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Sakai, Takaaki; ; ;
JNC TN9400 2000-012, 43 Pages, 2000/03
JNC-TN9400-2000-012.pdf:2.12MB
Experimental validation of the design method to prevent the failure of a thermometer well by the vortex-induced vibration has been performed for the effect of structure damping of a cylinder. The available experimental data in piping were very limited for the high damping region in water flow, because of the difficulty to increase the structure dumping for the one-side supported cylinder in experiments. ln this experiment, high viscosity fluid was charged into the tested cylinders to control the cylinder's damping. Resulting values of the reduced damping are 0.49, 0.96, 1.23, 1.98, 2.22 in the experiments. Reduced velocity(Vr) was increased gradually in the range of 0.7 
Vr 5(Reynolds number at Vr=1 is 8
10
). The displacements of the cylinder by the vortex-induced vibration were measured. As the results, Tested cylinders of reduced damping 0.49 and 0.96 showed vortex-induced vibration in flow direction at Vr 
1 region. However, in case of reduced damping of 1.23, 1.98 and 2.22, the vortex-induced vibrations in flow direction were suppressed lower than the 1% displacement of the cylinder diameter. ln conclusion, it is confirmed that the suppression criteria of the "Vr 
3.3 and Cn 1.2" for vortex-induced vibration in flow direction, which is used in ASME code; "Boiler and Pressure VesseI Code Sec.III Appendix N-1300" and the "FIV design guide in JNC", is reasonably applicable to the one-side supported cylinder in water flow piping.
; ; Kawata, Tomio
PNC TN8410 92-012, 47 Pages, 1991/12
[Purpose] We confirmed that modified (6000rpm type) centrifugal clarifier arose the unstable vibration during the reduction of rotating speed under the condition of bearing undissolved residue after the clarification operation. This report describes the cause of unstable vibration that arise in the clarification body set on the rack which induced resonance vibration and the measurement results of vibration characteristic after taking countermeasure for vibration decrease. [Method] It was considered that the causes of the unstable vibration were following; (1)Unbalance between damping force of the lower bearing damper and the vibration force arisen by the rotational bowl (2)Effect of feed condition (3)Effect of self-excited vibration of the free liquid surface (4)Effect of frame strength The test has been conducted to make quantitative measure of vibration characteristic (amplitude of the rotational bowl and shaft) by changing the load in the rotational bowl. We also conducted the test to reconfirm the effect of the circumferential baffle plate which has shown the most effective effect to the vibration decrease in the preceding report. [Results] The effects of the circumferential baffle plate placed on the inside wall of the rotational bowl are shown as follows; (1)The unstable vibration during the reduction of rotating speed has been suppressed By this result, we verified that the vibration on the free liquid surface in the rotational bowl caused the vibration for the bowl without the circumferential baffle plate. (2)It was able to run the clarification operation in the standard condition(100
/h 6h) for the rotational speed ranging from 4000 to 6000rpm. [Conclusion] By the results of this test and of the preceding report, the feed condition and the condition of setting the circumferential baffle plate are showed in the following, considering the aspects of rotational stability. (1)Condition of feed nozzle - feed 55㎜ in height from the lower ...