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Internal Flow: Spray C/D Comparison and Spray A Needle Transient Opening

This presentation discusses the internal flow dynamics of sprays and needle transient opening in the context of computational fluid dynamics simulations. It explores the differences between spray C and D and predicts the exit temperature of fuel injection. Supported by Sandia National Laboratories.

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Internal Flow: Spray C/D Comparison and Spray A Needle Transient Opening

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  1. Topic 1 – Internal flow Presenter: Marco Arienti, Sandia National Laboratories Support by Sandia National Laboratories’ LDRD (Laboratory Directed Research and Development) is gratefully acknowledged. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

  2. Spray C/D (4 contributors) • Politecnico di Milano - OpenFoam: •     Ehsanallah Tahmasebi,  Tommaso Lucchini and Gianluca D'Errico • ANSYS-FLUENT: Saeed Jahangirian, Aleksandra Egelja-Maruszewski, and Huiying Li • Università di Perugia - Converge:Michele Battistoni • CMT - CavitatingFoam (OpenFoam)Pedro Martí

  3. Spray D Spray C Wireframe of the tangentially-averaged interior wall of the sac Radius Axial coordinate

  4. EOS models [1] Caudwell et al., Int. J. of Thermophysics 25(5) 2004 [2] To match Khasanshin, et al. Int. J. of Thermoph. 24(5) 2003 [3] Zwart et al. ICMF 2004 [1] Salvador et al., Mathematical and Computer Modelling 52 2010 [1] Desantes et al., SAE l Paper 2014-01-1418 [2] Khasanshin, et al. Int. J. of Thermophysics 24(5) 2003 Schmidt et al., Int. J. of Multiphase Flow (2010)

  5. Fixed fully open needle configuration

  6. Internal flow: sharp (spray C) vs. smooth (spray D) pressure decrease Spray C Spray D

  7. Without cavitation, Spray D produces a slightly longer liquid core length and a narrower cone angle Spray C Spray D

  8. This effect is recognized in new measurements of the spray width and length From spray boundary contrast (threshold 0.37 KL) using the diffuse backlit illumination (DBI) technique:* *from Fredrik Westlye’s presentation

  9. Comparison against measured mass flow rate [g/s] • CONVERGE and FLUENT-ANSYS simulations are the only that capture the increase between spray C and D • In the aggregate, there is more variation amongst models for the same spray type than between the sprays for the same model

  10. Comparison against measured momentum [N] • CONVERGE and FLUENT-ANSYS simulations are the only to capture the increase between spray C and D (by a rather small margin)

  11. Mass flow rate and momentum values (*) std. dev. from the CMT measurements on 5 different specimens

  12. Spray C: noticeable differences in boundary thickness between simulations

  13. Spray D vs. spray C at the exit orifice • Similar velocity/density profiles are obtained for spray D • Cavitation displaces mass flow toward the orifice axis in spray C Spray D Spray C

  14. The effect of cavitation for spray C • Note the different models’ effectiveness in generating cavitation at the orifice’s wall liquid core boundary

  15. Conclusions • Relatively small variations in the amount of cavitation at the wall result in differences of mass flow rate and momentum for spray C simulations • Even when the variation is correctly predicted, its magnitude is underestimated • The trend in spray penetration/width from spray C to spray D is correctly captured by the only non-submerged simulation (UniPG with Converge) • Cannot quantify agreement for lack of averaged data • Passing pockets of vapor in the liquid core are shown in the only LES simulation (UniPG with Converge) • A frequency analysis of this feature is recommended

  16. Topic 1.2 – Spray A needle transient opening Presenter: Marco Arienti, Sandia National Laboratories Support by Sandia National Laboratories’ LDRD (Laboratory Directed Research and Development) is gratefully acknowledged. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

  17. Two of the remaining questions for Spray A from ECN3: What is the exit temperature of the fuel? Is the injection transient modeled realistically?

  18. Spray A (3 contributors) • CMT - OpenFOAM w/ Eulerian Spray AtomizationPedro Martí • Bosch - Cascade Technologies Edward Knudsen, Eric Doran (Bosch Research & Technology Center) • SNL - CLSVOFMarco Arienti

  19. Spray A reference and actual laboratory conditions At SNL and ANL, ambient density is matched at cooler, non-vaporizing conditions. From Lyle et al. SAE 2014-01-1412 *Tfuel,intern.< 363 K +Tfuel,intern. = 343 K

  20. Exit temperature predictions from ECN3 DT ≅ 0 DT << 0 DT << 0 DT < 0 DT = 0 T [K]

  21. Contributions to DT = Texit-Tinlet Expansion through the orifice  Viscous energy dissipation  Heat transfer through injector’s wall DT 

  22. Peng-Robinson Calibrated Tait p = 2000 bar 100% C12H26 Liquid phase compression r = r0(T), p0 = 1 bar Tc = 658 K rc =226 kg/m3 [Caudwell et al., Int. J. of Thermophysics, 2004]

  23. Isentropic expansionupper bound: Dp = -1440 bar DT = -22 K from calibrated Tait EOSDT = 0 K from isobaric EOS DT = -217 K from adiabatic p.g. EOS (g =1.4) 787 kg/m3363 K 1500 bar Temperature [K] 646 kg/m3341 K 60 bar adiabatic p.g.: g = 1.4 Density[ kg/m3]

  24. SNL results show limited temperature increasewith adiabatic walls Temperature [K] Density [kg/m3] Adiabatic w. Constant TW = 383 K Adiabatic w. Constant TW = 383 K 343 351 359 367 375 383 720 736 752 768 784 800 DTL,exit = +3 K DTL,exit = +18 K rL,exit = 716 kg/m3 rL,exit = 720 kg/m3

  25. CMT results also show small DT except near the wall Temperature [K] Density [kg/m3] Adiabatic343 K Constant TW = 363 K Adiabatic343 K ConstantTW = 363 K

  26. The viscous dissipation of turbulent energy is the main source of temperature increase Orifice cross-sections: 273 K 303 K 323 K Adiabatic 343 K 363 K

  27. However, the opening transient displays a bulk temperature increase Simulation with moving needleTw = 383 K • Interpretation: the fuel heats up while passing through the narrow gap between needle and injector • This effect disappears once the passage is fully open

  28. Independent study: transient and non-isothermal modeling of cavitation with GFS* Variation of the outlet temperature in one injection cycle Steady-state temperature field 500 K 350 K Minimum gap: 5 mm(with standard wallfunction) Minimum cell size Dx = 0.5-0.83 mm *By Salemi, McDavid, Koukouvinis, Gavaises, and Marengo, in ILASS 2015

  29. Conclusions on DT = Texit-Tinlet • Expansion through the orifice: • Moderate but constant during injection • Potentially under-estimated depending on EOS • Viscous energy dissipation: • Potentially large but transient • Puts under scrutiny the choice of standard wall function in micron-size gap

  30. The measured Rate of Injection (ROI) and Rate of Momentum (ROM) of Spray A Diagram from SAE 2013-24-0001

  31. Initial conditions: injection delay as a function of partially filled sac/orifice Vgas = 0.065 mm3 (1/3of the sac) Tdelay = (339-330) ms = 9 ms Fully open fuel passage Time of apparent injection Tdelay = 3 ms (instantaneous opening) Vgas = 4 mm3 (half orifice)At t < 0 the pressure in the sac is ~Pinj/2

  32. Mass flow rate during opening transient* *After removing all injection delays

  33. Momentum flow rate during opening transient

  34. Jet penetration during opening transient

  35. A request: establish a common set of properties and reliable EOS correlations • Example: speed of sound calculation for liquid n-dodecane • Khasanshin et al., Int. J. of Thermophysics, 24(5) 2003 • Padilla-Victoria, Fluid Phase Eq. 2013 Speed of sound [m/s] T = 353 K Pressure [MPa]

  36. Backup

  37. Note 3: Dependence of internal energy on pressure New fit: P = 0.1 MPa P = 20 MPa P = 140 MPa NIST data: P = 0.1 MPa P = 20 MPa P = 140 MPa Supercritical Supercritical [JSAE 20159137 SAE 2015-01-1853]

  38. Experiment set-up and reference parameters Thermodynamic properties from NIST web-book (for dodecane):

  39. Details of mesh preparation

  40. Meshing Flow Domain Chamber: 45 mm Long • New meshing tool by Bosch-Cascade • Start from CAD surfaces • Seed domain with points • Build Voronoi diagram, connectivity • No sliver cells at boundaries • Face normals point to cell centers • Minimal cell skew • More ‘sampling’ than hexes Voronoi Mesh

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