has been developed, incorporating pressure oscillation measurements. This test method addresses the historical lack of correlation between RON and high-frequency pressure oscillation intensity during knock. Using toluene standardization fuels (TSFs) as a reference, the obtained results demonstrate excellent high-frequency knock intensity-based RON estimations for gasoline. The method is able to differentiate between two fuels that share the same ASTM RON, associating them with a RON-like metric that is more aligned with their performance in a modern SI engine. This alternative method could potentially serve as a template for an upgrade to the existing ASTM RON method without significantly disrupting the current approach. Additionally, its capability to evaluate fuels beyond RON 100 opens the door to assessing a wider range of fuels for antiknock properties and the intensity of fuel oscillations during knocking combustion.</p>}},
  author       = {{Robeyn, Tom and Sileghem, Victor and Larsson, Tara and Verhelst, Sebastian}},
  issn         = {{1996-1073}},
  keywords     = {{knock; knock intensity; octane number; pressure oscillations; spark ignition}},
  language     = {{eng}},
  number       = {{6}},
  publisher    = {{MDPI AG}},
  series       = {{Energies}},
  title        = {{A Pressure-Oscillation-Based RON Estimation Method for Spark Ignition Fuels beyond RON 100}},
  url          = {{http://dx.doi.org/10.3390/en17061362}},
  doi          = {{10.3390/en17061362}},
  volume       = {{17}},
  year         = {{2024}},
}