Computational investigation of flow fields and detailed chemistry impacts on ignition delays
Ritter, David B.
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This work investigated the impacts of a complex piston head geometry on the aerodynamics and chemical kinetics in a Rapid Compression Machine. Utilizing 2D axisymmetric Computational Fluid Dynamics, a single stage compression and ignition was simulated for three different piston head geometries. The numeric framework resolved the flow structures through a hybrid RANS–LES model, and simulated the reaction with a diluted 29 species, 52 equation reduced global mechanism for n-heptane. The hybrid viscosity model was found to provide excellent qualitative information regarding the aerodynamic structures within a reasonable run time. Differences across geometry in vortex formation and interaction with the piston is presented. Negligible differences in global temperature or ignition delay were observed for the different piston geometries. The variable piston geometry was found to highly impact the cold roll up vortex, alter the chemical reaction pathways and acoustic resonance in the fluid domain. Geometric features were identified as possible alternative solutions to vortex mitigation compared to other strategies currently used in RCMs.