A Coupled PIV-LES Approach to Understand PortGenerated Structures
(English)Manuscript (preprint) (Other academic)
Inside an engine cylinder the flow field is very complex due to high gas velocities, flowseparation and pressure pulses at the ports. Historically, simple characteristic numbers such as swirland tumble have been used in order to quantify the flow in the cylinder. These integral quantities are likely to be insucient for optimization of the mixing process and combustion in IC engines. Instead,there is a need for detailed data with adequate temporal and spatial resolution. We simulate the flowpast the valves and validate these simulations using PIV measurements. By using LES data upstreamof the measurement plane an explanation to the structures seen in the PIV measurement plane can begiven.Here we show that at low valve lifts, the flow was blocked in such a way that the inertia created at theports were counteracted leading to the formation of two unstable counter rotating vortices. We alsodetected that the fluctuations in swirl number was one order of magnitude larger at the lower valvelifts. Furthermore, the small scale turbulence created at lower lifts was more anisotropic than for thehigher valve lifts. This work has thus increased the confidence in the CFD simulations in addition toproviding an explanation to the structures identified in PIV data.
Fluid Mechanics and Acoustics
IdentifiersURN: urn:nbn:se:kth:diva-124233OAI: oai:DiVA.org:kth-124233DiVA: diva2:633837
FunderSwedish Energy Agency
QS 20132013-06-272013-06-272015-04-20Bibliographically approved