Experimental and Numerical Study of Efficiency Improvement by Surface Coating on the Impellers and Diffusers of Mixed Flow Submersible Borewell Pumps

This study focuses on the effect of surface coating on the impellers and diffusers in improving the efficiency of mixed flow submersible borewell pumps. It consists of two parts. In the first part, a 3 stage pump was constructed with uncoated bronze impellers and cast iron diffusers having a surface roughness value of 2.5μm Ra and tested for pump performance. Then the same 3 stage pump was tested with impellers, diffusers coated with a polymeric coating having a surface roughness of 0.2μm Ra and ceramic enamel having a surface roughness of 0.8μm Ra. Experimental results showed considerable improvement, upto 4.5% in pump efficiency. In the second part, performance of the 3 stage pump was simulated using CFD tool Ansys Fluent for a surface roughness of 2.5μm Ra in the cast iron diffuser passage and bronze impeller passage. The same model was simulated with reduced surface roughness values viz. 0.2μm Ra surface roughness of polymeric coating and 0.8μm Ra surface roughness of ceramic enamel coating. The pressure and velocity distributions were analysed and input power calculations were made. Simulation results also show that the pump efficiency has improved and found matching with experimental results.