Solids effect on the performance of centrifugal slurry pumps
Experimental research on the so-called Stepanoff effect
W. Pont (TU Delft - Mechanical Engineering)
R.L.J. Helmons – Mentor (TU Delft - Mechanical Engineering)
G.H. Keetels – Mentor (TU Delft - Mechanical Engineering)
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Abstract
Main objective of this thesis is:
"Verify & Improve an existing, or develop a new, formulation to estimate the solids effect on the centrifugal pump for the transported slurries. Furthermore, find knowledge or data gaps and perform experiments to fill these gaps."
In the slurry transport industry, such as the dredging industry, the clear water pump curves are not applicable for transport calculations. This is due to the decrease in pump performance, expressed in meter mixture head, during the hydraulic transport of the mixture. This decrease occurs due to the presence of solids in the mixture. In the past 60 years, lots of researchers have investigated the effect of solids in centrifugal pumps.
Each researcher formed a formulation which described a specific data set of particles with certain particle size and density with a specific pump size.
The purpose of this thesis is to determine which formulation is the best formulation for the dredging industry. This industry is characterised by pumping quartz particle size ranging from d50 = 0.1 - 2 mm, with a density around 2650 kg/m3, using pump impellers ranging from Dimpeller = 0.4 - 2.5 m. These specific characteristics are evaluated with scaled experiments in this thesis.
An extensive literature study is conducted, where all known formulations are evaluated and checked against each other. After analysing this comparison, the most relevant formulations are selected to be evaluated deeper by conducting experiments at the dredging lab of the Delft University of Technology.
The experiments took place from August 2018 till February 2019 and were performed at the dredging lab. During the experiments three narrow graded quartz materials are tested with d50 values of: 0.139 mm, 0.285 mm and 0.859 mm. The test set up uses a centrifugal pump with Dimpeller = 0.4 m. Each material is tested over the range from 0 - 40% concentration by volume for three different flow rates at constant RPM. With the help of a butterfly valve, the flow rate is tested over the range from 60%to 140%Q/QBEP . Q/QBEP is the ratio of the actual flow rate to the best efficiency flow rate of the pump, for the selected RPM setting. The range 60% to 140% is the usual operating windows for the dredging industry.