Design And Performance Investigation For Submersible Sewage Pumps With Different Impellers

The submersible sewage pump plays an important role in elevating and transporting sewage.Successful applications of submersible sewage pumps have been witnessed in engineering fields such as sewage processing,municipal drainage and underwater desilting.Efficiency and through capacity are two aspects that significantly influence the energy consumption and the stability of pump operation.The impeller is a vital component of the submersible sewage pump.Thus far,studies on the channel-type impeller have been reported.In comparison,literature on the blade-type impeller has seldom been found.In consideration of the pump structure and pump hydraulics,the double-bladed impeller can maintain its balance during operation;high efficiency and good through capacity are anticipated to accomplish as well.Therefore,such an impeller is expected to flourish in both academia and industry.Major works and conclusions embraced in this dissertation are as follows.(1)The hydraulic design methods and theoretical foundation for the dual-channel and double-blade sewage pumps were analyzed.Based on experience in practical design,the principles for determining the coefficients in the calculation of hydraulic parameters were proposed.The hydraulic design scheme was constructed.With this work,the approach for calculating geometric parameters that constitute the meridional sketch of the impeller is established,enabling high hydraulic efficiency and through capability.The methods of calculating primary volute parameters such as the volute throat diameter and the setting angle of the cut-water are suggested.The length of the convergent segment of the volute is taken as a critical parameter;a supplement of current knowledge in calculating such a length is substantiated.(2)Three-dimensional numerical simulations were carried out for flows in the two sewage pumps considered.The Reynolds averaged Navier-Stokes equations served as flow-governing equations.Flow features were considered comprehensively at small,design and large flow rates.A comparison between the two pumps was performed based on the simulation results.Total energy of the transported liquid increases continuously from the pump inlet to outlet,which is shared by the two pumps considered.At the inlet of the dual-channel pump,a large-scale vortex is formed.In comparison,flow parameter distributions in the flow passage of the double-bladed pump are more regular.Meanwhile,the energy delivery from the impeller to the medium is sufficient in the double-bladed pump.In the volute channel,flows diffuse remarkably,as is common for the two pumps.(3)Prototype pumps equipped with the two different impellers were designed and manufactured.Strength examination was conducted for the major components of the two pumps.Main steps in the structural design of the two pumps were analyzed.Along with an integrated consideration of the operation characteristics of the sewage pump,the motor performance and processing techniques for the pump components are interpreted.Both axial and radial forces exerted on the major pump components are acquired.For the pump shaft,the impeller and the pump casing,the materials are predefined,and it is proved that the strength obtained fulfills relevant requirements.(4)Performance test was conducted for the two pumps manufactured.The performance of the two pumps was tested within the whole range of flow rates.The test data are in good accordance with the numerical results.Experimentally obtained pump head and pump efficiency are lower than their counterparts obtained using numerical simulation.For the two pumps,no hump is detected in the pump headcurves;the shaft power varies smoothly with the flow rate.Furthermore,within the whole flow rate range,overload is absent.The test results validate the pump design.In comparison,the efficiency of the double-bladed pump is higher than that of the dual-channel pump.Suitable and efficient design schemes for the dual-channel and double-bladed sewage pumps were established in the dissertation.A systematic investigation of the two pumps was performed through hydraulic design,flow simulation,structural design,strength examination and performance test.A multiple-aspect comparison was enabled based on the obtained results.Pros and cons of the two impellers were explained.The conclusions provide a sound support for the design of the hydraulic components of the sewage pump as well as the selection of the pump structure.