Pressure-Based Knock Measurement Issues

Shahlari, Arsham J.; Ghandhi, J. B.

doi:10.4271/2017-01-0668

Cited by 22 publications

(8 citation statements)

References 17 publications

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“…The knock intensity described by K400 was found to agree very well with MAPO for the conditions covered in this work, and this is seen in panel (b) of Figure 11. This finding is different than that observed by Shahlari and Ghandhi [32], and could be due to the simple, nearly cylindrical combustion chamber design found in the CFR engine, as well as the lower engine speed conditions used in the current work. The nearly exact correlation between K400 and MAPO provides confidence in the use of MAPO as a metric for knock, since there is good correspondence between the initial peak measured pressure disturbance, and the later stages of knock where the pressure waves resonate.…”

Section: Resultscontrasting

confidence: 99%

“…The procedure followed is shown in Figure 3 The parameter Ko in the function describes the knock intensity which is then employed to determine the pressure at 400 microseconds after knock onset, as shown by the red dot. The delay period was chosen in order to avoid the potential transducer shock period [32]. For this trace it is apparent that K400 is slightly lower than MAPO and that the pressure oscillation detected by MAPO overshoots the exponential decay fit slightly.…”

Section: High Frequency Data Analysismentioning

confidence: 99%

“…Challenges associated with the accurate measurement and prediction of knock intensity were recently highlighted [28,30,31,32].…”

Section: Introductionmentioning

confidence: 99%

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Insights into Engine Knock: Comparison of Knock Metrics across Ranges of Intake Temperature and Pressure in the CFR Engine

Rockstroh¹,

Kolodziej²,

Jespersen³

et al. 2018

SAE Int. J. Fuels Lubr.

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Of late there has been a resurgence in studies investigating parameters that quantify combustion knock in both standardized platforms and modern spark-ignition engines. However, it is still unclear how metrics such as knock (octane) rating, knock onset and knock intensity are related, and how fuels behave according to these metrics across a range of conditions.As part of an ongoing study, the air supply system of a standard Cooperative Fuel Research (CFR) F1/F2 engine was modified to allow mild levels of intake air boosting while staying true to its intended purpose of being the standard device for ASTM-specified knock rating, or octane number tests. For instance, the carburation system and intake air heating manifold are not altered, but the engine was equipped with cylinder pressure transducers to enable both, logging of the standard knockmeter read-out, as well as state-of-theart indicated data.For this study, the engine was operated using primary reference fuel 90 (PRF90) at 600 rpm, first following the procedures of the ASTM D2699 research octane number test protocol in order to define the geometric compression ratio set point for standard knock number. Thereafter, compression ratio sweeps were conducted at intake temperatures ranging from 30 to 150 °C and intake air boost extending from 0 to 0.3 bar above ambient. The resulting operating map provided a broad envelope of compressed in-cylinder conditions relevant to modern spark ignition engines. Detailed analysis of the indicated data highlighted a poor correlation between established knock intensity metrics and the knockmeter reading, which is used to characterize a fuel's octane number. It was further found that the autoignition characteristics of PRF90 could be perturbed by means of intake air boosting and heating without being captured by the knockmeter reading.

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Section: Resultscontrasting

confidence: 99%

Section: High Frequency Data Analysismentioning

confidence: 99%

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Insights into Engine Knock: Comparison of Knock Metrics across Ranges of Intake Temperature and Pressure in the CFR Engine

Rockstroh¹,

Kolodziej²,

Jespersen³

et al. 2018

SAE Int. J. Fuels Lubr.

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“…Specifically, the hypotheses necessary for its applicability in accurately describing the pressure oscillations in a combustion chamber are as follows 31,32 :…”

Section: Resultsmentioning

confidence: 99%

“…This was observed consistently throughout the study of all 23 cycles, and has also been previously proposed in experimental studies. 32,37…”

Section: Resultsmentioning

confidence: 99%

Analysis of in-cylinder pressure oscillation and its effect on wall heat transfer

Kassa

Leroy

Robert

et al. 2020

International Journal of Engine Research

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In-cylinder pressure oscillations in internal combustion engines have been associated with increased heat losses and damages to the engine components. The links between the acoustic waves and the increased heat transfer (and potentially ensuing engine damages) have not yet been well understood. In this study, a high-fidelity large eddy simulation model incorporating an auto-ignition model is used to simulate the combustion process and the associated pressure oscillation at various engine operating conditions. The study serves to develop a better understanding of the acoustic waves in a combustion chamber and their effect on wall heat transfer. First, a simplified model of the pressure oscillations is proposed and shown to accurately characterize the pressure in the combustion chamber. Second, the simplified pressure model and acoustic theory are leveraged to develop a model of the in-cylinder gas velocities. Finally, a heat transfer model is presented that takes into consideration the pressure/velocity oscillations and the inherent acoustic properties of the trapped gas. The increase in heat transfer is shown to primarily stem from an increased heat transfer coefficient due to the velocity oscillations of the trapped gas. The results are consistent with previously observed experimental measurements of the heat flux in the presence of pressure oscillations.

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Knocking and Combustion Noise Analysis

Maurya

2019

Mechanical Engineering Series

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Pressure-Based Knock Measurement Issues

Cited by 22 publications

References 17 publications

Insights into Engine Knock: Comparison of Knock Metrics across Ranges of Intake Temperature and Pressure in the CFR Engine

Insights into Engine Knock: Comparison of Knock Metrics across Ranges of Intake Temperature and Pressure in the CFR Engine

Analysis of in-cylinder pressure oscillation and its effect on wall heat transfer

Knocking and Combustion Noise Analysis

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