Research Papers: Gas Turbines: Structures and Dynamics

Including Housing–Casing Fluid in a Lateral Rotordynamics Analysis on Electric Submersible Pumps

[+] Author and Article Information
Clay S. Norrbin

Texas A&M Turbomachinery Laboratory,
College Station, TX 77843
e-mail: clay.norrbin@gmail.com

Dara W. Childs

Leland T. Jordan Professor
Texas A&M Turbomachinery Laboratory,
College Station, TX 77843
e-mail: dchilds@tamu.edu

Stephen Phillips

Texas A&M Turbomachinery Laboratory,
College Station, TX 77843
e-mail: sphillips@tamu.edu

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received August 29, 2016; final manuscript received September 2, 2016; published online February 1, 2017. Editor: David Wisler.

J. Eng. Gas Turbines Power 139(6), 062505 (Feb 01, 2017) (12 pages) Paper No: GTP-16-1428; doi: 10.1115/1.4035358 History: Received August 29, 2016; Revised September 02, 2016

Stability and synchronous-response predictions, which were presented by Childs et al. (2014, “A Lateral Rotordynamics Primer on Electric Submersible Pumps (ESPs) for Deep Subsea Applications,” 43th International Pump Users Symposium, Texas A&M University, College Station, TX, pp. 1–18), are re-evaluated to include the effect of the fluid between the pump housing and well casing. Conclusions are made based on these new findings. The same two-line rotor–housing model is used to model the pump's rotor and its housing. The model dimensions are based on direct measurements of an ESP. The pump rotor and pump housing are only connected together at each stage by reaction forces and moments from seals and bushings. The rotor model is pinned to the housing at the rotor's ends. The housing model is pinned to ground at its ends. Synchronous response predictions are presented for: (1) relative rotor–housing motion and (2) housing velocity-response amplitudes. When handling viscosity of water, the rotor–housing model is predicted to be stable at new (centered) 1× clearances but rapidly becomes unstable with enlarged clearances (2× and 3×), primarily due to rapidly dropping rotor–housing natural frequencies. The impact of introducing effective swirl brakes for the stages' wear ring seals was investigated for a pump running at 3600 rpm. Their predicted impact on stability and synchronous response was: (1) Onset speeds of instabilities (OSIs) were elevated well above running speed and (2) synchronous response amplitudes were reduced modestly. Housing-response amplitudes varied considerably with the choice of housing-termination locations. For a pump rotor length of Lr, varying the lengths of a centered housing over 1.5 Lr, 2 Lr, and 3 Lr changes the housing's natural frequency. This natural frequency can coincide with the running speed with proper termination conditions. If the running speed and natural frequency coincide, large housing vibration amplitudes associated with resonance would exceed most vibration regulations; however, relative rotor–stator response amplitudes were a small fraction of clearances for all the cases. When handling emulsions at markedly higher viscosities, with a pump speed of 3600 rpm and new centered clearances, the predicted OSI was below 300 rpm. The OSI rapidly increased as the seals were displaced eccentrically, quickly elevating the first rotor–stator natural frequency above 1800 rpm and the OSI above 3600 rpm. With the model stabilized at 0.2 eccentricity, the synchronous relative rotor–housing amplitudes were a small fraction of seal clearances. Swirl brakes were not predicted to be effective in elevating pump OSIs for high viscosity fluids with new clearances; however, they became effective as clearances were increased. An ESP housing can contact the well casing in many possible scenarios (axial locations, contact-area length or girth, etc.). A midspan, point radial contact was examined and modeled as a stiff-spring connection from the housing to ground. For both water and oil–water emulsions, a stiff housing-to-casing contact produced major elliptical housing motion (versus circular motion without contact). However, it had a comparably minor impact on relative rotor–housing response amplitudes or rotordynamic stability.

Copyright © 2017 by ASME
Your Session has timed out. Please sign back in to continue.



Grahic Jump Location
Fig. 1

Synchronous (right peak) and subsynchronous (left peak) motion amplitudes versus frequency in rpm after Valantas and Bolleter [6]

Grahic Jump Location
Fig. 2

Swirl brake used to solve Massey's pump instability problem [5]

Grahic Jump Location
Fig. 3

ESP stage with balance holes showing annular and axial seals

Grahic Jump Location
Fig. 4

The Lomakin effect, Childs [9]

Grahic Jump Location
Fig. 5

Model of ESP pump cross section. Added damping and mass to the housing are not shown.

Grahic Jump Location
Fig. 6

Predictions of the damping and added-mass for a viscosity of water between the pump housing and well casing: (a) Black's damping coefficient and (b) Black's and Blevins's added-mass coefficient

Grahic Jump Location
Fig. 7

Effect of including the fluid interaction of the housing-to-casing cavity for (a) relative response versus speed and (b) housing vibration versus speed

Grahic Jump Location
Fig. 8

Forsberg's measured housing assembly response (from accelerometer output) at 3600 rpm [13]

Grahic Jump Location
Fig. 9

Predicted pump housing response amplitude at 3600 rpm

Grahic Jump Location
Fig. 10

Impeller dimensions for hydraulic imbalance definition, Childs [9]

Grahic Jump Location
Fig. 11

Predicted synchronous response due to mechanical imbalance, hydraulic imbalance, and bent-shaft excitation for the base-line ESP model with water: (a) midrotor, relative rotor–housing response amplitude (mil) and (b) housing velocity amplitude (in./s)

Grahic Jump Location
Fig. 12

Impact of varying seal offset on (a) relative rotor–housing amplitudes and (b) housing vibration levels

Grahic Jump Location
Fig. 13

The impact on predicted synchronous response due to changing the seal clearances: (a) relative rotor–housing amplitudes and (b) housing vibration levels

Grahic Jump Location
Fig. 14

Impact of changing the housing-termination location for new clearances on (a) predicted relative rotor–housing motion and (b) housing vibration amplitudes

Grahic Jump Location
Fig. 15

Predicted impact of a stiff elastic connection from midspan of the pump housing to midspan of the housing: (a) relative rotor housing response orbit amplitudes, (b) housing velocity amplitudes in the X (connection) direction, and (c) housing velocity amplitudes in the Y (transverse-to-connection) direction

Grahic Jump Location
Fig. 16

Emulsion, no swirl brakes: OSI versus ε0; 1×, 2×, and 3× clearances

Grahic Jump Location
Fig. 17

Impact on predicted synchronous response due to changing the seal static eccentricity ratios; new clearances, water–oil emulsion: (a) relative rotor–housing amplitudes and (b) housing-vibration levels

Grahic Jump Location
Fig. 18

Emulsion predictions for WFR versus ω with and without swirl brake at 1×, 2×, and 3× clearances

Grahic Jump Location
Fig. 19

Response with and without housing–casing contact, new clearances, ε0 = 0.2

Grahic Jump Location
Fig. 20

Comparison of adding moment coefficients to the interstage seal with a viscosity similar to water: (a) relative rotor–housing amplitudes and (b) housing vibration levels




Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In