| 1. |
- Kärrholm Peng, Fabian, 1980, et al.
(author)
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MODELLING INJECTOR FLOW INCLUDING CAVITATION EFFECTS FOR DIESEL APPLICATIONS
- 2007
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In: ASME Fluids Engineering Conference.
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Conference paper (peer-reviewed)abstract
- In this paper, cavitation and pressure parameters measuredin a model diesel injector are compared to data acquired by numericalsimulations using a new code developed for the Open-FOAM platform, which uses a barotropic equation of state togetherwith the homogeneous equilibrium assumption. It is aviscid code, allowing both compressible liquid and vapour tobe modelled. The mass flow and cavitation probabilities obtainedfrom the simulations are compared to data obtained inexperiments performed at AVL’s laboratories, in which the flowthrough an almost two-dimensional nozzle was examined. Theexperimental data used include pressure profiles and cavitationimages. The model proved to be able to predict cavitation probabilities,mass flows, and the occurrence of super-cavitation inthe channel. In addition, it proved to be stable in its dependencyon physical parameters, and grid independent.
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| 2. |
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| 3. |
- Kärrholm Peng, Fabian, 1980, et al.
(author)
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Three-Dimensional Simulation of Diesel Spray Ignition and Flame Lift-Off Using OpenFOAM and KIVA-3V CFD Codes
- 2008
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In: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627.
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Journal article (peer-reviewed)abstract
- Three-dimensional simulations of ignition and combustion of a dieselspray were conducted. The primary goal of the work was to compare twodifferent CFD codes: OpenFOAM, an object-oriented C++ based code, andKIVA-3V. The spray is modelled by the Eulerian-Lagrangian approach inboth codes, with several common submodels. Some important sub-modelsimplemented include \emph{inter alia} aKelvin-Helmholtz/Rayleigh-Taylor (KH/RT) model for spray break-up, animproved spray collision model, and a Partially Stirred Reactor (PaSR)model for turbulence-chemistry interaction. Both CFD codes solve thechemical reaction equations in a fully coupled manner. A cubic-shaped Cartesianmesh was used in the KIVA-3V simulations, while a polyhedral meshincluding a combination of hexagonal and prism-shaped cells wasconstructed for the OpenFOAM computations.The effects of high EGR and ambient temperature on the ignition and flamelift-off processes of a diesel spray were investigated. Sandia experimentsconducted in a high-pressure and high-temperature constant-volume vessel werechosen for the simulations and validations. A single spray was injected intothe vessel, and EGR was mimicked by reducing the oxygen concentration. Thediesel reference fuel (n-heptane) was considered. For the study, a medium-sizemechanism involving 83 species and 338 reactions was employed. The mechanismwas validated using the CHEMKIN II package and the reaction rate constantswere adjusted on the basis of measurements of auto-ignition delays ofn-heptane/air mixtures in shock-tube experiments (with equivalence ratiosranging from 0.2 to 0.4 at 50 bar, and from 0.5 to 2.0 at 13.5 bar and 41.0bar), laminar flame speeds (1 atm and 3 atm), and flame structure inburner-stabilized premixed flames (1 atm).The simulations demonstrate that both CFD codes are capable of spray ignitionand combustion studies, though both show stronggrid-dependence. The numerical results show that the ignition delay,flame lift-off and combustion temperature of the spray are stronglyinfluenced by EGR and ambient gas temperature. These predictions arein agreement with measurements. Nevertheless, differences are observedbetween the results predicted by OpenFOAM and those from KIVA-3V, forexample, the flame predicted by the former is thinner and longer than that by thelatter, which requires further investigation.
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| 4. |
- Magnusson, Alf, 1958, et al.
(author)
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A Comparison of Experiments and Numerical Calculations of Diesel Sprays
- 2004
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In: VAFSEP. ; , s. 42-47
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Conference paper (other academic/artistic)abstract
- Validation of diesel spray behaviour is a necessity when simulating direct injected diesel combustion engines. A problem is that model fuels instead of standard diesel often must be used in both experiments and spray calculations. Therefore a study was carried out where atwo-component model fuel (IDEA-fuel) was used both in calculations and in experiments using different optical methods. Penetration and evaporation of a two-component model fuel were calculated using the FOAM C++ CFD library which allows for multi-component treatment of the liquid. The experiments were carried out in the high-pressure, high temperature spray rig at Chalmers. The injection pressure were altered between 700 and 1350 bar and injected through a single-hole nozzle with a diameter of 0.19 mm. The opticalmethods used were Mie-scattering/LIF, Schlieren/Shadowgraph and direct photography capturing the size and shape of the sprays. Also Phase Doppler Anemometry which measures droplet size and velocity in the periphery of the spray was used.The results show that the model used underestimates spray penetration and droplet size. A comparison of the measurement results indicates that by combining the methods one can achieve a good understanding of the spray characteristics.
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| 5. |
- Nordin, P. A. Niklas, 1968
(author)
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Complex Chemistry Modeling of Diesel Spray Combustion
- 2001
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Doctoral thesis (other academic/artistic)abstract
- The thesis illustrates the application of computational fluid dynamics (CFD) to turbulent reactive two-phase flows in piston engines. The focus of the thesis lies on numerical simulations of spray combustion phenomena with an emphasis on the modeling of turbulence/chemistry interaction effects using a detailed chemistry approach. The turbulence/chemistry interaction model accounts for the effects of turbulent micro-mixing on the chemical reaction rates. The models have been implemented in the {\bf KIVA3-V} code and successfully applied to spray combustion analysis in a constant volume and a DI Diesel engine. The limitations and difficulties of representing the spray in a Lagrangian fashion are also adressed. Three different liquid fuels have been used in the simulations: n-heptane, methanol and dimethyl ether (DME). Detailed and reduced chemical mechanisms have been developed and validated for all these fuels and reasonable agreement between experimental data and numerical simulations has been obtained.
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