Session: 05-01-02 Applied CFD

Paper Number: 87040

87040 - Slurry Pumps Instability Investigation Using High Fidelity CFD Simulation 

Slurry pumps are widely used in a variety of applications in the mining, dredging, and aggregate industries.  Slurry systems and their hydraulic resistance curves are often variable, due to the nature of the slurry processes, and well behaved pump head characteristics are needed in order to allow stable operation over a wide range of flow conditions.  On the other hand, the slurry pump hydraulics themselves are often distorted from the ideal geometries developed for handling clear fluids, since the slurry pump must often pass large solids to prevent blockages.  This results in a hydraulic mismatch between the impeller and casing hydraulic designs which can lead to unexpected results in pump performance.

In the current study, two slurry pumps are compared which differ only in the design of their casing hydraulics, both using the same exact impeller.  The test results showed that a severe instability was formed in the head curve when the smaller casing was used which persisted over a large portion of the curve and resulted in a much lower operating efficiency. Changing to the larger casing eliminated the instability and restored the expected pump efficiency. The root cause of this difference was not immediately apparent at the time of testing and did not have any well know corollary in the experience of clear liquid pumps. In order to investigate the root cause by examining the underlying flow patterns, a high fidelity, transient, full machine model, including impeller side gap, was developed and applied in a flow range from about 110 to 30 % of the pump best efficiency flowrate or BEPQ.  The CFD simulation results were in good agreement with the measured performances, detecting the instability at the same flow rate for the smaller casing, and no instability when the larger casing is used.  Surprisingly, considerable difference between the models appears within the impeller passages, even though its hydraulic did not change.  These differences are characterized, some theories offered regarding the underlying physical effects, and design guidelines proposed for avoiding the undesirable instability in future designs.   

Key words: Slurry pump, Performance Instability, High Fidelity simulation.

Presenting Author: Mohamed Garman GIW Industries