Design Evaluation of a Duplex Circular Wet Well Pumping Station Under Steady State and Dynamic Operating Conditions

• Main Author: Mailloux, James Thomas
• Other Authors: Paul P. Mathisen, Advisor
• Format: Others
• Published: Digital WPI 2010
• Subjects: Dynamic pump operation; Circular pump station design
• Online Access: https://digitalcommons.wpi.edu/etd-theses/471; https://digitalcommons.wpi.edu/cgi/viewcontent.cgi?article=1470&context=etd-theses

Duplex Circular Wet Well (DCWW) lifting pump stations are utilized for pumping clear and solid-bearing liquid. Understanding the effect of design criteria on pump performance is important to minimize maintenance costs and maximize efficiency. There are currently no known full-scale laboratory studies that have been performed to investigate the overall design of DCWWs. The objective of the research was to evaluate the impact of various design criteria, such as internal geometry and operating conditions on the performance of DCWW pump stations and provide documentation and recommendations which will be used to augment the current Hydraulic Institute/American National Standard for Pump Intake Design (ANSI/HI 9.8-1998), (HI) guidelines. The research was conducted in two phases; Phase 1 consisted of performing a comparative analysis of the basic flow patterns within the wet well by means of Computational Fluid Dynamics (CFD), Phase 2 consisted of performing detailed evaluations of various design aspects on pump performance using a full-scale Physical Model constructed for the research. The CFD research provided indications regarding potential performance problems that may occur due to poor flow patterns and potential pump suction swirl, while the physical research provided a basis for determining the relative advantages of different designs. The physical research included the evaluation of general flow patterns, free-surface and subsurface vortices, air entrainment and pump suction swirl. Measurement of the steady state swirl within the pump showed unacceptable performance in accordance with the HI acceptance criteria. Swirl data collected under real-world dynamic operating conditions showed that the pump typically did not experience the adverse conditions indicated at steady state. Normal (symmetrical) pump orientation resulted in more favorable operation in terms of pump swirl and ingestion of entrained air than a coplanar (inline) condition. A minimum water elevation was established to minimize air-entrainment and swirl entering the pumps, reducing possible effects such as cavitation and vibration of the pump impeller. Air-core subsurface vortices were present under the pumps, requiring pump-cones to be installed. The collection of real-time dynamic data will allow design engineers to better understand actual pump performance under normal cycling and clean-out modes, reducing the operating time under unfavorable conditions and overall maintenance requirements.