Session: 27-02: Damping, Stability, Swirl-Induced Effects & Seal Dynamics.

Submission Number: 178024

Rotordynamic Damping Forces in a Mixed-Flow Pump With a Shrouded Impeller 

In pumps, misalignment between the impeller rotational axis and the casing center can generate rotordynamic instability. Yet, studies on rotordynamic forces in mixed flow pumps remain scarce. Therefore, this study presents first detailed investigation of the dependence of the tangential force on the whirling speed, or direct damping, in a high performance mixed-flow pump using steady 3-D Reynolds-Averaged Navier-Stokes (RANS) simulations. Concentric RANS simulation results are validated against experimental data, and an eccentric model is subsequently analyzed to quantify the lateral forces and identify their driving mechanisms. Normal force depends quadratically on the whirling speed and remains positive at all whirling speeds. Tangential force decreases almost linearly with increasing whirling speed ratio from –1.00 to 1.25. At positive whirling speed ratios between 0 and 0.85, the tangential force can promote forward whirling motion. Thus, the direct damping is positive and has a nondimensionalized value of 12.35. The tangential force is attributed to the non-axisymmetric pressure field caused by non-axisymmetries in tangential and meridional velocities in the secondary flow path. Furthermore, the circumferential pressure non-uniformity depends linearly on the tangential velocity in the whirling frame. Therefore, the tangential force decreases linearly with the whirling speed. Thus, the kinematics of the impeller’s whirling motion is the physical driver for the positive direct damping.

Presenting Author: Tien-Dung Vuong Seoul National University

Presenting Author Biography: Tien-Dung Vuong received his Bachelor degree in Aviation Engineering at Hanoi University of Science and Technology in Vietnam in 2020. In 2022, he received his Master degree in Mechanical Engineering at Inha University. Since then, he has been working as a PhD candidate at the Turbomachinery Laboratory at Seoul National University. His work focuses on rotordynamics in pumps and compressors.

Authors:

Tien-Dung Vuong Seoul National University
Youngkuk Yoon Seoul National University
Daehee Jeong Doosan Enerbility Nuclear Business Group
Seung Jin Song Seoul National University