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

Ding, Carl-Philipp; Peterson, Brian; Schmidt, Marvin; Dreizler, Andreas; Böhm, Benjamin

doi:10.1016/j.proci.2018.06.215

Cited by 19 publications

(10 citation statements)

References 22 publications

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“…The spark timing was adjusted for each operating condition to have a maximum in-cylinder pressure at about 9 • CA (crank-angle degrees) aTDC (after compression top dead center). The measurements presented in this manuscript coincide with a comprehensive velocimetry and reacting flow database for this optical engine (Baum et al 2014;Zentgraf et al 2016;Peterson et al 2019), which includes recent investigations of engine boundary layer flows (Ding et al 2019;Renaud et al 2018). Figure 1 shows the experimental setup for the simultaneous flame and flow measurements.…”

Section: Engine and Operating Conditionsmentioning

confidence: 80%

“…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%

“…While previous investigations provide an improved understanding to boundary layer flow in engines, they have been limited to non-reacting flow conditions. Ding et al (2019) recently performed PIV/PTV measurements above a piston in an optically accessible engine to resolve the transient near-wall flow development associated with an approaching flame front. Their measurements revealed unburnt gas flow acceleration ahead of the flame as the flame approached the piston surface.…”

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

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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: Engine and Operating Conditionsmentioning

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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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“…Fig. 14, but since these measurements were not specifically designed to study flame/wall interaction, the negative velocities near the piston surface are merely discussed as an observation at this stage. Improved spatial resolution of LIF and PIV such as presented in [52] or spatio-thermochemical probing of flame/wall interactions using short-pulse CARS measurements [53] are better suited to further investigate the flame behavior near solid surfaces. The velocity maps ( Fig.…”

Section: Individual Cycle Analysismentioning

confidence: 99%

An experimental study of the detailed flame transport in a SI engine using simultaneous dual-plane OH-LIF and stereoscopic PIV

Peterson

Baum

Dreizler

et al. 2019

Combustion and Flame

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Understanding the detailed flame transport in IC engines is important to accurately predict ignition and combustion phasing, rate of heat release and assess engine performance. This is particularly important for RANS and LES engine simulations, which often struggle to accurately predict flame propagation and heat release without first adjusting model parameters. Detailed measurements of flame transport in technical systems are required to guide model development and validation. This work introduces an experimental dataset designed to study the detailed flame transport and flame/flow dynamics for spark-ignition engines. Simultaneous dual-plane OH-LIF and stereoscopic PIV is used to acquire 3D measurements of unburnt gas velocity (⃑ ⃑), flame displacement speed () and overall flame front velocity (⃑ ⃑) during the early flame development. Experiments are performed in an optical engine operating at 800 and 1500 RPM with premixed, stoichiometric isooctane-air mixtures. Analysis reveals several distinctive flame/flow configurations that yield a positive or negative flame displacement for which the flame progresses towards the reactants or products, respectively. For the operating conditions utilized, exhibits and inverse relationship with flame curvature and a strong correlation between negative and convex flame contours is observed. Trends are consistent with thermo-diffusive flames, but have not been quantified in context of IC engines. Flame wrinkling is more severe at the higher RPM, which results in a broader distribution towards higher positive and negative velocities. Spatially-resolved distributions of ⃑ ⃑ and are presented to describe in-cylinder locations where either convection or thermal diffusion is the dominating mechanism contributing to flame transport. Findings are discussed in relation to common engine flow features, including flame transport near solid surfaces. Findings provide a first insight into the detailed flame transport within a technically relevant environment and are designed to support the development and validation of engine simulations.

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“…Laser diagnostics and advanced numerical simulations have been instrumental to understand transient BL behavior in combustion [3,[5][6][7][8][9][10][11][12]. Much research has primarily focused on hydrodynamic BLs (e.g., [3,[5][6][7]), while less research has focused on transient thermal BLs (TBL).…”

Section: Introductionmentioning

confidence: 99%

Simultaneous 1D hybrid fs/ps rotational CARS, phosphor thermometry, and CH* imaging to study transient near-wall heat transfer processes

Escofet-Martin

Ojo

Mecker

et al. 2021

Proceedings of the Combustion Institute

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Near-wall transient heat transfer and flame-wall interaction (FWI) are topics of great importance in the development of downsized internal combustion (IC) engines and gas turbine technology. In this work we perform measurements using 1D hybrid fs/ps rotational CARS (HRCARS), thermographic phosphors (TGP) and CH* imaging in an optically-accessible chamber designed to study transient near-wall heat transfer processes relevant to IC engine operation. HRCARS provides single-shot gas-phase temperatures (40μm spatial resolution and up to 3mm wall-normal distances), while thermographic phosphors measures wall temperature and CH* measures the flame front position. These simultaneous measurements are used to resolve thermal boundary layer (TBL) development and associated gaseous heat loss for three important processes of gas/wall interactions: (1) an unburned-gas polytropic compression process, (2) FWI, and (3) post-flame and gas expansion processes. During a mild polytropic compression process, measurements emphasize that even a relatively small wall heat flux (≤ 5kW/m 2 ) yields an appreciable temperature stratification through a developing TBL. During FWI, thermal gradients induced by the flame are resolved within the TBL. Gases closest to the wall (y<0.2mm) continue to experience thermal loading from polytropic compression until the flame is within ~1.4mm from the wall. Immediately afterwards, the wall first senses the flame as the wall temperature begins to increase. During FWI, gas temperatures up to 1150K impinge on the wall, producing peak wall heat fluxes (620kW/m 2 ) and the wall temperature increases (ΔTwall=14K). Gaseous heat loss in the post-flame gas occurs rapidly at the wall, yielding a TBL of colder gases extending from the wall as wall heat flux slowly decreases. HRCARS further captures the rapid cooling of gases in the TBL and core-gas during the mild expansion and exhaust process.

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

Cited by 19 publications

References 22 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

An experimental study of the detailed flame transport in a SI engine using simultaneous dual-plane OH-LIF and stereoscopic PIV

Simultaneous 1D hybrid fs/ps rotational CARS, phosphor thermometry, and CH* imaging to study transient near-wall heat transfer processes

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