Multiple spark plugs coupled with pressure sensors: A new approach for knock mechanism study on SI engines

Shi, Hao; Uddeen, Kalim; An, Yanzhao; Pei, Yiqiang; Johansson, Bengt

doi:10.1016/j.energy.2021.120382

Cited by 25 publications

(54 citation statements)

References 35 publications

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“…The FFT analysis is applied to estimate the governing frequencies of pressure oscillation caused by knock, regarding the various spark plug approaches. Since the top sensor is more sensitive towards response, the FFT results based on the top sensor signal are represented in Figure 16 for all the distinct spark plugs locations and with the same spark timing of ST = -13 CAD aTDC [41,42].…”

Section: Frequency Analysismentioning

confidence: 99%

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Investigations into the Effects of Spark Plug Location on Knock Initiation by using Multiple Pressure Transducers

Uddeen¹,

Shi²,

Tang³

et al. 2021

SAE Technical Paper Series

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Despite a long history of development, modern spark-ignition (SI) engines are still restricted in obtaining higher thermal efficiency and better performance by knock. Knocking combustion is an abnormal combustion phenomenon caused by the autoignition of unburned airfuel mixture ahead of the propagating flame front. This work describes investigations into the significance of spark plug location (with respect to inlet and exhaust valve position) on the knock formation mechanism. To facilitate the investigation, four spark plugs were installed in a specialized liner at four equispaced distinct locations to propagate flames from those locations, which provoked a distinct flame propagation from each and thus individual autoignition profiles. Six pressure transducers were arranged to precisely record the pressure oscillations, knock intensities, and combustion characteristics. Four of the six transducers were mounted on the circumference of the liner (each next to one of the spark plugs), one was placed at the center of the cylinder head, and one at a slight offset from the center of cylinder head. The results showed that the spark plug which was close to the exhaust valves triggered higher knock intensity along with earlier CA50, but the spark plug near the inlet valves caused weaker knock intensities for the same operating conditions. In addition, the study also covered the effect of swirl direction to suppress knock. A band pass filtering analysis was applied to estimate the pressure oscillations with respect to the spark plug locations, using data from the multiple pressure sensors. Furthermore, Fast Fourier Transform (FFT) analyses were implemented to estimate the frequency of the pressure oscillation resulting from knock. It was found that firing the spark plugs, near the inlet and between the inlet and exhaust valves promoted the (1, 0) acoustic mode effectively, while the spark plug near the exhaust valves caused the (1, 0) mode along with the (2, 0) acoustic mode for the same operating conditions, indicating that the autoignition was initiated near the cylinder walls.

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Section: Frequency Analysismentioning

confidence: 99%

“…The maximum amplitude of pressure oscillation (MAPO) is considered as the knock indicator parameter to determine the knock intensities based on the filtered pressure data, and is described in equation 3, as [13,41,42]:…”

Section: Mapo Analysis For Peaksmentioning

confidence: 99%

Investigations into the Effects of Spark Plug Location on Knock Initiation by using Multiple Pressure Transducers

Uddeen¹,

Shi²,

Tang³

et al. 2021

SAE Technical Paper Series

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“…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]. Therefore, the study of knocking combustion must be adequately understood to meet the future demands of advanced engines.…”

Section: Introductionmentioning

confidence: 99%

“…In-cylinder pressure analysis is the most promising direct detection method to determine the knock combustion, whereas knock can be identified indirectly by the combustion noise and vibrational signals [21]. When auto-ignition occurs, the pressure inside the chamber oscillates strongly, and an installed pressure sensor can detect the oscillation response, and a high pass band filter can then be used to differentiate the knocking combustion versus normal combustion; therefore this analysis is highly accurate in monitoring knock [5,6,21]. However, this method is limited by transducer reliability and cost [22].…”

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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“…However, being operated at elevated pressure and high-load conditions leads to a higher propensity of undesired preignition, knock, and even superknock [1][2][3][4][5][6][7][8]. Superknock is characterized as a developing detonation process featuring excessive pressure oscillations and extremely high-pressure amplitudes that can damage combustion-chamber components [7,[9][10][11][12][13][14][15][16][17][18][19][20]20]. Improved understandings of the superknock propensity and a reliable criterion to predict it are needed to prevent destructive operation of combustion devices [2,4,5,7,[21][22][23][24][25][26][27].…”

Section: Introductionmentioning

confidence: 99%

Knock propensity in a thermally inhomogeneous DME/air mixture: a DNS study

Luong

2022

AIAA SCITECH 2022 Forum

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Superknock propensity in a stoichiometric dimethyl-ether (DME)/air mixture with temperature inhomogeneities under realistic IC engine conditions is investigated using two-dimensional direct numerical simulations (DNS). The developing detonation regime at different conditions is identified by varying the initial mean temperature lying in the low-, intermediate-, and high-temperature chemistry regimes, the level of temperature fluctuations, and its characteristic length scale. We found that the cool flame from the first-stage ignition induces synergistic effects on promoting knock tendency. First, it significantly decreases a minimum run-up distance requirement for developing detonation due to the low-temperature chemistry. Second, analyzing the temporal evolution of the spatial distribution of ignition delay field reveals that the heat release rate from the first-stage ignition effectively modifies the initial field of the ignition delay time, thereby shifting the mixture towards the developing detonation regime. The interaction of multiple ignition kernels is also found to play an important role in enhancing the onset of detonation.

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Multiple spark plugs coupled with pressure sensors: A new approach for knock mechanism study on SI engines

Cited by 25 publications

References 35 publications

Investigations into the Effects of Spark Plug Location on Knock Initiation by using Multiple Pressure Transducers

Investigations into the Effects of Spark Plug Location on Knock Initiation by using Multiple Pressure Transducers

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

Knock propensity in a thermally inhomogeneous DME/air mixture: a DNS study

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