Endoscopic high-speed particle image velocimetry (eHS-PIV) in a high tumble production engine

Kim, Dongchan; Rao, Lingzhe; Oh, Hyondong; Kook, Sanghoon

doi:10.1007/s00348-020-03055-w

Cited by 6 publications

(20 citation statements)

References 31 publications

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“…It is noticeable that the flow direction of the advanced IVC and the default IVC is directly opposite at the spark timing and afterwards. As discussed in the previous study, 19,20 the no bounce-back flow of the default IVC is the result of lower intake air momentum, which led to decreased surging flow strength. This once again suggests the strong surging flow impinging on the exhaust side is a major cause of the unique bounceback structure of high-tumble engines.…”

Section: Intake Valve Timing Variationmentioning

confidence: 66%

“…This is a characteristic of a high-tumble engine with the strong lateral and straight intake airflow creating an asymmetric flow structure. 19,20,27 This asymmetry also leads to a new distinct flow component formed within the pent-roof region as illustrated by a blue arrow. Named as a surging flow, the flow vectors do not follow the tumble vortex direction but laterally flow across the pent-roof region and with increasing engine speed, their magnitude becomes higher, which is related to the increased piston speed.…”

Section: Engine Speed Variationmentioning

confidence: 99%

“…The field of view of this endoscopic PIV setup is shown on the bottom-left corner of Figure 2. To capture the expected flow development in the high-tumble engine, 20,27 the synchronised, high laser repetition and imaging rate of 35 kHz was used, leading to a fine frame separation of 28 ms. The images were recorded on 256 3 256 pixel area, which provided 220 mm/pixel based on the calibration with the installed original spark plug.…”

Section: Ehs-piv/flame Diagnostics Setupmentioning

confidence: 99%

“…Three flow structure components newly found at the late compression stroke from a high-tumble spark ignition engine. 19,20 …”

Section: Introductionmentioning

confidence: 99%

“…5 Two-dimensional high-speed PIV (HS-PIV) revealed further details such that the first formation of an intake-shifted tumble vortex occurs at the lower half of the cylinder and then it moves upwards while being exhaust-shifted later in the compression stroke. 15,17 Endoscopic HS-PIV (eHS-PIV) 18 implemented in multi-cylinder production engines 19,20 achieved major new findings specific to high-tumble engine flow structures. As illustrated in Figure 1, new engines employing a very high tumble ratio (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Flow directed spark stretch and flame propagation in a high-tumble production engine

Kim

Rao

Kook

et al. 2021

International Journal of Engine Research

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This study performs endoscopic high-speed imaging to enhance the fundamental knowledge of in-cylinder flow structure and flame development process in a selected high-tumble production engine. The endoscopic high-speed particle image velocimetry (eHS-PIV) was performed for varied engine speeds and intake valve closing (IVC) timings to evaluate their impact on the in-cylinder flow structure in a motored engine condition. On another endoscope engine sharing the same hardware, high-speed flame imaging was conducted to visualise spark stretch and flame propagation. The flow and flame measurements were repeated for over 100 cycles and the ensemble-averaged results are compared. The eHS-PIV showed that a strong tumble vortex is generated during the piston compression with the flow directed towards the exhaust side. As the piston reaches top dead centre (TDC), however, a complex flow breakup involving multiple flow components occurs. This is followed by lateral flow vectors travelling back towards the intake side, which is termed as the bounce-back flow. For a tested engine speed range of 1700–2700 revolutions per minute (rpm), 2500 rpm shows the most significant bounce-back flow as a result of competition between the remaining exhaust-ward tumble flow strength and the newly formed bounce-back flow strength. At a retarded IVC timing, the flow loss leads to a weakened tumble flow and subsequently no bounce-back flow formation to maintain the exhaust-ward TDC flow direction. From the comparison between the flow results and spark/flame high-speed images, a strong positive correlation is found between the TDC flow direction and spark plasma stretch, and subsequently the flame propagation direction. The findings indicate that the TDC flow direction should be considered as a key parameter in the engine design and operating condition settings.

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Section: Intake Valve Timing Variationmentioning

confidence: 66%

Section: Engine Speed Variationmentioning

confidence: 99%

Section: Ehs-piv/flame Diagnostics Setupmentioning

confidence: 99%

“…Three flow structure components newly found at the late compression stroke from a high-tumble spark ignition engine. 19,20 …”

Section: Introductionmentioning

confidence: 99%