Non-Isotropic Length Scales During the Compression Stroke of a Motored Piston Engine

Breuer, Stephan; Oberlack, Martin; Peters, Norbert

doi:10.1007/s10494-005-5457-8

Cited by 10 publications

(40 citation statements)

References 15 publications

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“…The idea is simple, a change in sign of the correlation R yy along the horizontal sampling line or R xx along the vertical sampling line can be considered as a very coarse estimation of the radius of the vortex [37]. More detailed explanation and discussion of the method can be found in the papers [12,38]. Figure 10 shows the calculated two-point correlation function R(r) along two chosen sampling lines.…”

Section: Dissipation Ratementioning

confidence: 99%

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Investigation of Numerical Effects on the Flow and Combustion in LES of ICE

Nguyen

Kempf

2017

Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles

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-This work investigates the influence of numerical dissipation on the modeled combustion in Large Eddy Simulations (LES). It is well known that capturing the dynamics of the in-cylinder flow is crucial for engine simulations, as it strongly affects flame propagation. The flame propagation during the power-stroke highly depends on the turbulence level that is developed throughout compression. This turbulence level will be strongly influenced by the accuracy of the numerical schemes employed. Even a small extent of upwinding, filtering, low-order implicit time-stepping, cell-stretching or mapping between grids may affect the flow field, the turbulence level, and hence the turbulent flame speed and the pressure curve. To provide a reference, the LES in-house code PsiPhi is used, which ensures a minimum of dissipation due to high order explicit time-stepping, homogeneous and isotropic filters and cells. Good stability of the code permits the use of a second-order Central Differencing Scheme (CDS) for the transport of momentum, avoiding numerical dissipation. To analyse the effect of numerical dissipation, simulations of a fired engine are performed using different numerical schemes for the convection of momentum. Physical quantities including the total kinetic energy, the velocity gradient, the turbulent viscosity, the in-cylinder pressure, the flame propagation or the burning rate of different test cases are evaluated and compared to each other to show the numerical effects on combustion. Furthermore, the suitability of common LES quality criteria including an energy criterion and viscosity ratio is discussed based on the comparison of simulations with less and more accurate numerics. It is shown that these LES quality indicators can be highly misleading.

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Section: Dissipation Ratementioning

confidence: 99%

“…Determination of good or bad LES quality with a given resolution and numerical scheme has been extensively discussed in many studies [13,[38][39][40][41][42]. Focusing on engine simulations, some authors [12,37] have applied several LES quality indices [11,13].…”

Section: Les Quality Criteriamentioning

confidence: 99%

Investigation of Numerical Effects on the Flow and Combustion in LES of ICE

Nguyen

Kempf

2017

Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles

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“…Numerical research into engineless test bed allows to investigate inlet manifold properties and the influence of inlet manifold shape on charge swirl rate at the end of compression stroke (Sak et al, 2007;Wigley and Hawkins, 1978). This is a typical method, which is commonly used to comparative investigations (Breuer et al, 2005). A suitable level of charge turbulence in the combustion chamber of the IC engine is one of the methods of improving the combustion process.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of the flow field in the combustion chamber of the internal combustion test engine

Tutak¹,

Jamrozik²

2011

Chemical and Process Engineering

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Results of a research study into the velocity field in combustion chamber of internal combustion engine are presented in the paper. Measurements of fresh charge flow velocity in the cylinder axis and near the cylinder squeezing surface were performed. The hot-wire anemometer was used. The measurement results were used for analysis of turbulence field in the examined combustion chamber. It turned out that in the axis of cylinder the maximum of velocity occurs 30 deg before TDC and achieves 6 m/s. In the studied combustion chamber, the maximum value of turbulence intensity was close to 0.2 and it was achieved 35 deg BTDC. Additionally, the maximal velocity dispersion in the following cycles of the researched engine was at the level of 2 m/s, which is 35% of the maximum value of flow velocity. At a point located near the squeezing surface of the piston, a similar level of turbulence, but a the smaller value of the average velocity was achieved. The turbulence field turned out to be inhomogeneous in the combustion chamber.

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“…Concerning turbulence in SI-engines, an interesting recent paper [1] studied the integral turbulent length scale of the flow. Breuer et al [1] pointed out that turbulence in an engine is essentially non-isotropic, which requires introducing at least two different integral length scales: one in the radial direction, r , and the other one along the axis of piston motion, z .…”

Section: Introductionmentioning

confidence: 99%

“…Breuer et al [1] pointed out that turbulence in an engine is essentially non-isotropic, which requires introducing at least two different integral length scales: one in the radial direction, r , and the other one along the axis of piston motion, z . The study in [1] was both theoretical and experimental. The theory was constructed under the assumption of axisymmetric turbulence and developed previous ideas and methods of [17,18].…”

Section: Introductionmentioning

confidence: 99%

Turbulent Flow Produced by Piston Motion in a Spark-ignition Engine

Akkerman

Иванов

Bychkov

2008

Flow Turbulence Combust

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Turbulence produced by the piston motion in spark-ignition engines is studied by 2D axisymmetric numerical simulations in the cylindrical geometry as in the theoretical and experimental work by Breuer et al. (Flow Turbul Combust 74:145, 2005). The simulations are based on the Navier-Stokes gas-dynamic equations including viscosity, thermal conduction and non-slip at the walls. Piston motion is taken into account as a boundary condition. The turbulent flow is investigated for a wide range of the engine speed, 1,000-4,000 rpm, assuming both zero and non-zero initial turbulence. The turbulent rms-velocity and the integral length scale are investigated in axial and radial directions. The rms-turbulent velocity is typically an order-of-magnitude smaller than the piston speed. In the case of zero initial turbulence, the flow at the top-dead-center may be described as a combination of two large-scale vortex rings of a size determined by the engine geometry. When initial turbulence is strong, then the integral turbulent length demonstrates selfsimilar properties in a large range of crank angles. The results obtained agree with the experimental observations of Breuer et al. (Flow Turbul Combust 74:145, 2005).

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Non-Isotropic Length Scales During the Compression Stroke of a Motored Piston Engine

Cited by 10 publications

References 15 publications

Investigation of Numerical Effects on the Flow and Combustion in LES of ICE

Investigation of Numerical Effects on the Flow and Combustion in LES of ICE

Characteristics of the flow field in the combustion chamber of the internal combustion test engine

Turbulent Flow Produced by Piston Motion in a Spark-ignition Engine

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