Two-Point Spatial Velocity Correlations in the Near-Wall Region of a Reciprocating Internal Combustion Engine

MacDonald, J.; Fajardo, Claudia M.; Greene, Mark; Reuss, David L.; Sick, Volker

doi:10.4271/2017-01-0613

Cited by 8 publications

(5 citation statements)

References 16 publications

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“…Similar deviations from the law-of-the-wall have also been reported in recent DNS studies of an engine-like flow (Schmitt et al 2016). Based on such findings, MacDonald et al (2017) hypothesized that the turbulence in the boundary layer depends on the balance between the turbulence generated by wall-shear and the core flow. Shimura et al (2019) performed PTV measurements in an engine above the piston and found a closer resemblance to the laminar Blasius solution than to the law-of-the-wall.…”

Section: Introductionsupporting

confidence: 80%

“…Investigations utilizing PIV/PTV techniques have revealed several sub-millimeter vortices moving through the outer boundary layer in engines and have shown discrepancies of the engine boundary layer compared with the law-ofthe-wall. For example, previous investigations have shown velocity profiles exhibiting a viscous sublayer region, but no evidence of a logarithmic layer (Jainski et al 2013;MacDonald et al 2017). Similar deviations from the law-of-the-wall have also been reported in recent DNS studies of an engine-like flow (Schmitt et al 2016).…”

Section: Introductionsupporting

confidence: 78%

“…law-of-the-wall, originally developed for steady channel flows (Schlichting and Gersten 2017)). Recent experimental and Direct Numerical Simulations (DNS) studies report strong deviations of engine boundary layers compared to the law-of-the-wall (Jainski et al 2013;MacDonald et al 2017;Renaud et al 2018;Schmitt et al 2016). Most empirical formulas are based on heat flux measurements associated with individual engines and operating conditions (Borman and Nishiwaki 1987;Rakopoulos et al 2010).…”

Section: Introductionmentioning

confidence: 99%

“…In comparison to conventional particle image velocimetry (PIV) approaches, hybrid PIV and particle tracking velocimetry (PTV) techniques are better suited to resolve flow gradients (Kähler et al 2012). Hybrid PIV/ PTV and micro PIV techniques have significantly advanced the ability to measure near-wall flow fields and study boundary layer flows within engines (Alharbi and Sick 2010;Jainski et al 2013;MacDonald et al 2017;Renaud et al 2018;Shimura et al 2019;Ding et al 2019). Investigations utilizing PIV/PTV techniques have revealed several sub-millimeter vortices moving through the outer boundary layer in engines and have shown discrepancies of the engine boundary layer compared with the law-ofthe-wall.…”

Section: Introductionmentioning

confidence: 99%

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Near-Wall Flame and Flow Measurements in an Optically Accessible SI Engine

Schmidt

Ding

Peterson

et al. 2020

Flow Turbulence Combust

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Near-wall processes in internal combustion engines strongly affect heat transfer and pollutant emissions. With continuously improving capabilities to model near-wall processes, the demand for corresponding measurements increases. To obtain an in-depth understanding of the near-wall processes within spark-ignition engines, flame distributions and flow fields were measured simultaneously near the piston surface of an optically accessible engine operating with homogeneous, stoichiometric isooctane-air mixtures. The engine was operated at two engine speeds (800 rpm and 1500 rpm) and two different intake pressures (0.95 bar and 0.4 bar). Flame distributions were obtained at high spatial resolution using high-speed planar laser induced fluorescence of sulfur dioxide (SO 2). Particle tracking velocimetry was utilized to measure the flow field above the piston at high spatial resolution, which enabled the determination of hydrodynamic boundary layer profiles. Flame contours were extracted and statistical distributions of the burnt gas area determined. The burnt gas distributions were compared with the simultaneously recorded high-speed flow field measurements in the unburnt gas. A direct comparison with motored engine operation showed comparable boundary layer profiles until the flame approaches the wall. Flow acceleration due to flame expansion rapidly increases velocity gradients and the boundary layer development becomes highly transient. The interaction of flame and flow depends on the operating conditions, which results in a different evolution of burnt gas positions within the field-of-view. This has additional implications on the development of the velocity boundary layer. Depending on the operating conditions, the flame strongly affects the velocity boundary layer profiles resulting in boundary layer thicknesses (defined by 50% maximum velocity) in the order of 80−180 μm.

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Section: Introductionsupporting

confidence: 80%

Section: Introductionsupporting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Near-Wall Flame and Flow Measurements in an Optically Accessible SI Engine

Schmidt

Ding

Peterson

et al. 2020

Flow Turbulence Combust

View full text Add to dashboard Cite

show abstract

“…Vectors at positions where the local standard deviation was low (indicating a weak particle signal) were removed. The piston position was determined using phase averaged images from which the peak intensity location was determined [21].…”

Section: Data Processingmentioning

confidence: 99%

Flame/flow dynamics at the piston surface of an IC engine measured by high-speed PLIF and PTV

Ding

Peterson

Schmidt

et al. 2019

Proceedings of the Combustion Institute

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Resolving fluid transport at engine surfaces is required to predict transient heat loss, which is becoming increasingly important for the development of high-efficiency internal combustion engines (ICE). The limited number of available investigations have focused on non-reacting flows near engine surfaces, while this work focuses on the near-wall flow field dynamics in response to a propagating flame front. Flow-field and flame distributions were measured simultaneously at kHz repetition rates using particle tracking velocimetry (PTV) and planar laser induced fluorescence (PLIF) of sulfur dioxide (SO2). Measurements were performed near the piston surface of an optically accessible engine operating at 800 rpm with homogeneous, stoichiometric isooctane-air mixtures. High-speed measurements reveal a strong interdependency between near-wall flow and flame development which also influences subsequent combustion. A conditional analysis is performed to analyze flame/flow dynamics at the piston surface for cycles with 'weak' and 'strong' flow velocities parallel to the surface. Faster flame propagation associated with higher velocities before ignition demonstrates a stronger flow acceleration ahead of the flame. Flow acceleration associated with an advancing flame front is a transient feature that strongly influences boundary layer development. The distance from the wall to 75% maximum velocity (δ75) is analyzed to compare boundary layer development between fired and motored datasets. Decreases in δ75 are strongly related to flow acceleration produced by an approaching flame front. Measurements reveal strong deviations of the boundary layer flow between fired and motored datasets, emphasizing the need to consider transient flow behavior when modelling boundary layer physics for reacting flows.

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Ridge-type roughness: from turbulent channel flow to internal combustion engine

et al. 2021

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While existing engineering tools enable us to predict how homogeneous surface roughness alters drag and heat transfer of near-wall turbulent flows to a certain extent, these tools cannot be reliably applied for heterogeneous rough surfaces. Nevertheless, heterogeneous roughness is a key feature of many applications. In the present work we focus on spanwise heterogeneous roughness, which is known to introduce large-scale secondary motions that can strongly alter the near-wall turbulent flow. While these secondary motions are mostly investigated in canonical turbulent shear flows, we show that ridge-type roughness—one of the two widely investigated types of spanwise heterogeneous roughness—also induces secondary motions in the turbulent flow inside a combustion engine. This indicates that large scale secondary motions can also be found in technical flows, which neither represent classical turbulent equilibrium boundary layers nor are in a statistically steady state. In addition, as the first step towards improved drag predictions for heterogeneous rough surfaces, the Reynolds number dependency of the friction factor for ridge-type roughness is presented. Graphic abstract

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Two-Point Spatial Velocity Correlations in the Near-Wall Region of a Reciprocating Internal Combustion Engine

Cited by 8 publications

References 16 publications

Near-Wall Flame and Flow Measurements in an Optically Accessible SI Engine

Near-Wall Flame and Flow Measurements in an Optically Accessible SI Engine

Flame/flow dynamics at the piston surface of an IC engine measured by high-speed PLIF and PTV

Ridge-type roughness: from turbulent channel flow to internal combustion engine

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