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High Power Hg Target Conceptual Design Review

This review analyzes the conceptual design of a high power Hg target, focusing on the Hg jet nozzle. The computational fluid dynamic analysis reveals cavitation at the nozzle inlet and suggests design changes to eliminate this undesirable phenomenon.

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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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