The time scale bounded k-ε turbulence model and its assessment for automotive applications

Pržulj, Vlado; Tiney, Nick; Shapiro, Evgeniy; Penning, Richard; Shala, Muzafer

doi:10.1615/ichmt.2012.procsevintsympturbheattransfpal.1900

Cited by 7 publications

(3 citation statements)

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“…Default first order in time, second order in space pressure-correction solver is used to resolve the flow field with a realizable k-e turbulence model using turbulent viscosity limiting after [25] with standard wall functions.…”

Section: Pc-c1mentioning

confidence: 99%

Experimental and Numerical Analysis of Pre-Chamber Combustion Systems for Lean Burn Gas Engines

Shapiro

Tiney

Kyrtatos

et al. 2019

SAE Technical Paper Series

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The current trend in automobiles is towards electrical vehicles, but for the most part these vehicles still require an internal combustion engine to provide additional range and flexibility. These engines are under stringent emissions regulations, in particular, for the reduction of CO2. Gas engines which run lean burn combustion systems provide a viable route to these emission reductions, however designing these engines to provide sustainable and controlled combustion under lean conditions at λ=2.0 is challenging. To address this challenge, it is possible to use a scavenged Pre-Chamber Ignition (PCI) system which can deliver favorable conditions for ignition close to the spark plug. The lean charge in the main combustion chamber is then ignited by flame jets emanating from the prechamber nozzles. Accurate prediction of flame kernel development and propagation is essential for the analysis of PCI systems. A modelling approach is proposed based on the Dynamic Discrete Particle Ignition Kernel model coupled with the G-equation combustion model. The model is validated for an air/methane academic benchmark. The approach is then applied to the investigation of performance of three pre-chamber designs developed within Horizon 2020 GASON project in conjunction with the experimental investigation of these pre-chambers mounted on Rapid Compression Expansion Machine (RCEM). The investigated prechamber designs vary with respect to the tangential nozzle angle and volume. The study focusses on a lean limit of the proposed system's operation with the main charge at λ=2.0 and a variation of prechamber design and scavenging level. The comparison of the simulation results with the experimental observations demonstrates good accuracy of the developed model. In addition, the combined experimental and modelling provides insights into the effect of prechamber geometry on potential performance.

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Section: Pc-c1mentioning

confidence: 99%

Experimental and Numerical Analysis of Pre-Chamber Combustion Systems for Lean Burn Gas Engines

Shapiro

Tiney

Kyrtatos

et al. 2019

SAE Technical Paper Series

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“…RANS equations are solved using the finite volume method. The effects of turbulence are solved by means of Reynolds Averaged Navier-Stokes (RANS) methods, specifically the k-ε model time-scale bounded (TSB) model after [12]. As a baseline mesh, a homogeneous grid size of 0.18 mm has been used within the entire pre-chamber.…”

Section: Rans Modelmentioning

confidence: 99%

Numerical study of fuel and turbulence distributions in an automotive-sized scavenged pre-chamber

et al. 2019

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This article presents a numerical study of the fuel and turbulence distributions in a pre-chamber at spark-time. The study has been conducted in the framework of the H2020 Gas-On project, dealing with the development of a lean-burn concept for an automotive-sized gas engine equipped with a scavenged pre-chamber. The test case considered studies a 7-hole pre-chamber with circumferentially-tilted orifices mounted on the cylinder head of a rapid compression-expansion machine (RCEM), consistent with the experimental test rig installed at ETH Zurich. An accurate description of turbulence and fuel distributions are key quantities determining the early flame development within the pre-chamber. Both quantities have an influence on the overall combustion characteristics and therefore on the engine performance. For this purpose, computational fluid dynamics (CFD) is employed to complement experimental investigations in terms of data completeness. The performance of the Reynolds-averaged Navier-Stokes (RANS)-based turbulence model is compared with large-eddy simulation (LES) through ensemble averaging of multiple LES realizations, in which the fuel injection rate evolution into the pre-chamber has been perturbed. Overall, RANS results show that the distributions of the turbulent kinetic energy and fuel concentration at spark-time agree well with the LES ensemble-averaged counterparts. This constitutes a prerequisite in view of the combustion phase and the accuracy reported provides further confidence in this regard.

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“…The grid contains 335, 802 cells with 6 cells along the z direction so that the size of a nominal 2D grid is 55, 967 cells. The current steady-state results are obtained by using the low Reynolds number variant of the time -scale bounded k − ε turbulence model 28,22 . The runs are performed on 6 CPUs, starting with simple uniform fields, i.e.…”

Section: Vc 2d Hypersonic Shock-wave/turbulent Boundary Layer Intermentioning

confidence: 99%

Generalised SIMPLE-Based Pressure Correction Method for Unstructured Co-located Grids

Pržulj

2015

22nd AIAA Computational Fluid Dynamics Conference

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This paper reports on the SIMPLE-like solution algorithm which significantly improves velocity-pressure coupling, leading to the accelerated convergence. The algorithm is applicable to both incompressible and compressible flows. It is implemented within the framework of a cell-centred finite-volume method using co-located storage of flow variables on unstructured grids. The convergence acceleration is an outcome of the novel treatment of the pressure correction equation which accounts for two commonly neglected terms appearing in a general pressure correction equation. These terms, namely neighbour and non-orthogonal corrections, represent velocity corrections from neighbouring cells and the cell-face pressure correction gradient associated with the grid non-orthogonality, respectively. Reminiscent of the PISO method, both neighbour and non-orthogonal corrections are taken into account by performing two or more correction steps. However, the full inclusion of neighbours velocity corrections can prevent the solution convergence. Following an analogy between time-marching and a steady-state iterative approach, this problem has been resolved by introducing a pseudo unsteady term into discretised velocity correction equations. Using this term, the contribution of neighbour corrections is under-relaxed, enabling satisfactory convergence rate. The algorithm is applied to several benchmark test-cases, covering laminar and turbulent as well as incompressible and compressible flows. For all test cases, the convergence rate can be significantly improved by performing two or more pressure correction steps. An optimal number of pressure corrections exists for which a meaningful reduction of computing time is possible.

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The time scale bounded k-ε turbulence model and its assessment for automotive applications

Cited by 7 publications

References 0 publications

Experimental and Numerical Analysis of Pre-Chamber Combustion Systems for Lean Burn Gas Engines

Experimental and Numerical Analysis of Pre-Chamber Combustion Systems for Lean Burn Gas Engines

Numerical study of fuel and turbulence distributions in an automotive-sized scavenged pre-chamber

Generalised SIMPLE-Based Pressure Correction Method for Unstructured Co-located Grids

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