Axial-Flow High-Volume / Low-Head Pump Design – Energy Method

It has been common practice to use classic pump curves when designing axial flow high-volume / low-head pumps.  This presentation discusses axial pump design that is based on performance equations derived from an energy balance perspective.  A specific real-world design case is presented for a pump with an output of 11,400 gallons per minute @ 6 foot head.  Propeller 18.25 inch design OD was a required precondition.  Primary design goal - maximize pumping efficiency.  Leading edge prop geometry computed from incoming flow vector.  Trailing edge prop geometry derived from energy-based performance equations with a slip-factor term borrowed from the world of marine prop design.  Computational Fluid Dynamics (CFD) was used to predict the rotation-flow component of the fluid flow exiting the prop which was used to design the flow-straightener.  A method for predicting a reasonable test RPM range will be discussed.  A full-scale lab test was performed to pinpoint the final operating RPM within the predicted range and to verify the expected design performance. CAD models were made using 3-D parametric CAD from PTC (Wildfire^TM 4.0).  Performance of pump was simulated using the mathematic computation software Mathcad^TM.  Part design strength was verified by Finite Element Analysis (FEA, Pro/Mechanica).  Fluid flow was predicted by CFD software from Fluent^TM.  Pump test conformed to Hydraulics Institute HI 2.6 and US Army Corps of Engineers standard EM 1110-2-3105.  Pump test evaluation included DigitalFlow^TM ultrasonic flow meter, pressure transducers, and strain gauge based shaft power measurement using Microstrain Inc’s V-link^TM wireless RF telemetry.