Numerical Investigation of the Soot Initiated Formation of Ultra Fine Particles in a Jet Turbine Engine Using Conventional Jet Fuel
Authors
Bering, Rasmus Møller ; Buskov, Kåre Elgaard
Term
4. term
Education
Publication year
2012
Submitted on
2012-05-31
Abstract
Denne afhandling bruger en 3D-computersimulation (ANSYS Fluent, et værktøj til beregningsmæssig fluiddynamik, CFD) til at undersøge, hvordan sod begynder at dannes, når Jet A-flybrændstof brænder i en SR-30 turbojetmotor ved fuld last. Studiet fokuserer kun på forbrændingskammeret og de tidligste sod 'primærpartikler'. Simulationen modellerer ikke-forblandet forbrænding, hvor brændstof og luft blandes, mens de brænder. Der anvendes en reduceret kemisk reaktionsmekanisme med 38 reaktioner og 24 kemiske arter (stoffer), baseret på et surrogatbrændstof, der efterligner Jet A’s forbrændingsegenskaber og indeholder sodforstadier—molekyler, som ifølge tidligere studier kan føre til sod under gunstige forhold. Randbetingelserne i modellen stammer fra forsøg på SR-30-motoren. Ud fra CFD-resultaterne analyseres og forudsiges en sandsynlig vej for soddannelse, som sammenlignes med den soddannelsesmodel, der findes i ANSYS Fluent. Selvom det ikke var muligt at opnå en fuldt udviklet sodmodel, tyder sammenligningen på, at den forudsagte soddannelse er rimelig. For at beskrive alle veje for soddannelse er der behov for en mere detaljeret reaktionsmekanisme.
This thesis uses a 3D computer simulation (ANSYS Fluent, a computational fluid dynamics tool, CFD) to study how soot begins to form when Jet A aviation fuel burns in an SR-30 turbojet engine at full load. The study looks only at the combustor (combustion chamber) and the earliest soot 'primary particles.' The simulation models non-premixed combustion, where fuel and air mix as they burn. It uses a reduced chemical reaction mechanism with 38 reactions and 24 species (chemical components), based on a surrogate fuel that reproduces Jet A’s combustion behavior and contains soot precursors—molecules that, according to prior studies, can lead to soot under favorable conditions. Model boundary conditions were taken from experiments on the SR-30 engine. From the CFD results, a likely pathway for soot formation is analyzed and predicted, and compared with the soot formation model available in ANSYS Fluent. Although a fully developed soot model could not be obtained, the comparison indicates that the predicted soot formation is reasonable. A more detailed reaction mechanism would be needed to predict all soot formation pathways.
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