The waterjet nozzle wear effect on jet pump performance

Abstract

A finite-elemental model of a jet pump was created. The pump consisted of a case, in which there were eight jets, situated in a circle, symmetrically relative to the circle axis, on the equal distance of each other around the outlet of a pipeline, along which the pulp was pumped. The basic element size of the net in creating the model amounts to 50 mm, whereas the net elements size was diminished in the region of jets. The numerical experiment was carried out in order to evaluate the influence of the jets hydroabrasive wear parameters on the pump output. In conducting the computations, the assumptions were as follows: the liquid columns in the suction and force-feed pipelines were neglected; there was pure water modelled in the suction pipeline instead of the pulp taking into account that the concentration of the sand in the pulp does not exceed 10% by volume. The computations were realized in the stationary formulation of the problem. As basic parameters of the hydroabrasive wear of the jets the following were chosen: the angle of the skew of the jet forward end; a jet shortening – the displacement of the jet forward end center along the jet axis. As a result of the numerical experiment the body of data was obtained. Using the least squares method to process the data, the second order model was created, describing the dependence of the pump output on the jets wear parameters. The analysis of the model showed that the change of the angle of the forward end skew of the jets has a weak influence on the output of the pump, whereas the shortening of the jets by each millimeter causes the decrease of 1% to the nominal value of the pump output.