A phenomenological model of knock intensity in spark-ignition engines

Li, Tie; Yin, Tao; Wang, Bin

doi:10.1016/j.enconman.2017.06.078

Cited by 28 publications

(6 citation statements)

References 50 publications

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“…As is illustrated in Fig. 9, except for single spark ignition, the spark timing is started from TDC and swept with 2-3 CAD intervals, which provoke transitions from normal combustion to conventional knock at naturally aspirated condition [38][39][40]. In addition, to get rid of potential risks caused by knock, the knock limited timings for different spark strategies are adjusted to keep the mean knock intensity below 6 bar, which is determined by the AVL Indicom operating system.…”

Section: Different Sparking Strategiesmentioning

confidence: 99%

Experimental Study on Knock Mechanism with Multiple Spark Plugs and Multiple Pressure Sensors

Shi¹,

Uddeen²,

An³

et al. 2020

SAE Technical Paper Series

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Engine knock is an abnormal phenomenon, which places barriers for modern Spark-Ignition (SI) engines to achieve higher thermal efficiency and better performance. In order to trigger more controllable knock events for study while keeping the knock intensity at restricted range, various spark strategies (e.g. spark timing, spark number, spark location) are applied to investigate on their influences on knock combustion characteristics and pressure oscillations. The experiment is implemented on a modified single cylinder Compression-Ignition (CI) engine operated at SI mode with port fuel injection (PFI). A specialized liner with 4 side spark plugs and 4 pressure sensors is used to generate various flame propagation processes, which leads to different auto-ignition onsets and knock development. Based on multiple channels of pressure signals, a bandpass filter is applied to obtain the pressure oscillations with respect to different spark strategies. Finally, the relationships among in-cylinder pressure, knock intensity, pressure fluctuation, heat release and measurement location, are analyzed to get better understanding on knock mechanism, influence factors and measurement methods. The main results show that: Igniting two spark plugs simultaneously brings higher knock amplitude than single spark ignition, however, adding more spark sites could effectively suppress the knock strength and rate of recurrence. A function (Y =-0.25X + 2.82) is fitted to illustrate the relations between the crank angle of 1st peak of knock oscillation and MAPO. Besides, the correlations among MAPO and other influential factors are evaluated. Moreover, the pressure sensors installed around the liner give different pressure fluctuations, which indicate the directionality of pressure wave transmission in cylinder during knock process.

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Section: Different Sparking Strategiesmentioning

confidence: 99%

Experimental Study on Knock Mechanism with Multiple Spark Plugs and Multiple Pressure Sensors

Shi¹,

Uddeen²,

An³

et al. 2020

SAE Technical Paper Series

View full text Add to dashboard Cite

show abstract

“…The LMS was sensitive to correlated data since its convergence depended on input values, as shown in Eq. (8). As a result, the LMS characterization of knock phenomenon was poor, given that the knock is a highly correlated signal.…”

Section: A Real-time Implementation and Software Workflowmentioning

confidence: 99%

Real-Time Knock Characterization Using Adaptive Filters and Power Estimators

et al. 2020

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We combined adaptive filters associated with power estimators to characterize the knock signal, obtained from a knock sensor, in an internal combustion engine. The filters were implemented using the automotive model-based design methodology, and the resulting software was embedded into hardware for a real-time evaluation of the proposed solution. The knock signals could be qualitatively identified in real-time, and thus have the potential to aid in the management of flexible-fuel engines. This approach has an extensive range of applications within the automotive industry, since it can be implemented within any model-based control strategy. For example, this methodology can be applied in commercial ECUs, currently used in most vehicles for knock detection, by simply eliminating an internal, dedicated, integrated circuit for knock identification, or by serving as a redundancy device (i.e: for safety purposes). Finally, this methodology can identify the knock signal, obtained from a knock sensor, just by using an algorithm implemented in the ECU's processor, which we show is identifiable in real-time.

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“…They mostly utilize hydrocarbon fuel and so produce many harmful species such as CO2, NOx, CO, and HC, as well as generating particulates in the exhaust [1]. Modern engine research is focused towards less fuel consumption, less exhaust emissions, and higher engine efficiency [2,3]. Modern spark-ignition (SI) engines generally use a three-way catalyst (TWC) along with a particulate filter to convert the emissions [4], and many advanced technologies such as downsizing, supercharging, and higher compression ratio (CR) have been introduced to improve engine efficiency; however, all these technologies are restricted by knock phenomena in achieving higher efficiency [5,6].…”

Section: Introductionmentioning

confidence: 99%

“…1 Modern engine research is focused toward less fuel consumption, less exhaust emissions, and higher engine efficiency. 2,3 Modern spark-ignition (SI) engines generally use a three-way catalyst (TWC) along with a particulate filter to convert the emissions, 4 and many advanced technologies such as downsizing, supercharging, and higher compression ratio (CR) have been introduced to improve engine efficiency; however, all these technologies are restricted by knock phenomena in achieving higher efficiency. 5,6 Therefore, the study of knocking combustion must be adequately understood to meet the King Abdullah University of Science and Technology, Thuwal, Saudi Arabia future demands of advanced engines.…”

Section: Introductionmentioning

confidence: 99%

The effects of compression ratio and combustion initiation location on knock emergence by using multiple pressure sensing devices

Uddeen

Shi

Tang

et al. 2022

International Journal of Engine Research

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Knock research is an essential study because knock limits spark-ignition (SI) engine power output, durability, noise, fuel consumption, and emission performance. The thermal efficiency of an engine can be improved by increasing the compression ratio, but at the same time it leads to the possibility of end gas autoignition inside the chamber. The objective of this work was to show the effect of three different compression ratios (CRs) 8.5, 9.5, and 10.5 on the mechanism of knock. In order to achieve this four equispaced spark plugs were fitted around the circumference of a special metal liner to initiate flame fronts from those plugs by firing with different spark approaches (e.g. spark timing, number, and location). In addition, six pressure sensors were installed at various locations to precisely record the autoignition event by monitoring pressure oscillations, combustion characteristics, and knock intensity. In-cylinder pressure and heat release rate (HRR) analyses were applied to distinguish the knocking combustion for the three different CRs. The results showed that a greater number of spark plugs produced more stable combustion even for a delayed spark timing (ST) than a single spark plug, but also increased pressure oscillations, HRR and knock propensity with higher CRs due to an increase in pressure and temperature inside the cylinder. The maximum amplitude of pressure oscillation (MAPO) method was used to determine the knock intensity, and it was observed that at the lowest CR of 8.5 three spark plugs gave higher MAPO values compared to four spark plugs for the same operating conditions. However, four spark plugs instigated higher MAPO values than three spark plugs for the higher CRs of 9.5 and 10.5 because, with the increase of CR and spark plug numbers, the pressure and temperature were increased during the combustion event, which was coupled with the compression effect on the unburned end gas mixture. Additionally, Fast Fourier transform (FFT) and wavelet methods were implemented to observe the frequencies induced during knock. It was found that sparking four plugs provoked various vibration modes in different amplitude ranges with the different CRs.

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A phenomenological model of knock intensity in spark-ignition engines

Cited by 28 publications

References 50 publications

Experimental Study on Knock Mechanism with Multiple Spark Plugs and Multiple Pressure Sensors

Experimental Study on Knock Mechanism with Multiple Spark Plugs and Multiple Pressure Sensors

Real-Time Knock Characterization Using Adaptive Filters and Power Estimators

The effects of compression ratio and combustion initiation location on knock emergence by using multiple pressure sensing devices

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