Hydroabrasive wear of jet pump nozzles

Abstract

The measurements of hydroabrasive wear of the jet pumps nozzles, used on dredges operating on transferring pulp, are carried out. The measurement result is compared with the result of modelling the flow in the pump suction chamber near the nozzles. The modelling is carried out using the Fluent program complex as a part of the Ansys program; the pure water is being modelled in the suction pipe. This assumption is made taking into account that pulp contains approximately 10 percent by volume of sand, therefore the trajectories of sand particles movement coincide with the streamlines of water. The results of modeling have shown, that the angle of attack on the surface of nozzle nose part nearest to the pulpline outlet is close to zero, whereas the angles of attack on the surface of the nozzle nose part furthest from the pipeline outlet differ considerably from the zero and range from 20 to 50 degrees, that is the values at which the hydroabrasive wear increases severalfold compared to the angles close to zero. The results of modelling are confirmed by the examination of the worn nozzles. It is turned out that the nose part of the nozzles wears out along a circle unevenly, the part furthest from the pipeline outlet wears at higher rate, that leads to the bevel of the plane of the nozzle nose opening, the bevel angle reaches 20–25 degrees. The microhardness values of the nose part of the worn nozzle are also in agreement with the results of modelling. The measurements have shown, that the microhardness of the nose part of the worn nozzle is uneven along a circle, and the microhardness of the most worn side of the nozzle nose is least. This fact indicates that the different zones of the surface of the nozzle nose part differ from each other by the rigidity of stress state scheme in hydroabrasive attack. It can be used later in choosing the regime of laboratory tests on hydroabrasive wear.