Static Characteristics of Annular Damper Seals With Square-Hole Pattern Stators in Turbulent Regime

2006 Fiscal Year Final Research Report Summary

• Project/Area Number: 17560117
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Design engineering/Machine functional elements/Tribology
• Research Institution: Nagaoka University of Technology
• Principal Investigator: KANEKO Satoru Nagaoka University of Technology, Dept.of Mechanical Engineering, Professor, 工学部, 教授 (90161174)
• Co-Investigator(Kenkyū-buntansha): TAURA Hiroo Nagaoka University of Technology, Dept.of Mechanical Engineering, Research Associate, 工学部, 助手 (20334691)
• Project Period (FY): 2005 – 2006
• Keywords: Annular damper seals / Square-hole pattern / Annular plain seals / Leakage flow rate / Liquid-film pressure distributions / Pressure loss at steps / Dynamic fluid force / Dynamic coefficients

Research Abstract

For improving the efficiency and the stability margin of pumps, various seal configurations have been proposed. The previous experimental results confirmed that damper seals with intentionally different stator roughness surface pattern would yield smaller cross-coupled stiffness coefficients, larger main damping coefficients and a lower leakage flow rate than conventional annular plain seals with smooth surfaces. In the present study, the theoretical and experimental investigations of the static and dynamic characteristics are carried on the annular damper seals with square-hole pattern stators. Averaged Navier-Stokes equation with turbulent coefficients and continuity equation are applied to the theoretical investigation, which are numerically solved in consideration of the pressure loss due to the flow passage across each step of square holes. The turbulent coefficients are calculated based on the "law of the wall" and Prandtl's mixing length hypothesis.
The results are summarized as follows:
(1) The numerical results of the static characteristics, i.e., the leakage flow rate and the pressure distributions in the seal clearance obtained only by the rotor spinning motion at the seal center are good agreement with the measured results, which verifies the validity of theoretical analysis.
(2) The numerical results of the dynamic characteristics, i.e., the dynamic fluid force and the dynamic coefficients obtained by both spinning and whirling motions of the rotor, qualitatively agree with the measured results. In particular, the quantitative agreement of the main damping coefficients is obtained between the numerical and measured results.
(3) The pressure loss at the steps in the circumferential direction influences mainly the tangential dynamic fluid force and increases the main damping coefficients, whereas the pressure loss at the steps in the axial direction decreases the leakage flow rate. These facts contribute to the design for the annular seals with the optimum configurations yielding better seal characteristics.