Cai, Xuan

Deutschmann, Olaf

Marschall, Holger

Wörner, Martin

English

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KIT – The Research University in the Helmholtz AssociationCFD simulation of liquid back suction and gas bubble formation inconnected tubes of different cross-sectionXuan Cai1, Martin Wörner2, Holger Marschall3, Olaf Deutschmann1,21 Karlsruhe Institute of Technology Institute for Chemical Technology and Polymer Chemistry2 Karlsruhe Institute of Technology Institute of Catalysis Research and Technology3 Technische Universität Darmstadt Mathematical Modeling and Analysis, Dep. of Mathematics In urea-water-solution (UWS) dosing system of SCR, UWS is drained from delivery line and sucked back to UWS tank, when vehicle is out of operation During the above process, there is a risk of air being sucked into delivery unit. Such gas bubble formation adversely affects working pressure for atomization and thus should be prevented This study is devoted to numerical investigation of the UWS back suction in expanding pipes and exploration of effective means to prevent gas bubble formationMotivation and goalReferences Contact: Xuan Cai (xuan.cai@kit.edu)Engesserstr. 20, 76131 Karlsruhe, Germany MODEGAT V03.- 05. Sept. 2017Bad HerrenalbNumerical method and setupPhase-field method Interface-capturing method where interface is treated as being of certain thickness Especially suited for moving contact linephaseFieldFoam A novel OpenFOAM solver for a Cahn-Hilliard coupled with Navier-Stokes equations Developed by the authors (Marschall and Cai)Influence of mesh  Cai, Wörner, Marschall and Deutschmann, Emission Control Science and Technology, in press, 2017, DOI: https://doi.org/10.1007/s40825-017-0073-3We acknowledge the financial support by Deutsche Forschungsgemeinschaft (DFG ) through SFB/Transregio 150 project B05(c)(d)Effect of geometry on bubble formationD1 = 4 mmD2 = 6 mmD2/D1 = 1.5α = 90°D1 = 3 mmD2 = 4 mmD2/D1 = 1.3α = 90°D1 = 3 mmD2 = 6 mmD2/D1 = 2α = 90°D1 = 3 mmD2 = 6 mmD2/D1 = 2α = 35°D1 = 3 mmD2 = 6 mmD2/D1 = 2α = 50°D1 = 3 mmD2 = 6 mmD2/D1 = 2α = 55°GasUWS liquidGas-liquid interfaceConclusions  Mesh alignment near wall is vital Reducing diameter ratio D2/D1 can delay bubble formation  Decreasing inclination angle αcan suppress bubble formationUWS tankDelivery lineSCRImage source: Stola et al. SAE Int. J. Engines, 2015Physical parameter Liquid: UWS (32.5% urea) under room temp. Contact angle θ0 = 52° Fixed outlet mass flow rate Q = 700 mm3/sAll the simulations here are 2D-axisymmetric; mesh cell size = 30 µm Effect of diameter ratio D2/D1 Effect of cone inclination angle α

CFD simulation of liquid back suction and gas bubble formation in connected tubes of different cross-section

https://publikationen.bibliothek.kit.edu/1000074471/5319250

CFD simulation of liquid back suction and gas bubble formation in connected tubes of different cross-section

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