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A platform for research: civil engineering, architecture and urbanism
Large eddy simulation of in-cylinder phenomena in spark ignition engines
The motivation for this thesis is the development of a simulation tool that can deliver spatially- and time-resolved information to better understand the highly unsteady and irregular flow motion and combustion inside spark ignition engines. The key element of the method is that the large eddies are directly solved on the computational grid and the smaller structures are modelled, i.e. large eddy simulation (LES). High order numerical schemes for an accurate solution are applied, which are still not state-of-the-art for most of the industrially relevant problems. The simulation tool is integrated into an existing open source software and is successfully validated against Particle Image Velocimetry (PIV) and Magnetic Resonance Velocimetry (MRV) measurements of optically accessible research engines. A generic simulation workflow based on a mapping-strategy is proposed with a mesh-morphing strategy without topological changes in-between the mapping intervals. The simulation workflow includes an automated grid generation for complex engine geometries with inclined valves and the piston top-land crevice. It is applied to three different engine geometries. A criterion is established for estimating the number of cycles needed in a simulation, if experimental data is available. A visualization strategy is developed and an analysis for the tumble flow based on auto-correlation coefficients is proposed, which allows quantify- ing the tumble break-down process. The tumble visualization and quantification methods are used to study the sensitivity of the turbulent flow field based on cold-flow multi-cycle simulations of two different cylinder-head geometries. In a next step, the flow fields of the two different cylinder-head geometries are taken to study the flame propagation by a flame-surface-density modelling approach with different algebraic expressions for the flame wrinkling. Furthermore, fired multi-cycle simulations with internal exhaust gas recirculation are carried out and compared to Mie-scattering images of the ...
Large eddy simulation of in-cylinder phenomena in spark ignition engines
The motivation for this thesis is the development of a simulation tool that can deliver spatially- and time-resolved information to better understand the highly unsteady and irregular flow motion and combustion inside spark ignition engines. The key element of the method is that the large eddies are directly solved on the computational grid and the smaller structures are modelled, i.e. large eddy simulation (LES). High order numerical schemes for an accurate solution are applied, which are still not state-of-the-art for most of the industrially relevant problems. The simulation tool is integrated into an existing open source software and is successfully validated against Particle Image Velocimetry (PIV) and Magnetic Resonance Velocimetry (MRV) measurements of optically accessible research engines. A generic simulation workflow based on a mapping-strategy is proposed with a mesh-morphing strategy without topological changes in-between the mapping intervals. The simulation workflow includes an automated grid generation for complex engine geometries with inclined valves and the piston top-land crevice. It is applied to three different engine geometries. A criterion is established for estimating the number of cycles needed in a simulation, if experimental data is available. A visualization strategy is developed and an analysis for the tumble flow based on auto-correlation coefficients is proposed, which allows quantify- ing the tumble break-down process. The tumble visualization and quantification methods are used to study the sensitivity of the turbulent flow field based on cold-flow multi-cycle simulations of two different cylinder-head geometries. In a next step, the flow fields of the two different cylinder-head geometries are taken to study the flame propagation by a flame-surface-density modelling approach with different algebraic expressions for the flame wrinkling. Furthermore, fired multi-cycle simulations with internal exhaust gas recirculation are carried out and compared to Mie-scattering images of the ...
Large eddy simulation of in-cylinder phenomena in spark ignition engines
Janas, Peter (author) / Kempf, Andreas
2017-09-12
Theses
Electronic Resource
English
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