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High Power Hg Target Conceptual Design Review

A review of the conceptual design for a high-power molecular mercury jet nozzle with CFD analysis, highlighting cavitation risks, pressure differentials, and design recommendations. The study includes simulations of flow patterns, pressures, and potential improvements. Recommended for future work are analyses of refined nozzle designs and literature reviews on intake nozzle design.

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High Power Hg Target Conceptual Design Review

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  1. High Power Hg Target Conceptual Design Review Hg Jet Nozzle Analysis M. W. Wendel Oak Ridge National Laboratory February 7-8, 2005

  2. An Initial Computational Fluid Dynamic Analysis was completed. 2 1.9-cm supply lines at 2.8 m/s 1 cm Hg nozzle at 20 m/s Conceptual Design Review 7-8 Feb 05

  3. Only the mercury itself was modeled in the simulation. No-slip walls at all other boundaries. Constant pressure at outlet. 21.3 kg/s inlet. Boundary conditions Conceptual Design Review 7-8 Feb 05

  4. The computational mesh consisted of 230,545 hexahedral control volumes. Conceptual Design Review 7-8 Feb 05

  5. The computed flow shows smooth streamlines for the inlet lines and reservoir, but extreme conditions near the nozzle inlet. Conceptual Design Review 7-8 Feb 05

  6. The computed pressures show cavitation will occur at the nozzle inlet. Computed pressure differential is 722 psi Conceptual Design Review 7-8 Feb 05

  7. The computed pressures are particularly low where the flow accelerates around the corners. NOZZLE FLOW NOZZLE FLOW TOP VIEW Conceptual Design Review 7-8 Feb 05

  8. A shorter (1/2-inch) orifice was also analyzed Conceptual Design Review 7-8 Feb 05

  9. Computed stream-lines are similar and the total pressure drop is just under 800 psi. Conceptual Design Review 7-8 Feb 05

  10. Again, cavitation is predicted, although the conditions are less severe. Conceptual Design Review 7-8 Feb 05

  11. Cavitation is highly likely because of the low pressure at the nozzle exit, and the high velocity in the nozzle. • Pstatic = Pstagnation – ½  V2 •  is density • V is velocity • If Pstatic < Psat, then mercury will cavitate • The CFD model is not conservative in predicting cavitation due to the transient aspect of the flow which is not simulated. • In the SNS Target Test Facility mitered bends, CFD results showed much less severe conditions than computed here. for 20 m/s, ½  V2 = 400 psi for 30 m/s, ½  V2 = 900 psi Conceptual Design Review 7-8 Feb 05

  12. Cavitation in the nozzle is undesirable. • Short nozzle lifetime • Choked flow • Erratic jet flow pattern • Noise Conceptual Design Review 7-8 Feb 05

  13. Design changes can reduce or eliminate cavitation. • Redesign the nozzle • Rounded corners • Contoured inlet • Increase the chamber pressure • Ultimately the nozzle design needs to be tested. Conceptual Design Review 7-8 Feb 05

  14. Recommended Future Work • Analyses on improved nozzle designs • Literature searches on intake nozzle designs Conceptual Design Review 7-8 Feb 05

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